economic geology 2011 vol.106 p.93–117

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IntroductionSince first applied by Walker et al. (1991), the application

of the 190Pt-186Os decay system as a tracer of deep Earthprocesses has been the focus of a surge in interest (e.g.,Walker et al., 1997a; Brandon et al., 1998, 2007; Luguet et al.,2008). However, the application of this decay system togeochronology has been limited (Walker et al., 1997b), withvery few applications to ore genesis, despite the economic rel-evance of the parent and daughter isotopes. The reasons forthis stem from the very low decay constant of 190Pt (λ = 1.477× 10–12 yr–1 ± 1%; Begemann et al., 2001) and the very smallresultant variations in the 186Os/188Os ratio. These practicaldifficulties make PGE alloys and certain other PGM clear tar-gets for study because of the wide range of potential Pt/Os ra-tios that these mineral groups may have (Harris and Cabri,1991). Nowell et al. (2008b) recently showed that it is possi-ble to produce accurate and precise 186Os/188Os measure-ments of PGM grains via laser ablation-multicollector-ICPMS (LA-MC-ICPMS) and the additional Re-Os isotopedata produced from such analyses can be used to examinemantle Os isotope variations on a global scale (Pearson et al.,2007). The former study also demonstrated that the substan-tial variation in Pt/Os within and between PGM can be usedto obtain geochronological information for samples from ul-tramafic rocks that are often difficult to date. This offers ob-vious opportunities in terms of the dating of ophiolite massifs,which is notoriously problematic when using traditionalgeochronology methods.

In this study we apply the Pt-Os chronometer to a suite ofdetrital PGM grains derived from the Meratus ophiolite, Bor-neo. The source of the PGM grains is well constrained andcomparison with existing geochronology and geochemistry al-lows us to evaluate the accuracy of the Pt-Os age. The resultillustrates the potential for the Pt-Os isotope system in con-straining the age and origin of alluvial PGM deposits.

Samples and ProvenancePGM grains from Borneo were provided for this study by

the Smithsonian Institution National Museum of Natural His-tory from sample NMNH96511. The grains were collected byA. Lacroix from the Pontyn River, Tanah Laut, in the provinceof South Kalimantan, Indonesian Borneo, and were labeled as“laurite.”

Regional geology and provenance

The Pontyn River drains the southern Meratus Mountainsand flows into the Java Sea near the town of Asemasen on thesoutheast coast of Borneo (Fig. 1). The catchment of theriver and its tributaries is geologically varied. It includes var-ious clastic sedimentary rocks, limestones, intermediate tofelsic volcanic rocks, metamorphic rocks and the ultramafic,gabbroic, and leucocratic rocks that make up the Meratusophiolite (Sikumbang, 1990; Guntoro, 1999). Trace elementabundances (particularly negative Nb-Ta anomalies and(La/Nb)N ratios of 1.7–3.5) of Meratus lavas have been inter-preted as evidence that a back-arc basin setting may haveproduced the oceanic lithosphere that forms the Meratusophiolite (Monnier et al., 1999). However, the same authorsconclude that Cr# of spinel, orthopyroxene, and clinopyrox-ene in peridotites, along with low Na2O and TiO2 contentsand depletion in incompatible elements, demonstrates that

APPLICATION OF THE 190Pt-186Os ISOTOPE SYSTEM TO DATING PLATINUM MINERALIZATION AND OPHIOLITE FORMATION: AN EXAMPLE FROM THE MERATUS MOUNTAINS, BORNEO

J. A. COGGON,1,†,* G. M. NOWELL,1 D. G. PEARSON,1 AND S. W. PARMAN2

1 Northern Centre for Isotopic and Elemental Tracing, Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, United Kingdom

2 Department of Geological Sciences, Brown University, Providence, Rhode Island 02912

AbstractThe formation age of platinum-group minerals (PGM) in placer deposits has traditionally been difficult to

constrain. We have applied the Pt-Os and Re-Os isotope systems to this problem by analyzing a suite of PGMfrom a placer deposit in southeastern Borneo that are derived, by mechanical processes, from chromitites ofthe Meratus ophiolite. Published subduction and emplacement ages and biostratigraphy of pelagic sedimentsof the ophiolite sequence define a minimum age for genesis at a spreading ridge. However, igneous compo-nents of the ophiolite have previously been undateable. Alluvial PGM grains (n = 260) from the Pontyn River,which drains the Meratus Mountains, were analyzed by laser ablation-multicollector-inductively-coupled massspectrometry (LA-MC-ICPMS). Re-Os data do not show any isochronous relationship. Despite a significant rangein 187Os/188Os (0.122–0.141), 187Re/188Os values show a very narrow range (0.000005–0.002980). In contrast, thePGM have a wide range in both 186Os/188Os (0.119801–0.120315) and 190Pt/188Os (<0.00001–1.493430), yield-ing a precise Pt-Os isochron age of 197.8 ± 8.1 Ma (2σ). This age fits well with published age constraints forthis ophiolite and we argue that it dates the crystallization of the PGM. Previous studies have shown that thePontyn PGM are derived from ophiolitic chromitite; therefore, the PGM Pt-Os isochron age also provides thefirst absolute age constraint for the genesis of igneous rocks of the Meratus ophiolite. These results highlightthe potential of the Pt-Os geochronometer as a tool for dating the crystallization age of PGM found in placerdeposits, for dating primary platinum mineralization in general, and for use in ophiolite geochronology.

† Corresponding author: e-mail, [email protected]*Present address: Mineralogisch-Petrologisches Institut, Universität Bonn,

Poppelsdorfer Schloss, 53115 Bonn, Germany.

©2011 Society of Economic Geologists, Inc.Economic Geology, v. 106, pp. 93–117

Submitted: November 3, 2009Accepted: September 5, 2010

Meratus peridotites represent subcontinental lithosphericmantle that underwent low degrees of localized partial melt-ing during the final stages of an episode of continental rifting.

Burgath and Mohr (1986) and Burgath (1988) reported theoccurrence of PGE-rich chromitite seams in the serpentinizeddunite of the Meratus ultramafic rocks. Hattori et al. (1992)analyzed the osmium isotope composition of laurite grainsfrom these chromitites by SIMS. All these authors also ana-lyzed PGM from associated alluvial placers and concluded thatthe isotopic data support a detrital origin for the placer grains,which were mechanically eroded from their host chromitites.

PGM mineralogy and morphology

A total of 260 placer PGM grains were analyzed in thisstudy. Electron microprobe analyses confirmed two maincompositional groups: 82 grains of Os-bearing laurite(14.3–31.1 wt % Os) and 174 grains of Pt-Fe alloy (73.8–91.5wt % Pt, 0.4–4.0 wt % Os) (Fig. 2, Tables A1, A2). Two grainsof Ir-Os-Pt alloy (iridium), with 53.0 wt percent Ir (BRN-2-076 and BRN-3-024), one of PtAs2 (sperrylite) (BRN-2-045)and one of PGE-bearing Au-Ag alloy were also identified.

Long-axis dimensions range from ca. 250 to 2,000 µm. Thethree largest grains are alloys; sulfide grains are generallysmaller, with a maximum diameter of 800 µm. Sulfides are

predominantly equidimensional and subrounded to rounded,although rare examples of more elongate and subangulargrains are present in this population. Subhedral grains showcubic systems (e.g., Fig. 3A). PGE alloys have more variedmorphologies; rounded, subspherical to ellipsoid alloys (e.g.,Fig. 3C) are uncommon, with the majority displaying irregu-lar, angular, and “nodular” forms (e.g., Fig. 3D-F). Two grainsin this group are subhedral; they have cubic crystal systems(e.g., Fig. 3B), which are typical of isoferroplatinum (Pt3Fe)(Harris and Cabri, 1991). Surface features are varied and in-clude pits (rounded and irregular, cubic, linear) ranging fromapproximately 1 to 40 µm in diameter, scratches, and frac-tures (Fig. 3G-L). These surface features, with the exceptionof euhedral pits, are typical of alluvially transported PGMgrains (Cabri et al., 1996; Oberthür et al., 2004). Euhedralpits are likely to represent negative crystals or melt inclusions,removed by weathering, that inherited the morphology of thehost PGM grain, as described by Brenker et al. (2003).

Methods

Laser ablation-multicollector-ICPMS (LA-MC-ICPMS)

Grains were mounted in 10 × 10 grids on adhesive carbonSEM tabs fixed to glass microscope slides. Samples were im-aged prior to isotopic analysis at Durham University using aHitachi TM-1000 tabletop scanning electron microscope.

Pt-Os isotope analyses were carried out at Durham Univer-sity Northern Center for Isotopic and Elemental Tracing(NCIET) using a New Wave UP 213 nm laser and ThermoFisher Neptune MC-ICPMS via the method presented inNowell et al. (2008b). Borneo samples were analyzed over sixsessions between 17-12-2007 and 18-02-2008. Laser spotsizes of 120 to 125 µm were used for Os-rich grains, while250-µm spots were used for Pt-rich/Os-poor samples. Laserrepetition rate was varied between 9 and 20 Hz, and laserpower density from 40 to 100 percent. Fixed value laser pa-rameters used are given in Nowell et al. (2008b).

At the start of each analytical session a 1 µg ml–1 DROsSstandard solution was analyzed 10 times in order to assess in-strument accuracy and reproducibility. Over the six analyticalsessions, the reproducibility was 122 ppm for 187Os/188Os and125 ppm for 186Os/188Os. Mean 187Os/188Os and 186Os/188Os ra-tios of 0.160918 ± 0.000020 and 0.119917 ± 0.000015, re-spectively (2 SD, n = 60) (Table A4) are identical to the val-ues of 0.160921 ± 0.000018 and 0.119917 ± 0.000020 (2 SD,n = 5) reported for this standard by Nowell et al. (2008b).

The 189Os/188Os ratio is free of elemental interferences so itwas used to correct for mass bias. A value of 1.21978 (Nowellet al., 2008b) was assumed for this correction.

184W, 186W, and 187Re occur as elemental isobaric interfer-ences on 184Os, 186Os and 187Os during laser ablation. To correctfor these interferences, 182W and 185Re were monitored dur-ing analyses and, assuming 182W/184W = 0.863376 ± 15, 182W/186W = 0.930700 ± 13, and 185Re/187Re = 0.598050 ± 13 (derivedfrom analyses of a 1 µg ml-1 DROsS solution doped with vary-ing concentrations of W and Re (see Nowell et al., 2008a), theappropriate level of interference was subtracted for each 1 sintegration to yield the corrected Os isotope ratios.

Interferences on 190Os and 192Os by 190Pt and 192Pt cannot becorrected in the same way since the faraday cup configuration

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Cretaceous flysch

Cenozoic sedimentary cover

Cretaceous volcanics

Cretaceous plutonic rocks

Ultramafic rocks, chert and melange

Schist and phyllite

E°611E°511

3° S

4° S

Pontyn R.

Java SeaLaut Island

SouthKalimantan

Mer

atus

Mou

ntain

s

Asemasem

N

Fig. 1. Map showing the geology of the Meratus Mountains, includingophiolitic rocks (DeWit et al., 1992), schists formed by subduction zone meta -morphism (purple), and location of the Pontyn River (after Wakita et al., 1998).

used does not provide a Pt monitor isotope. Instead Os mustbe treated as the interfering element, with 188Os taken as themonitor isotope. The mean 190Os/188Os ratio determined frommeasurements of the DROsS standard at the start of each ses-sion was used to subtract the Os interference on mass 190 andthereby derive the 190Pt intensity and the 190Pt/188Os ratio.

Each analysis is made up of 40 1-s integrations. After massbias and interfering element corrections were applied to eachmeasurement, the analyses were subject to a 2σ rejection.The method and corrections are discussed in greater detail byNowell et al. (2008b).

For plotting Pt-Os isochrones, total errors in 186Os /188Osratios were calculated to incorporate external reproducibility.A value of 176 ppm was used for grains with 188 beams of 1V or more; grains with 188 beams <1 V were assigned exter-nal reproducibility values of 352 ppm. These values were de-rived from repeat analyses over one year of an in-house stan-dard (Urals Os-rich PGE alloy 36720 G1, Nowell et al.,2008b). No such data is available for 190Pt/188Os since there isno Pt-rich homogeneous ablation standard. However, small-scale isotopic heterogeneity of individual samples leads to rel-atively large within-run precision, contributing a major com-ponent of the overall uncertainty on this ratio. In addition, asignificant portion of the uncertainty on 190Pt/188Os measure-ments may result from Pt-Os fractionation at the ablation site.Such interelement fractionation is poorly understood, but isestimated by Nowell et al. (2008b) to be 5 percent or less.Total uncertainty on the 190Pt/188Os ratio, therefore, includes

the within-run error and 5 percent uncertainty to account forexternal reproducibility and potential elemental fractionationthat may occur at the ablation site.

Electron microprobe and SEM

The PGM were transferred to polished sections for compo-sitional analysis using a CAMECA SX-100 electron microprobeat Brown University, Rhode Island. WDS analyses were carriedout with an accelerating voltage of 20 keV, beam current of 25nA and beam diameter of ~1 µm. Measurement times of 10 swere used on peaks, with 5-s measurements on the back-grounds above and below each peak. Pure metal standardswere used for all elements analyzed, with the exception of Sand As, for which FeS and GaAs were used, respectively. De-tection limits are 3σ and range from 0.088 to 0.589 wt percentfor analyses of sulfides. During analyses of alloys (high Pt sam-ples), Pt interference occurs on the Fe L alpha peak; therefore,Fe was analyzed on the K alpha peak for these samples witha detection limit of 1.37 wt percent. Full details of detectionlimits are given in Table A5. Silicate and base metal sulfide in-clusions were analyzed qualitatively, using EDS analyses.

Results

Inclusions and other internal features of Borneo PGM grains

BSE images of polished grains reveal distinct groups of in-ternal features. Sulfides are poorly polished since there is aconsiderable contrast in hardness between these grains and

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Ru

Os

Ir

BPt

Ir

Fe

DPt

Ir

Fe

Pt

Ir

Fe

F F’

F’

Pt

Os

Fe

C Pt-Fe alloysRu

Os

S

A SulfidesPt

Os

Fe

EPGE alloy rims

Os-IrOs>Ru>Ir>RhIr>Os>Pt>Rh,Ru

Pt-FeInclusions:

Fig. 2. Ternary plots showing relative (wt %) compositions of dominant elements in Borneo placer PGM and their inclu-sions, measured by electron microprobe. A, B. Sulfides. C, D. Alloys. E, F. PGE alloy rims on Pt-Fe alloy grains and inclu-sions in alloy grains. Full compositional data are displayed in Tables A1–A3.

PGE alloys, with which they are mounted. Despite this, it ispossible to identify inclusions hosted within many of the Bor-neo laurites. These appear as dark patches, approximately 5 to30 µm in diameter, that range from rounded to euhedral(hexagonal) and are crystallographically orientated (Fig. A1).The shape of euhedral inclusions and their orientation relativeto each other suggests that they may have been included as liq-uids and their morphological features are inherited from thehost grains. EDS analyses of the inclusions show a range ofphases; silicates (amphibole, epidote, clinopyroxene, serpen-tine, olivine, anorthite, and melt), base metal sulfides (pyrite,pyrrhotite, pentlandite, and chalcopyrite) and two compositeinclusions of silicate + sulfide + alloy were identified.

Silicate inclusions in alloy grains have diameters as great as75 µm and may be sub- or euhedral and crystallographicallyorientated, or anhedral—in the form of linear “blebs” (Fig.A2A, B). Additional internal features of alloys can be grouped

together: inclusions or intergrowths of Os- and Ir-dominatedPGE alloys (Fig. A2C-E, Table A3) ranging from ~20 to 100µm in length; micro-PGE alloy inclusions, up to 15 µm in diameter (Fig. A2F, H); and PGE alloy rims (Fig. A2K, L), upto ~200 µm on composite grains. BSE images also highlightsets of bright (or rarely, dark), submicron thickness linear fea-tures (Fig. A2G, I, J) which may be cogenetic or a product ofexsolution (Cabri and Genkin, 1991).

