An Alteration Study Of The Archean Kidd Creek Volcanogenic Massive Sulphide Deposit,

Abitibi Greenstone Belt, Canada:

Implications For Genetic Models And Exploration Criteria

David M. Richardson, BSc.

Thesis subrnitted to the Faculty of Graduate Studies in partial fulfillment of the requirements for the degree of Master of Science

Department of Geology Laurentian University

Sudbury, Ontario, Canada April 15, 1998

@ 1 998, David M. Richardson

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ABSTRACT

Kidd Creek is one of the world's largest volcanogenic massive sulphide deposits.

From discriminant anaiysis F-tests and visual cornparison of 3992 whole rock and

trace element analyses it has been determined that normalized and percent mass

change NasO, FezOs. MgO, Cao, Cu, and Zn best outline discordant chlorite

aiteration associated with the deposit. Si02 and KzO effectively outline areas of

silicification and sericitization. It has also been determined that the principal

conduits for ascending hydrothemal fluids responsible for the Kidd deposit are

defined by elevated MgO. FezOs, and Cu values that transect both host rhyolitic

and footwall ultrarnafic rocks. The data also indicate that the alteration "footprint"

surrounding the Kidd Creek deposit is 6x the cross-sectional area of the deposit

itself.

TABLE OF CONTENTS

ABSTRACT ................................................................................................. i

AKNO WLEDGEMENTS .........a............................................................... iv

INTRODUCTION ...................................................................................... 1 Discovery Of Kidd Creek ................. ....... ............... .. Production Figures ................................................................................ ................... 2

.............................................................................. Purpose ....................................... 3

GEOLOGY .....a........~.................................................................................. 5 Structure ........... ... .............................................................................................. 11

....................... ..........*.....................*........................................ Previous Studies .. 15 ............................................................................... Additional Observations ...0.....20

.............. Sumrnary of Geoehemicai Changes Related To Alteration Mineralogy 28

WHOLE ROCK SAMPLE DATA BASE ....................o.......................... 30 Analytical Techniques . ...............*..................m..w.............m.o...a....................... .....30 Analytical Error ..................................................................................................... 31 Content of Whole Rock Sample Database ............................................................ 33

.................................................................................................. Sampiing Patterns 33

PROCEDURES FOR IDENTIFYING ALTERATION TRENDS .................................................... WITHIN VARIABLE ROCK TYPES 36

Contouring Methods ........................................................................................... *.% ........................................................................................... Fhw Whole Rock Data 39

Population Separation ................................................................................. a.e00*.o..41 Data N o d z a t i o n Technique .......m...................................................................... 45 Mass Change ......................................................................................................... 47 Discrlminat Analysis ................................................................................. .............50 Cornparison of Techniques And Elements ........................................... .................57

APPLICATION OF LITHOGEOCHEMICAL TECHNIOUES TO KIDD CREEK GENETIC MODELS ..................................................... 61

Morphology And Size Of Alteration Zones ........................................................... 61 Volcanologieal Considerations ............................................................................... 78 Stmctural Considerations ............. ...................................................................m... *.79 Discussion ................................................................................................... ...w...*....83

AKNOWLEDGEMENTS

1 would like to thank Phi1 Olson and Al Coutts for supporting my thesis, Ray Band

for his careful review of this document, and Falconbridge Ltd. for providing funds

to purchase siteview the 3D modeling software. 1 am indebted to Ron Cook, Ron

Lemery, Dean Crick. Dean MacEechm. Dave Luckett, Paul Simonovic, Marilyn

Schonfedlt, Paul Roos, Peter Jurenovskis, Greg Collins, Dean Rogers, Pete

Calloway. Pete Manojlovic, Gary Potts. Dan Brisbin. Deb Archibald, Paul Coad,

Glen Prior, Liz Koopman, and many other geologists who provided the accurate

and essential database of geological information on which this thesis is based.

1 wish to express my sincere thanks to my supervisors: Bob Whitehead for his the

and input; Harold Gibson who proved it was possible for me to do a masters; and

Mark Hannington who first introduced me to the Kidd Creek Mine as a summer

student.

INTRODUCTION

The Archean Kidd Creek Zn-Cu-Ag Volcanogenic Massive Sulphide (VMS)

deposit (located within the western part of the Abitibi greenstone belt) lies 27

kilometers north of the historic gold producing town of Timmins (Fig. 1).

Ultramafic to felsic volcanic rocks are found north of the Kidd Creek deposit and

rnetasediments (greywackes in mine terminology) to the south.

*

Figure 1: Location of The Kidd Creek Ore Deposit Wittiin The Abitibi Greenstone Belt, after Goodwin and Ridler, (1970), Nal&et (1973), and Walker and Mannard (1975)

b

Discovery Of Kidd Creek

Kidd Creek was a combined geological and geophysical discovery. Texasgulf

Sulfur Company identified the presence of felsic fragmental rocks (now called the

east outcrop). basaltic rocks, and a distal cherty tuff horizon. This geological

setting was deerned favourable for hosting a VMS deposit. A geophysical survey

was undertaken and numerous electromagnetic conductors were found with a large

anomaly located over the site of the Kidd Creek orebody. No magnetic anomalies

were detected as Kidd Creek contains ni1 to trace amounts of magnetite and minor

amounts of magnetic pyrrhotite. On November 9Ih, 1963 Texas Gulf started the

first hole (K-55) targeted over the E.M. anomaly. It collared in massive

chalcopyrite (after 27ft of overburden) followed by a zinc-pyrite unit that averaged

17% zinc. Texasgulf moved quickly to secure land position around the area

without infonning others of their results.

The question is, could Kidd Creek have been discovered using lithogeochemical

methods if sufficient outcrop was available for samples or the initial drill holes

missed the orebody?

Production Figures

As of December 1996, the total amount of ore contained at Kidd (past production

3

plus current reserves) was 138 million tonnes (Mt) grading 2.35% Cu, 6.5 8 Zn,

0.23% Pb, and 89 g/t Ag. An additional 17 Mt resource at 1.85% Cu and 8.43%

Zn is indicated below the 6800 level bringing the total amount of ore to almost 150

million tonnes (Canadian Mining Journal, 1996). Cu grade and resource tonnage

should increase with the release of results from further sectional drilling conducted

in 1996-97. Indium and cadmium are currently extracted as by-products and tin

was previously extracted. Gold is not present in economic concentrations (Crick et

al.. 1994). Kidd Creek is very large when considering the fact that 80% of VMS

deposits are between O. 1 to 10 Mt (Gibson and Kerr, 1993). As more ore is mined

from the Kidd Creek orebody, it becomes increasingly important to replenish the

mine's reserves. Understanding the pattern of alteration around Kidd Creek aids in

the detection of similar patterns that could lead to the discovery of other orebodies.

Pur pose

To determine if the contouring of irregularly distributed whole rock data from

varying lithologies can effectively outline areas affected by primary alteration

associated with the ore fomiing event at Kidd Creek. If so, how rnany sarnples or

percent outcrop would be needed to detect the possible presence of a nearby

orebody in a similar setting.

To evaluate the geochemical techniques of using raw data, mass balance, and data

nomalization. Evaluation will determine the most effective techniques, oxides,

and elements to outline alteration associated with a Kidd Creek type orebody. Raw

data is defined as data from the lab without nomalization or any other calculations

applied to it.

To use these techniques to &termine the size morphology of primary alteration

sunounding the Kidd Creek orebody and evaluate current genetic models. The

alteration pattern will be studied to determine the location of a potential feedtr

zone(s) utilized by fluids associated with the ore forming event.

Descriptions of rock units in the Kidd Creek stratigraphic succession are taken

from Waiker and Mannard (1974). Coad (1 985). and personal experience as a

Kidd mine geologist (1993-1997). Surface geology is given in Figure 2 and a

stratigraphic section is also provided (Fig. 3). The Kidd Creek volcanic pile has

been overtumed and dips 70' to 80° to the north-east. In this orientation, al1 plan

maps represent paleo-cross sections through the vertically continuous stratigraphy.

Units are described below, in stratigraphic order from footwall to hangingwail. Al1

directions in this thesis are relative to mine grid bearing 20' east of m e nonh.

Ultramafic rocks exhibiting local spinifex textures are found at the base of the

Kidd Creek stratigraphy (Barrie et al., in press). Banie et al. consider the

ultramafics to be kornatiitic flows but other workers have identified intrusive

characteristics within the ultramafics (Ron Cook. pers. comrn.). Intrusive features

within the ultramafics may have forrned during structural transposition (faulting or

folding) of ductile ultramafic rocks around comparatively competent rhyolite units.

Schandl and Wicks (1 993) observed alteration in the fonn of intense talc-

carbonate. serpentinization. or quartz-carbonate aiteration within the ultramafk

units. They hypothesized that an early silicification and carbonatization event

K I O D C R E E K M I N E S U R F A C E P L A N

Figure 2: Surface Gedogy Plan View Of The Kidd Creek Mine, fkom Waker and Mannard. 1975

A

P

QUARTZ PORPHYRY RWOLlTE WME

1 ANDESlWûlORiT€ (GABBRO) 1

1 MASSIVE \PWOLIE) 6b

Figure 3: Simplified sîratigraphic section of the Kidd Creek volmic cornplex. MS = Massive Sulphide

may have been preserved in the ultramafics and overlying rhyolites. Contour

diagrams presented below show the possible distribution of an ore related remnant

primary alteration signature within the ultramafics.

A felsic fragmental unit containing large flow banded and altered (sencitized and

silicified) clasts lies stratigraphicaily above the ultramafics and is exposed in the

east outcrop (east side of pit).

Two massive rhyolite units overly the east outcrop fragmental unit. These rhyolite

units have sericitic margins and dark massive interiors due to their fine-grained

nature. Mapped as having both sharp and gradational contacts with the overlying

crackle brecciated rhyolite. they may be endogenous intrusions in a rhyolite

cryptodome.

"Cherty breccia" is a term used for the crackle brecciated, silicified massive

rhyolite that hosts the copper stringer ore. Crackle brecciation may have been the

result of brecciation due to flow or a later explosive hydrothermal brecciation

event (Coad, 1985). Brisbin et ai. (1990) and Gibson (pers. comm.) interpret the

cherty breccia to be the autobrecciated flow portion of a cryptodome. Copper

stringer ore (ore outline +0.8% Cu in Fig. 2) lies at or near the top of the Cherty

Breccia unit.

Massive sulphide lenses (>50% sulphides by definition but atmost always close to

100% sulphides) lie at or just above the contact between the cherty breccia and

overlying volcaniclastic rocks. Sulphides may have precipitated from an ascending

hydrothemai fluid at the point of dramatic thermal and chernical changes at the

contact between the cherty breccia and the overlying rhyolite volcaniclastic rocks.

The South, Central, and North are terms refemng to the three main massive

sulphide orebodies (Faiconbridge staff, pers. comrn.).

Rhyolite volcaniclastic rocks ranging from fine-grained tuffs to coarse fragmenta1

units directly overly the three main massive sulphide lenses. Fragments within the

coarse volcaniclastic rocks consist of rounded/elliptical altered rhyolite. sulphide

(pyrite-sphalerite). rue olive green mafic fragments. and occasional flow banded

rhyolite fragments.

A relatively restricted unit of quartz (+/- feldspar) porphyritic rhyolite (the QP

rhyolite) lies near the top of the Kidd stratigraphic sequence. It is distinguished

from other rhyolites by having greater than 5% quartz eyes, a dominantly dark

"glassy" massive texture, and a stratigraphic position above the hangingwall

rhyolite volcaniclastic unit. Local flow banding and basal flow breccias have been

mapped within this unit (Prior et al.. in press). Feldspar phenocrysts have been

locally destroyed by sencite alteration.

A mafic synvolcanic si11 separates the Rhyolite volcaniclastic units from the

overlying Quartz Porphyry. It is called Andesite/Diorite ( A D ) in mine

terminology but its emplacement charactenstics and composition is gabbroic. The

A/D si11 may have intnided dong the rhyolite volcaniclastic/QP contact shortly

after emplacement of the Quartz Porphyry. Regionaliy, the volume of A/D is quite

extensive making it difficult to reconstmct the original rhyolite stratigraphy.

