the diversity of sodium metasomatic processes and their …. diversity of na... · 2015-05-20 ·...
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The diversity of sodium metasomatic processes and their relations to
uranium deposits
inpl nancy
UNIVERSITE DE LORRAINE – GEORESSOURCES CREGU – CNRS
54 506, Vandoeuvre les NANCY France
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Also named : albitite-type uranium deposits
This class of deposit is economically significant with very larges resources especially in Ukraine & Brazil in the Lagoa Real district
Some of these deposits are transitional with other deposit types: Related to magmatic fractionation: Bokan Mountain Vein type deposits with the episyenitization (dequartzification): Beaverlodge Volcanic related deposits, when volcanic rocks are albitized: Michelin Metamorphic deposits: Lagoa Real
In these district albitisation is always associated with U mineralization but the albitized zones extend on much arger volumes. There is a large diversity of albitite types & only some are mineralized
The diversity of sodium metasomatic processes and their relations to uranium deposits
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TYPOLOGY OF ALBITITES This word has been used widely covering different meanings TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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Albitite: definition A name proposed by Turner (1896) for granular igneous rocks consisting essentially of albite. Occur in dikes in the Sierra Nevada mountains, California http://www.wordnik.com/words/albitite A coarse-grained porphyritic dike rock composed almost wholly of albite McGraw-Hill Dictionary of Scientific & Technical Terms A granular dike rock consisting essentially of albite http://www.merriam-webster.com/dictionary/albitite
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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1 2
4
Eutectic
QUARTZ
ALBITE K-FELDSPAR
EFFECT of FLUORINE on the EUTECTIC of the GRANITE SYSTEM
Increasing F content : decrease Qz and K-Feld contents increases albite content convergence with true albitites
Manning, 1981 C.M.P., 76, 206-215
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE I : MAGMATIC ALBITITES Ia – Albitites associated to peraluminous leucogranites
Ultimate intrusions of peraluminous leucogranitic complexes Li-Muscovite, Lepidolite, Li-Be-phosphates, Rich in P, Ta, Nb, Sn, U, Li, Cs, F, Be, Rb … Very poor in REE, Th, Zr … During magma fractionation with increasing F content in melt: Decreasing SiO2 content K increasingly hosted in lepidolite Increasing Na2O content Increasing albite porportions But not real albitites because: still 15 to 20% quartz in the rock
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GPF DRILLING LOUROUX DE B. SERVANT
S N
0
2
4
6
km
BEAUVOIR GRANITE
COLETTES GRANITE
PRESUMED LA BOSSE GRANITE
PRESUMED DIORITIC BODY
POUZOL-SERVANT GRANITE
FERBERITE STOCKWORK
LA SIOULE MICASCHIST
GNEISS & MIGMATITES
X X X X
X X X X X
X X X X X
X X X X X
X X X X X X
X X X X X X
X X X X X X
X X X X X X
X X X X X
X X X X X
X X X X X
X X X X
X X
X X
X X
X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X
X X X
X X X
X X X
X X X
771 m
X X
BEAUVOIR « ALBITITE » in the ECHASSIERES GRANITIC COMPLEX (FRENCH MASSIF CENTRAL)
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TYPE I : MAGMATIC ALBITITES Ia – Albitites associated to peraluminous leucogranites