Pt-Os isotopes and age

A total of 260 PGM grains were analyzed by LA-MC-ICPMS. Values for 190Pt/188Os measured range from <0.00001to 1.493430 and values for 186Os /188Os range from 0.119801 to0.120315 (Table A6). This range in 186Os /188Os is more than 25times greater than that observed in typical convecting mantle(Brandon et al., 1999). Measured 186Os /188Os correlates posi-tively with 190Pt/188Os. The initial 186Os/188Os ratio calculated


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100 µm100 µm

J

30 µm30 µm

L

100 µm100 µm

K

200 µm200 µm

A

300 µm300 µm

B

200 µm200 µm

C

300 µm300 µm

D

300 µm300 µm

E F

300 µm300 µm

100 µm100 µm

G

300 µm300 µm

I

100 µm100 µm

H

BRN-1-031 BRN-1-035 BRN-1-041

BRN-1-015 BRN-1-026 BRN-2-085

BRN-2-033 BRN-2-036 BRN-1-030

BRN-2-052 BRN-1-064 BRN-1-082

Fig. 3. BSE images showing examples of grain morphologies and surface textures seen in Borneo placer sulfides (A, I, K,L) and Pt-Fe alloys (B-H, J). A. Subhedral laurite showing cubic crystal habit. B. Subhedral, cubic Pt-Fe alloy. C.Subspher-ical Pt-Fe alloy. D-F. Irregular, angular and “nodular” forms, typical of Pt-Fe alloys in this population. G, K. Irregular pits ongrain surfaces, often infilled with granular (dark) material, possibly chromite. H, I. Scratches and fractures consistent withtransport in an alluvial system. J. Rounded pits following linear trends. L. Cubic, parallel pits in the surface of a Pt-Fe alloy.

from the data is 0.119830 ± 0.000003 and the resultingisochron has an MSWD of 0.90, a probability of fit of 0.88 andan age of 197.8 ± 8.1 Ma (2σ: Fig. 4). The uncertainty on theage incorporates the 1 percent uncertainty on the decay con-stant of 190Pt as estimated by Begemann et al. (2001).

Variation in 190Pt/188Os is dominated by mineralogy (Pt-Fealloys vs. Os-rich laurites), whereas 186Os /188Os ratio variationis minor and is most likely dominated by radiogenic in-growth. This is addressed further in the Discussion section.Pt-Fe alloys and sperrylite have ~76 to 91 wt percent Pt, 0.4to 4.0 wt percent Os, 190Pt/188Os ratios that range from0.00098 to 1.494, and 186Os /188Os values of 0.119801 to0.120315; these phases are predominant in defining the slopeof the isochron. Laurite grains in this population have <0.2 wtpercent Pt, 14.3 to 31.1 wt percent Os and 190Pt/188Os valuesup to only 0.0743 and therefore contribute to defining the ini-tial 186Os/188Os ratio.

Re-Os isotopes

Despite a very restricted range in 187Re/188Os values(0.000005–0.002980), there is considerable variation in 187Os/188Os (0.122117–0.140674). The extremely low Re/Os ratiosresult in calculated initial 187Os/188Os values that are almostidentical to measured 187Os/188Os, illustrating that these sam-ples do not share a common initial 187Os/188Os value. Hence,Re-Os isotope systematics are scattered and do not exhibit anisochronous relationship. Studies of other ophiolite-relatedPGM have shown considerable variation in 187Os/188Os that isnot related to Re/Os variation (Meibom et al., 2002; Walkeret al., 2002; Pearson et al., 2007).

Variations in 187Re/188Os and 187Os/188Os ratios may be re-lated to R-factor fractionation (Campbell and Naldrett, 1979)during PGM growth. Alternatively, these variations may re-sult from the PGM population being derived from several dif-ferent chromitite pods, essentially formed from isolated meltswith differing initial 187Os/188Os.

Discussion

PGM genesis

There has been much debate over the formation of alluvialor detrital PGM grains. Bowles (1988) has proposed a sec-ondary origin for PGM associated with the Freetown layeredintrusion in Sierra Leone by lateritic-type crystallizationwithin placers in a tropical environment. Perhaps morewidely applicable on a global scale is the proposal of a mag-matic origin for these minerals. Several scenarios have beensuggested for crystallization of PGM in the deep mantle orcore (Bird and Bassett, 1980; Bird et al., 1999); however,many workers now conclude that ophiolitic PGM grains areformed during chromitite genesis (Ahmed, 2007; Pearson etal., 2007; Tsoupas and Economou-Eliopoulos, 2008) in thelithospheric upper mantle (podiform chromitites) or base ofthe crust (stratiform chromitites; Paktunc, 1990).

In the case of Borneo and the Meratus grains, the tropicalclimate provides the potential for secondary crystallization ofPGM by the weathering mechanism described by Bowles(1988). If the PGM grains analyzed in this study were formedby a secondary process involving recrystallization within lat-erites, then the Pt-Os isochron must represent a mixing lineand not a true or meaningful age because lateritization is wellbelow any likely diffusional reequilibration temperature forthe Pt-Os (or Re-Os) isotope system. In such a scenario, PGMformation would be late in the geologic history of the Mera-tus ophiolite, occurring after high-level exhumation of themantle section. This greatly reduces the time available for ra-diogenic Os in-growth and means that any proposed precur-sors to the PGM grains, such as ultramafic rocks or chromi-tite veins, would need to have evolved to high 186Os/188Osratios rapidly and with unusually high Pt/Os ratios. Becausethe initial 186Os/188Os ratio of typical mantle materials variesso little, both spatially and throughout geologic time, such ascenario seems very unlikely on this basis alone.

Further evidence against a secondary origin for the Mer-atus PGM grains comes from Re-Os isotope systematics andS isotope data. The similarity of 187Os/188Os ratios in placerand in situ chromite-hosted PGM in the Meratus area ledHattori et al. (1992) to conclude that mechanical processesare responsible for transporting the PGE (in the form of al-loys and sulfides) to the placer deposits and that the placergrains are direct samples of the mantle-hosted PGM grains.Sulfur isotopes along with arsenic and selenium contents ofplacer laurite (RuS2) from the Pontyn and Tambanio Rivers,southeast Borneo, confirm that these grains are derivedfrom their host chromites by purely mechanical processes.The sulfur isotope ratio of the PGM grains originating fromS-bearing inclusions such as laurite has a clear mantle sig-nature as opposed to the fractionated and variable S isotopesignatures expected if these grains had formed in near-sur-face environments (Hattori et al., 2004). Hence, there is


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0.1197

0.1200

0.1203

-0.1 0.5 1.1 1.7

190Pt/188Os

186 O

s/18

8 Os

197.8 ± 8.1 MaInitial 186Os/188Os = 0.119830 ± 0.000003

MSWD = 0.90Probability of fit = 0.88

n = 260

2σ errors

Fig. 4. Pt-Os isochron diagram for 260 Borneo placer PGM. Fill color oferror ellipse indicates mineralogy: gray = Pt-Fe alloy, black = laurites and oneAu-Ag alloy; white = grains not exposed by or lost during polishing. Errors on186Os/188Os incorporate within run uncertainties and long term external re-producibility on this ratio based on repeat analyses of an in-house standardgrain. 190Pt/188Os errors include 5 percent uncertainty to account for poten-tial elemental (Pt/Os) fractionation that may occur at the ablation site (Now-ell et al., 2008b). The uncertainty quoted on the isochron age incorporates anuncertainty of 1 percent on the decay constant of 190Pt (Begemann et al.,2001). Plotted using Isoplot version 3.1 (Ludwig, 2003).

powerful evidence against a low-T secondary origin for theMeratus alluvial PGM.

Silicate, sulfide, and multiphase or composite inclusions areobserved in the Borneo PGM grains. Composite inclusionsmay represent inclusions of trapped melt that later under-went fractional crystallization. Peck et al. (1992) and Brenkeret al. (2003) have used the presence of mineral and melt in-clusions, respectively, within PGM from alluvial deposits toargue strongly for a magmatic origin for such grains. A mag-matic origin is further supported by the presence of PGM(both sulfides and PGE alloys) as inclusions in chromite grains(Hattori et al., 2004; Ahmed, 2007; Tsoupas and Economou-Eliopoulos, 2008; Petrou and Economou-Eliopoulos, 2009).Ophiolitic chromitite formation may occur by crystallizationfrom a partial mantle melt after melt-rock interaction (Pak-tunc, 1990; Zhou et al., 1998) or by magma mixing (Ballhaus,1998). In either case, significant volumes of partial meltingmust occur to produce the parent magmas; thus, chromititemineralization is interpreted as a near-ridge process (Paktunc,1990) that takes place relatively soon after generation ofoceanic lithosphere.

Age of the Meratus ophiolite

The varied Pt-Os fractionation within the Meratus PGMgrains clearly offers possible geochronological constraints onthe timing of formation of the Meratus ophiolite. The firstissue to consider in evaluating this potential is the likelihoodof a single source for the PGM grains and the possibility thatthe correlation observed on the Pt-Os isochron diagram (Fig.4) may be a mixing line. Addressing the first of these issues, wespecifically selected the Meratus samples because their prove-nance is well constrained. There is good consensus that thePGM grains were derived directly from the single ophiolitebody based on close proximity and lack of any other plausiblehost rock units in the area (Hattori et al., 1992; Monnier et al.,1999). These factors mean that it is unlikely that our PGMgrain population is derived from a mixture of ultramafic bodieswith differing ages. Nonetheless, it is possible that several dif-ferent chromitite bodies within the single massif may have con-tributed to the population of grains that we have analyzed.Analyses of different chromitite bodies within a single ophioliteconfirm that such bodies can have variable 187Os/188Os ratios(e.g., Walker et al., 1996). This variability in initial 187Os/188Osratios, combined with subsequent postformation in-growth,may be a major reason why the Re-Os data for Meratus PGMare scattered, with no correlation on the isochron diagram. Incontrast to the Re-Os decay system, any variability in initialisotopic ratios due to the derivation of grains from multiplechromitite bodies would be masked in the Pt-Os system be-cause the variation in 186Os/188Os of the convecting mantlethroughout the whole of the Phanerozoic is less than 100 ppm(Brandon et al., 2006). Hence, the Pt-Os isochron correlation,in this instance, is unlikely to reflect mixing phenomena be-tween bodies with significantly different initial 186Os/188Osand seems best explained as reflecting radiogenic in-growthfrom variable Pt-Os since the time of PGM formation.

Taking the Pt-Os isochron age for Meratus PGM grains asa genesis age allows us to examine its potential accuracy in thecontext of other geochronologic data. Published plate recon-structions for the tectonically complex Java Sea allow imprecise

but independent age estimates for the Meratus ophiolite thatrange from Jurassic (Monnier et al., 1999) to Cretaceous(Parkinson et al., 1998). The application of traditional geo -chronological techniques to constrain the emplacement of theMeratus ophiolite body has proven problematic. K-Ar datingof terrigenous sediments within the infra-ophiolitic sole givesan estimated age of ophiolite accretion to the continental mar-gin of ~145 Ma, and obduction at ~90 Ma (Monnier et al.,1999). Uncertainty estimates are not provided and we note theinherent problems of dating the deposition of sediments usingthe K-Ar system (Dickin, 2005; Selby, 2009). Perhaps the mostextensive work on dating the Meratus ophiolite is that ofWakita et al. (1998), who used the K-Ar system to analyzemicas from the Hauren schist. This work yielded K-Ar ages of102 to 190 Ma, suggesting that subduction of oceanic lithos-phere was occurring as early as 190 m.y. ago; thus, bothoceanic plates at this convergent margin must be at least 190Ma. Chromitite ore forms relatively early in the history of thehost lithosphere, and certainly before the slab is subducted;thus, a subduction age for this lithosphere provides a mini-mum age for the chromitite and hence the PGM grains.Wakita et al. (1998) provide support for an Early Jurassic orlatest Triassic age for the ophiolite in the form of radiolarianbiostratigraphy of the chert that was originally deposited as asiliceous ooze overlying the igneous succession of the ophio-lite. They observed an assemblage that is assigned as earlyMiddle Jurassic to late Early Cretaceous (equiv to ~180–100Ma). Assuming that sedimentation began immediately afterformation of the crust at a spreading center, and completepreservation of the pelagic assemblage, this gives an estimatedformation age for the oceanic lithosphere at about 180 Ma.

Our Pt-Os isochron age of 197.8 ± 8.1 Ma is conformablewith the available age constraints. The initial 186Os/188Os ratioof the isochron is well within error of that expected for de-rivation from a convecting mantle source (Brandon et al.,2006). These factors, together with the low MSWD and highprobability of fit, indicate a viable age for the Pt-Os isochron;hence, we propose that the precise Pt-Os isochron age deter-mined on the Meratus PGM grains is an accurate representa-tion of the genesis of the PGE mineralization.

Further interpretation of the Pt-Os age is possible when weconsider the event that it most likely represents. The likelyformation of PGM grains during chromitite genesis is aclearly definable event in the early evolution of the oceaniclithosphere. The crystallization of the PGM grains from mag-mas, with each grain acquiring a distinct Pt-Os ratio depend-ing on its mineralogy, most likely occurred at this time. If eachgrain is isolated from others via chromite or olivine, it is likelythat the radiometric clock is set at this instant, despite the rel-atively high temperatures of this part of the oceanic lithos-phere. This early formation of PGM grains means that any Pt-Os isochron derived from them will give an age that isequivalent to the genesis age of the lithosphere itself anddates one of the earliest events recorded in the evolution ofthe rocks of the ophiolite complex.

Conclusions and Prospects for Dating Detrital PGM Deposits

We have analyzed a suite of PGM grains collected from al-luvial deposits derived from the Meratus ophiolite massif for


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their Pt-Os and Re-Os isotope systematics. These grains dis-play a wide variety of Pt/Os fractionations while Re/Os valuesare restricted to a narrow range. In the case of the Re-Os sys-tem, no correlation exists on a Re-Os isochron diagram andno chronological information can be derived. We attributethis largely to inherent Os isotope heterogeneity in the origi-nal magmas from which the PGM grains formed. The meanvalue of the initial 187Os/188Os(197.8 Ma) ratios of the grains ana-lyzed is similar to the average value found in other PGMsuites of Mesozoic age (Hattori and Hart, 1991; Büchl et al.,2002; Meibom et al., 2004). This composition most likely rep-resents that of the depleted upper convecting mantle at thetime of lithosphere formation.

In contrast to the nonsystematic Re-Os isotope characteris-tics, a well-defined correlation exists on a Pt-Os isochron dia-gram, defining an age of 197.8 ± 8.1 Ma that we interpret asthe age of formation of the PGM grains in the lower oceaniclithosphere. This age is consistent with radiometric and bio -stratigraphic age constraints available for the Meratus ophio-lite (Wakita et al., 1998). This result, along with other exam-ples recently documented by Nowell et al. (2008b), illustratesthe potential of the laser ablation Pt-Os isotope method indating PGM mineralization associated with ultramafic rocks.This type of LA-MC-ICPMS analysis can be applied to detri-tal or in situ populations but a given sample type needs toyield a large population of PGM grains, preferably >100, witha variety of Pt/Os ratios. Not all PGM suites possess this rangeof Pt-Os ratios. Alternatively, Nowell et al. (2008b) haveshown that there may be sufficient Pt/Os variation in exsolvedor polycrystalline PGM to enable geochronological data to beobtained. This approach thus provides a new way of datingPGE mineralization both within ophiolites and within placeror detrital deposits derived from these sources.

AcknowledgementsThis research was supported by a National Environment

Research Council (NERC) research studentship to JAC and aNERC research grant (NE/F006497/1). We thank Paul Poh -wat of the Smithsonian Institution National Museum of Nat-ural History for the provision of the Meratus samples. JoeDevine and Kassandra Costa are thanked for their assistancewith electron microprobe analyses. KH and BE are thankedfor providing valuable critical reviews of the manuscript.