Mafic fragmental rocks and piliow basalts ('Dacite" mine term) are the

stratigraphically highest units within a 1 km radius of the mine. Pillow basalts are

light olive green in colour and mafic fragmenta1 units contain mafc clasts mixed

with a fine mafic, pyrrhotite, and local graphite matrix.

A possible distal unit (Bleeker. 1994) called the "North Rhyolite" (Fig 4) exhibits

strong silicification and sericitization. It contains a graphitic argillite with semi

massive pyrite-pyrrhotite and minor sphalerite staining (fine disseminated

sphalerite) hosted by mafic and felsic fragmental units. Its position within the Kidd

Creek S uatigraph y is widel y debated (Falconbridge Geological Staff, pers.

corn..) .

A younger metasedirnentary Porcupine Group unit (Greywacke in mine

terminology) lies against the southem end of the Kidd Creek Felsic pile. Its contact

has been interpreted to be a thnist fault or an unconfonnity (Bleeker, 1994).

Zircons within the Greywacke yield ages of 2699 Ma (Table 1) indicating that the

Greywacke unit is younger than the 27 17-27 1 1 Ma Kidd volcanic sequence.

Table 1 gives the age of units for which U-Pb zircon ages have been deterinined.

ROCK UNIT AGE (Ma)

Table 1: Relative age dates of selected uni& 6om Bleeker, 1994

Structure

Structural geology presented here is summarized from Falconbridge geology staff

(pers. comrn.) and Bleeker (1994). Figure 4 shows important structural features

with respect to geology on the 2800 level. An initial F, folding is inferred but is

not cornrnonly visible in the rock exposure at the mine.

FI Folding: The Kidd Creek orebody lies at the nose or hinge of a regionai fold

with an axis defined by S 1 schistosity that strikes E-W and dips 75' to the north.

Most chalcopyrite stringers, chlorite, and sericite mineral grains are oriented

pardlel or subparallel to the direction to the S 1 plane. Faults also tend to strike in

a direction subparallel to the S 1. The location of the deposit at the hinge of a

regional scale fold may be related to the ductile nature of the massive sulphides

and surrounding altered rhyolites as compared to the massive gabbro and pillow

basalts (Bleeker, 1994). The presence of synvolcanic feeder stnictures may have

GWKE = Greywacke (Metasediments) DAC = Pillow Basalt MR = Massive Rhyolite ND = Gabbro RHY = Rhyolite Volcaniclaçtics and Cherty Breccia - - - = Fault - TC = Ultramafic Solid Fiil = Ore QP = Quartz Porphyry

Figure 4: Structure and geology of 2800 level after Falconbridge &i;i and Huston et al.. 1995

concentrated folding and faulting events in the area around the orebody. Ductile

ultramafic units are also located at the hinge of the F1 fold.

F2 Folding: F2 folding occurs in the fonn of local parasitic folds and a weak S2

crenulation cleavage that dips 80' east.

East- West Shear Zone: Located between the North Orebody and the South

Orebody, the East-West shear zone is at least 4m wide and it passes through. and

displaces the Central orebody between the 1600 and 2500 levels (Ron Cook. pers

cornm.. Fig. 5). It is characterized by intense foliation. Huston (1 995) and other

workers interpret this shear to be a reactivated synvolcanic structure.

South Dipping Faults: A senes of reverse. 80' south dipping enechelon faults

labeled "North B, C, D, E, and F' can be traced from surface to at least the 6000

level. The latest movement dong these structures is much later than the orebody as

they cross-cut stratigraphy and are identified by intense. localized south dipping

shear zones (dipping opposite io S 1). Between 2600 and 2800 levels the East-West

shear zone is cut off by the North "B" Fault (Fig. 5). The North Shear splays off

the North "B9'/East-West shear extension to the south (Fig. 4).

Gouge Fault: A pronounced north (65') dipping gouge filled fault can be traced

from surface to below the 6800 level and is aptly named the "Gouge Fault". This

fault also cross cuts stratigraphy and has normal strike slip movement.

STRUCTURAL CROSS SECTION (AZ 32')

GOUGE FAULT -i

M SHEAR NORTH "B" FAULT NORTH "û" FAULT

n L

Cu STRINGER

FAULT

U ' No.3 Shafl Yc GOUGE FAUT SPLAY

3?

Figure 5: Structural cross section lhrough the Kidd Creek orebody, azimulh 32' alter Cook (1996)

ALTERATION

Previous research into alteration characteristics of the Kidd Creek sequence was

conducted by Coad (1 985). Beaty et al. (1988), Slack and Coad (1989), Schandl

(1989), Schandl and Gonon (1991). Schandl and Wicks (1993). Huston et al.

(1995). Muirhead and Hutchinson (in press), Koopman et al. (in press), and

Falconbridge geologists (pers. cornm., and unpubl. reports).

Previous Studies

Coad (1985) found that it was possible to correlate geochernical values with visual

observations of alteration. He devised an alteration mode1 based on visual data as a

guide to mineralization within rhyolites. Tight unfiactured massive rhyolite devoid

of sulphide mineralization was deemed to be unaltered. Intensely crackle

brecciated or hydrofractured rhyolite units coincident with zones of mature

chlorite-sericite hydrothermal aiteration were regarded as zones with the highest

potential for the discovery of economic sulphides. Coad (1985) observed that iron

rich chlorite is present in the footwall stnnger zone and that the magnesium

content of chlorite is higher in the hangingwall units.

Koopman et al. (in press) documented 5 major alteration types at Kidd Creek, that

are summarized with their corresponding gewhernical changes in Table 2.

Koopman et al. also discussed hangingwall alteration which is an important part of

the alteration sequence. Strong chlori te and serici te alteration c haracterizes the

rhyolite volcaniclastic units directly overlying the Massive Sulphides and Cu

stringer zones.

Mass balance calculations using Gresen's (1967) formula on Kidd rhyolite

samples by Koopman et al. (in press) are summatized in Figure 6 and Table 2.

Muirhead and Hutchinson (in press) completed rnass balance calculations using

MacLean and Barrett's (1993) method. Their main conclusions were that alteration

progressed from the destruction of feldspars by chloritization and sericitization

(leaching of Na and Ca, enrichment of Mg and Fe) and continued with the

development of chlorite with progressive enrichment of Fe content. Most VMS

deposits exhibit this type of geochernical alteration (Franklin et al., 198 1). This

alteration pattern did not change down plunge of the orebody. Muirhead and

Hutchinson (in press) d v e d at similar conclusions to those of Koopman et al.

with respect to chlorite and sericite alteration but they did not identify alteration

associated with low temperature silicification.

Huston et al. (1995) examined oxygen isotope and raw sodium values from

Hcmging Wall Alteration (High 6lW)

-- -- -

lEnri~hwott lad Dq@o<rr lincd in otda af- h p r t a m

Table 2: Summary of Kidd Creek alteration types listed by Koopman et al. (in press)

Figure 6: contoured percent masi change for MgO, S i 4 , and &O within rhyolites on 2 8 0 level. Frm Koopman et al, in press. Similar patterns are outiined below in Figures 27.28, & 3 1

rhyolite samples gathered €rom the 2800 level. An early low temperature (QOO°C)

alteration event producing high 8 0 l 8 , silicification. and no signûicant sodium

depletion was identified. Low temperature aiteration was followed by high

temperature (>300°C) alteration producing strongly silicified and chloritized rocks

with stringer chalcopyrite and low ml8 values. Huston et al. found that contoured

raw sodium values distinguish the Kidd Creek orebody just as well as contoured

oxygen isotope values with only a few differences in the morphology of the

resulting anomalies. For instance. the oxygen isotope anomaly penetrates fwther

into the hangingwall whereas the raw sodium anomaly has greater lateral extent

dong strike.

Schandl and Wicks (1993) identified two alteration types within the Hernrningway

ultrarnafïc rocks located 1.5 km north of the Kidd deposit. Their study identified

early primary carbonate alteration in ultramafk rocks and silicification in rhyolite.

Quartz and carbonate may have locally been replaced by sericite and chlorite

during the waning stages of volcanism. A later pst-ore metasomatic alteration

forming sericite-fuchsite and chlorite was dated at 2624 f 62 Ma and 2659 f 3

Ma. This alteration was corretated with alteration observed in Timmins gold

deposits in close proximity to the Porcupine Destor structure.

Addi tional Observations

Table 3 is a summary of visible alteration observed during mapping.

Footwall Alteration FW & HW alteration Proximal Central Distal Cherty Breccia Massive R hyolite

Strong Quartz (silicic.) Strong Quartz (silicic.) Pervasive Silicification Moderate To Strong Moderate Yel & Grey Weak Yel & Grey Sericite

Black Fe-Chlorite Sericite PY Fe Carbonate Local Sphalerite Staining CPY, PY Py, Sph Photo 1 & 2 Photo 3 Photo 4

Hanging Wall Alteration Proximal Distal Rhyolite Tuff, R hyalite Lapillistone R hyolite

Volcaniclastics

St rong Green Mg-C hlorite Moderate to Strong Sericite Local Sphalerite Staining Fe Carbonate Photo 5 & 6

Pervasive Silicif ication W k-Mod Yellow Sericite PY

Photo 7

Table 3: Kidd Creek aiteraiion sumaiary

Table 4 gives the chernical formulae determined by scanning electron microscope

(S.E.M.) (Richardson, 1997) for chlorites and sericites gathered from footwall to

hangingwall locations in the #3 mine (Fig. 7). The Fe/Fe+Mg ratios in both sericite

and chlorite decrease up stratigraphy except for sample S09 which has a low

FelFe+Mg ratio. Albite was detected by X-ray diffraction in a sample of fuie

grained massive rhyolite (sample SI0 Fig. 7, Table 5). This was determined not to

in Cu ore.

Photo 2: Strong proximal footwall silicification and chlorite alteration

51-85 XC.

Photo 3: Reddish brown sphalerite staining and strong silicification.

Photo 4: Pervasive silicification and weak sericite aiteration associated with low temperature

aiteration underlying the orebody. 47 HW Dr Dr.

Photo 7: Weak to moderate silicification and sericite alteration.

be a late metamorphic albite overprint by contour diagrams yielding spatial

relationships to a primary lithological signature. This rhyolite may have been

subjected to silicification that did not destroy feldspar which corresponds to the

low temperature alteration observed by Huston et al. (1 995) and Koopman et al.

(in press). Subsequent contour diagrams outline the morphology of this alteration.

Table 5 gives the rnineralogy of three representative altered rhyolite samples

ranging from high temperature to low temperature alteration assemblages. Strongly

altered rhyolite units do not contain albite consistent with the strong sodium

depletion that accompanies chlorite and sericite alteration within the rhyolites.

Although the hangingwall alteration was interpreted by Koopman et al. (in press)

to be low temperature, it replaced feldspar with sericite and chlorite (Na20

depletion). and in this regard, is more typical of high-temperature chlorite and

sericite alteration.

Elevated tin (locally up to 3%), fluorine (>6ûû ppm), selenium (>IO00 ppm),

indium (>2W ppm), and bismuth (pl000 ppm) values in mineralized samples

could favour a magmatic component to the ore beruing fluids (metal values from

Hannington, et al., in press and unpublished Faiconbndge data).

RHY

LEGEND

O1 = C77 SOI = AHlB902 OQ=C77SCü=AH>B935 03=C77S03=AFOBBOl 04=CTIS04 = AFûû941 05=CTISû5=AF08444 06=CTIW=AH39936 07 = C77 SOT = A M oe=cnsœ=AFoesoe m=cnsoe=AiMesio 10 = c n sio = ~ ~ o e s o e

4 TALC-CARB

Figure 7: 5200 Level, geologically projected simple locations bom Richardson (1997). Smples gathered Gom the 4700 to 5600 levels and projected dong plunge to 5200 level.