F-rich ALBITIC F-poor GRANITE GRANITE
SIO2 67.50 72.10
Al2O3 17.40 16.00
Fe2O3 0.18 0.72
Na2O 5.07 4.01
K2O 3.71 3.81 Be= 260 ppm; Cs= 612 ppm; Nb= 158 ppm; Ta= 425 ppm; Rb= 4000 ppm, Sn= 1400 ppm
Th = 1 ppm Zr = 20 ppm REE = 2 ppm
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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Late Neoproterozoic intrusive Taar
albitite Southern Sinai,
Egypt
Azer et al., 2010 IGES, 99, 245-267
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TYPE I : MAGMATIC ALBITITES Ib1 – Albitites associated to peralkaline/calcalkaline granites
TAAR ALBITITE
SIO2 69.13
Al2O3 18.69
Fe2O3 0.33
Na2O 10.55
K2O 0.15
Be= 1.8ppm; Li= 0.5ppm; Nb= 18ppm; Ta= 1.5ppm; Rb= 1.9ppm; U= 1ppm; Th= 6ppm Zr= 277 ppm; REE= 135 ppm
Azer et al., 2010 IGES, 99, 245-267
Magmatic textures : Porphyritic varieties, with tabular euhedral albite crystals in a fine-grained groundmass
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Tarr albitites
In fact it is an albitic granite because there is up to 11% quartz Mantle origin : Low εNd = +4 to +6.5 ; Sri = 0.70356 very low Rb (1.9 ppm), Li (0.5 ppm)
Residual magma remaining after near-total crystallization of an A-type granite pluton at depth, emplaced into the roof above the cooling pluton
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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BOKAN MOUNTAIN ALASKA
MAGMATIC/HYDROTHERMAL U-DEPOSIT (ROSS ADAMS)
RELATED TO A PERALKALINE GRANITE
TYPE I : MAGMATIC ALBITITES Ib2 - Magmatic/hydrothermal
Associated to peralkaline/calc-alkaline granites
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BOKAN MOUNTAIN INTRUSION
ALASKA
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BOKAN MOUNTAIN, ALASKA
MAGMATIC/HYDROTHERMAL
U-DEPOSIT (Ross Adams mine) Production 1000 t U @ 1% U
U-Th deposit
REE veins
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granites
-50
0
100
200
300
-400 -300 -200 -100 0
P = K- (Na+Ca)
Q = A
l/3-(N
a+K+
2Ca/3
)
0
K Na exchange
dequartzification and albitization
argillization silicification
quartz
K-feldspar albite
GAg GAgAr GAgArf
GAgArs GAgAra
n.m.abtz.Ag. m.abtz.Ag. m.abtz.dq.Ag
GAgArh syn-ore alteration
granites
post-ore alteration
BOKAN MOUNTAIN
ALASKA
QUARTZ / FELDSPAR
PROPORTIONS GRANITE ALBITITE
SIO2 74.90 61.90
Al2O3 10.30 12.40
Fe2O3 4.80 6.00
Na2O 4.50 9.50
K2O 4.20 0.40
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GAg
GAgAr
GAgArf
n.m.abtz.Ag.
m.abtz.Ag. m.abtz.dq.Ag
GAgArh
syn-ore alteration
granites
BOKAN MOUNTAIN ALASKA
Th - U FRACTIONATION ?
Granites 10 < Th < 70 ppm 2 < U < 30 ppm
Mineralization 400 ppm < Th < 3 % 100 ppm < U < 1.8 %
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granites
mineralization BOKAN MOUNTAIN
ALASKA
Th - Zr
FRACTIONATION
Granites 300< Zr <2000ppm
Mineralization 600 ppm < Zr < 1%
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Bokan Mountain granite peralkaline magmas derive from low degree of partial melting of the mantle with subsequent fractionation
most fractionated and most apical part of a larger magmatic complex existing at a relatively shallow depth.
U mineralization derived nearly directly from mantle, extreme magma fractionation and magmatic fluids unmixing
Initial U-Th enrichment of the mantle through subduction of oceanic slab & sediments, enhance the U and Th concentrations in melts
Th/U ratios remain close to chondritic ratio of 3.5 during magma fractionation, even in the mineralized albitites.