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TABLE A1. Compositions of Borneo Placer PGM Sulfides Analyzed by Electron Microprobe at Brown University, RI, USA

(wt %)

Grain Ru Rh Pd Re Ir Pt Os Fe Co Ni Cu W S As Total

BRN-1-001 33.514 0.400 0.011 11.788 20.268 0.630 0.002 0.231 33.146 99.990BRN-1-005 32.564 0.658 0.078 0.037 11.896 21.152 0.475 0.065 0.292 0.085 34.227 101.529BRN-1-007 34.104 0.021 0.119 5.033 27.480 0.362 0.106 0.119 33.112 100.456BRN-1-008 33.718 0.052 0.050 5.207 27.303 0.214 0.026 0.073 0.085 33.708 100.435BRN-1-013 34.507 0.075 2.541 29.263 0.067 0.061 33.045 99.557BRN-1-016 34.708 0.043 0.032 2.555 29.062 0.062 0.140 32.411 99.012BRN-1-020 30.601 0.042 0.159 6.061 30.196 0.093 0.033 0.193 32.709 100.086BRN-1-022 36.228 0.141 0.068 7.155 22.367 0.135 0.005 0.180 33.352 99.630BRN-1-027 35.670 0.596 0.010 8.933 0.085 20.187 0.758 0.079 0.278 34.502 101.098BRN-1-028 41.395 0.158 0.110 7.199 16.258 0.605 0.179 34.748 100.651BRN-1-030 34.912 0.094 0.074 6.785 22.119 0.168 0.206 32.743 97.101BRN-1-031 35.088 0.384 0.056 0.037 7.768 21.991 0.439 0.057 0.223 33.640 99.682BRN-1-033 34.173 0.042 0.014 5.119 26.334 0.199 0.050 0.131 0.060 33.194 99.317BRN-1-036 36.902 0.019 0.033 4.213 24.399 0.153 0.138 33.818 99.674BRN-1-040 33.247 0.051 0.014 0.007 5.065 27.927 0.232 0.007 0.070 32.313 98.933BRN-1-055 34.650 0.009 0.026 4.525 25.898 0.185 0.238 32.827 98.358BRN-1-059 34.306 0.725 0.110 10.324 20.038 0.136 0.063 0.168 0.010 33.662 99.541BRN-1-063 37.643 0.009 0.128 6.279 21.801 0.106 0.097 33.759 99.822BRN-1-064 34.709 0.097 3.009 0.071 28.671 0.488 0.000 0.060 0.067 33.185 100.356BRN-1-066 33.582 0.130 0.003 3.117 28.292 0.028 0.132 32.100 97.383BRN-1-067 36.989 0.810 0.053 6.617 20.225 0.063 0.142 33.696 98.596BRN-1-068 31.514 0.037 5.097 27.979 0.016 0.157 0.120 31.695 96.616BRN-1-071 34.225 0.023 0.013 3.323 28.547 0.318 0.120 32.340 98.908BRN-1-072 34.961 0.269 0.078 0.062 5.451 0.088 23.040 0.188 0.002 0.145 0.133 32.491 96.905BRN-1-073 36.781 0.164 0.037 7.732 0.022 21.420 0.123 33.545 99.825BRN-1-075 35.561 0.116 0.078 0.015 8.474 20.799 0.868 0.029 0.230 33.672 99.841BRN-1-082 35.352 0.194 0.056 0.001 6.351 23.225 0.357 0.030 0.105 0.026 32.973 98.670BRN-1-085 37.902 0.055 0.067 0.076 3.311 0.006 23.351 0.000 0.096 0.133 33.386 98.383BRN-1-086 34.388 0.003 0.029 5.765 24.993 0.506 0.015 0.167 0.112 32.908 98.886BRN-1-088 34.502 0.034 0.082 4.427 26.851 0.009 0.048 0.010 32.521 98.483BRN-1-091 34.473 0.213 0.075 10.374 0.126 20.440 0.423 0.196 32.958 99.279BRN-1-092 35.475 0.058 0.102 0.107 7.176 22.566 0.815 0.047 0.295 0.087 33.491 100.217BRN-1-093 37.291 0.149 3.902 23.457 0.207 0.005 0.207 0.010 33.254 98.481BRN-1-094 34.966 0.052 0.074 9.770 20.434 0.526 0.027 0.185 0.235 33.210 99.477BRN-1-099 36.171 0.097 0.047 0.062 7.033 21.538 0.029 0.169 0.033 0.046 32.949 98.173BRN-2-004 38.505 0.298 0.001 0.051 11.861 23.150 0.287 0.182 0.658 22.485 2.161 99.639BRN-2-008 38.314 0.004 0.142 6.732 0.018 20.388 0.520 0.176 33.554 99.846BRN-2-012 36.060 0.046 0.149 8.199 21.511 0.024 0.166 0.048 32.986 99.188BRN-2-013 36.094 0.083 5.328 23.994 0.068 0.002 0.190 0.141 33.310 99.210BRN-2-017 32.707 0.454 0.104 0.012 11.241 22.235 0.441 0.004 0.093 0.024 32.706 100.020BRN-2-019 34.869 0.077 0.073 0.098 10.104 20.213 0.119 0.077 0.169 33.146 98.944BRN-2-026 36.248 0.171 0.129 8.576 20.609 0.401 0.114 32.887 99.135BRN-2-028 33.476 0.104 5.545 27.434 0.135 0.048 0.089 32.150 98.980BRN-2-029 43.572 0.251 0.065 9.062 23.120 0.194 0.435 0.556 22.630 99.883BRN-2-037 34.542 0.495 0.089 10.191 20.633 0.374 0.062 0.200 0.036 33.806 100.427BRN-2-039 33.749 0.222 0.125 4.609 28.035 0.658 0.078 0.016 0.015 32.708 100.214BRN-2-042 34.158 0.219 0.191 11.729 19.037 0.373 0.075 0.271 33.319 99.371BRN-2-043 37.835 0.152 3.726 23.996 0.860 0.042 0.091 0.046 33.281 100.028BRN-2-0451, 2 0.081 0.499 0.650 76.235 1.079 1.143 0.005 0.007 0.417 4.853 14.821 99.845BRN-2-053 37.628 0.468 0.025 7.949 19.751 0.155 0.086 0.121 33.829 100.012BRN-2-055 35.782 0.074 0.099 8.228 21.313 0.577 0.009 0.245 33.619 99.946BRN-2-059 33.430 0.254 0.103 11.602 20.165 0.505 0.030 0.202 0.173 33.348 99.813BRN-2-061 37.165 0.127 0.136 0.026 9.774 18.063 0.823 0.024 0.223 33.846 100.206BRN-2-066 36.276 0.080 0.032 0.084 4.661 24.851 0.358 0.015 0.101 0.010 33.074 99.542BRN-2-084 40.520 0.055 0.054 0.055 12.271 0.008 20.319 0.969 0.537 0.599 0.014 13.891 3.792 93.083BRN-2-088 32.667 0.099 0.034 10.620 0.048 21.771 0.184 0.016 0.224 0.167 32.574 98.404BRN-2-089 37.662 0.087 0.014 2.975 24.553 0.172 0.014 0.136 0.077 33.151 98.841BRN-2-090 36.748 0.075 0.050 8.499 19.647 0.241 0.024 0.304 32.857 98.445BRN-2-092 35.161 0.893 -0.009 9.405 19.089 1.443 0.100 0.144 34.438 100.672BRN-2-093 32.376 0.045 3.672 0.067 31.084 0.031 0.079 31.983 99.337BRN-2-094 34.724 0.372 0.036 10.281 19.805 0.661 0.066 0.243 0.017 0.005 33.436 99.646BRN-3-0083 34.491 0.290 0.093 10.965 19.276 0.403 0.025 0.280 33.296 99.161BRN-3-009 41.107 0.610 0.148 0.050 11.329 24.992 0.638 0.087 0.802 0.024 19.145 98.931BRN-3-019 35.659 0.341 0.173 8.942 20.315 0.322 0.024 0.178 0.001 33.054 99.008BRN-3-022 34.532 0.563 0.068 7.748 21.258 0.320 0.019 0.285 32.744 97.536BRN-3-028 34.843 0.098 9.897 20.495 0.353 0.062 0.298 33.165 99.212BRN-3-035 35.578 0.069 8.141 20.666 0.254 0.052 0.377 32.798 97.934


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BRN-3-041 37.960 0.017 3.839 23.572 0.019 0.065 32.808 98.280BRN-3-052 37.284 0.012 0.079 0.065 9.651 18.319 0.005 0.108 0.015 33.362 98.900BRN-3-057 37.829 0.084 0.045 11.874 14.298 0.481 0.066 0.344 0.000 33.776 98.796BRN-3-065 32.943 0.404 0.046 10.863 20.566 0.383 0.049 0.303 0.019 32.776 98.353BRN-3-072 35.031 0.118 5.227 25.581 0.034 0.012 0.140 0.071 32.644 98.857BRN-3-073 35.853 0.020 7.851 21.267 0.237 0.033 0.100 0.207 32.441 98.009BRN-3-077 36.969 0.011 0.097 0.002 6.306 0.001 21.713 0.027 0.125 32.385 97.636BRN-3-082 34.911 0.216 0.075 10.223 20.542 0.399 0.190 0.158 33.062 99.776BRN-3-084 35.819 0.041 2.225 27.392 0.016 0.059 0.166 32.250 97.969BRN-3-091 33.451 1.100 0.057 9.982 19.593 0.051 0.003 0.227 33.206 97.668BRN-3-093 37.224 0.190 3.552 23.628 0.120 0.137 32.495 97.345BRN-3-097 34.093 0.246 0.091 11.889 19.024 0.134 0.049 0.260 0.061 33.036 98.883BRN-3-100 34.823 0.110 0.132 0.064 8.976 20.628 0.723 0.258 0.096 32.580 98.391BRN-4-005 40.947 0.896 0.103 9.862 22.322 0.097 0.994 23.075 98.295BRN-4-011 35.468 0.045 0.117 5.448 24.699 0.454 0.043 0.166 32.901 99.341BRN-4-014 36.761 0.121 2.857 25.898 0.187 0.025 0.089 32.365 98.302

1 Sperrylite2 mean (n = 3)3 mean (n = 5)

TABLE A1. (Cont.)

(wt %)

Grain Ru Rh Pd Re Ir Pt Os Fe Co Ni Cu W S As Total


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TABLE A2. Compositions of Borneo Placer PGM Alloys Analyzed by Electron Microprobe at Brown University, RI, USA

(wt %)

Grain Ru Rh Pd Re Ir Pt Os Fe Co Ni Cu Mo W Total

BRN-1-002 0.037 1.132 0.505 0.091 3.162 86.155 0.433 7.930 0.003 0.833 0.089 100.368BRN-1-003 0.016 0.813 0.795 2.960 86.192 0.454 8.031 0.023 0.025 0.567 0.024 99.899BRN-1-004 0.022 0.930 0.555 0.063 1.940 87.596 0.456 7.519 0.039 0.033 0.872 0.140 0.170 100.334BRN-1-009 0.852 1.273 0.053 0.420 87.310 0.508 7.720 0.029 1.191 0.145 99.500BRN-1-010 0.013 0.304 0.625 0.070 2.675 87.479 0.510 7.606 0.015 0.036 1.066 0.062 100.462BRN-1-015 0.227 1.033 0.886 1.303 89.028 1.353 4.920 0.021 0.080 0.394 0.033 99.276BRN-1-019 0.054 0.822 0.391 0.014 2.987 86.901 0.456 8.105 0.035 0.635 0.097 100.499BRN-1-024 0.106 1.129 1.168 0.957 89.336 0.993 4.375 0.031 1.604 0.073 99.773BRN-1-025 0.044 0.865 0.348 0.089 0.737 89.557 0.990 5.688 0.042 1.520 0.104 99.982BRN-1-026 1.056 0.461 0.033 2.853 87.157 0.466 7.678 0.042 0.602 0.078 100.424BRN-1-029 0.021 0.839 0.915 1.991 87.186 0.528 7.678 0.015 0.859 0.063 0.090 100.184BRN-1-032 0.212 1.212 0.877 0.091 1.641 88.967 1.270 4.820 0.030 1.102 0.093 100.314BRN-1-034 1.042 0.599 0.016 3.592 85.676 0.443 7.768 0.047 0.009 1.201 0.073 0.201 100.666BRN-1-035 0.085 1.186 0.691 1.193 87.663 0.471 8.138 0.539 0.021 99.988BRN-1-037 0.011 0.468 0.340 2.900 87.288 0.494 7.788 0.008 0.004 0.604 0.062 99.967BRN-1-041 0.046 0.076 0.258 0.080 0.468 91.487 0.774 5.592 0.020 0.066 0.854 0.070 99.791BRN-1-042 0.850 0.434 0.059 3.113 87.078 0.475 7.729 0.058 1.101 -0.002 0.265 101.161BRN-1-044 0.007 0.503 0.505 0.043 0.928 88.711 0.461 8.130 0.004 0.015 0.561 0.063 0.141 100.072BRN-1-045 0.031 0.855 0.509 3.501 85.730 0.419 7.707 0.034 1.164 0.002 99.951BRN-1-046 1.045 0.870 0.028 2.227 86.784 0.474 7.810 0.073 0.029 0.659 0.066 0.064 100.128BRN-1-047 0.465 0.402 0.002 2.679 87.125 0.472 7.361 0.023 0.963 0.011 99.502BRN-1-048 0.362 1.218 1.553 0.017 1.448 86.087 1.040 5.589 0.046 1.854 0.148 99.362BRN-1-049 0.043 1.026 0.974 0.056 1.167 87.682 0.507 7.380 0.018 1.059 0.103 0.047 100.059BRN-1-051 0.023 1.139 0.903 3.664 85.541 0.486 8.021 0.059 0.022 0.656 0.050 100.565BRN-1-052 1.406 0.546 0.035 3.229 86.036 0.440 7.292 0.016 0.037 1.060 0.064 100.162BRN-1-054 0.009 1.273 0.556 2.311 86.421 0.479 7.795 0.004 0.036 0.533 0.063 0.047 99.526BRN-1-056 0.214 0.980 0.782 1.120 89.745 1.420 5.224 0.040 0.057 0.483 0.068 100.131BRN-1-058 0.048 1.204 0.543 0.017 3.334 86.500 0.459 7.784 0.033 0.574 0.050 0.150 100.695BRN-1-061 0.090 1.146 0.551 1.102 89.207 1.212 4.980 0.015 1.234 0.146 0.266 99.949BRN-1-062 0.016 0.481 0.776 0.051 1.841 87.409 0.652 7.846 0.069 0.634 0.073 0.158 100.006BRN-1-065 0.009 1.002 0.655 0.070 2.901 86.746 0.421 7.625 0.019 0.001 0.586 0.024 0.200 100.259BRN-1-070 0.007 0.972 1.206 0.009 0.525 86.263 0.479 8.280 0.024 0.017 0.217 0.010 98.006BRN-1-074 0.021 0.646 0.947 0.086 1.020 87.969 0.450 8.232 0.021 0.532 0.112 100.037BRN-1-076 0.047 0.448 0.682 0.103 0.855 88.059 0.549 7.448 0.026 1.073 0.060 99.350BRN-1-077 0.012 0.989 0.652 3.217 85.638 0.442 7.732 0.074 0.032 0.615 0.045 99.449BRN-1-078 0.010 0.480 0.758 0.056 2.246 84.959 2.623 7.962 0.006 0.003 0.715 0.065 99.882BRN-1-079 0.006 1.009 1.081 4.185 84.446 0.467 7.990 0.043 0.710 0.061 99.998BRN-1-080 0.167 1.106 0.354 1.358 90.257 1.899 4.450 0.006 0.102 0.328 0.082 100.110BRN-1-087 0.008 0.690 0.387 2.895 87.498 0.420 7.892 0.020 0.058 0.408 0.063 0.153 100.492BRN-1-090 0.160 1.405 0.868 0.604 90.612 0.707 4.820 0.050 0.574 0.143 0.165 100.106BRN-1-095 0.130 1.563 0.318 13.185 75.769 2.974 6.415 0.032 0.492 0.040 0.072 100.989BRN-1-096 0.065 1.121 0.888 0.019 2.223 86.163 0.441 7.669 0.009 0.025 0.767 0.129 99.520BRN-1-097 0.055 1.315 1.002 0.007 2.508 85.346 0.471 8.144 0.054 0.040 0.824 0.050 99.814BRN-1-098 0.052 0.635 0.263 0.113 4.075 85.920 0.456 7.429 0.032 0.035 0.721 0.066 0.101 99.895BRN-1-100 0.099 1.266 0.534 6.430 82.975 0.466 7.545 0.031 0.006 0.754 0.043 100.149BRN-2-001 0.965 0.543 3.170 85.751 0.472 7.708 0.014 0.995 0.018 99.636BRN-2-003 0.038 1.028 0.947 0.089 3.204 86.111 0.495 7.889 0.015 0.025 0.899 0.064 100.805BRN-2-005 0.332 0.877 2.850 85.702 1.404 8.299 0.006 0.575 0.035 100.080BRN-2-0061 0.040 0.260 0.267 0.023 2.585 87.784 0.445 7.742 0.033 0.772 0.038 0.051 100.046BRN-2-007 0.047 1.200 0.704 0.054 4.114 84.987 0.634 7.625 0.030 0.657 0.070 100.122BRN-2-009 0.105 0.689 1.860 0.118 1.269 89.066 1.118 4.886 0.022 0.857 0.101 100.090BRN-2-010 0.037 0.198 0.168 0.994 89.169 0.492 8.716 0.066 0.096 0.232 0.070 100.236BRN-2-014 0.036 1.156 0.745 0.033 1.811 86.936 0.427 8.206 0.045 0.009 0.671 0.079 100.154BRN-2-015 0.019 0.558 0.754 0.033 1.997 87.049 0.492 8.180 0.013 0.023 0.831 0.146 100.093BRN-2-016 0.025 1.069 1.002 0.040 3.257 85.579 0.403 7.978 0.030 0.019 0.579 0.058 100.039BRN-2-020 0.035 1.127 0.529 0.058 4.015 85.220 0.444 8.099 0.003 0.042 0.424 0.023 100.017BRN-2-021 0.023 1.019 0.685 0.106 2.975 85.986 0.473 7.803 0.769 0.050 0.127 100.016BRN-2-022 0.042 1.019 0.747 0.078 2.373 86.578 0.423 7.263 0.003 0.002 1.399 0.118 100.043BRN-2-023 0.023 0.518 0.293 0.028 0.582 89.024 0.479 8.006 0.041 0.882 0.137 100.014BRN-2-024 0.031 0.310 0.335 0.057 3.223 86.968 0.572 8.135 0.011 0.495 100.137BRN-2-025 0.064 1.059 0.726 0.051 4.173 84.965 0.504 7.900 0.019 0.038 0.652 0.062 100.211BRN-2-027 0.050 0.575 0.681 0.039 2.191 87.235 0.491 7.760 0.023 0.959 0.050 100.053BRN-2-030 0.498 1.012 0.004 1.382 88.025 0.493 8.034 0.025 0.026 0.500 0.029 100.028BRN-2-032 0.112 1.210 0.665 5.187 86.363 1.333 5.092 0.101 0.353 0.098 100.514BRN-2-033 0.006 0.679 0.991 0.080 1.015 87.792 0.432 8.497 0.014 0.025 0.299 0.088 0.089 100.008BRN-2-034 0.006 0.992 0.723 0.087 3.504 85.425 0.476 7.754 0.004 0.009 0.758 0.010 0.047 99.793BRN-2-035 0.052 1.281 0.384 0.019 3.387 86.365 0.445 7.738 0.039 0.879 0.002 100.590