Sample S I O S09 s01 S06 S07 505 S08

MR Sil MR Sil MR Chl RLST Chl RT Chi RLT Gabbro

Rk Type Sample

S I O MR S09 Sil MR SOI Sil MR S02 Ser RLT S06 Chl RLST 508 Gabbro

Average Chlorite Formula In Stratigraphic Order Bottom To Top

Note 1) decreasing FdFe+Mg ratio towards hangingwall in both sericite and chlorite 2) Fe:Mg ratios are different for chlorite and sericite in the same hand sample indicating tw minerals formed separately under differing chernical conditions or that Fe and Mg do not partition into sericite in the same way as chlorite 3) no signilicant incïease in Cu or Zn with closer proximity to orebody or up stratigraphy 4) Mn values for chlorite which are enough to account for al1 the Mn in the samples without the presence of a carbonate mineral 5) Si:Al ratio increases up stratigraphy

Table 4 Chlorite and sericite minaal formulae determineci by S.E.M. data. Magnesium enrichment in lam contaur diagrams is attributed io inaeased dilorite content.

MR Albite 32.0 Albite 21 Oistal Sericite 7.7 Muscovite (Sericite) 3' FW Calcite 2.0 Chlorite 2'

Low Temp Chlorite 1.2 Silicif ication Pyrite 0.7

Sample #

tr. Pyrite

~ o t a i 101.5 S09 Quartz 70.6 Quartz 80 Quartz, Chlorite,

CH-BX Sericite 16.5 Chlorite 15 tr. Chalcopyrite, FW Chlorite 16.2 Muscovite (Sericite) 3' tr. Sericite

High Temp Calci te 0.3 Silicification Total 103.6

I.C.P. Normative Minerals

& Chlorite S06 Quartz 61.2 Quartz 70 Quartz, Chlorite,

SI0 Quartz 57.9 Quartz 73 Quartz, Sericite

RLST Chlorite 21 -1 Chlorite 25 Sericite, tr. Py Proximal Sericite 14.6 Muscovite (Sericite) 3.5' tr. Calcite

HW Pyrite 2.2 Calcite tr. ' Calcite 1.5

Moderate to Rutile 0.2 Low Temp Apatite O. 1

Abund (5%)

Strona Sil

Strong Sil Wk Chl

Strong Chl WC< Ser Wk Sil

XRD Detected Minerals (Detection Limit r 5%)

1 ~lteration Total 1 00.9 1 RT = Rhyolite TL# Chl = ChIotitiration HW = Hangingwall RLT = Rhyolite Lapilli Tuff Ser = Seticitization FW = Footwall RLST = Rhyolite LapiIli Stone Sil = Silicif ication MR = Massive Rhyolite CH-BX = Silicified Massive Rhyolite Am3 = Strongly CarbonatizdChloritized(Sericitized Gabbro ND2 = Moderately Altered Gabbro ' Minerat abundances detected in quantities less than 5% with XRD methods were guessed by measuring very maIl anomalies

Table 5: Examples of thrce alteration assemblages in rhyolile. X-Ray diffraction (XRD) valus and X-Ray fluoresance (XRF) normative mineral oilculaiions $i

Abund (O/ ) Minerals Seen Visually Visual Alt

None of the above studies have documented alteration within rock types other than

rhyolite except that of Schandl(1989), and Schandl and Wicks (1993) who

documented dteration in the uliramafk units. Visual observations from mapping

and drill core are effective at detecting silicification. sericitization. and

chloritization in Kidd Creek rocks. However it is difficult to compare the degree of

alteration between samples from different rock types and this results in uncertainty

regarding the proximity of sarnples to the ore zone or paieo-fluid conduits. For

example, how does the dteration within a rhyolite compare to the alteration in an

ultrarnafic rock when both alteration types were produced by the sarne fluid? The

two rocks will look different even though they have been affected by the sarne

alteration event.

Rivenn and Hodgson (1980) show that as alteration at the Millenbach VMS

deposit progressed, the chemistry of both felsic and mafic rocks converged to a

sirnilar chernical composition in equilibrium with the alteration fluid. However if

alteration stops before both rock types are converted to sirnilar compositions, then

techniques such as data norrnalization and mass change must be used to determine

the relative degree of alteration between samples in a geochemical database of

varying rock types.

Summary of Geochemicai Changes Related To Alteration Mineralogy

In order to assess the changes in major element chemistry associated with

alteration it is perhaps advisable to examine what geochemical variations would be

expected of chlorite and sericite alteration as well as silicification. Understanding

these variations, and their mineralogical expressions. will help to interpret the

geochemical variations described in the following sections.

Silicification adds Si02 to the rock while diluting other elements. Sencitization

adds K ( e ~ c h i n g whole rock K20) and breaks down feldspar thus depleting Na20

and Cao. Rather than adding externally derived K20 to a rock mass, the

hydrolysis of primary K-feldspar (partially mobilizing K 2 0 ) within the rhyolite

itself could also be a source of KzO for sericite. Trace to significant amounts of Zn

may also be added to the rock during sericitzation. Chloritization breaks down

sericite and any remaining feldspar resulting in a depletion of KzO, Na20, Ca0 and

enrichment of MgO. Fe203, MnO.

Mineralogicai reactions that illustrate geochemical variations attributable to Kidd

Creek (VMS) alteration are summarized in Table 6. It is these reactions and

chernical changes that were used to interpret aiteration types outlined by

geochemical contour diagrams produced below.

Low temperature Silicification (addition of SiO? to rock)

SiOl (aq) ¢3 SiOt quartz

other oxides are diluted

Serici tization (albite @ sericite)

3NaAlSi308 + K+(aq) +2H'(aq) Q KA13Si30t~(OH)t + 3Na+(aq) +6Si02 albite adds K sericite quartz

KtO is ennched and Na@ and Ca0 (desmction of Na & Ca plag) are depleted

Chloritization (sericite @ chlorite)

3 KA13Sis0 o(OH)2 + 2 ~ ~ ' + ( a ~ ) 2 ~ e ' + ( a ~ ) + 32H20 sericite adds Mg adds Fe

@ 2MgFeAi2Si30 c hlorite

MgO, Fe2@ are e ~ c h e d

@H)s + 3Si(OH)a + 5AI(OH)i + 3K+(aq) + 22H+(aq) removes K

and K'O is depleted

Table 6: Summary of wxhemical changes durine. hvdrothermai aiteration.

WHOLE ROCK SAMPLE DATA BASE

in most exploration programs. whole rock geochemistry is considered to be just

one of the many tools for determining alteration trends (or rock identification) and

rnay not be considered a high priority compared with well established exploration

methods such as geophysical surveys. As such, whole rock samples may be

gathered haphazardly from surface andor drill core and sarnple distribution

patterns are not ideaily spaced for contouring. Analytical error can further

complicate the picture. The question arises. is it worth contouring irregularly

distributed lithogeochernicd samples?

Analytical Techniques

Whole rock samples from Kidd Creek used in this study have been gathered from

the 1970's to the present day. Smples were analyzed at X-Ray Assay

Laboratories (X-Ral, Don Mills, ON) and TSUAssayers Laboratories

(Mississauga. ON). Xral used X-ray fluorescence and TSL laboratones used

I.C. A. P analyticd techniques.

Analytical Error

Seven I.C.A.P. analyses of the Kamiskotia RhyoIite Standard by TSL laboratories

cornpleted from 1993 to 1996 are given in Table 7. The amount of variance in the

numbers for these sarnples provides an approximation of the arnount of error in the

numbers. Variability between samples is due to lab error (e.g. SiOz varies from

Pulps of seven samples mn at XRAL's facilities in the 1980s were reanaiyzed at

Laurentian University's Central Analytical Facility using XRF. Graphical

cornparison charts are given in Figure 8. The slope of a set of assays which have

the same result should be 1. The closer the sample points lie to a line with a slope

of 1 the better. The correlation between results from the two labs is very good. A

table listing Laurentian and XRAL values can be found in the Appendix.

Table 7: Kamiskotia rhyclite standard whole rock results, 1994- 1996 TSL Laboratories. Majors expressed in wt.% and traces in ppm.

0.24

0.23

Y 122 120 120

120 120 122

120

KR-#@

KR-AP I

Hole

KR-AP KR-AP KR-AP KR-AP KR-AP KR-AP KR-AP

p ~ ~ 0 8 7 ? 1 p

AF08172

Sampleü AF08116

AF08140 AF08781 AF 09307

AF08085 AF08771

AF08172

74.01

73.46

Rb c0.05

~ 0 . 0 5

c0.05 , c0.05 c0.05 <0.05

~ 0 . 0 5

0.55

0.56

Zr 290

290 294

294 290

292 292

-G.80 11.12

Sr

20 20

20

20

20

20

1.21 1.27

6.94

6.96

0.24

0.24

C u Z n N i 90

.90 90 95

85 90

95

35 30 35

35 30

35

30

2.88

2.95

6û

6û

6û

60

55 55

55

0.04

0.06 0.03 0.03

F cl00

cl00 cl00 cl00 cl00 cl00

cl00

Nb 1 Ba cl0

cl0 cl0

cl0

10 C I O

<IO

0.05 0.05

740

740 710

740 720 710

730

1.1 1 t.19

98.13 98.07

Si02 XRAL vs Si02 L.U.

55

45

XRAL Si02

1 35 40 45 50

Laurentian Si02

XRAL vs L.U. Na20

XRAL Ti02 vs L.U. Ti02

O. 6 1 1.4 1.8

L.U. Ti02

Zr XRAL Vs L.U.

O 50 1 O0 LU. Zr

Figure 8: Error of XRAL samples run between 1980-1990 vs. Laurentian X-Ray fluorescence check of o u l ~ s run in 1998.

Whole rock values were entered into a database format (dbf) by Falconbridge staff

and TSL laboratory staff. It is possible that human error may have introduced a

few errors into the database during data entry. For this study. data was converted

from dbf format and manipulated in a Microsoft Excel format (xls).

33

It should be noted that in most cases large distinct alteration pattems would show

up regardless of the above sample variance.

Content of Whole Rock Sample Database

Rhyolites comprise only 20% (by volume) of the rocks siirrounding the mine

(Bleeker, 1994) whereas the whole rock database contains 63% rhyolites (Table

8). Samples of sedimentary rocks and serni massive sulphides were avoided for

geochemical contouring purposes. A total of three thousand nine hundred and

ninety two samples were used for this study.

ROCK TYPES USED FOR CONTOURING

MAFICS (Basalt & Gabbro) RHYOLITES ULTRAMAFIC ROCKS SEDIMENTARY ROCKS INTERMEDIATES AND LATE DYKES

TOTAL

# OF PERCENT OF SAMPLES CONTOURED

DATABASE 1276 32 251 1 63 205 5

O O O O

VOLUME W ITHIN

REGION (%)* 60 20 10 5 4

Table 8: Breakdown of whole rock samples used for contouring purposes. *Approximate volume of region considered is within 1 .S kilometres of the orebody.

Sampling Patterns

Whole rock sarnpling pattems at Kidd are concentrated in areas of interest such as

around the orebody, and dong rhyolite stratigraphy. Small to medium sized

sampling gaps of 100-300m exist within some rhyolite uni ts and very large >lkm

gaps exist within the mafics. Sample distribution for this study may not be ideal

but it does represent the redity of exploration. It would be prohibitively expensive

(not to mention bad methodology) for most exploration prograrns to have drill

holes targeted for gathering a smple database on a regularly spaced grid rather

than practical geological purposes. Figure 9 illustrates the irregular distribution of

whole rock sarnples on the 2800 level.

Oxide and element distribution examined in detail are as follows

SiOz Na20 W J LOI Ni A l 2 0 3 K20 Cu F CO Fe203 Ti02 M n 0 Y Ba Ca0 M g 0 Zn Zr

Some trace elements were not included in al1 sarnples (e.g. F, Co, Ni) and F-test

values from discriminant analysis were not calculated for these elements

(Table 9).

GWKE

m Orn 2 Som I I I I

X U ltramafic A M afic n ~ h y o l i t e

Figure 9: Rock type and sample distribution on 2800 level. base geology outline Born Falconbridge data and Husion et al. (1995)

PROCEDURES FOR IDENTIFYING ALTERATION TRENDS WITHIN VARIABLE ROCK TYPES

To obtain the complete regional geochemical alteration pattern associated with

Kidd Creek. sarnplcs from every rock type must be considered. This section will

discuss some of the problems associated with assessing the degree of alteration

between whole rock sarnples of different rock types. Techniques to solve these

problems are then presented.