GENETIC MODEL
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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Lherzolite massifs with albitite dikes in the north Pyrenean metamorphic zone (Azambre & Monchoux,1998)
FRANCE
SPAIN
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Lherzolite (dark grey) intruded by albitic dykes (white)
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Dikes of albitite cross-cutting serpentinized lherzolite in the Pyrénées, France
Paragenesis : Albite + muscovite + biotite + chlorite, epidote, zircon, titanite, thorite, pyrochlore, aeschynite-(Ce), Fe-columbite, allanite-(Ce), chevkinite-(Ce), apatite, monazite-(Ce), rutile, ilmenite, magnetite Textures: pegmatitic & reflect a rapid magmatic crystallization Large crystals of albite predate the fine-grained minerals of Ca, Sr, Fe, Mg, Zr, Ti, Y, REE, U, Th.
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Urdach (with corundum: open circles; without corundum: asterisks), Garba Tula (solid square) and Finero (solid circles) albitites in the diagram of Cox et al. (1979).
Positive εNdi values (+1.9 to +3.4) derivation from a mantle source low rate of partial melting (0.5-0.7%) of a metasomatized peridotite
Dikes of albitite in lherzolite, Pyrénées, France
ALBITITE SIO2 63.50 Al2O3 20.60 Fe2O3 1.63 Na2O 10.20 K2O 0.39 Rb = 3.9ppm; Zr = 231ppm
Nb=239 ppm; Ta=17ppm; Th=82ppm U = 106ppm; REE = 1950ppm
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Ultimate intrusion of ultrabasic complexes Rospigliani albitites (Corsica, France)
No dequartzification (albitic syenites of albitic granite) Albite + quartz ± Na amphibole or pyroxene Zr-rich (1640 ppm) Low U (0.2 – 0.5 ppm), Th (0.3 – 2 ppm), Rb (0,09 ppm), Li
ALBITITE SiO2 59.90 Al2O3 17.23 Fe2O3 6.32 Na2O 10.80 K2O 0.10
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) Dequartzification may represent the unique alteration Followed or synchronous with albitization: - of plagioclase (removal of the anorthite component) - of K-feldspar - new formation of albite in the vugs Followed or not by Ca-metasomatic and/or uranium mineralization Rarely followed by K-metasomatism Most trace elements are stable except Rb, Ba, Sr Low saline aqueous fluids Common in granite plutons, but also occur in metasedimentary rocks Generally post-magmatic phenomena, variable extension
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Albitisation of K-feldpar
K Na exchange
Albite-Microcline-Qz metasomatite
QUARTZ
K-FELDSPAR 200 100 0
K – (Na+Ca) -100 -200
MQ SQ DQ
T
M S
D Si
/3-(N
a+K
+2C
a/3)
400
GENERAL CHEMICAL-MINERALOGICAL EVOLUTION OF Na-METASOMATISM
granite field
AD G
Albitite
Na K exchange
Quartz dissolution
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TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) Margeride, France
(i) Locally developped in granitic intrusion, can be mineralized
GRANITE EPISYENITE
SIO2 76.38 69.57
Al2O3 12.86 17.75 (increase due to volume loss)
Fe2O3 0.27 0.21
Na2O 3.8 9.16
K2O 4.23 1.21
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EPISYENITE BERNARDAN
MARCHE OCCIDENTALE
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Albite replacing K-feldspar with a chessboard microstructure
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ALBITITE – EPIDOTE EPISYENITE
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May 2001 The last U ton leaves the Bernardan mine in France = end of U mining in France, more than 200 mines operated from 1954 to 2001
Open pit mine BERNARDAN
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3 D MODEL OF THE
BERNARDAN EPISYENITE U DEPOSIT
France, by GOCAD
J.J. ROYER, 1992
Up to 1 km
vertical extension
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Ashton, 2010
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Zone of episyenite alteration (Gunnar open pit), Ashton, 2010
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Cross section throught the Gunnar episyenite (after Evoy, 1986)
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TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type)
(2) developped at the regional scale, with the largest U resources Developed along regional, transcrustal shear zones (>2.4 km depth)
High temperature processes (600 to >300°C)
May affect any type of rock (granite, banded iron formation, metased.