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BRN-2-036 0.022 0.832 1.019 0.014 2.066 85.977 0.500 7.234 1.234 0.106 0.076 99.079BRN-2-038 0.021 1.157 0.532 2.644 86.083 0.459 7.659 0.061 0.005 0.753 0.032 99.406BRN-2-044 0.178 1.280 1.050 0.043 1.290 88.423 1.225 5.142 0.015 0.073 0.633 0.090 0.202 99.643BRN-2-046 0.002 0.854 0.710 0.001 1.855 86.451 0.553 8.033 0.018 0.019 0.577 0.090 99.162BRN-2-047 0.017 1.216 0.584 0.079 3.238 85.136 0.473 7.974 0.063 0.041 0.469 0.060 99.351BRN-2-048 0.675 0.508 3.014 86.260 0.538 7.570 0.059 0.025 0.930 0.079 99.658BRN-2-049 0.010 1.006 0.847 2.166 85.828 0.501 7.970 0.640 0.024 0.136 99.127BRN-2-051 0.021 1.020 0.480 2.737 86.539 0.417 7.934 0.820 0.087 100.056BRN-2-052 0.019 1.142 0.823 2.147 86.325 0.456 7.490 0.030 0.026 0.810 0.098 99.367BRN-2-054 0.116 1.109 1.554 0.027 1.043 87.564 1.124 6.100 0.008 0.005 1.392 0.097 0.026 100.162BRN-2-057 0.104 1.533 1.003 5.352 80.025 4.036 7.141 0.015 0.711 0.003 99.922BRN-2-058 0.141 1.186 1.971 0.076 0.595 87.644 1.031 5.474 0.003 0.017 1.624 0.047 0.149 99.957BRN-2-060 0.008 1.086 0.896 0.023 2.822 85.919 0.462 7.931 0.015 0.570 0.048 99.781BRN-2-062 0.278 0.576 0.022 3.332 87.122 0.475 7.852 0.056 0.640 0.083 100.435BRN-2-064 0.927 0.437 3.331 86.045 0.444 7.313 0.020 0.968 0.011 99.496BRN-2-067 0.150 1.657 0.895 1.063 89.682 1.363 4.597 0.112 0.040 0.750 0.066 100.376BRN-2-068 0.005 1.213 0.909 1.966 86.132 0.429 8.548 0.031 0.021 0.403 0.106 0.086 99.849BRN-2-070 0.002 1.047 0.901 2.863 85.963 0.509 8.083 0.640 0.063 0.325 100.397BRN-2-071 0.035 0.730 0.604 0.021 5.228 84.927 0.477 7.282 0.030 0.781 0.044 100.157BRN-2-072 0.384 1.047 0.451 0.065 1.459 90.344 1.664 4.515 0.036 0.070 0.540 0.052 0.013 100.640BRN-2-075 0.003 0.957 0.659 0.024 3.313 86.292 0.444 7.826 0.040 0.531 0.005 0.051 100.146BRN-2-0762 1.466 0.956 52.973 20.708 22.274 98.416BRN-2-0773 0.009 0.348 0.073 0.003 1.732 88.378 0.477 8.129 0.032 0.259 99.534BRN-2-0794 0.022 0.364 0.293 2.318 87.961 0.476 7.971 0.029 0.485 100.000BRN-2-0805 0.201 1.162 0.461 1.137 87.792 1.214 5.818 0.007 0.056 0.623 0.031 98.620BRN-2-081 0.007 0.725 1.291 0.705 87.531 0.514 8.273 0.034 0.009 0.540 0.093 0.013 99.734BRN-2-0831 0.043 0.348 0.614 0.006 1.580 87.398 0.485 7.964 0.025 0.663 0.076 99.276BRN-2-085 0.025 0.637 0.709 2.788 85.811 0.434 7.594 0.000 0.009 0.992 0.055 99.052BRN-2-086 0.109 1.281 0.863 0.033 1.019 90.385 0.919 4.026 0.040 0.084 0.332 0.073 99.162BRN-2-087 0.050 0.372 0.443 3.110 85.941 0.426 7.754 0.006 0.002 0.990 0.170 0.135 99.400BRN-2-095 1.109 0.848 2.280 85.405 0.432 7.952 0.084 0.031 0.525 0.022 98.687BRN-2-096 0.042 0.635 0.505 0.059 2.549 86.442 0.458 8.015 0.049 0.049 0.509 0.029 99.339BRN-2-097 0.038 0.758 0.505 0.726 87.867 0.450 8.362 0.068 0.287 0.015 99.076BRN-2-098 1.062 0.578 0.107 3.095 85.512 0.499 7.564 0.024 0.026 0.618 99.082BRN-2-099 1.178 0.455 0.079 2.912 85.196 0.432 7.983 0.004 0.574 0.058 0.021 98.892BRN-2-100 0.141 1.256 0.412 0.058 2.002 86.686 0.513 7.291 0.027 1.115 0.104 99.605BRN-3-001 0.058 1.072 0.736 0.069 2.319 86.514 0.623 7.982 0.707 0.030 100.111BRN-3-002 0.016 1.378 0.831 0.001 2.814 83.859 0.467 8.048 0.028 0.022 1.084 0.096 98.643BRN-3-003 0.037 0.461 0.341 2.598 87.185 0.435 7.679 0.019 0.802 0.040 99.596BRN-3-004 0.006 0.790 0.497 0.030 3.518 85.656 0.473 8.514 0.015 0.367 0.093 99.961BRN-3-005 0.032 0.837 0.620 0.012 3.406 85.332 0.665 7.841 0.058 0.732 0.034 0.042 99.609BRN-3-006 0.100 0.926 1.080 0.033 0.607 89.416 0.535 5.520 0.005 0.110 0.718 0.145 99.196BRN-3-007 0.000 0.391 0.525 0.106 3.088 86.195 0.496 8.153 0.017 0.714 0.069 99.754BRN-3-012 0.008 1.006 1.082 0.081 2.150 85.278 0.492 8.060 0.053 0.020 0.853 0.092 0.112 99.287BRN-3-014 0.071 1.186 0.676 0.001 3.042 85.427 0.635 7.504 0.048 0.729 0.054 99.371BRN-3-015 0.220 1.132 0.861 0.064 1.467 87.554 1.205 5.419 0.004 0.072 1.385 0.073 0.196 99.652BRN-3-016 0.820 0.571 0.043 3.581 85.548 0.406 7.930 0.034 0.772 0.031 99.735BRN-3-017 0.022 0.656 0.900 2.115 86.090 0.498 8.382 0.031 0.605 0.063 99.363BRN-3-018 0.047 0.485 0.529 0.031 2.646 86.339 0.396 7.595 0.019 0.847 0.097 0.263 99.294BRN-3-020 0.012 0.954 0.737 0.041 3.215 85.061 0.534 7.951 0.027 0.015 0.748 0.016 99.309BRN-3-021 0.060 0.275 0.425 0.008 3.236 86.647 0.515 7.874 0.070 0.058 0.780 0.065 0.050 100.061BRN-3-023 0.036 1.083 0.694 0.054 1.754 86.084 0.530 7.890 0.023 0.758 0.059 98.964BRN-3-024 0.361 2.265 0.196 0.037 52.935 37.726 3.919 2.784 0.000 0.029 0.872 101.125BRN-3-025 0.666 0.403 0.005 1.481 87.317 0.459 8.159 0.614 99.102BRN-3-026 0.010 0.415 0.370 2.386 86.748 0.430 8.281 0.019 0.022 0.530 0.061 99.271BRN-3-027 0.009 0.611 0.639 2.283 87.215 0.460 8.022 0.066 0.016 0.590 0.083 0.040 100.033BRN-3-030 0.050 1.111 1.139 1.217 86.364 0.452 8.005 0.010 0.741 0.041 99.128BRN-3-031 0.037 0.388 0.370 3.226 87.728 0.460 7.585 0.029 0.619 0.049 100.490BRN-3-032 0.010 0.883 1.272 2.777 86.607 0.451 7.550 0.033 0.041 0.611 0.018 100.252BRN-3-036 1.126 0.501 0.064 3.343 87.032 0.440 7.456 0.015 0.041 0.575 0.142 0.000 100.735BRN-3-038 0.023 1.152 0.570 3.451 86.495 0.472 7.483 0.013 1.043 0.029 0.135 100.867BRN-3-039 0.071 1.247 0.664 2.063 89.335 1.321 4.952 0.084 0.567 0.015 0.050 100.368BRN-3-040 0.026 0.304 0.468 0.029 2.955 88.200 0.465 7.575 0.014 0.711 0.047 100.793BRN-3-043 0.064 0.942 0.610 2.748 87.115 0.464 7.504 0.009 0.004 0.841 0.114 100.413BRN-3-044 0.122 1.116 0.787 0.093 1.143 88.007 1.360 7.587 0.000 0.031 1.198 0.051 0.085 101.579BRN-3-046 0.037 0.332 0.497 2.395 88.200 0.453 7.958 0.015 0.023 0.571 0.145 0.017 100.642BRN-3-047 0.016 1.056 0.760 3.978 85.165 0.432 8.157 0.040 0.012 0.549 100.163

TABLE A2. (Cont.)

(wt %)



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BRN-3-048 0.006 1.021 0.488 2.796 87.197 0.500 7.719 0.048 0.657 0.081 0.320 100.832BRN-3-050 0.031 0.426 0.357 0.069 3.234 87.472 0.421 7.529 0.036 0.014 0.772 0.013 0.217 100.589BRN-3-051 0.032 0.811 1.055 0.056 2.598 86.929 0.464 7.697 0.039 0.027 0.599 0.011 100.317BRN-3-056 0.080 1.073 1.007 1.558 90.745 0.664 4.057 0.075 0.456 0.070 0.013 99.797BRN-3-058 0.941 0.803 2.845 87.410 0.484 7.131 0.072 0.533 0.028 0.077 100.323BRN-3-060 0.143 1.217 1.240 0.103 1.123 86.776 1.458 6.605 0.032 0.038 0.869 0.042 0.128 99.775BRN-3-061 0.012 0.671 0.118 0.052 3.648 86.924 0.503 7.720 0.068 0.781 0.073 100.571BRN-3-062 0.206 0.935 0.120 0.044 1.367 89.133 1.701 5.331 0.044 0.064 1.278 0.062 100.284BRN-3-063 0.030 0.254 0.531 0.007 2.260 88.020 0.478 8.007 0.028 0.572 0.021 100.209BRN-3-064 0.029 1.194 2.391 0.094 0.319 86.334 1.590 7.794 1.142 0.058 0.039 100.983BRN-3-067 0.051 1.354 0.576 2.849 86.886 0.435 7.559 0.018 0.009 0.957 0.061 0.184 100.939BRN-3-068 0.243 1.143 0.546 0.063 1.036 91.170 0.897 4.791 0.073 0.348 0.090 0.169 100.569BRN-3-069 1.086 0.682 2.638 86.308 0.443 7.767 0.027 0.501 0.055 99.506BRN-3-070 0.029 1.117 0.765 0.020 3.293 85.583 0.478 7.978 0.000 0.001 0.684 0.057 0.086 100.090BRN-3-071 0.041 0.698 0.706 0.034 1.949 87.904 0.474 7.848 0.012 0.758 0.086 0.056 100.564BRN-3-075 0.053 1.154 0.750 0.022 3.185 86.052 0.440 7.965 0.003 0.032 0.349 0.054 0.129 100.188BRN-3-078 0.039 0.211 0.442 0.013 2.793 87.442 0.445 8.010 0.025 0.005 0.759 0.080 100.264BRN-3-079 0.019 1.219 0.728 2.470 86.079 0.498 7.422 0.034 0.029 1.137 0.016 99.652BRN-3-080 0.269 0.428 0.067 2.965 87.207 0.479 7.626 0.047 0.596 0.070 99.753BRN-3-081 0.456 0.728 2.854 87.601 0.437 7.795 0.040 0.004 0.632 0.044 0.047 100.638BRN-3-085 0.029 0.993 1.074 0.031 2.504 86.159 0.438 8.635 0.060 0.229 0.057 100.208BRN-3-086 0.394 0.487 0.018 2.789 87.943 0.426 7.493 0.957 0.094 100.601BRN-3-087 0.018 1.000 0.476 0.016 3.321 86.418 0.426 7.577 0.051 0.029 0.579 0.089 99.999BRN-3-088 0.021 0.498 0.296 1.004 89.110 0.508 7.720 0.042 0.037 0.964 100.200BRN-3-092 0.656 0.239 0.031 3.465 87.041 0.450 7.577 0.024 0.612 0.052 100.146BRN-3-094 0.874 0.629 0.012 2.906 87.123 0.413 7.714 0.020 0.012 0.348 0.028 100.080BRN-3-095 0.175 1.355 0.698 0.025 1.841 88.610 1.456 4.854 0.006 0.026 0.788 0.039 99.872BRN-3-099 0.049 0.816 0.475 1.121 88.068 0.560 7.681 0.037 0.023 0.894 0.080 0.090 99.894BRN-4-006 0.013 0.472 0.564 2.902 85.742 1.299 8.134 0.002 0.483 0.075 0.026 99.713BRN-4-007 0.056 0.501 1.370 0.034 2.258 86.678 0.455 8.046 0.544 0.036 99.977BRN-4-008 0.628 0.741 8.981 1.336 80.977 0.959 4.744 0.030 1.375 0.033 99.803BRN-4-009 1.039 0.600 0.047 3.708 85.493 0.434 7.973 0.010 0.054 0.606 0.041 0.180 100.184BRN-4-012 0.008 0.325 0.318 0.104 3.345 87.173 0.479 8.029 0.011 0.022 0.736 0.002 0.158 100.709BRN-4-013 0.062 1.067 0.542 3.454 86.612 0.444 7.641 0.022 0.652 0.013 100.507BRN-4-016 0.036 0.894 0.560 0.014 1.942 87.528 0.466 7.270 0.039 0.034 0.945 0.034 99.763BRN-4-017 0.036 1.156 0.611 3.238 86.165 0.417 7.457 0.016 0.567 0.140 99.803BRN-4-018 0.168 1.290 0.764 0.502 90.844 1.495 4.869 0.024 0.016 0.251 0.077 0.097 100.398

1 mean (n = 2)2 mean (n = 9)3 mean (n = 11)4 mean (n = 3)5 mean (n = 4)b.d.l. = below detection limits; detection limits are 3 sigma - given in Table A5

TABLE A2. (Cont.)