Contouring Methods

Contouring geochemicd data can be done by hand or using a computer. Hand

contouring data is usually the best method as contour lines can be drawn taking

into consideration stratigraphy or structure. Figure 10 is a diagram of hand

contoured percent rnass change Mg0 values on the 2800 level. Geological contacts

are taken into consideration with hand contoured diagrams and contours are not

drawn where data is not available. Conversely computers do not take into account

stratigraphy or structure and draw contours within a specified area whether there is

enough data or not (Fig 11). Although computers do not have stratigraphic and

structural knowledge, they do provide unbiased contours in a relatively short

penod of tirne. Unbiased contours provide additional interpretations. Two

computer contouring programs (surfer, and siteview) were used for this study.

PERCENT MASS - CHANGE Mg0

Mg0 Enrichment Above 50% Mass

1 GWKE Change MgCl

1 -

Om 25ûm 5ûûm i I 1 I , A

Figure 10: Hand contoured a m of M g 0 enrichment on 2800 level. Al1 rock types contoured. Contours are drriwn witli geologicril contacts triken into consideration and are not

drawn in weas without data points.

Selection criteria for these programs were: 1) Windows compatible on PC

platform; 2) relatively inexpensive price 3) easy to use; 4) able to create

representative contour diagrams 5) irnportlexport DXF and raster files (e.g.

postscript or BMP); and 6) 3D contouring and graphics ability if possible.

Surfer Software: The only category that surfer did not meet was the 3D contouring

but its performance in the other categories was outstanding. It was very easy to use

Figure I l : Cornputer contoured data (surfer) of 2800 level mass change Fe2O3(T). Note contours in areas w i h no srunples.

and concise diagrarns were created with a minimum amount of effort. 2D plan

rnaps were created by contouring sarnples projected plus or minus O to 200 metres

elevation onto the level. Surfer can be set to contour using a number of different

contouring methods. For irregularly spaced Kidd Data, the inverse distance

squared contouring method seemed to be not only the simplest, but also the most

representiitive of al1 contouring options. Figure 11 is a diagra.cn created with surfer.

Siteview Sofnuare: Siteview met 5 of the 6 required categones with the exception

being that, although it was able to import 2D and 3D DM: files. siteview DXF

files could not be exported. It's postscript output was also faûly crude. Sitview

contours in 3D and can constnict plan. cross section. and long section contour

diagrams. Siteview uses the inverse distance to a power equationl to contour data

with x,y,z coordinates.

Inverse Distance Tu A Power Equation

wi = constant / (d i~ tance)~

wi = weight of measured value constant = 1 (based on normalization of sums of weights to be 1.0) k = arbitrary power (assigned as 70 in my diagrams) distance = 3D distance between data points

Figures 34 and 35 were created with siteview. Contour maps produced by both

prograrns were very similar.

Raw Mole Rock Data

For some elements iike zinc, the orebody is seen as a distinct anomaly when raw

zinc values are contoured (Fig. 12). Median zinc values for both rhyolites and

Figure 12: 2800 levcl raw Zn values (ppm) show distinct anornaiy over orebody. Al1 rock types

mafic rocks at Kidd Creek are between 50 and 120 ppm. Contouring of raw zinc

data is effective because anomalous values can be well over 600 ppm or 6 times

larger than median values in rhyolite, mafïc, and ultramafic rocks. What happens

when anomalous elevated values of an element or oxide in rhyolites are below

median values of that element or oxide for mafic rocks? Total iron is an example

of this. Kidd Creek rhyolites have a median of 3.23% total iron (expressed as

Fe203) whereas mafic rocks ai Kidd Creek have a median of approxirnately 12%

Fez03. If the Kidd Creek whole rock database is contoured with respect to Fe2O3,

contours reflect lithology rather than an alteration anomaly surrounding the

orebody (Fig. 13). This example illustrates that raw data does not always detect

alteration in a geochemical database containing 3 distinct rock types. Other

techniques must be employed to "see through" the effects of lithology.

Population Separation

Prîor to using any technique to determine alteration within heterolithic rock types.

samples must be separated into populations based on lithology. Populations were

first separated based on visud identification. Secondly, a geochemical population

separation based on an immobile element (or elements) is undertaken. Zirconium

was selected as the immobile element by Koopman et al. (in press) and Muirhead

and Hutchinson (in press) as titanium was shown to be mobile under extreme

silicification. Despite being slightly mobile titanium was used in this study

because it was anaiyzed in al1 samples. whereas Zr was not available for al1

samples (300 samples in the Kidd Creek whole rock database were not analyzed

for Zr). in addition, titanium is a common element (actually an oxide but referred

to as an element in this section) in major element whole rock packages offered by

geochemical laboratories and may have a greater level of accuracy due to its

higher abundance. Titanium has been used as an immobile element for alteration

calculations in other VMS camps. Yttrium was not used as an immobile element

because it may be subject to incomplete digestion using 1.C.P analytical methods.

Figure 13: 2800 level contoured raw Fe203(T) data. Contours show lithology rather than the orebody.

A diagram of Ti02 vs. Zr for the database illustrated that in most cases TiOî is

immobile and clear dilution lines are drawn for rhyolite and mafic populations

(Fig. 14). A dilution line on a binary diagram passes through the origin and

indicates a constant ratio between two immobile elements (in this study TiOl and

Zr). T i 0 vs. Y was also plotted (as a check on the dilution lines) and two distinct

dilution lines were also visible. The chance of Ti02, Y, and Zr being added or

subtracted from the rock in the exact same ratio producing false dilution lines is

Figure 14: Ti02 (wt. %) vs. Zr (ppm) for 3692 unnormalized amples. Note dilution lines.

very unlikely.

Histograms and probability plots of the Ti02 content for every population were

constructed. Figure 15 shows a Ti02 histograrn for the mine rhyolites. Only one

population is visible. Figure 16 is a TiOz histogram of al1 the mafxc samples and

three sepante populations are visible. Mdic rocks were separated into groups M l ,

M2, and M3 on the basis of their TiOz content. It was important to separate the

mafic rocks into three populations as each has a slightly different chernistry that

could influence the results of normalization techniques described below. Zr was

also tried as a separator and the 3 populations were also detected but Zr did not

separate them as distinctiy as did Ti03

Figure 15: Ti02 Histogram and probability plot for mine rhyoliie population. only one population is visible. Ti02 expressed in wt.% (Ti02 chia is normdized to a LOI free basis)

Figure 16: TiOz histogram and probability plot of maf~c rocks. noie 3 populations. Ti02 expressed in wt.% (TiOz data is nomalized to LOI free basis)

Before population separation was undertaken. al1 major oxides were nomalized to

an LOI free basis. Trace elements were not nomalized LOI free. Any graphs

cornparhg majors and traces (e.g. Ti02 vs. Zr) were drawn using unnormalized

data. Contouring using mass balance and data normalization techniques was based

on 3 populations for mafic rocks and one population for both felsic and Ultrarnafic

rocks.

Data Normaüzation Technique

Byron and Whitehead (1993) used the technique of data normalization to contour

anomalous values in a geochemicd database of variable lithology from the

Whiskey Lake Greenstone Belt. Whole rock data is normalired by dividing an

element's abundance by its median abundance for that lithological population.

(median values for each lithological population are given in the Appendix). For

example, Si02 in unaltered mine rhyolite has a rnedian value of 78.13 wt.% at

Kidd Creek. If a whole rock smple of a mine rhyolite returns a value of 82 wt.%

SiO?, then the normalization calculation is as follows:

wt. 96 Si02 in whole rock sample = 82% median wt.% SiOl for rhyolite population = 78.13%

wt% sample -1= 82wt%Si02 Normalized Value = - 1 = 0.05

wtQ median for population 78,13wt%Si02

Negative 1 is added to the formula for convenience so that a value of O represents

no change with respect to the unaltered value. A value of less than O reflects

depletion, and a value greater than O reflects enrichment with respect to median

values. Hence 0.05 represents an enrichment of Si02 by 5% of the median. Steps

for using the data normalization technique are surnmarized as follows:

1) Normalize geochernical database to LOI free basis. 2) Separate data into populations based on visual lithology observations 3) Use geoc hemical methods to further subdivide populations if necessary (e.g .

Ti02 histograms/probability plots) 4) Determine the median values of each element/oxide for each population

5) Calculate normalized values for each sample by the equation

wt% element in somple NormalizedValrie = - 1

wt% median for element in population

6) Contour normalized values.

Least altered precursor values could be used instead of median values for the

populations. However using median values provides a result independent from

least aitered precursor values. Data normalization cm be used as a cornparison for

the mass balance method which is based on a least altered precursor.

Byron and Whitehead ( 1993) determined threshold values (numerical boundaries

for the determination of whether elements are anomalous) for elements within each

rock type. Probability plots and histograms were used for the determination of

threshold values. If an element had an abundance above (or below for depleted

elements) its threshold value it was anomaious. Conversely if the element was

below (or above for depleted elements) its threshold value it was not anomalous.

For the Kidd Creek geochemical database, threshold values can be determined

from contour diagrarns. Threshold values are determined by the value at which

point the contour anomaly around the orebody is anomalous with respect to the

region. Contoured normalized Fe203(T) data in Figure 17 shows a distinct

anomaly over the orebody for which 0.5 (50% enrichment from median FezOp

values) is the threshold value.

Figure 17: 2800 Ievel, normalized FelO,(T). Al1 rock types are included and samples are projected between 2400 and 3200 levels (2630-2320 elev.). FQO, is enriched over the orebody. sulphides may

riccount for some Fe203 enrichment but the rnajority is attributed io chlorite alteration substantiated by XRD and S.E.M. work (Richardson, 1997; Koopman et al., in press).

Mass Change

Mass change lithogeochemical techniques developed by Gresens (1967) and

promoted by MacLean and Barrett (1993) involve the assumption that certain

elements (and oxides) in a rock may not be mobilized during hydrothermal

alteration. It is a simple technique for determining which elements are mobile

(removed or enriched as opposed to conserved) during hydrothermal alteration.

Mass balance calculations utilize least altered precursor values and immobile

elements. TiOz, selected as an immobile element for population separation

analysis, was also used as an immobile element for the mass balance calculations.

Mass change was caiculated using the equation from MacLean and Bmett (1993):

RC = reconstituted composition RC = immobile component,,,,,/ immobile cûmponentalfered * % mobile

componentarted

Absolute mass change is calculated as Mass Change = RC - element's abundance in precursor composition

Figure 18 visually demonstrates this equation and mass change Fe203 values are

contoured in Figure 11 above.

A normalization calculation was added in order to take into consideration differing

initial elemcntal abundances between lithologies. This normalization step was also

used for mass change data by Koopmm et al. (in press).

Percent Mass Change = Mass Change / Element 's Abundance In Precursor Composition

Normalization of mass change values was done because a 0.35% loss of sodium in

a rhyolite with a precursor composition of 2.4% sodium is not as significant as a

0.35% loss of sodium within an ultramafic unit with an initial composition of 0.4%

sodium. Percent mass change Fez03 data is contoured in Figure 19.

Reconstructed composition

Analysis of Analysis of unallered rock altered rock

Mobile components 0 \

Figure 18: Illusiration of mass change calculations for an altered rock sample, based on 100 units of precursor. Tbe amounts of immobile elements in the chernical analysis of the altered rock appear to have deaeased, but simply have been diluted by added mobile m a s . Since the immobile elernents have n a lost mas , they must be restored to their initial content, with the mer components restored by the same factor.

This produces Lhe recmsîructed composition (R.C.) Mass change for each component is the difference between RC. and the precursor composition. (Fmn MacLean aod Barret, 1993)

Figure

Percent M a s s Change F e 2 0 3

19: 2800 IeveI percent mas change Fe203. Al1 rock types. Later diagrarns will demonstrate tha lower Fez03 enrichment pattern is not just an artifsict of the original uluamafic rock composition

Discrimina t Analysis

Discriminant Analysis is a statistical technique applied to Kidd Creek whole rock

sarnples in order to find the best oxides and elements that determine the degree of

primary alteration a rock sample has been subjected to. In this study, discriminant

anaiysis compared a subset of three user defined populations and divided the

geochemical database into three separate populations by computing the probability

of each sample of being in one of the three groups. Three groups were selected

because three alteration types have been outlined at Kidd Creek. Calculations were

completed by a statistical computer p r o g m called Systat.