(wt %)



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TABLE A3. Compositions of Alloy Inclusions and Composite Grains in Borneo Placer PGE Alloy Grains Analyzed by Electron Microprobe at Brown University, RI, USA

(wt %)


Inclusions

Pt-FeBRN-2-005 0.181 0.338 1.340 0.064 1.993 85.323 1.180 8.896 0.041 0.589 0.106 100.051BRN-2-023 0.467 0.385 0.719 89.409 0.501 8.044 0.023 0.825 0.131 100.503BRN-2-097 0.016 0.773 0.551 0.830 86.837 0.498 8.656 0.010 0.339 0.068 98.576

Ir>Os>Pt>Rh, RuBRN-2-006 1.598 2.397 52.634 12.278 31.403 0.223 0.047 0.014 0.413 101.005BRN-2-020 3.941 2.654 54.917 12.401 25.999 0.344 0.037 0.032 0.467 100.792BRN-2-021 0.613 3.293 0.119 0.159 56.945 9.011 29.747 0.151 0.055 0.513 100.607BRN-2-025 0.492 3.017 0.076 56.381 10.451 29.728 0.122 0.077 0.004 0.555 100.902BRN-2-096 2.423 2.612 0.039 54.027 11.330 28.454 0.162 0.009 0.518 0.049 99.622

Os>Ru>Ir>RhBRN-2-005 32.851 1.921 0.126 8.013 0.780 55.803 0.130 0.023 0.064 1.752 101.463

Os-IrBRN-2-079 1.652 0.497 0.053 21.294 1.440 76.717 0.024 0.003 0.182 0.057 101.919BRN-2-100 0.975 0.438 0.005 14.218 2.134 80.121 0.098 0.148 98.137

Composite Grains

Ir>Os>Pt>RhBRN-2-007 0.952 3.954 0.025 0.123 67.425 12.124 15.543 0.228 0.018 0.687 101.077BRN-3-036 0.754 2.413 0.042 61.643 10.846 24.659 0.220 0.593 101.170


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TABLE A4. Mean Os Compositions and Reproducibility for 1 ppm DROsS Reference Material Solution Measured at the Start of MC-ICPMS Sessions during which Borneo PGM Were Analyzed

ConcentrationAnalytical session (µg ml-1) n 190Os/188Os ± 2SD 187Os/188Os ± 2SD 186Os/188Os ± 2SD 184Os/188Os ± 2SD

12/17/07 1 10 1.984009 0.000156 0.160916 0.000017 0.119915 0.000015 0.001303 0.00000312/18/07 1 10 1.984026 0.000096 0.160911 0.000015 0.119914 0.000013 0.001307 0.0000061/15/08 1 10 1.983989 0.000142 0.160915 0.000018 0.119923 0.000015 0.001312 0.0000081/16/08 1 10 1.984087 0.000110 0.160922 0.000014 0.119919 0.000013 0.001305 0.0000071/31/08 1 10 1.984076 0.000176 0.160915 0.000015 0.119915 0.000012 0.001306 0.0000062/18/08 1 10 1.984030 0.000139 0.160926 0.000013 0.119918 0.000010 0.001301 0.000004All 1 60 1.984033 0.000156 0.160918 0.000020 0.119917 0.000015 0.001306 0.000009Reproducibility (ppm) 79 122 125 7227

Nowell et al. 2008a 2.5 21 1.983979 0.000030 0.160916 0.000004 0.119909 0.000004 0.001298 0.000002Nowell et al. 2008b 0.2 5 1.983943 0.000089 0.160921 0.000018 0.119917 0.000020 0.001303 0.000007Durham N-TIMS 8 1.983803 0.000016 0.160924 0.000004 0.119932 0.000006 0.001306 0.000006(Luguet et al., 2008)

All MC-ICP-MS data corrected for mass bias using an exponential law and a 189Os/188Os ratio of 1.21978

TABLE A5. Detection Limits for EMP Analyses of Borneo PGM

Element Peak Detection limit (%)

Ru La 0.120Rh La 0.088Pd Lb 0.220Re La 0.308Ir La 0.352Pt La 0.473Os Ma 0.163

Fe (low Pt) La 1.37Fe (high Pt) Ka 0.120

Co Ka 0.135Ni Ka 0.097Cu La 0.297W La 0.589S Ka 0.090As Lb 0.482Mo La 0.109

Detection limits are 3 sigma standard deviation; for high Pt samples, Fewas analyzed on the K alpha peak since Pt interference occurs on the Fe Lalpha peak


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100µm

100µm

50µm

20µm

A B

C D

BRN-3-35BRN-3-35 BRN-3-65BRN-3-65

OlOl

EpEp

CpyCpyAmphAmph

AmphAmph

EpEp

Fig. A1. BSE images of inclusions in laurite grains. Dashed lines highlight the parallel orientation of different inclusionswithin the same grain, indicating that the habit of inclusions is likely dominated by the host PGM grain. Boxes in A and Bshow areas enlarged in C and D, respectively. Irregular pits and fractures are an artifact of poor polishing, due to polishingboth sulfides and PGE alloys in the same mount.


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100µm

100µm

100µm

100µm

100µm100µm100µm

500µm

200µm200µm

20µm

20µm

LKJ

IHG

FED

CBA

BRN-3-071 BRN-3-088 BRN-3-021

BRN-1-009 BRN-2-075 BRN-1-034

BRN-1-100 BRN-2-071 BRN-2-033

BRN-2-022 BRN-3-067 BRN-3-036

Fig. A2. BSE images of internal features in Pt-Fe alloy grains show that internal heterogeneity in this population spans arange of scales and compositions. A, B. Silicate inclusions. C-E. PGE alloy inclusions or intergrowths dominated by Os andIr. F and H. Micro-PGE alloy inclusions. G, I and J. Linear features that may be cogenetic or products of exsolution. K, L.Irregular PGE alloy rims.


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TABLE A6. Os Isotope Compositions of Borneo Placer PGM

Analyticalsession Grain 188Os (V) ± 2SE 187Os/188Os ± 2SE 186Os/188Os ± 2SE 184Os/188Os

12/17/07BRN-1-001 9.244316 0.147436 0.125873 0.000024 0.119825 0.000021 0.001303BRN-1-002 0.679799 0.079623 0.126519 0.000057 0.119884 0.000037 0.001278BRN-1-004 0.244059 0.016647 0.126932 0.000127 0.120006 0.000086 0.001292BRN-1-005 8.525510 0.172158 0.127040 0.000042 0.119838 0.000038 0.001303BRN-1-007 12.477661 0.183836 0.128486 0.000048 0.119825 0.000040 0.001303BRN-1-008 9.948902 0.086762 0.125841 0.000017 0.119823 0.000015 0.001305BRN-1-009 2.714675 0.517789 0.134094 0.000066 0.119809 0.000054 0.001301BRN-1-010 0.490920 0.101095 0.127048 0.000132 0.119983 0.000070 0.001339BRN-1-011 0.723123 0.099806 0.125900 0.000044 0.119879 0.000049 0.001314BRN-1-013 7.708241 0.313601 0.125342 0.000044 0.119834 0.000038 0.001302BRN-1-015 1.869295 0.094864 0.128177 0.000038 0.119859 0.000025 0.001301BRN-1-016 11.294411 0.150858 0.126765 0.000023 0.119825 0.000021 0.001305BRN-1-020 9.867744 0.154250 0.126822 0.000017 0.119828 0.000015 0.001303BRN-1-022 6.326812 0.192548 0.126091 0.000044 0.119823 0.000037 0.001301BRN-1-024 0.649657 0.059846 0.129498 0.000046 0.119873 0.000046 0.001304BRN-1-025 1.085074 0.059664 0.128679 0.000032 0.119836 0.000031 0.001294BRN-1-027 9.764844 0.196689 0.126794 0.000024 0.119838 0.000022 0.001304BRN-1-028 9.569385 0.177823 0.126011 0.000017 0.119832 0.000015 0.001302BRN-1-030 9.101708 0.168355 0.125367 0.000015 0.119834 0.000015 0.001304BRN-1-031 9.345755 0.244132 0.124937 0.000027 0.119833 0.000027 0.001304BRN-1-032 2.646593 0.308906 0.127900 0.000031 0.119821 0.000027 0.001306BRN-1-033 10.301858 0.273034 0.126544 0.000023 0.119833 0.000020 0.001304BRN-1-034 0.820826 0.055970 0.125063 0.000042 0.119872 0.000030 0.001277BRN-1-035 3.453786 0.583656 0.129417 0.000033 0.119902 0.000030 0.001303BRN-1-036 10.707207 0.193947 0.125596 0.000025 0.119839 0.000025 0.001303BRN-1-040 8.356679 0.140745 0.125945 0.000011 0.119828 0.000010 0.001304BRN-1-041 1.103928 0.088347 0.129241 0.000036 0.119879 0.000030 0.001308BRN-1-042 0.293746 0.019282 0.127543 0.000090 0.119955 0.000079 0.001269BRN-1-044 0.363977 0.037758 0.128232 0.000081 0.119885 0.000074 0.001281BRN-1-048 0.806255 0.059540 0.127343 0.000035 0.119889 0.000031 0.001322BRN-1-049 0.318572 0.039543 0.127212 0.000122 0.119866 0.000080 0.001282BRN-1-051 0.757646 0.054539 0.126181 0.000036 0.119876 0.000050 0.001288BRN-1-054 0.235435 0.021554 0.128209 0.000129 0.119924 0.000108 0.001244BRN-1-055 11.794360 0.180029 0.129116 0.000024 0.119821 0.000021 0.001302BRN-1-056 2.158801 0.133504 0.128641 0.000030 0.119817 0.000033 0.001304BRN-1-058 0.377753 0.025339 0.127777 0.000076 0.119879 0.000066 0.001280BRN-1-059 9.654951 0.162652 0.124465 0.000016 0.119818 0.000012 0.001305BRN-1-060 0.423110 0.048983 0.126188 0.000063 0.119869 0.000056 0.001265BRN-1-061 1.137550 0.080481 0.128696 0.000062 0.119859 0.000034 0.001296BRN-1-063 10.230531 0.105402 0.127636 0.000017 0.119826 0.000014 0.001304BRN-1-064 11.819136 0.098093 0.134450 0.000014 0.119820 0.000013 0.001303BRN-1-065 1.016277 0.106152 0.125678 0.000054 0.119839 0.000047 0.001304BRN-1-066 11.734826 0.174809 0.125439 0.000019 0.119828 0.000018 0.001303BRN-1-067 7.178940 0.133582 0.125673 0.000019 0.119828 0.000021 0.001303BRN-1-068 9.118705 0.157779 0.126071 0.000015 0.119838 0.000015 0.001303BRN-1-071 8.662027 0.238004 0.126692 0.000030 0.119828 0.000026 0.001306BRN-1-072 7.190005 0.146209 0.133848 0.000028 0.119830 0.000025 0.001306BRN-1-073 6.634865 0.173321 0.125618 0.000031 0.119828 0.000028 0.001306BRN-1-075 8.433645 0.115035 0.124569 0.000022 0.119826 0.000020 0.001305BRN-1-078 0.400882 0.030999 0.127253 0.000059 0.119874 0.000049 0.001247BRN-1-079 0.454439 0.029750 0.126227 0.000064 0.119893 0.000052 0.001326BRN-1-080 4.711550 1.042558 0.128845 0.000067 0.119869 0.000033 0.001303

12/18/07BRN-1-082 7.604715 0.223104 0.129502 0.000046 0.119833 0.000039 0.001302BRN-1-085 6.787721 0.329580 0.125857 0.000043 0.119817 0.000042 0.001302BRN-1-086 7.294725 0.400419 0.126936 0.000062 0.119823 0.000059 0.001305BRN-1-088 7.991274 0.329460 0.128085 0.000048 0.119824 0.000037 0.001304BRN-1-091 6.623584 0.177043 0.126999 0.000043 0.119827 0.000037 0.001305BRN-1-092 8.122341 0.414357 0.127113 0.000060 0.119855 0.000055 0.001304BRN-1-093 7.290614 0.268865 0.125551 0.000064 0.119828 0.000059 0.001305BRN-1-094 6.604850 0.400042 0.125395 0.000077 0.119830 0.000067 0.001305BRN-1-095 0.669655 0.156922 0.128753 0.000168 0.119960 0.000111 0.001325BRN-1-096 2.424266 0.479056 0.128077 0.000068 0.119825 0.000051 0.001308BRN-1-099 7.325213 0.301643 0.125892 0.000032 0.119837 0.000027 0.001307BRN-1-100 1.422423 0.096013 0.126986 0.000040 0.119848 0.000041 0.001293BRN-2-001 0.541022 0.027195 0.127950 0.000070 0.119864 0.000060 0.001311BRN-2-003 0.980651 0.161859 0.127901 0.000078 0.119891 0.000072 0.001316


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Grains Analyzed by LA-MC-ICPMS at Durham University, UK

± 2SE 185Re/188Os ± 2SE 182W/188Os ± 2SE 190Pt/188Os ± 2SE 187Re/188Os ± 2SE

0.000002 0.000035 0.000002 0.000001 0.000001 -0.000004 0.000724 0.000058 0.0000030.000028 0.000027 0.000018 0.000279 0.000149 0.144857 0.003601 0.000046 0.0000380.000079 -0.000008 0.000057 0.000048 0.000057 0.605802 0.015149 0.000036 0.0001130.000002 0.000021 0.000003 0.000001 0.000001 -0.000282 0.001387 0.000036 0.0000050.000002 0.000004 0.000002 0.000001 0.000001 -0.000001 0.001508 0.000006 0.0000040.000002 0.000019 0.000002 0.000000 0.000001 0.000192 0.000511 0.000031 0.0000030.000008 0.000026 0.000007 0.000022 0.000012 0.092117 0.016224 0.000041 0.0000150.000053 0.000062 0.000037 0.000063 0.000059 0.457664 0.071846 0.000102 0.0000770.000023 0.000041 0.000022 0.000036 0.000022 0.181456 0.007146 0.000070 0.0000410.000002 0.000006 0.000003 0.000003 0.000001 -0.000382 0.001331 0.000009 0.0000050.000009 0.000024 0.000007 0.000014 0.000007 0.065544 0.002350 0.000037 0.0000130.000001 0.000020 0.000002 0.000001 0.000001 0.000172 0.000708 0.000033 0.0000030.000002 0.000012 0.000002 0.000001 0.000001 0.000018 0.000540 0.000020 0.0000030.000003 0.000021 0.000003 0.000002 0.000002 0.000040 0.001392 0.000037 0.0000060.000029 0.000040 0.000022 0.000014 0.000025 0.185847 0.002102 0.000080 0.0000400.000017 0.000101 0.000011 0.000016 0.000011 0.153589 0.006360 0.000166 0.0000210.000002 0.000018 0.000002 0.000001 0.000001 -0.000086 0.000713 0.000029 0.0000030.000002 0.000041 0.000002 0.000002 0.000001 -0.000209 0.000494 0.000069 0.0000030.000002 0.000021 0.000002 0.000002 0.000001 -0.000117 0.000473 0.000033 0.0000030.000002 0.000018 0.000003 0.000002 0.000002 0.000007 0.000936 0.000030 0.0000040.000008 0.000016 0.000005 0.000050 0.000015 0.078254 0.011248 0.000030 0.0000100.000002 0.000009 0.000002 0.000002 0.000001 -0.000093 0.000751 0.000014 0.0000030.000025 0.000034 0.000013 0.000027 0.000021 0.154178 0.002995 0.000054 0.0000260.000007 0.000005 0.000006 0.000022 0.000019 0.026392 0.010369 0.000018 0.0000170.000002 0.000007 0.000002 0.000001 0.000001 -0.000403 0.000857 0.000011 0.0000040.000003 0.000006 0.000002 0.000000 0.000002 -0.000015 0.000312 0.000010 0.0000030.000020 0.000038 0.000013 0.000016 0.000012 0.152409 0.003394 0.000068 0.0000240.000059 0.000064 0.000035 0.000056 0.000046 0.440468 0.044455 0.000133 0.0000670.000050 0.000048 0.000032 0.000055 0.000041 0.321415 0.018249 0.000080 0.0000590.000028 0.000065 0.000016 0.000001 0.000017 0.152528 0.002356 0.000110 0.0000310.000064 0.000042 0.000038 0.000031 0.000038 0.371527 0.039205 0.000137 0.0000970.000025 0.000047 0.000019 0.000027 0.000012 0.158292 0.003968 0.000089 0.0000360.000091 0.000053 0.000056 0.000085 0.000040 0.518269 0.016151 0.000089 0.0001070.000002 0.000020 0.000002 0.000002 0.000001 0.000253 0.000692 0.000033 0.0000030.000011 0.000022 0.000005 0.000011 0.000008 0.036894 0.002406 0.000044 0.0000120.000046 0.000043 0.000035 0.000016 0.000030 0.155223 0.005774 0.000040 0.0000710.000002 0.000037 0.000002 0.000001 0.000001 0.000083 0.000556 0.000063 0.0000030.000048 0.000027 0.000032 0.000048 0.000030 0.248924 0.007646 0.000064 0.0000680.000015 0.000026 0.000013 0.000013 0.000011 0.116283 0.001937 0.000033 0.0000260.000002 0.000012 0.000002 0.000001 0.000001 -0.000077 0.000489 0.000021 0.0000030.000001 0.000007 0.000001 0.000001 0.000001 -0.000022 0.000445 0.000012 0.0000020.000021 0.000021 0.000010 0.000024 0.000019 0.136961 0.031799 0.000048 0.0000290.000002 0.000007 0.000002 0.000001 0.000001 0.000163 0.000580 0.000011 0.0000030.000002 0.000013 0.000002 0.000001 0.000002 -0.000246 0.000674 0.000022 0.0000040.000002 0.000015 0.000001 0.000002 0.000002 -0.000173 0.000466 0.000025 0.0000030.000002 0.000003 0.000003 0.000001 0.000001 0.000010 0.000999 0.000006 0.0000050.000003 0.000009 0.000003 0.000001 0.000002 0.000304 0.000920 0.000014 0.0000050.000002 0.000021 0.000003 0.000001 0.000002 0.000242 0.000959 0.000036 0.0000060.000003 0.000038 0.000002 0.000001 0.000001 -0.000021 0.000720 0.000062 0.0000040.000066 0.000031 0.000030 0.000111 0.000046 0.322896 0.024303 0.000056 0.0000580.000047 0.000071 0.000027 0.000022 0.000029 0.222629 0.006249 0.000121 0.0000500.000006 0.000011 0.000004 0.000003 0.000003 0.033565 0.004533 0.000020 0.000007

0.000002 0.000004 0.000003 0.000001 0.000001 0.000125 0.001306 0.000012 0.0000070.000003 0.000010 0.000004 0.000002 0.000002 -0.000086 0.001418 0.000016 0.0000080.000003 0.000013 0.000005 0.000001 0.000002 -0.000396 0.002397 0.000021 0.0000080.000003 0.000007 0.000004 0.000007 0.000003 -0.000143 0.001287 0.000009 0.0000070.000003 0.000010 0.000003 0.000002 0.000002 -0.000554 0.001223 0.000016 0.0000070.000003 0.000026 0.000004 0.000000 0.000001 -0.000686 0.001945 0.000043 0.0000080.000003 0.000008 0.000004 -0.000001 0.000002 0.000096 0.002119 0.000014 0.0000080.000004 0.000045 0.000004 -0.000002 0.000002 -0.000174 0.002517 0.000077 0.0000090.000059 0.000062 0.000055 0.000622 0.000369 0.425662 0.059383 0.000149 0.0001290.000019 0.000012 0.000011 0.000000 0.000015 0.217392 0.071291 0.000016 0.0000260.000003 0.000007 0.000002 -0.000001 0.000001 -0.000546 0.001095 0.000011 0.0000050.000013 0.000013 0.000009 0.000013 0.000007 0.123233 0.002940 0.000021 0.0000170.000036 0.000046 0.000021 -0.000012 0.000028 0.269601 0.022440 0.000076 0.0000390.000020 0.000035 0.000016 0.000022 0.000020 0.279480 0.045039 0.000073 0.000033


0361-0128/98/000/000-00 $6.00 112

BRN-2-004 7.606621 0.447061 0.126763 0.000048 0.119820 0.000044 0.001304BRN-2-005 0.508700 0.099095 0.128453 0.000132 0.120000 0.000111 0.001294BRN-2-006 1.802552 0.475332 0.126899 0.000105 0.119914 0.000089 0.001303BRN-2-007 7.463414 0.990228 0.126410 0.000041 0.119801 0.000037 0.001305BRN-2-008 9.415560 0.308813 0.125562 0.000059 0.119834 0.000051 0.001302BRN-2-009 1.785932 0.111780 0.127473 0.000036 0.119852 0.000039 0.001305BRN-2-012 11.598072 0.476385 0.124824 0.000060 0.119842 0.000050 0.001303BRN-2-013 10.121060 0.283863 0.129951 0.000058 0.119814 0.000049 0.001303BRN-2-017 10.163963 0.282112 0.125833 0.000031 0.119831 0.000027 0.001304BRN-2-019 8.334160 0.320769 0.125920 0.000053 0.119831 0.000047 0.001304BRN-2-020 4.407149 1.152252 0.126430 0.000114 0.119893 0.000107 0.001297BRN-2-021 0.329813 0.025655 0.126073 0.000088 0.119961 0.000075 0.001345BRN-2-022 2.022758 0.087032 0.126448 0.000022 0.119830 0.000022 0.001296BRN-2-024 1.035163 0.152249 0.127476 0.000072 0.119837 0.000055 0.001317BRN-2-026 9.426375 0.309477 0.125190 0.000036 0.119826 0.000031 0.001305BRN-2-028 12.160259 0.407075 0.127107 0.000053 0.119820 0.000048 0.001304BRN-2-029 9.166894 0.262902 0.128389 0.000025 0.119822 0.000023 0.001304BRN-2-030 0.636619 0.044727 0.128787 0.000059 0.119872 0.000056 0.001311BRN-2-032 1.374380 0.109577 0.139067 0.000059 0.119860 0.000050 0.001312BRN-2-035 0.503963 0.042976 0.128954 0.000075 0.119890 0.000072 0.001316BRN-2-036 0.299407 0.026175 0.132809 0.000098 0.120008 0.000079 0.001351BRN-2-037 10.777411 0.297364 0.127406 0.000026 0.119841 0.000024 0.001307BRN-2-039 14.396037 0.585851 0.127463 0.000039 0.119824 0.000036 0.001305BRN-2-042 11.333515 0.370935 0.128746 0.000037 0.119820 0.000027 0.001304BRN-2-043 7.052495 0.290666 0.125567 0.000066 0.119846 0.000053 0.001305BRN-2-044 3.547738 0.905904 0.127445 0.000068 0.119895 0.000061 0.001314BRN-2-045 1.963388 0.128904 0.127210 0.000048 0.119828 0.000043 0.001315BRN-2-047 0.671710 0.060733 0.126976 0.000083 0.119863 0.000058 0.001299BRN-2-048 0.300421 0.018127 0.136693 0.000089 0.119952 0.000083 0.001339BRN-2-049 0.404836 0.039670 0.127468 0.000077 0.119920 0.000106 0.001354BRN-2-051 0.404455 0.029369 0.128089 0.000098 0.119928 0.000078 0.001288BRN-2-053 11.687221 0.503873 0.122117 0.000035 0.119807 0.000032 0.001303BRN-2-054 1.298331 0.121047 0.128331 0.000033 0.119863 0.000030 0.001303BRN-2-055 12.672083 0.635829 0.126791 0.000043 0.119852 0.000038 0.001304BRN-2-057 0.625578 0.048728 0.126904 0.000058 0.119850 0.000063 0.001289BRN-2-058 1.031029 0.095884 0.128335 0.000049 0.119894 0.000034 0.001306BRN-2-059 8.289012 0.287069 0.125701 0.000040 0.119846 0.000034 0.001303BRN-2-060 0.724614 0.051349 0.126963 0.000059 0.119906 0.000061 0.001330BRN-2-061 7.048330 0.211463 0.127875 0.000028 0.119848 0.000025 0.001306BRN-2-062 1.813453 0.311595 0.128118 0.000107 0.119869 0.000090 0.001302BRN-2-064 1.306189 0.082383 0.125921 0.000035 0.119859 0.000037 0.001294BRN-2-066 10.252952 0.438538 0.127002 0.000055 0.119854 0.000050 0.001304BRN-2-067 6.623811 1.035372 0.128275 0.000065 0.119890 0.000058 0.001304BRN-2-068 0.576647 0.120702 0.133681 0.000086 0.119886 0.000075 0.001350BRN-2-070 0.944227 0.115279 0.125521 0.000053 0.119840 0.000044 0.001305BRN-2-071 0.908604 0.063470 0.127975 0.000083 0.119867 0.000055 0.001321BRN-2-072 2.654148 0.202112 0.127371 0.000039 0.119830 0.000034 0.001301BRN-2-075 0.634131 0.100956 0.125547 0.000102 0.119918 0.000094 0.001318BRN-2-076 3.029628 0.138855 0.127124 0.000077 0.119836 0.000070 0.001309BRN-2-079 1.004052 0.422522 0.127107 0.000136 0.119885 0.000105 0.001319BRN-2-080 1.605915 0.083789 0.126076 0.000035 0.119841 0.000028 0.001308BRN-2-082 2.344320 0.105930 0.127026 0.000037 0.119841 0.000040 0.001303BRN-2-084 8.704764 0.402997 0.126842 0.000057 0.119841 0.000043 0.001304BRN-2-086 0.904207 0.076420 0.130632 0.000053 0.119885 0.000043 0.001312BRN-2-087 0.288816 0.026256 0.130328 0.000099 0.119933 0.000106 0.001349BRN-2-088 8.614386 0.274770 0.127222 0.000026 0.119815 0.000023 0.001305BRN-2-089 9.145439 0.363778 0.125555 0.000035 0.119829 0.000032 0.001303BRN-2-090 7.808022 0.283811 0.124926 0.000045 0.119835 0.000036 0.001307BRN-2-092 6.315623 0.162447 0.125965 0.000028 0.119836 0.000028 0.001305BRN-2-093 8.513198 0.262939 0.127139 0.000033 0.119831 0.000031 0.001302BRN-2-094 8.428058 0.271953 0.126890 0.000041 0.119813 0.000040 0.001303BRN-2-095 0.342772 0.029367 0.127356 0.000102 0.119928 0.000066 0.001318BRN-2-096 0.522200 0.119254 0.126310 0.000094 0.119915 0.000083 0.001357BRN-2-099 0.768994 0.063458 0.127405 0.000048 0.119868 0.000043 0.001289

1/15/08BRN-3-001 0.579868 0.037459 0.128485 0.000058 0.120036 0.000047 0.001320BRN-3-008 8.104626 0.438973 0.128588 0.000064 0.119837 0.000025 0.001307BRN-3-009 6.980487 0.573447 0.126432 0.000075 0.119832 0.000028 0.001306

TABLE A6.