User defined populations consisted of samples that were thought io represent

unaltered (low chlorite, sericite), moderately altered (moderate silicification andor

serici te), and strongly altered populations (strong chloritization). Raw Na20 values

were the main criteria for dividing sarnples into alteration groups. By using NazO

to separate the three user defined populations (teaching set). the probability of a

sample being altered may be biased towards the Na20 content of samples.

However sodium best defines the three populations and it was deemed not to be

significant that that the discriminant analysis calculation was biased towards

Na20.

Strongly c hloritized samples characterized by feldspar destruction had NazO

values below 0.5 %, moderately altered 0.7- 1.5%, and unaltered samples above 2%

Na?O. Representative samples were selected without consideration of their

proximity to ore. The location, rock type. and values (normalized LOI free) for 98

representative samples that defined the three populations are given in the

Appendix dong with a brief description of Discriminant Analysis.

F-test values were produced for each oxide and element during discriminant

analysis. Formulae and assumptions for caiculating the F-test can be found in

Davis (1 986). F-test values were used to determine the effectiveness of each

oxide/element and technique in determining the degree of alteration of a sarnple.

Raw. percent mass change, and normalized data using SiO2,Al2O3,CaO,Mg0.

Na20,K20,Fe2O3,MnO,Cu,Zn were compared in order to determine which

technique and oxides or elements best defined the degree of alteration of a sample.

In the Fust run of discriminant analysis, al1 oxides and elements were used to

define the degree of alteration of a sample. Figure 20 is a contour diagram of the

probability of sarnples being in the strongly altered population using al1 oxides and

elements for discriminant analysis. A large anomaly is visible over the orebody.

Probability Of Sample Being Strongly

Altered

igure 20: Contour diagram of probability of sarnples bcing strcngly altered using al1 major oxides techniques with raw Cu and Zn to define the discriminant iùnction. Samples from al1 rock types

and 1.

A more distinctive anornaly was created by only using oxides and elements with

high F-test values. F values were higher for Na20,FezOp.Mg0,Ca0,Cu, Zn than

Si02,Ai203.K20.Mn0 (depending on what technique was used (Table 9)) making

them potentially the best oxides and elements to use for defining alteration.

Depleted oxides Ca0 and Na10 (chlorite alteration) had the highest F-test values

when normalized data was used. F values for Fe203 and Mg0 were highest using

the percent mass change technique. It is significant to note that these are the same

oxides that are mobile dunng chlorite and sencite alteration.

Copper and zinc (canied by ore forming fluids) had sirnilar F-values for raw data

and percent mass change data. Figure 21 was constructed by contounng the

probability of a sarnple being strongly altered based on normalized data and

percent mass change data for the oxides Ca0,Na20. MgO, FeiOs and raw Zn,Cu.

Contours of the probability of a sarnple being strongly dtered by percent mass

change data were very similar to the contours of probabilities based on normalized

data. Both appear to have effectively targeted the Kidd orebody (Fig. 21) and both

provide sharper anomalies and (potential) alteration conduits than discrimination

based on al1 oxides and elements. Discrimination based on percent mass change

was slightly more restrictive on the number of strongly altered samples (19% of

2800 database) than discrimination based on normalized data (22.7% of 2800

Robabilities detemiined by discriminant aaalysis of nomalized data.

6eing.strongly Altered

Probablllty 01 Sarnple Belng Slrongb

Altered

Probabili ties determined by discriminant anal ysis of mas change data. Three distinct alteration trends leading to the orebody are evident. Note relatively unaltered core in the footwall.

Figure 2 1: 2800 level contour plot of probability of sample being suongly altered from discriminant anaiysis based on percent mass change MgO, Cao, Na20, F& and raw Cu, Zn (top), and data

normalized values for MgO, Cao, Na20, FeO, and raw Cu, Zn (bottom).

database). Normalized data had a slightly larger anomaly and defined stronger

hangingwall alteration than did percent mass change data.

As a test, the probability of a sample being included in the medium altered

category was contoured (Fig. 22). An irregular ring shaped anomaly of moderately

altered samples cm be seen surrounding the orebody in Figure 22. This pattern

resembles the distribution of percent mass change K20 outlined in Figure 30.

Prabablllty 01 Sample Being Moderately

Altered

Figure 22: Probability of a sample king moderately aitered from discriminant analysis based on percent mass change MgO, Cao, NazO, F e 0 3 and raw Cu, Zn, 2800 level. Al1 rock types.

A ratio using percent mass change (%mc) data (%mcFet03 + %mcMgO + %mcCu

+ %mc Zn)/(%mcNazO + %mcCaO) was set up to approxirnate the probability

contour diagram produced by discriminant analysis (Fig. 23). The orebody was

distinguished but potential feeder zones were defined with reasonable success.

Figure 23: 2800 level contoured ratio (%mcFe2Q3 + %mcMgO + %mcCu + %mc Zn) / (%mcNa20 + %mcCaO). Al1 rock types. The ratio effectively ootlined the orebody and

moderately deftned zones of chlorite aiteration Ieading to the orebody.

Coinparison of Techniques And Elements

Which oxides, elements, and lithogeochernical technique best define a Kidd Creek

type orebody? 1s raw data sufficient or are mass change and data nomalization

calculations required? Are there regional and proximal pathfinder elernents? Table

9 addresses these questions.

Contour diagrarns of the oxides and elements listed in Table 9 were made for raw

data, normalized data, and mass change data. A rating of no, poor, good. and

excellent was given for each oxide, element, and technique based on visual

inspection of resulting anomalies. If the oxide (or element) and technique

produced a strong distinctive anomdy over the orebody a rating of E or excellent

was given. Conversely if the technique did not produce any anomaly over the

orebody a rating of No was given. For example, a contour diagram of percent mass

change A1203 (Fig. 24) did not locate the orebody whereas percent mass change

Fez03 (Fig. 19) reiated to sulphide and chlorite alteration did locate the orebody.

Visual inspection can be subjective so in order to have a relatively unbiased

opinion, the F-test results from discriminant anaiysis are given. The higher the F-

test the better the oxide and technique are as pathfinders. Table 9 includes a

column indicating whether elements are depleted (e.g. NazO, Fig. 25) or enriched

(e.g. Cu, Fig. 26) near the orebody. In summary. percent mass change MgO, Na20,

Element Raw Data Normalized Oata Percent Mass Change Distance FWI

Anom. Visual F-test Anom. Anom

b -20% a 100% a1 00% a1 50% a100% b -40%

a 200% a 50%

a 100%

al 50%

distal HW distal FW

mod distal FW mod distal HW proximal FW

mod distal FWI HW

distal only Donut distal HW

proximal FW

proximal FW proximal FW

I

E = excellent indicator Visual = good indicator based on visual inspection of contour diagram M = moderate indicator F-test = F-test value for element in discriminant analysis P = poor indicator (higher the F-value the better the element indicates alteration) N = not an indicator FW = preferentially anomalous in the footwall HW = preferentially anomalous in the hangingwall proximal = anomalous close to orebody distal = anomalous at distances far away from the orebody Anom. = limit at which the element is anomalous, a = above limit element is anomalous

b = below limit element is anomalous

Cao, Fe203, and raw Cu and Zn are the best oxides elements and techniques to use

for defining chlorite alteration. F and Co defined alteration very well but because

they were not analyzed in al1 samples. they were not included in the discriminant

func tion.

Figure 24: 2800 level percent mass change IU203. Al1 rock types. This oxide is considered to be relatively inunobite during primary alteration as it does not provide a distinct anomaly over or feeder zone

Mass A 120 3

I to the orebody.

Figure 25: 2800 level percent mass change Na20

Figure 26: 2800 level percent m a s change Cu (ppm)

APPLICATION OF LITHOGEOCHEMICAL TECHNIQUES TO KIDD CREEK GENETIC MODELS

The identification of areas around the Kidd Creek orebody that have been enriched

or depleted in oxides considered to be mobile during alteration may outline

potential conduits or feeder zones used by ore forming fluids. Genetic models can

then be constructed and evaiuated.

Morphology And Size Of Alteration Zones

A distinct alteration trend was recognized from percent mass change Mg0 and

norrnaiized Si@ diagrams on the 2800 level. An area of SiO? enrichment in the

footwall of the orebody (Fig. 27) is surrounded by an area of M g 0 e ~ c h m e n t

(Fig. 28 & Fig. 3 1).

Koopman et al. (in press) outlined a sirnilar pattern in their study of the Kidd

Creek rhyolites (Fig. 6). Their contour diagram of the distribution of chlorite

within rhyolites demonstrates that chlorite enrichment (Fig. 29) directly

corresponds with M g 0 enrichment (Fig. 28) dong the "B" Fault East-West shear

zone extension (Fig. 4). XRD, I.C.P., and S.E.M. data from Richardson (1997)

ako link Mg0 enrichment with chlorite alteration.

Figure 27: 2800 level nonnalized SiO2. Al1 rock types. Note silicitied zone under orebody.

Figure 28: 2800 level percent m a s change MgO. Al1 rock types. Note possible M g 0 enriched feeder zones and Mg0 depletion within silicified zone.

lp O 1T 2p

Chlorite Peak lntensity (Whole Rock XRD) m

Seficite Peak lntensity m o l e Rock A) f Figure 29: XRD determined chlorite and sericite abundances on 2800 level kom Kooprnan et al. (in

Contours of sericite abundance in Figure 29 match contours of percent mass

change K20 in Figure 30. Enrichment of K20 values are the direct result of an

increase in sericite content. K20 is e ~ c h e d in the region around the orebody but

replacement of sericite by chlorite (as described by Riveren and Hodgson. 1980)

during a later aiteration event rnay have depleted K 2 0 values in the vicinity of and

within the orebody.

1 Figure 30: 28W level percent mass change K20 Al1 rmk types. KIO is enricbed arovnd the orebody but the re~lacement of sericite bv chlorite de~leted KîO values over the orebodv.

Na20 depletion has a sirnilar rnorphology to Mg0 enrichment but it also

corresponds with areas of K20 enrichment (Figs. 3 Ic & d). Sodium depletion is

interpreted to be the result of the formation of chlorite and to a lesser extent

sericite at the expense of feldspar. Least altered rhyolites at Kidd Creek have a

very low Na20 precursor composition of 2.24%. It is reasonable to assume that to

a certain extent, most rhyolites in the Kidd stratigraphy have been depleted of

Na20 and the contour diagram of percent mass change sodium shows only the

strongest Na20 depletion zones. An early pwasive low temperature alteration

event may be responsible for moderately low regional Na20 values.

Fe203 and Cu are sirnilar to Mg0 (chlorite alteration) in their distribution and

collectively are interpreted to define zones of discordant dteration that define up-

flow zones below Kidd Creek (Figs. 19 & 26). The presence of elevated Cu values

having the sarne distribution as M g 0 enrichment in the ultrarnafics supports the

interpretation that the M g 0 conduit defines a primary alteration signature within

the ultramafics. It is difficult to e ~ c h ultramafics in Cu without dteration by Cu

bearing fluids.

Normalized Si02 was used to define silicification because titanium may be mobile

d u h g extreme silicification events (Koopman et al., in press) and because it's F-

value was higher in discriminant analysis. Normalized M g 0 and percent mass

change Mg0 contour diagrams show very similar patterns. Normalized diagrams

are derived separately from the least altered precursors from Barrie et al. (1997) so

the possibility of an anomalous least altered ultramafk sample biasing percent

mass change M g 0 values is discounted. Discriminant analysis plots of percent

mass change NazO, Cao, MgO, Fez03 with raw Zn and Cu also indicate a strong

alteration zone sunounding the Si02 enriched core.