0361-0128/98/000/000-00 $6.00 113

0.000003 0.001777 0.000024 0.000001 0.000002 0.000221 0.001637 0.002980 0.0000420.000051 0.000069 0.000028 0.000120 0.000127 0.624848 0.091928 0.000154 0.0000610.000023 0.000031 0.000018 0.000173 0.000068 0.274781 0.072643 0.000069 0.0000380.000003 0.000022 0.000003 0.000002 0.000004 0.008826 0.001616 0.000039 0.0000070.000002 0.000014 0.000003 0.000002 0.000001 -0.000200 0.001884 0.000027 0.0000070.000008 0.000041 0.000008 0.000010 0.000012 0.145523 0.003209 0.000068 0.0000140.000002 0.000042 0.000003 0.000000 0.000001 0.000075 0.001955 0.000072 0.0000060.000003 0.000023 0.000004 0.000002 0.000001 0.000533 0.001785 0.000038 0.0000080.000002 0.000055 0.000002 0.000001 0.000001 -0.000305 0.000953 0.000092 0.0000040.000003 0.000018 0.000003 0.000002 0.000002 -0.000663 0.001682 0.000031 0.0000070.000021 0.000013 0.000012 0.000110 0.000087 0.099080 0.042415 0.000011 0.0000300.000058 0.000068 0.000045 0.000010 0.000033 0.507349 0.011555 0.000095 0.0000810.000011 0.000022 0.000006 0.000009 0.000006 0.087266 0.005107 0.000043 0.0000120.000028 0.000017 0.000014 0.000021 0.000036 0.215580 0.061822 0.000039 0.0000320.000002 0.000030 0.000002 -0.000001 0.000001 0.000098 0.001182 0.000050 0.0000050.000002 0.000005 0.000003 0.000002 0.000001 0.000170 0.001719 0.000009 0.0000070.000002 0.000390 0.000003 0.000000 0.000001 0.000181 0.000814 0.000653 0.0000050.000024 0.000004 0.000024 0.000023 0.000061 0.324446 0.025313 0.000014 0.0000420.000015 0.000017 0.000009 0.000001 0.000009 0.109427 0.001716 0.000023 0.0000190.000031 0.000028 0.000022 -0.000001 0.000028 0.297551 0.006122 0.000029 0.0000420.000074 0.000112 0.000052 -0.000014 0.000046 0.638845 0.018904 0.000188 0.0000950.000001 0.000015 0.000002 -0.000001 0.000001 -0.000528 0.000838 0.000025 0.0000050.000002 0.000025 0.000002 0.000000 0.000001 0.000066 0.001270 0.000042 0.0000050.000002 0.000031 0.000003 0.000000 0.000001 0.000497 0.001024 0.000054 0.0000050.000004 0.000006 0.000004 -0.000001 0.000002 0.000204 0.002125 0.000009 0.0000070.000008 0.000030 0.000007 -0.000001 0.000005 0.076640 0.010862 0.000054 0.0000130.000010 0.000049 0.000008 0.000011 0.000007 0.074309 0.006794 0.000083 0.0000150.000026 0.000021 0.000020 0.000011 0.000021 0.229429 0.035361 0.000057 0.0000440.000058 0.000084 0.000040 0.000005 0.000042 0.526413 0.015990 0.000148 0.0000800.000051 0.000082 0.000027 -0.000016 0.000034 0.393291 0.014552 0.000124 0.0000590.000049 0.000055 0.000033 0.000217 0.000145 0.510778 0.027856 0.000096 0.0000640.000002 0.000007 0.000002 0.000001 0.000001 0.000546 0.001187 0.000012 0.0000050.000015 0.000025 0.000011 0.000028 0.000011 0.122549 0.001678 0.000054 0.0000220.000002 0.000023 0.000003 0.000000 0.000001 -0.000976 0.001380 0.000037 0.0000060.000037 0.000069 0.000022 0.000004 0.000026 0.200580 0.006683 0.000108 0.0000440.000019 0.000089 0.000017 0.000167 0.000167 0.154100 0.002636 0.000161 0.0000320.000003 0.000029 0.000003 0.000001 0.000002 -0.000070 0.001386 0.000049 0.0000060.000024 0.000028 0.000014 -0.000004 0.000014 0.236098 0.012400 0.000038 0.0000300.000003 0.000017 0.000002 -0.000001 0.000002 -0.000687 0.000900 0.000025 0.0000050.000015 0.000005 0.000012 0.000002 0.000013 0.093506 0.013078 0.000005 0.0000360.000017 0.000019 0.000011 0.000010 0.000010 0.128965 0.003555 0.000032 0.0000200.000002 0.000014 0.000004 0.000003 0.000001 -0.000899 0.001641 0.000021 0.0000070.000004 0.000009 0.000005 0.000006 0.000002 0.028402 0.003735 0.000015 0.0000100.000053 0.000044 0.000037 0.000648 0.000259 0.242419 0.018076 0.000106 0.0001330.000027 0.000035 0.000013 0.000009 0.000013 0.144292 0.008102 0.000060 0.0000240.000017 0.000014 0.000014 0.000023 0.000014 0.154509 0.004109 0.000040 0.0000320.000007 0.000011 0.000004 0.000027 0.000013 0.061481 0.002910 0.000022 0.0000080.000035 0.000013 0.000026 0.000020 0.000022 0.257623 0.056968 0.000059 0.0000580.000008 0.000013 0.000007 0.000000 0.000004 0.000979 0.002480 0.000020 0.0000120.000040 0.000057 0.000032 0.000043 0.000042 0.278849 0.053105 0.000102 0.0000720.000010 0.000012 0.000009 0.000011 0.000008 0.113156 0.001393 0.000021 0.0000150.000007 0.000017 0.000006 0.000003 0.000005 0.059825 0.001236 0.000029 0.0000120.000003 0.000032 0.000003 0.000002 0.000002 -0.000090 0.001825 0.000054 0.0000070.000022 0.000013 0.000015 0.000011 0.000013 0.205850 0.002488 0.000024 0.0000300.000057 0.000081 0.000050 0.000004 0.000038 0.536562 0.015451 0.000120 0.0000870.000003 0.000031 0.000002 0.000000 0.000002 0.000105 0.000621 0.000052 0.0000050.000002 0.000006 0.000002 0.000001 0.000001 -0.000169 0.001100 0.000010 0.0000050.000002 0.000032 0.000003 0.000000 0.000002 -0.000366 0.001267 0.000053 0.0000060.000003 0.000026 0.000004 0.000001 0.000002 -0.000174 0.000921 0.000042 0.0000070.000003 0.000024 0.000003 0.000002 0.000001 -0.000097 0.001070 0.000040 0.0000050.000002 0.000019 0.000004 0.000001 0.000002 0.000296 0.001310 0.000032 0.0000060.000060 0.000042 0.000038 0.000018 0.000039 0.418842 0.010426 0.000072 0.0000720.000056 0.000036 0.000032 0.000002 0.000039 0.382162 0.056305 0.000066 0.0000640.000023 0.000018 0.000018 0.000003 0.000019 0.165996 0.005034 0.000042 0.000033

0.000034 0.000108 0.000021 0.000026 0.000024 0.693101 0.023271 0.000193 0.0000440.000003 0.000052 0.000003 -0.000003 0.000002 0.000527 0.001253 0.000088 0.0000070.000003 0.000096 0.000007 0.000003 0.000003 -0.000177 0.001495 0.000165 0.000012

(Cont.)



0361-0128/98/000/000-00 $6.00 114

BRN-3-011 1.201956 0.081619 0.127228 0.000048 0.119985 0.000025 0.001361BRN-3-015 2.202769 0.081243 0.128002 0.000052 0.119871 0.000030 0.001318BRN-3-016 3.478962 1.025108 0.127773 0.000077 0.119855 0.000044 0.001300BRN-3-017 0.976955 0.139694 0.126564 0.000072 0.119954 0.000039 0.001327BRN-3-018 2.461602 0.312371 0.127797 0.000066 0.119884 0.000031 0.001302BRN-3-019 8.875525 1.239115 0.125490 0.000043 0.119840 0.000018 0.001303BRN-3-020 2.944795 0.175730 0.126253 0.000040 0.119877 0.000016 0.001310BRN-3-022 9.156643 0.547901 0.126543 0.000096 0.119854 0.000037 0.001306BRN-3-023 2.415142 0.118320 0.125759 0.000064 0.119868 0.000028 0.001307BRN-3-024 1.801203 0.115611 0.127367 0.000055 0.119934 0.000025 0.001321BRN-3-027 0.974338 0.038840 0.126815 0.000054 0.119916 0.000035 0.001320BRN-3-028 9.891650 0.239284 0.125290 0.000054 0.119818 0.000022 0.001306BRN-3-030 0.510840 0.036281 0.129252 0.000070 0.120008 0.000052 0.001346BRN-3-031 1.815880 0.090406 0.129536 0.000052 0.119899 0.000025 0.001307BRN-3-032 0.665835 0.047726 0.127372 0.000072 0.120011 0.000039 0.001307BRN-3-033 4.033013 0.210831 0.128069 0.000055 0.119843 0.000021 0.001309BRN-3-035 7.250784 0.572140 0.126336 0.000081 0.119851 0.000031 0.001304BRN-3-036 2.521065 0.173719 0.127777 0.000059 0.119837 0.000021 0.001310BRN-3-037 1.889294 0.294849 0.125762 0.000068 0.119880 0.000039 0.001304BRN-3-039 2.101006 0.065630 0.127922 0.000033 0.119879 0.000019 0.001300BRN-3-040 5.061588 1.329606 0.126777 0.000081 0.119895 0.000033 0.001305BRN-3-041 9.736699 0.260511 0.125090 0.000067 0.119825 0.000025 0.001305BRN-3-044 4.325815 0.426418 0.127797 0.000100 0.119850 0.000023 0.001306BRN-3-046 1.282800 0.205192 0.126249 0.000124 0.119845 0.000065 0.001330BRN-3-047 0.985877 0.075595 0.125554 0.000053 0.119965 0.000030 0.001325BRN-3-048 0.850249 0.039392 0.130191 0.000067 0.119997 0.000040 0.001316BRN-3-050 1.086793 0.059317 0.127872 0.000041 0.119920 0.000034 0.001314BRN-3-051 1.368949 0.091581 0.126192 0.000052 0.119905 0.000031 0.001317BRN-3-052 12.350073 0.339667 0.125336 0.000065 0.119825 0.000024 0.001306BRN-3-056 0.725661 0.032953 0.140674 0.000056 0.119946 0.000035 0.001306BRN-3-057 8.136099 0.157325 0.125416 0.000058 0.119831 0.000023 0.001306BRN-3-060 6.413443 0.339923 0.127417 0.000041 0.119845 0.000018 0.001309BRN-3-061 5.742474 0.335356 0.125415 0.000048 0.119835 0.000020 0.001308BRN-3-062 3.268250 0.330950 0.127791 0.000043 0.119849 0.000026 0.001312BRN-3-065 8.130820 0.301898 0.126810 0.000118 0.119826 0.000043 0.001307BRN-3-067 2.280164 0.184273 0.127244 0.000049 0.119875 0.000017 0.001307BRN-3-068 1.012840 0.046747 0.133150 0.000049 0.119911 0.000027 0.001316BRN-3-069 0.911584 0.047604 0.127057 0.000049 0.119974 0.000034 0.001321BRN-3-070 0.794545 0.093355 0.129543 0.000069 0.119981 0.000041 0.001336BRN-3-072 7.720748 0.201943 0.130744 0.000059 0.119843 0.000027 0.001305BRN-3-073 8.646160 0.192829 0.125945 0.000062 0.119828 0.000025 0.001305BRN-3-075 1.404149 0.196011 0.125974 0.000031 0.119918 0.000030 0.001312BRN-3-077 9.077549 0.248254 0.129370 0.000054 0.119838 0.000023 0.001304BRN-3-078 3.183043 0.265115 0.125786 0.000049 0.119876 0.000022 0.001305BRN-3-080 0.685077 0.024996 0.132387 0.000064 0.119912 0.000038 0.001315BRN-3-081 0.450372 0.026018 0.126994 0.000072 0.119990 0.000058 0.001314BRN-3-082 6.026067 0.223118 0.124954 0.000061 0.119854 0.000027 0.001309BRN-3-084 10.774372 0.242336 0.126567 0.000087 0.119831 0.000033 0.001306BRN-3-085 0.712463 0.102394 0.127209 0.000058 0.119999 0.000035 0.001319BRN-3-087 1.759863 0.072607 0.127787 0.000047 0.119863 0.000027 0.001316BRN-3-091 7.687747 0.464038 0.125806 0.000048 0.119823 0.000019 0.001304BRN-3-092 1.981562 0.044392 0.126032 0.000028 0.119915 0.000017 0.001314BRN-3-093 7.872409 0.777933 0.127332 0.000060 0.119835 0.000023 0.001309BRN-3-094 0.648655 0.113116 0.129716 0.000070 0.119993 0.000042 0.001304BRN-3-095 2.054451 0.516901 0.130196 0.000062 0.119828 0.000040 0.001314BRN-3-097 6.171121 0.299190 0.128773 0.000039 0.119824 0.000016 0.001307BRN-3-099 1.205107 0.123688 0.126061 0.000038 0.119895 0.000028 0.001310BRN-3-100 5.483927 0.268432 0.126837 0.000057 0.119841 0.000024 0.001308

1/16/08BRN-3-014 0.587520 0.016281 0.126261 0.000062 0.120053 0.000045 0.001329BRN-3-025 0.902845 0.034827 0.131632 0.000054 0.120079 0.000033 0.001338BRN-3-043 1.349722 0.059744 0.129324 0.000069 0.119978 0.000028 0.001328BRN-3-063 1.931496 0.484015 0.125893 0.000108 0.120016 0.000078 0.001333BRN-4-005 9.623873 0.604846 0.125259 0.000121 0.119819 0.000047 0.001306BRN-4-006 1.052940 0.080178 0.129433 0.000107 0.119954 0.000046 0.001324BRN-4-007 1.672896 0.111609 0.128283 0.000079 0.119903 0.000038 0.001309BRN-4-008 10.073524 0.830124 0.128094 0.000083 0.119830 0.000026 0.001306BRN-4-009 3.823689 0.214550 0.128940 0.000083 0.119876 0.000031 0.001309

TABLE A6.



0361-0128/98/000/000-00 $6.00 115

0.000014 0.000054 0.000013 -0.000041 0.000014 0.275925 0.009537 0.000098 0.0000230.000008 0.000052 0.000006 0.000005 0.000006 0.132139 0.001715 0.000088 0.0000130.000018 0.000130 0.000031 0.000023 0.000013 0.189550 0.043994 0.000218 0.0000530.000023 0.000112 0.000019 0.000066 0.000019 0.523243 0.055634 0.000203 0.0000360.000010 0.000034 0.000006 0.000018 0.000007 0.109083 0.013378 0.000064 0.0000130.000002 0.000040 0.000003 0.000001 0.000001 -0.000177 0.000898 0.000066 0.0000050.000007 0.000034 0.000004 0.000008 0.000005 0.140731 0.002678 0.000058 0.0000080.000002 0.000023 0.000003 0.000001 0.000001 -0.000691 0.001908 0.000036 0.0000060.000008 0.000036 0.000005 0.000079 0.000036 0.193354 0.007712 0.000059 0.0000090.000008 0.000056 0.000009 0.000057 0.000015 0.259406 0.017477 0.000101 0.0000180.000018 0.000067 0.000016 0.000032 0.000013 0.353659 0.021790 0.000123 0.0000290.000002 0.000027 0.000002 0.000000 0.000001 0.000256 0.001134 0.000046 0.0000050.000043 0.000146 0.000023 0.000030 0.000031 0.706198 0.028600 0.000258 0.0000520.000012 0.000081 0.000007 0.000079 0.000020 0.215286 0.011539 0.000137 0.0000140.000028 0.000165 0.000020 0.000058 0.000022 0.583687 0.019033 0.000277 0.0000420.000005 0.000023 0.000005 0.000005 0.000003 0.080947 0.003007 0.000040 0.0000090.000003 0.000026 0.000004 0.000000 0.000002 -0.000705 0.001618 0.000042 0.0000070.000008 0.000021 0.000006 0.000030 0.000011 0.088847 0.006321 0.000040 0.0000120.000015 0.000054 0.000011 0.000064 0.000048 0.218955 0.026945 0.000103 0.0000230.000012 0.000023 0.000006 0.000012 0.000007 0.122184 0.000814 0.000043 0.0000110.000008 0.000028 0.000008 0.000076 0.000044 0.094696 0.022056 0.000051 0.0000160.000002 0.000009 0.000003 0.000001 0.000001 0.000037 0.001332 0.000016 0.0000060.000004 0.000021 0.000004 0.000101 0.000039 0.081520 0.004979 0.000037 0.0000070.000027 0.000080 0.000021 0.000715 0.000439 0.174811 0.018444 0.000204 0.0000870.000022 0.000080 0.000012 0.000015 0.000012 0.353092 0.017768 0.000140 0.0000250.000022 0.000116 0.000013 0.000020 0.000013 0.469934 0.012329 0.000189 0.0000250.000018 0.000074 0.000012 0.000011 0.000011 0.287239 0.006176 0.000124 0.0000200.000015 0.000059 0.000010 0.000005 0.000010 0.221441 0.018194 0.000093 0.0000190.000002 0.000054 0.000003 0.000000 0.000001 0.000569 0.001342 0.000093 0.0000060.000024 0.000094 0.000017 0.000030 0.000017 0.428509 0.004388 0.000168 0.0000310.000002 0.000065 0.000003 -0.000001 0.000002 0.000051 0.001139 0.000109 0.0000050.000003 0.000031 0.000003 0.000016 0.000007 0.048879 0.002483 0.000050 0.0000050.000003 0.000010 0.000003 0.000000 0.000002 0.013133 0.002019 0.000020 0.0000060.000006 0.000021 0.000005 0.000005 0.000006 0.067195 0.007330 0.000037 0.0000090.000002 0.000022 0.000006 -0.000002 0.000002 0.000598 0.002365 0.000039 0.0000100.000009 0.000034 0.000005 0.000013 0.000006 0.146717 0.012198 0.000060 0.0000090.000019 0.000045 0.000009 -0.000002 0.000015 0.215043 0.001078 0.000067 0.0000210.000022 0.000075 0.000013 0.000032 0.000022 0.361354 0.013505 0.000136 0.0000280.000022 0.000089 0.000021 0.000204 0.000062 0.349445 0.026244 0.000149 0.0000340.000004 0.000018 0.000003 -0.000001 0.000002 0.000065 0.001156 0.000031 0.0000060.000002 0.000036 0.000003 0.000000 0.000001 0.000369 0.001258 0.000060 0.0000060.000019 0.000063 0.000012 0.000043 0.000018 0.202788 0.008344 0.000106 0.0000220.000002 0.000023 0.000002 0.000001 0.000001 -0.000577 0.001069 0.000037 0.0000050.000004 0.000033 0.000004 0.000014 0.000004 0.126072 0.008567 0.000056 0.0000080.000028 0.000115 0.000018 0.000037 0.000016 0.394677 0.023509 0.000198 0.0000310.000048 0.000121 0.000027 0.000156 0.000079 0.511723 0.035372 0.000203 0.0000500.000003 0.000039 0.000004 -0.000003 0.000002 0.000050 0.001297 0.000065 0.0000060.000002 0.000010 0.000004 -0.000001 0.000001 0.000294 0.001720 0.000018 0.0000060.000035 0.000097 0.000016 0.000030 0.000020 0.493112 0.018727 0.000163 0.0000290.000010 0.000038 0.000007 0.000005 0.000008 0.132304 0.003249 0.000065 0.0000130.000002 0.000009 0.000003 0.000000 0.000002 0.000169 0.000957 0.000016 0.0000060.000011 0.000065 0.000006 0.000034 0.000009 0.202404 0.002909 0.000111 0.0000110.000003 0.000020 0.000003 -0.000001 0.000002 -0.000329 0.001141 0.000035 0.0000060.000041 0.000089 0.000028 0.000369 0.000074 0.422880 0.013448 0.000186 0.0000600.000014 0.000035 0.000008 0.000006 0.000007 0.077479 0.002737 0.000059 0.0000140.000002 0.000033 0.000002 0.000000 0.000002 0.000143 0.000754 0.000056 0.0000040.000015 0.000060 0.000012 0.000020 0.000011 0.302281 0.014475 0.000097 0.0000210.000004 0.000039 0.000003 0.000000 0.000002 -0.000007 0.001127 0.000064 0.000006