Figures 3 1 to 33 are geochemical alteration summary plots for the 2800. 4700, and

6800 levels. Contour diagrams of data from the 4700 level show the same mutually

exclusive relationship between high temperature chlorite alteration that added

M g 0 and Fe20s while removing NazO and low temperature silicification that

enriched SiO? (Fig 33). This relationship was demonstrated on 5 levels (only 3

shown in thesis) from 1200 to 6800 feet below surface and in vertical section

diagrams (Figs. 34 & 35). A southem zone of M g 0 (chlorite) e ~ c h m e n t is

present on 2800 level (Fig. 3 1) but is not evident on 4700 level (Fig. 32). Reasons

for the absence of the southem conduit at this elevation could be that; 1) there may

not be enough samples on 4700 level; 2) the greywacke unit pinches out southern

stratigraphy; or 3) the southem chlorite enriched conduit did not extend below

what is now the 3000 level. Chlorite enrichment is associated with a massive

sulphide lem ("Greywacke Lens") near the greywacke contact on 6800 level (Fig.

33).

Finure 3 1 a: 2800 level neolom.

Northm Mg0 Enrichment Zone

-"i= /' ,. /' , ,

Southern Mg0 Enrichment Zone

Figure 3 1 b: 2800 level hand contour4 percent mass change M g 0 (>50%) and nomalized SiO, enrichment. Ail rock types. M g 0 is eievated around SiO, nch footwall rhyolites.

Ore related M g 0 bearing fluids flowed around impermeable silicified rhyolite and chloritized surrounding footwail ultramafic rocks and rhyolites.

Figure 3 1 c: 2800 level hand contoured percent mass change FqO,(T) and K,O ennchment. All rock types. FqO,(T) follows the same path as M g 0 around the

impermeable SiO, rich zone. K,O is enriched in the lower portion of the silicified zone. FqO, enrichment corresponds to an increase in both chlorite

and su1 phide. KzO enrichment is associated with increased sericite.

Figure 3 16: 2800 level hand contoured NqO depletion and Cu enrichment. Al1 rock types. NaQ is depleted in areas of FqO, and Mg0 enrichment. Chioritization

destroyed feldspar thus depleting NqO. Some sericite alteration also depleted N4O. Cu enrichment has a similar pattern to Mg0 enrichment.

M g 0 enrichment extends from ultramafic (TC) rocks into the rhyoiites. This pattern f o n d when alteration fluids responsible for chlorite alteration flowed around the impermeable SiO, enriched fmtwal 1 .

Figure 32a: 4700 leve1 hand contoured Mg0 and SiOz enrichment al1 rock types.

Figure 32b: 4700 level hand contoured percent mass channe Na,O and Cu data. Al1 rock types

4700 LEVEL GEOLOGY Uhramafic = TC Gabbm = AI0

Qua- Porphm = 9P Greywacke = GWKE

Cu enrichment and NqO depletion follow the same pattern as Mg0 enrichment around the area of strong SiO, e ~ c h m e n t

Figure 33a: 6800 level elevated Cu. Rhvolite and m a f k samules onlv.

Cu >2% Oreoutme

Sc*

25ûm

6800 LEVEL GEOLOGY Ultrarnafic = 1 C

Quartz Parphyry = QP Gretywvacke = GWKE

Gabbro = A/D

Mg0 EMHCHMEM

SO, ENRICHMEM

OVERLAPRNG MW & 3'2, ENRlCHMEM MASSM SblRIIcE

Cu STRihiGER ORE ( ~ 2 % Cu)

Figure 33b: 6800 level hand contoud MgO and SiO, enrichment. Rhyolites and mafics. no ultramafic samples available. Mg0 enrichment is slightiy more discordant hence it

cuts through more footwall rhyolite than an 4700 level.

Mine Grid - - I

Plan view cross section perspective. The Massive Sulphide lens and geochemical

data from 2800 to 6800 levels were rotated into the vertical plane

of the cross section.

Figure 34a: Percent mass change Mg0 cross section. The hangingwail and footwall zones of magnesium e~chment are verticalIy continuous. Occasional indents in patterns may be the result of

irregularly distributed data. See inset for perspective summary.

Figure 34b: Normatized SiOz values in cross section. The zone of footwail SiOl enrichment extends dow stratigraphy.

6800 MS Cross Section Perspective

Figure 34c: Percent mas change Fe03 cross section from 2800 to 68ûû ievel. enrichment follows the massive sul~hide lens

down plunge.

Figure 34d: Percent mass change NatO cross section from 2800 to 6800 level. Na20 depletion follows the massive sulphide lens down plunge.

igure 35a: Percent mass change M g 0 long section. Mg0 is depleted in the footwall rhyolites "behind the massive sulphide. M g 0 is enriched on the 2 sides around the zone of Mg0 depletion. Zones of M g 0 enrichment correspond to the northern and southeni zones of Mg0 enrichment in Figure 3 1

and may represent conduits for ore related fluids. See inset for perspective sumrnary.

2800 Level Ore

Figure 35b: Normalized SiOz values in long section. SiOz is e ~ c h e d in the footwall of the orebody forming an impermeable barrier to later Mg0 nch fluids which were diverted

around the silicified rhyolite.

II.

-1 4

Figure 36 dernonstrates the continuity of Mg0 enrichment fiom ulaamafic units

into the rhyolite units. Zones of Mg0 e ~ ~ h m e n t are not artifacts of the onginai

ultramafic composition. The observed Mg0 enrichment patterns are evident

regardless of what rock type is shown. Normalized SiOÎ values also demonstrate

an enrichment pattern that is preserved in both rhyolite and ultrarnafic units (Fig.

37). Not only do alteration patterns cross rock type contacts, but when linked.

define potential cross-stratal conduits for hydrothennal fluids.

Distribution of oxides interpreted to be indicators of silicification. chlorite, and

sericite alteration lends support to the interpretation by Huston et al. (1995) of a

lower temperature (c2ûû°C) alteration event producing high 6018 values without

significant sodium depletion (although 2 to 3 5 NazO is depleted relative to

unaltered rhyolites in other environrnents). Lower temperature alteration was then

overprinted by a focused high temperature (>3ûû°C) chloritization producing

chloritized rocks with stringer chalcopyrite and lower 60'' values. Earlier

silicification could have created an impermeable barrier to later fluids responsible

for chlorite/sericite alteration which were restricted to structures that passed

through the ultramaf~c and into the overlying rhyolite. Since the buk of the ore

may have been deposited by fluids related to chlorite alteration, explorationists

should focus on areas of Mg0 enrichment.

enrichment D.00

depletion

Figure 36a: N o d i z e d Si02 contours with only ultrarnafic sarnple locations plotted. Samples are classed with symbols Pattern of enrichment is relevant with only ultrarnafic samples.

1 ( enrichment

:igure 37a: Percent mass change Mg0 contours with only ultramafic sample locations plotted. Samples are

Figure 3%: Percent mass change M g 0 contours with only rhyoiite sample locations plotted. Alteration trends affect both rock types

As a test, a randomly distributed pattern of 1% outcrop exposure was laid over a

1.5 km x 1.5 km contour diagram of the 2800 level and two outcrops coincided

with the zone of M g 0 enrichment (>50 percent mass change MgO). At 5%

outcrop, enough rock was exposed to outline the alteration pattern. Thus 1%

outcrop may provide clues that an orebody may be nearby and 5% outcrop should

be enough to indicate proximity to the orebody (if the orebody isn't already

exposed). Unfortunately chlontized rocks are more easily weathered than silicified

rocks and in the case of Kidd Creek, the ultramafic unit is very soft and is not

likely to be exposed on surface.

Twenty percent of samples show Mg0 enrichment greater than 100 percent mass

change on 2800 level. Approximately 1 sample out of 5 randomly gathered

samples will show significant Mg0 e ~ c h . . e n t within a 1 km radius around the

orebody. The number of samples used to outline the alteration zone on 2800 level

was reduced from 500 to 51 and the alteration zone dong the East-West shear

zone was still evident however the northern zone was not detected. Thus about

five randornly gathered samples must be gathered within lkrn from the orebody in

order to detect Mg0 enrichrnent (related to chlorite alteration) and 5 1 samples

moderately outlines the area of chlorite alteration.

Volcanological Considerations

Permeable volcaniclastic units may have provided a favourable medium for the

passage of hydrothemal fluids resulting in a serni-conformable alteration zone as

evident by the area of NazO depletion which follows permeable volcaniclastic

units within the hangingwall. It may be argued that these vûlcaniclastic units were

silicified first and later Na20 depleted during sericitekhlorite alteration but there is

no argument that the underlying silicified massive rhyolite units were not

permeable to fluids associated with chlorite alteration as zones of M g 0 enrichment

and Na@ depletion are not detected in the massive rhyolite units. High Si02

content (above normal values expected for high Si02 rhyolites) and high 6180

values led Huston et al. (1995) to speculate that this alteration was early and low

temperature. Subsequent hydrothermal discharge, responsible for MgO. Fe203, uid

K20 enrichment attributed to chlorite and sencite alteration was restricted to

structures that cross cut the rhyolite and ultramafic units and now, because of

folding. lie parallel-subparallel to the rhyolite/ultramafic contact.

The ultramafics were permeable as they show zones of silicification and zones of

MgO. Fez03 (chlorite) and Cu e ~ c h m e n t dong areas interpreted to be

synvolcanic structures as identified below (Figs. 38 & 39).

Structural Considerations

Ore forming fluids for VMS deposits may reach the seafloor traveling through

stratigraphy dong synvolcanic structures (Gibson. pers. comm.). These structures

or faults may be infilled with magma (creating a dyke) or may be reactivated later

in life. Gibson et al. (1997) list characteristics of both primary and secondary

structures in Table 10.

A number of faults cut through the Kidd Creek stratigraphy. Table 1 1 sumarizes

the characteristics of these structures.

Svnvolcanic Faults Presence of dikes or apophyses of synvolcanic intrusions Intensification of discordant hydrothemal alteration andor abrupt change in alteration type Abrupt change in thickness of pyroclastic volcaniclastic or sedimentary unit Offset of unit with subsequent units not offset

r Localized monolithic to heterolithic coarse breccia deposits

Post-Volcanic Hicih Anale Faults

Offsets of al1 stratigraphic units Abundance of brittle fractures and/or fault gouge (lost core) Intense, localized foliation or shearing Abundance of quartz-carbonate veins and breccias

Post-Volcanic Thrust Faults 0 Intense shearing of lithologic units (commonly accompanied with decrease in grain

si te) r Displacement of older stratigraphic units to positions up-section from younger

stratigraphic units Presence of late dykes

Table 10: Criteria to distinguish fault types associa~ed wilh VMS âeposiis (Gibson, 1997)

Faults that partially mcet the critena for synvolcanic faults are:

East- West Shear Zone: Huston et al. (1995) concluded that the Kidd Creek

orebody was fed by a synvolcanic structure represented by the now reactivated

East-West Shear zone. Certainly the East-West Shear was active long after the

deposition of the Kidd Creek orebody as is evident by the intense shearing and

displacement of the Central Orebody. Whether the East-West shear zone

represents an earlier synvolcanic fault zone cannot be answered by the following

observations but they do lend some evidence for the synvolcanic argument; 1) The

East-West shear zone is in the right spot for a potential feeder; 2) NazO, Fe203.

Cu. and Mg0 are anomaious dong the footwall portion of the East-West shear

zone (Fig. 3 1); 3) and although it is a pronounced stnicture it cannot be traced

below 3000 level (Fig. 5) which is also where the south orebody begins to

disappear. The East-West shear zone may be a reactivated synvolcanic fault that

was initiaily a conduit for hydrothemal fluids that fed the south orebody.

Structure Now Occupied By Massive Rhyolite: Footwall massive rhyolite units if

part of a dome-ridge complex as proposed by Prior (1996) could occupy former

feeder structures. This is supponed by the fact that the North orebody's Cu

stringer zone and the Cu rich South orebody both overly massive rhyolite units.

Ultramafic-Rhyolite Contact: As discussed above. fluids associated with chlorite

alteration could have traveled via a graben like synvolcanic structure along the

rhyolite/ultrarnafic contact. Alteration summary diagrams from the 2800 and 4700

levels (Figs. 3 1 & 32) indicate MgO, Cu, and Fe203 enrichment attributed to

chlorite alteration occur along a path through the talc-carb unit, along the

synvolcanic graben like fault, and into the rhyolite units. This may have been a

major conduit for hydrothenal discharge and formation of the massive sulphide

lenses.

FAULT, SHEAR OR FEATURE

Enechellon reverse S dipping faults

Gouge Fault

North Shear

East-W est Shear Zone

Weak to strong minor faults

Massive Rhyolites

U ltramaf ic 1 R hyolite Contact

LOCATION

Surface to below 68L

Surface to below 68L

Hangingwall from surface to 3000L

Surface to 2800L

2 units South and North

Surface to below 6800

CHARACTE RISTICS

Cut al1 st ratigraphic units, seismically active from mineout, intense shearing, sub parallel to schistosity

1 -1 Ocm of Fault Gouge, Associated Shearing, cuts al1 stratigraphic units, Subparallel to schistosrty. Nomial strike slip movement

Wide shear zone

W ide shear zone separating North orebody frorn South orebody, Displaces Central Orebody, Minimal displacement on hangingwall Andesite/Diorite. Location is good for a potential synvolcanic fault.

Usually quartz-carb, weak gouge, or shears. Displacement of quartz-carb veins and joints

Possible late synvolcanic intrusions into synvolcanic faults, Sericitic margin and glassy relatively unaltered inte rior

Possible Graben like structure where rhyolite subsided into ultramafics, Normal movement, No displacement of overlying Andesite/Diorite

Table 1 1: Summary of suucturai features near the Kidd Creek orebody.

Discussion

Early low temperature alteration producing silicification but not sodium depletion

followed what is now an east-west path outlined by Si02 enrichment in the

ultramafic units into footwall rhyolites (Fig. 31). Low temperature fluids may have

followed a long lived synvolcanic structure now represented by massive rhyolite

domes that define a 7000' long "rhyolite ridge" along the length of the Kidd

Orebody. Early silicification decreased the permeability of rocks underneath the

orebody sealing parts of the massive rhyolite units from later sericite alteration

which along with ongoing silicification further decreased the permeability of

underlying rhyolite units. Subsequent high temperature (1300 OC) fluids

responsible for chlorite alteration (evident by enrichment of MgO. Fe203. and Cu)

were restricted to paths around the silicified zones through synvolcanic structures.

Two high temperature alteration zones (possibly synvolcanic faults) are outlined in

Figures 3 1 b and 39. One is a southem zone of chlorite e ~ ~ h m e n t now occupied

by the East-West shear zone which may have been a conduit that fed the south

orebody. Below 3000 level the south orebody pinches out as does the East-West

shear (Fig 6).

Figures 35 and 36 are volcanic reconstruction and alteration paragenesis diagrams

outlining the timing of volcanic events and potential paths for fluids related to the

Kidd Creek ore forming event. The proposed sequence of events is as follows:

A subaqueous rhyolite dome formed on top of ultramafic flows and was

explosively brecciated. Subsidence dong synvolcanic faults located on either side

of the brecciated dome resulted in a graben like structure. Another rhyolite dome

or cryptodome was emplaced on or within the volcaniclastics. Flows near the top

of this domefcryptodome were separated by intercalated clastic units. Low

temperatrire alteration (essentially silicification) effected al1 rock types at this

stage. During this event, two massive rhyolite intrusions (cryptodomes?) were

emplaced almg synvolcanic structures at the ultramafic/rhyolite contact. Pervasive

silicification of the massive rhyolites restricted later sericite alteration to peripheral

crackle brecciated rhyolite and rhyolite volcaniclastic units. Sericite alteration may

have been contemporaneous witb the formation of low grade Py-Sph proto lenses

on top of, and within. rhyolite volcaniclastic units in the subsidence structure. Luw

temperature silicification and sericite alteration were ongoing as was the burial of

vent complexes by debns shed from rhyolites structurally transposed to higher

elevations by synvolcanic faults.

Blocked by impermeable silicified footwall rhyolites, tluids responsible for

chlorite alteration (Fe20s and M g 0 enrichment) were restncted to a synvolcanic

fault represented by what is now the northem rhyolite/ultramafic contact.

Permeable interflow rhyolite volcaniclastic uni& provided a medium for high

temperature alteration fluids to migrate from the synvolcanic structure to fom a

Cu stringer zone and massive sulphide lenses within rhyolites near the seawater

interface. Sericite was replaced by Fe-rich chlorite (and sulphides) creating a zone

of K20 depletion and Fe203 e ~ c h m e n t in the ore zone. Chalcopyrite precipitated

within interfiow clastic units and crackle brecciated massive rhyolite below the

seafloor interface. Much of the zinc ore at Kidd Creek fonned below the seafloor

replacing felsic fragmental units underneath low grade proto lenses. When Cu rich

fluids were channeled through a narrow zone of volcaniclastics between the

overlying impermeable massive sulphide lens and the underlying impermeable

massive rhyolite they formed keels of massive chalcopyrite (and sphalerite in #3

mine) at the base of the massive sulphide lenses. The South Orebody (containing a

high grade bornite zone) may have formed from fluids associated with chlorite

alteration that flowed through a synvolcanic structure now occupied by the East-

West shear.

Narrow Mg0 rich alteration corridors evident in Figures 3 1-33 may have formed

during a late stage alteration event producing Mg-rich chlorite and the hangingwall

alteration documented by Koopman et al. (in press). Altematively the Mg-rich

chlorite comdor could have fonned prior to the high temperatures producing Fe-

chlorite and it wasn't overprinted.

SEAWATER

€)$LOSIVE BRECClATlON OF RHYOLITE DOME

LOW GRADE PROTO LENS

ERUPTION OF CRACKLE BRECCJATED MASSIVE RHYOLITE

PERVASIVE LOW TEMPERATURE SILICIFICATION EVENT FOUOWED BY SERlClTUSlLlClFlCAllON ALTERATION WENT AND FORMATION OF LOW GRADE PYRITE PROTO LENS ON TW OF RHYOLITE VOLCANICLASTICS

1-1 PVARTZ PORPHïRY (QP)

LO.1 W O L l T E VOLCANICVISTICS (RT)

WM SULPHlDE (Mç)

Cu STRINGER

CRACKLE BRECCiATED W i V E RHYSUTE (CH-BX)

[ ] MASSIM RHYOUTE (MU) = U L T W I C (TC)

AREA

HlGH TEMPERATURE CHLORE ALTERATION NENT ASSOCIATED WITH THE BULK OF THE ORE FORMlNG NEW. CHLORITE ALTERATION FLUlDS FLOW AROUND IMPERMEABLE SILICIFlED AREA

Figure 3 8: Voicanic reconstruction and alteration paragenesis of the 4700 level.

ALTERATION PARAGENESIS AND VOLCANIC RECONSTRUCTION OF THE

KlDD CREEK MINE

ZONE FROM EARtlER COW TEMPERATURE (<200 C) SILICIFICATION N E N T

HlGH TEMPERATURE p300 "C) Mg, Fe. Cu RICH FLUlDS

QUARTZ PORPHYRY (QP)

i:..:i RHYOLITE VOLCANlCLASTlCS

BORNITE ZONE MASSIVE SULPHIDE ORE Cu STRINGERS

0 CH-8X (CRACKLE 8RECClATED MASSIVE RHYOLITE) * a I S S l V E RHYOLITE (MR)

m ULTRAMAFIC (TC)

BASE0 ON LOGCINO AND MAPPiUG OATA THE 01 AND S3 MiNES AND ALlERATlûN PARAGENESIS

FRûM CU4TWRINO OF WHOLE ROCK MTA

Kidd Creek is interpreted to be set in a graben like structure filled with massive rhyolite domes and volcanicla~tics that accurnulated during graben

subsidence. Low temperature (2200 C) alteration Ruids silicified footwall rhyolites (adding SiO,), followed by a less extensive sericite alteration event (+ K,O, - Na,O). Later high temperature (>300° C) MgO, Fe20,, Cu rich fluids flowed around the impermeable silicified footwall rhyolites

along graben fault structures.

Figure 39: Nteration paragenesis volcanic reconstruction of the 2000-2800 levels fRr 1 Mine)

A quartz porphyry dome formed on top of the rhyolite volcaniclastics and a

gabbroic si11 (ND) separated the dome from the volcaniclastic units. Later faulting

and folding events deformed the orebody.

CONCLUSIONS

Contouring lithogeochemical data cm effectively outline areas affected by primary

alteration associated with the ore forming event at Kidd Creek. Normalized data

and mass balance calculations may be used successfully in exploration programs

w hen bulk rock compositions do not identify alteration. From discriminant

analysis F-tests and visual comparisons. it was detennined b a t nonnalized or

percent mass change values for MgO, N;iTO, Fez03, Ca0 (mobile oxides during

the destruction of feldspar by chlorite) and raw Cu and Zn are the most effective

indicators of primary chlorite aiteration associated with the bulk of the ore forming

event. When these oxides are used in the discriminant function, a contour diagram

can be constructed with the probabilities of samples being strongly altered. This

method outlines both the orebody and zones of chlonte alteration leading to the

orebody.

Conclusions of Huston et al. (1 995) regarding low temperature and high

temperature alteration events are substantiated by the identification of 1) a low

temperature zone of SiO2 e~chrnent with no associated strong NazO depletion

and 2) a zone of strong Mg0 enrichment around the zone of silicification. Mg0

enrichment herein attributed to chlorite alteration defines a conduit that channeled

hydrothermal fluids upwards and around impermeable silicified rhyolites. The

East-West shear zone is interpreted to represent a reactivated synvolcanic structure

that focused ascending hydrothermal fluids related to formation of the South

Orebody. This structure is traceable to about the 2800 level which aiso coincides

with the end of the South Orebody. Identified alteration patterns cross cut both

ultramafic and rhyolite uni& indicating that the ultramafic rocks recorded a

primary hydrothermal alteration event.

From the data points available, the alteration zone around the Kidd Creek orebody

is conservatively estimated at approximately 6x the area (in stratigraphic cross

section) of the orebody itself. Besides its relatively large area. there are no

characteristics of the alteration zone surrounding Kidd Creek that make it

distinctive from smaller VMS deposits. Silicification, chlorite. and sencite

alteration are characteristic of most VMS deposits.

REFERENCES

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Barrie, C.T., Hannington, M.D.. and Bleeker, W.. 1997. A Review Of The Kidd Creek VMS Deposit, Abitibi, Subprovince, Canada. in GAC VMS Short Course Notes, Volcanic-Associated Massive Sulfide deposits: Processes and Examples in Modem and Ancient Settings", T. Barrie and M. Hannington.

Beaty, D.W., Taylor, H.P., Coad, P.R., 1988, An Oxygen Isotope Study of the Kidd Creek, Ontario, Volcanogenic Massive Sulfide Deposit: Evidence for a High 180 Ore Fluid. Economic Geology, v. 83, pp. 1- 17.