0.000026 0.000159 0.000021 0.000084 0.000021 0.937605 0.014366 0.000265 0.0000400.000023 0.000199 0.000017 0.000085 0.000018 0.849518 0.035395 0.000333 0.0000320.000011 0.000104 0.000010 0.000058 0.000010 0.502040 0.015220 0.000174 0.0000170.000015 0.000141 0.000034 0.000057 0.000023 0.694388 0.166172 0.000300 0.0001400.000002 0.000033 0.000005 0.000001 0.000001 0.000500 0.002460 0.000053 0.0000090.000015 0.000061 0.000012 0.000155 0.000066 0.390974 0.031818 0.000100 0.0000230.000011 0.000086 0.000008 0.000020 0.000008 0.282118 0.010360 0.000148 0.0000170.000002 0.000018 0.000004 0.000019 0.000003 0.011579 0.003389 0.000031 0.0000070.000006 0.000029 0.000005 0.000008 0.000004 0.109258 0.003086 0.000046 0.000008

(Cont.)



0361-0128/98/000/000-00 $6.00 116

BRN-4-011 7.359791 0.763383 0.126360 0.000089 0.119808 0.000036 0.001305BRN-4-012 0.796429 0.081264 0.129351 0.000101 0.119986 0.000051 0.001343BRN-4-013 1.385688 0.086106 0.127062 0.000074 0.119891 0.000036 0.001310BRN-4-014 6.013745 0.499288 0.125033 0.000113 0.119858 0.000045 0.001303BRN-4-016 0.955627 0.047470 0.128971 0.000059 0.119996 0.000039 0.001321BRN-4-017 1.312178 0.104872 0.129903 0.000080 0.119993 0.000036 0.001332BRN-4-018 3.748512 0.243123 0.132986 0.000057 0.119850 0.000025 0.001302

1/31/08BRN-3-002 5.071107 0.401041 0.127496 0.000037 0.119854 0.000017 0.001309BRN-3-004 1.843409 0.073690 0.125729 0.000032 0.119881 0.000022 0.001323BRN-3-005 0.779294 0.049447 0.126306 0.000074 0.119984 0.000037 0.001310BRN-3-006 0.657370 0.013461 0.126799 0.000043 0.120021 0.000038 0.001304BRN-3-007 0.772815 0.016726 0.137238 0.000041 0.119975 0.000029 0.001321BRN-3-012 0.688867 0.032131 0.126521 0.000065 0.120063 0.000034 0.001344BRN-3-021 5.519299 0.731509 0.126339 0.000057 0.119864 0.000028 0.001306BRN-3-026 0.822305 0.036661 0.128329 0.000054 0.120010 0.000039 0.001314BRN-3-038 0.304368 0.005226 0.137169 0.000085 0.120204 0.000060 0.001274BRN-3-058 1.248474 0.035431 0.126219 0.000033 0.119941 0.000023 0.001304BRN-3-064 0.699842 0.025488 0.129776 0.000045 0.119969 0.000040 0.001292BRN-3-071 0.632215 0.019255 0.126680 0.000053 0.119995 0.000046 0.001323BRN-3-079 0.674634 0.024271 0.127536 0.000047 0.119969 0.000037 0.001317BRN-3-086 0.530972 0.018494 0.129117 0.000079 0.120043 0.000044 0.001307BRN-3-088 0.741392 0.116507 0.126834 0.000077 0.119969 0.000040 0.001286BRN-1-047 13.862740 1.272608 0.127151 0.000043 0.119839 0.000017 0.001305BRN-1-074 0.350473 0.006111 0.132372 0.000080 0.120032 0.000057 0.001309

2/18/08BRN-1-003 0.606364 0.012831 0.128390 0.000057 0.120092 0.000047 0.001323BRN-1-019 0.385066 0.008715 0.133199 0.000086 0.120194 0.000052 0.001310BRN-1-026 0.537193 0.021917 0.126249 0.000073 0.120178 0.000059 0.001312BRN-1-029 0.475614 0.012429 0.135444 0.000064 0.120127 0.000033 0.001273BRN-1-037 0.960169 0.066925 0.133509 0.000053 0.119992 0.000033 0.001291BRN-1-045 0.383108 0.011629 0.134646 0.000114 0.120291 0.000073 0.001279BRN-1-046 1.292354 0.163840 0.128105 0.000062 0.120000 0.000034 0.001319BRN-1-052 1.067761 0.039233 0.129648 0.000032 0.119945 0.000026 0.001305BRN-1-062 0.560708 0.029197 0.130488 0.000069 0.120132 0.000054 0.001317BRN-1-070 0.430361 0.025152 0.134480 0.000065 0.120108 0.000046 0.001316BRN-1-076 0.457135 0.013384 0.132639 0.000078 0.120055 0.000055 0.001277BRN-1-077 0.989600 0.038562 0.127442 0.000036 0.119918 0.000030 0.001307BRN-1-087 0.287037 0.004546 0.133614 0.000090 0.120182 0.000061 0.001300BRN-1-090 1.140672 0.020643 0.127506 0.000037 0.119951 0.000023 0.001315BRN-1-097 0.732477 0.010223 0.126697 0.000043 0.119973 0.000042 0.001310BRN-1-098 2.541498 0.152319 0.126600 0.000044 0.119906 0.000020 0.001301BRN-2-010 0.211042 0.003989 0.125361 0.000119 0.120315 0.000109 0.001228BRN-2-014 0.289925 0.005877 0.125599 0.000082 0.120221 0.000080 0.001299BRN-2-015 0.737222 0.013902 0.126961 0.000056 0.120019 0.000036 0.001321BRN-2-016 1.322476 0.032846 0.127854 0.000037 0.119916 0.000021 0.001298BRN-2-023 0.255567 0.004031 0.128239 0.000101 0.120158 0.000067 0.001309BRN-2-025 2.236836 0.161304 0.125395 0.000046 0.119843 0.000026 0.001303BRN-2-027 0.737953 0.034896 0.129261 0.000077 0.119977 0.000036 0.001314BRN-2-033 0.574725 0.020014 0.125918 0.000062 0.120038 0.000046 0.001310BRN-2-034 0.871899 0.033078 0.129036 0.000044 0.119961 0.000029 0.001308BRN-2-038 3.081350 0.233754 0.126916 0.000045 0.119837 0.000021 0.001306BRN-2-046 0.582393 0.038714 0.128517 0.000065 0.119993 0.000041 0.001339BRN-2-052 0.705524 0.021980 0.126749 0.000056 0.120016 0.000050 0.001339BRN-2-077 0.304109 0.007925 0.128267 0.000106 0.120037 0.000082 0.001267BRN-2-081 0.330557 0.031770 0.132601 0.000102 0.120144 0.000094 0.001237BRN-2-083 0.352921 0.006078 0.127139 0.000050 0.120147 0.000050 0.001268BRN-2-085 0.610671 0.028986 0.128905 0.000066 0.119933 0.000045 0.001257BRN-2-097 0.305697 0.009739 0.137995 0.000097 0.120252 0.000082 0.001238BRN-2-098 0.546955 0.006959 0.127524 0.000052 0.119982 0.000046 0.001304BRN-2-100 0.664543 0.071708 0.127794 0.000065 0.119923 0.000033 0.001289BRN-3-003 0.836398 0.034683 0.125676 0.000068 0.119929 0.000037 0.001318

Mineralogy is based on EMP analyses (see Tables A1 and A5)Within run uncertainties are quoted as 2SE; total absolute error for 186Os/188Os ratios incorporates an estimate of external reproducibility based on re-

peat analyses, over a period of one year, of an in-house LA standard (Urals Os-rich PGE alloy 36720 G1 (Nowell et al., 2008); for 190Pt/188Os ratios Total ab-solute error includes 5% uncertainty on elemental (Pt/Os) fractionation that may occur at the ablation site

TABLE A6.



0361-0128/98/000/000-00 $6.00 117

0.000002 0.000021 0.000004 -0.000001 0.000002 0.001141 0.001804 0.000036 0.0000080.000028 0.000067 0.000022 0.000080 0.000026 0.368771 0.007600 0.000104 0.0000390.000013 0.000036 0.000012 0.000039 0.000011 0.255372 0.010337 0.000060 0.0000220.000003 0.000006 0.000005 0.000001 0.000001 0.000157 0.002290 0.000014 0.0000100.000023 0.000075 0.000015 0.000032 0.000011 0.502776 0.018555 0.000129 0.0000270.000019 0.000078 0.000009 0.000031 0.000013 0.397542 0.017620 0.000135 0.0000180.000006 0.000014 0.000005 0.000015 0.000004 0.094627 0.001724 0.000027 0.000011

0.000004 0.000040 0.000003 0.000010 0.000002 0.100816 0.006644 0.000069 0.0000060.000011 0.000063 0.000007 0.000016 0.000007 0.210286 0.008460 0.000111 0.0000130.000025 0.000126 0.000017 0.000853 0.000589 0.608142 0.028121 0.000226 0.0000340.000026 0.000232 0.000019 0.000113 0.000018 0.754627 0.003088 0.000401 0.0000360.000020 0.000135 0.000018 0.000089 0.000012 0.552569 0.005971 0.000220 0.0000320.000029 0.000211 0.000020 0.000153 0.000040 0.728321 0.026758 0.000357 0.0000400.000003 0.000029 0.000006 0.000077 0.000047 0.098729 0.019033 0.000053 0.0000110.000019 0.000162 0.000016 0.000388 0.000279 0.554217 0.023188 0.000264 0.0000290.000057 0.000355 0.000046 0.000641 0.000358 1.492913 0.020780 0.000589 0.0000890.000015 0.000091 0.000009 0.000086 0.000014 0.359269 0.003082 0.000155 0.0000170.000029 0.000230 0.000019 0.000197 0.000057 0.654506 0.008286 0.000387 0.0000370.000030 0.000168 0.000023 0.000107 0.000016 0.632926 0.008467 0.000281 0.0000420.000032 0.000110 0.000019 0.000065 0.000019 0.514051 0.003753 0.000191 0.0000340.000029 0.000180 0.000026 0.000118 0.000026 0.776984 0.020728 0.000291 0.0000460.000032 0.000118 0.000022 0.000077 0.000022 0.620390 0.050311 0.000221 0.0000480.000002 0.000014 0.000002 0.000008 0.000002 0.027658 0.002101 0.000027 0.0000060.000035 0.000196 0.000030 0.000091 0.000034 0.833118 0.017300 0.000336 0.000058

0.000030 0.000211 0.000018 0.000074 0.000025 0.758499 0.026611 0.000361 0.0000340.000038 0.000228 0.000022 0.000093 0.000027 1.099101 0.035612 0.000380 0.0000400.000035 0.000224 0.000027 0.000113 0.000025 0.946689 0.031032 0.000383 0.0000520.000043 0.000229 0.000026 0.000137 0.000024 0.981190 0.007177 0.000372 0.0000480.000018 0.000133 0.000019 0.000125 0.000071 0.477689 0.029583 0.000231 0.0000350.000048 0.000285 0.000038 0.000120 0.000042 1.252129 0.041424 0.000502 0.0000700.000016 0.000118 0.000016 0.000042 0.000011 0.460976 0.044039 0.000215 0.0000310.000017 0.000104 0.000010 0.000046 0.000010 0.399026 0.003100 0.000173 0.0000190.000029 0.000211 0.000029 0.000139 0.000028 0.858079 0.055438 0.000343 0.0000560.000045 0.000262 0.000023 0.000169 0.000028 0.984218 0.025746 0.000437 0.0000460.000042 0.000183 0.000028 0.000129 0.000027 0.942256 0.008897 0.000332 0.0000590.000023 0.000073 0.000013 0.000112 0.000048 0.259992 0.003346 0.000122 0.0000240.000072 0.000218 0.000034 0.000121 0.000050 0.939724 0.010733 0.000375 0.0000650.000019 0.000140 0.000013 0.000048 0.000011 0.345966 0.002537 0.000231 0.0000220.000027 0.000108 0.000014 0.000061 0.000017 0.471897 0.012810 0.000181 0.0000230.000009 0.000056 0.000005 0.000027 0.000005 0.177011 0.007184 0.000093 0.0000090.000088 0.000319 0.000063 0.000186 0.000076 1.493430 0.022242 0.000519 0.0001280.000055 0.000243 0.000049 0.000107 0.000046 1.126832 0.023336 0.000406 0.0000820.000026 0.000134 0.000017 0.000039 0.000019 0.475499 0.012455 0.000232 0.0000320.000013 0.000063 0.000007 0.000031 0.000008 0.209319 0.001912 0.000112 0.0000160.000068 0.000235 0.000038 0.000131 0.000040 1.209434 0.004289 0.000415 0.0000830.000009 0.000029 0.000006 0.000017 0.000006 0.107501 0.009737 0.000051 0.0000110.000028 0.000116 0.000018 0.001372 0.001896 0.489553 0.022671 0.000196 0.0000340.000033 0.000342 0.000029 0.000235 0.000131 0.635474 0.025930 0.000574 0.0000530.000022 0.000090 0.000013 0.000042 0.000014 0.396414 0.016458 0.000156 0.0000240.000006 0.000023 0.000005 0.000010 0.000004 0.096849 0.004200 0.000041 0.0000100.000030 0.000158 0.000024 0.000046 0.000018 0.497335 0.026791 0.000264 0.0000410.000026 0.000106 0.000014 0.000061 0.000017 0.499418 0.008322 0.000183 0.0000280.000057 0.000160 0.000051 0.000133 0.000047 0.821658 0.007369 0.000289 0.0000920.000063 0.000435 0.000047 0.000254 0.000066 1.175726 0.068172 0.000751 0.0000910.000046 0.000253 0.000033 0.000147 0.000029 1.023179 0.038821 0.000422 0.0000610.000029 0.000131 0.000019 0.000078 0.000019 0.462604 0.012026 0.000219 0.0000370.000071 0.000345 0.000039 0.000161 0.000049 1.216429 0.032952 0.000594 0.0000720.000040 0.000119 0.000023 0.000052 0.000021 0.473857 0.006074 0.000192 0.0000400.000039 0.000107 0.000027 0.000075 0.000030 0.450953 0.061450 0.000179 0.0000520.000019 0.000066 0.000016 0.000033 0.000015 0.324823 0.012291 0.000110 0.000029

(Cont.)


economic geology 2011 vol.106 p.93–117

Documents

ptos age

os decay system

ptos isotope system

ptos chronometer

suite ofdetrital pgm

metamorphic rocks

leucocratic rocks

provenancepgm grains