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APPENDIX

SAMPLE Si02 Ti02 AL203 Fe203 Mn0 Caû Mg0 Na20 KX) P205 SUM LOI Sum A % % % % % % % % % % %

BE-N 38.15 2,62 10.11 12.82 0.198 13.89 13.18 3.11 1.4 1.06 M.53 B6.53 LUAA11444 47.96 1.52 12.78 14.63 0.203 6.39 5.14 0.17 4.29 0.15 93.24 6.64 99.88

Xral AAll644' 47.3 1.45 12.39 14.69 0.14 6.87 5.17 0.39 4.17 0.2 92.77 ' LU Ml1449 46.75 0.8 15.58 11.53 0.174 9.3 9.02 0.85 0.23 0.06 94.3 5.4 99.7 '

XralAAll449' 46.41 0.79 15.57 12.01 0.19 9.27 8.9 1.1 0.3 0.06 94.6 - LUAF03614 38.35 0.79 10.64 9.99 0.232 10.64 8.12 2.9 0.08 0.41 82.15 18.2 100.37'

XralAF03614' 38.6 0.75 10.5 10.3 0.23 10.9 8.34 2.92 0.11 0.43 99.38 16.3 99.38 LU AFO36l6 38.22 0.73 9.77 8.88 0.101 11.25 8.47 2.97 0.17 0.32 80.96 19.4 100.34

Xral AF03616' 38.7 0.7 9.8 9.23 0.17 11.3 9.04 2.6 0.2 0.32 99 17.5 99.56 LU AF03622 58.62 0.18 10.21 13.46 0.062 2.1 1.25 3.35 1.34 0.03 90.59 9.68 100.27 '

Xral AF03622' LUAF03625 65.94 0.14 11.64 9.95 0.065 1.51 1.99 0.47 2.79 0.02 94.53 5.71 100.24

Xral AF0362Sg LU AF07288 50.06 t.69 12.61 14.35 0.242 8.54 5.21 2.87 0.67 0.17 96.42 3.5 99.92 '

XralAF07288' 50.2 1.72 12.5 14.6 0.25 8.61 5.04 2.52 0.73 0.18 98.7 2.25 98.6 I LU AFO729O 48.09 0.71 15.84 10.8 0.163 10.13 7.64 1.05 1.72 0.12 96.27 3.87 100.14~'

XralAF07290' 48.1 0.73 15.9 11 0.17 10.3 7.57 0.96 1.79 0.12 100.1 3.3 98.94 LU AF07298 50.45 1.07 17.49 9.64 0.167 11.08 3.41 3.1 1 0.68 0.26 97.35 2.93 100.28

Xral AF0729P0 50.3 1.08 17.2 9.5 0.18 11.2 3.41 2.63 0.74 0.21 98.8 2.25 98.7

' XRAL sample analysis

Laurentian vs Xral Whole Rock Sample Cornparison

BE-N 229.5 343 57.4 255.6 73.4 113.7 111.4 266 32.1 1378 42.4 992 7.8

i

l

' tUAA11444 391 53.2 51.2 1.5 25.1 51.5 1.1 119.2 47.3 53.4 125.5 220 23 Xral Ml 1444' LU Ml1449 207.9 186.9 62.7 147.4 79.2 57.4 OP 40.2 18.8 122.9 1.8 50.7 t6.1

Xral Ml 1449' 30 120 10 LU AF03614 204.2 661.2 36.5 87.1 44.1 88.6 10.3 118.8 17.3 385.5 6.2 95.6 85.9

Xia1 AF036 1 4' 27 97 12 426 17 97 I LUAF03616 193.5 790.4 34.2 140.3 61 80.1 9.7 89.6 16.6 643.5 3.1 201 1.2

Xral AF036 1 6' 12 68 5 675 5 203 LU AF03622 20.8 373.5 41.8 54.3 102.6 758.1 5.4 231.8 89.4 67.4 66.7 326 101.6

, XralAF03622' 120 810 42 LU AF03625 12.6 165.3 15.9 57.9 47.1 595.1 0.3 239.8 388.9 41.2 120 622 54.8

Xnl AF0362S0 41 660 60 LUAFO7î88 384.4 134.6 58 0.5 92.6 105.1 1.3 130.5 45.9 9û.8 17.2 379 2.2

Xrol AF07288' 56 46 98 127 26 139 25 65 45 359 LUAF07290 190.6 175.7 48.9 222.1 49.1 83.1 1.4 39.4 14.8 220.9 64.3 736 7.5

Xral AF07290' 53 230 35 87 17 38 5 213 68 636 LU AF07298 270.4 397.9 47.4 146.6 82.8 111.9 1.9 73.2 25.7 284.1 11.1 202 0.8 hl AFO7298' 58 164 70 113 5 85 5 317 45 155

Rock Typo

Ti02 A1203

Fe203 (T) Mao Mn0 Cao Na20 K20 P205 LOI

Total

Co2 wP16 Zr Y

Nb

Ni Sr Cu Zn Sn Co F

Ml = Mafic Population 41 M2 = Mafic Population U2 M3 = Mafic Po~uhtion #3

Least Altered Precursor Geochemical Values Used For Mass Balance Calculations From Barrie et al., 1997

Rock Typa Mdlrinr

Ti02 Al203

Fe203 Mg0 Mn0 Ce0 Na20 K20 P205 LOI

Total

Co2 w o

Zr Y Nb

Ni Sr Cu Zn Sn Co F

# of Samples

Ml = Mafc Popuhtion #l M2 = Mafic Popufation #2 M3 = Mafic Popubtion #3

Medain Element Values Used For Data Normalization

Discriminant Analysis provides a hinction (linear combination of variables) that produces the maximum difierence between two previously defmed groups. Figwe Al visually demonstrates how discriminant analysis separates two populations. Since there is considerable overlap of variables X1 and X2 between populations A and B, one variable alone cannot be used to divide unluiown samples into separate groups. The discriminant analysû hrnction uses both variables to separate the two populations. Values of X 1 and X2 in unknown samples an compared with values for X1 and X2 within populations horn the representative data sets. The probabilities of unknown samples klonging to each group are then calculated. An unknown sarnple may have a O. 1 (10%) probability of belonging to group A and a 0.9 (90%) probability of belonging to group B.

Fi9ure AL pbt of mi manau ais;rttwmm. m n p mNg ba(ween gmps A and B akmg bom vanaMes X , oM X, G m q x can DI dbtlnguilhed Dy prqaVng membio Of VM two group Omo mr disaimin;int h r m Yn.

For this study, the percent mass changes of Cao, MgO, NazO, Fe203(T), and raw values (ppm) for Cu and Zn were the variables used for the discriminant function that separated the Kidd data set into three alteration groups. Discriminant analysis compares the values of variables in unknown samples to the variables in the user defmed unaltered, medium, and strongly altered groups. Considerable ovcrlap of values exists between these groups so it was not feasible to use just one variable to defhe the groups.

The predcfrned dataset of least, medium, and strongly altered samples used for the Kidd Creek data is given below. Samples were divided into three groups based on raw Na20

(wt. %) values and representative values (near median) for the other elements. For instance, if a sample had a Na20 content of 3.0% (making it part of the unaltered group) but a high Zn value of 1500 ppm (approx. 1400 ppm over median values) it would not be included as a representative sample (for any group). Representative samples were selected from many locations in the mine and applied on the 2800 level.

Assumptions For Application Of The Discriminant Andysis F-test of SigniOcance

1) The observations in each group are randomiy chosen 2) The probabilit y of an unknown sample belonging to either group is equal 3) Variables are normally distributed within each group 4) The variance-covariance matrices of the groups are equal in size 5) None of the observations used to calculate the function were misclassified

Percent mus change values for Na20, Cao, MgO, Fc203 and raw Cu and Zn are not normaliy distributed but the result of plotting probabilities detcrmined by discriminant analysis produces a large anomaly of over the orebody (Fig. 22) thus lending some support for this technique. Most geological data is noi norrnally distributed but the validation of using statistics for normaUy distnbuted populations on geological data that is not nomally distributed comes with cornparison to the orebody. If the statistical method is validated in a geological sense (e.g. the orebody is detected), the assumption that was not validated diâ not have had a great effect on the end result. The amount of separation between populations is a more important factor for discriminant analysis.

LIST OF REPRESENTATIVE SAMPLES USED FOR CLASSlFYiNG GROUPS IN DISCRIMINANT ANALYSIS. LEAST, MEDIUM, AND STRONGLY ALTERED GROUPS

Rktyp. Location Hola X Y ELEV Sampld Si02 A1203 Cd3 Mg0 Na2û K20 TOTFE TiOZ MnO u--08

unalt rhy unalt h y unel! rhy malt rhy malt rhy unalt rhy unelt rhy malt fhy uneft niy lJnalt rhy unatl *y umlt my uneh * y unal! rhy unatt rhy unalt rhy unah my unalt fhy wielt rhy wrelt rhy uneh my unatt rhy unal1 maf unatt maf unalt maf unalt maf unatt mef m n m e f malt maf unal! maf uneH maf

47 Dr Dr 4600 NRHY NRHY NRHY NRHY NRHY

MINESITE 8134 81 34 8134 816ô 8168 81 34 8168 81 31 81 34 81 33 81 31 81 33 8t34 4600

3MINE 3MINE MINE MINE 3MINE NINE NRHY MINE N I N E

RMypa Localion Holo Pm6 SUM C m 3 LOI Y Zr B. F Cu Zn NI Co u-w..

47 Dr Dr 4600 NRHY NRHY NRHY NRHY NRHY

MINESITE 8134 81 34 81 34 8168 8166 81 34 8168 81 31 81 34 81 33 81 31 81 33 81 34 4600

MINE MINE MINE MINE 3MINE 3MINE NRHY 3MINE 3MINE

NRHY NRHY NRHY MINE NRHY NRHY NRHY 4600 NRHY NRHY NRHY 5200 NRHY NRHY NRHY 3MINE 3NEW 5200

3NEW MINE 3MINE MINE 3MINE 3MINE NINE 3MINE 3MINE

€LW Sampleü Si02 AIZ03 C n ) Mg0 N.X) K?O TOTFE Ti02 MnO

NRHY NRHY NRHY MINE NRHY NRHY NRHY 4600 NRHY NRHY NRHY 5200 NRHY NRHY NRHY 3MINE 3NEW 5200

3NEW 3MINE MINE MINE MINE 3MINE 3MlNE NINE MINE

Rktyp. Locution Hdo StEonOt~-Sunpl-

stralt rhy 53-78 XC stralt rhy 5141 XC stralt rhy 48-70 XC strelt rhy 47QS Fr shlt &y 46-78XC stralt rtiy 4600 78 XC stralt rhy 52OO 78 XC stralt rtiy 5200 78XC stralt niy 5200 78 XC stralt rhy 49LEVEL 46%) stratt rhy ZWO 10 stralt rhy 3NEW 6304 stralt rhy 3NEW 6308 strattrhy 3NEW 6308 straltrhy 3MINE 5484 strait rhy WIN€ 5482 strait rhy MINE 5481 strah rhy WIN€ 5482 stratt rhy MINE 5483 strait h y 3NEW 6262 strall niy 3NEW 5991 stralt rtiy 3NEW 6265 Watt rhy WIN€ 5181 stralt rhy MINESITE 842 stralt r t~y 3MINE 5182 straH rhy 46W 4372 stralt rhy 46ûû 4383 stral maf 2600 1557 straltmaf Xûû 1611 stralt maf 26ûO 94 1 stralt msf 26ûO 1190 straltmaf NRHY 4799 straîtmaf NRHY 4985 straît mai ZHKl 941

K2û TOTFE i l 02 M d

R)rtyp. Location Hola X Y €LW SampleW SIOZ AI203 C.O Mgû N a 2 û K20 TOTFE Ti02 MnO sbonOl~Alt+ndSwnpl-

sîralt rnaf #1 MINE 66û20 66040.18 2896.3 45.78 16.98 14.75 6.87 0.05 3.13 11.33 0.85 0.21 sîraH mef 53-78 XC 65704 1708 Afû99û6 47.3 17.61 7.89 11.35 0.95 1.51 12.33 0.81 0.16 stralt maf 46-03 Fr 65656 1930 AFû9915 49.96 16.31 9.92 9.89 0.18 1.44 11.32 0.76 0.13 stralt mef 5200 78 XC 65708.4 1749 AF09942 49.28 17.24 7.93 9.65 1.94 0.97 12.01 0.77 0.13 strah maf MINE 6577 65905 1026.85 KA00771 49.08 15.24 6.39 10.35 0.08 1.52 15.89 1.13 0.2

Rktypa Location Haîe 9205 SUM CR03 LOI Y Zr E h F Cu Zn NI Co StronOl~-sMipl-

sûalt mef t 1 MINE a 2 0 0.05 85.41 13 5 1780 92 76 190 40 , stralt maf 53-78 XC 0.09 89,94 0.03 10.72 16 42 400 1000 55 Iôû t70 50 streitmef 46-û3Fr 0.09 89.05 0.02 1 . 9 14 42 160 900 80 125 160 45 sûalt muf 5200 78XC 0.09 91.1 0.025 8.9 16 44 220 400 40 60 190 50 rtreltmat MINE 6577 0.13 92.27 0.03 8.71 36 68 210 100 10 175 175 SO

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