Surficial origin of the fluids most commonly,
Na-metasomatism generally followed by Ca ± K metasomatism,
Albitization extends over much larger zones than U mineralization
Mineralization U ± Zr, no Th, low REE
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Michelin
Arjeplog-Arvidsjaur
Valhalla LAGOA REAL
CENTRAL UKRAINE
Timdrart
Kurupung
Small Medium LARGE
Coles Hill
Kitongo
Espinharas ITATAIA
1.8-1.5 Ga 0.5-0.2 Ga
Lianshanguan
North Rajasthan
WORLD DISTRIBUTION OF HYDROTHERMAL METASOMATIC DEPOSITS II-5a (HMtNa) associated with Na-metasomatism
Alio Ghelle
Gunnar Beaverlodge
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ParanaBasin
BazilianoBelt
40°20°
Atlantic
Ocean
SaoFrancisco
Craton
SouthernAmazonCraton
NorthernAmazonCraton
Amazon Basin
ParnaibaBasin
Arag
uaia
Belt
40°
10°
0°
10°60°
0 500 1000
km
0°
50°
Andean foreland basinAndes
10°
20°
Pacif
ic Oc
ean Apiacac-Xingu Platform
AndesBasins < 350 MaBraziliano 900-520 MaCratons > 1100 Ma
10°
70°
ItataiaEspinharas
LagoaReal
Poçosde Caldas
Salvador
ParanaBasin
BazilianoBelt
40°20°
Atlantic
Ocean
SaoFrancisco
Craton
SouthernAmazonCraton
NorthernAmazonCraton
Amazon Basin
ParnaibaBasin
Arag
uaia
Belt
40°
10°
0°
10°60°
0 500 1000
km
0 500 1000
km
0°
50°
Andean foreland basinAndes
10°
20°
Pacif
ic Oc
ean Apiacac-Xingu Platform
AndesBasins < 350 MaBraziliano 900-520 MaCratons > 1100 Ma
10°
70°
ItataiaEspinharas
LagoaReal
Poçosde Caldas
Salvador
Main U deposits in Brazil
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Map of the uranium deposits of the
Lagoa Real District
Bahia, Brazil
Undeformed St Timoteo granite
Orthogneissified St Timoteo granite
Uranium deposits
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QUARTZ –FELDSPAR PROPORTION VARIATIONS AT LAGOA REAL
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1
10
100
1 10 100 1000 10000 100000
U (ppm)
Th (p
pm)
amphibolites
Th-Nb G.
Granites
Albitized G.
Albit.dequart. G.
Barren A.D.G.
Th/U = 0.1Th/U=3.5
Th/U=10
Th/U = 1 Th/U = 0.01
Th – U VARIATIONS DURING Na-Ca METASOMATISM
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1
10
100
100 1000 10000
Zr (ppm)
Th (p
pm)
amphibolites
Th-Nb G.
Granites
Albitized G.
Albit.dequart. G.
Barren A.D.G.
Zr/Th = 10
Zr/Th = 100
Th – Zr VARIATIONS DURING Na-Ca METASOMATISM
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Bug-
Miro
novs
kfa
ult
Kriv
oroz
hsk
faul
t
Orek
hovo
-Pa
vlogr
adsk
ii
Krivoi Rog
Kremenshug
Nem
irovs
kfa
ult
Novounkrainska granite
Korsun-Novomirgorodsk granite
Monzo-gabbros-dioritesUranium deposits
100 km
N
Sevsk - Ingulets
KIEV
Sumy - DnieprVoronezh
Bug-
Miro
novs
kfa
ult
Kriv
oroz
hsk
faul
t
Orek
hovo
-Pa
vlogr
adsk
ii
Krivoi Rog
Kremenshug
Nem
irovs
kfa
ult
Novounkrainska granite
Korsun-Novomirgorodsk granite
Monzo-gabbros-dioritesUranium deposits
100 km
N
Sevsk - Ingulets
KIEV
Sumy - DnieprVoronezh
CENTRAL UKRAINE DISTRICT
I II
U districts: Kirovograd-Novoukrainka (I), Krivy Rig (II). Major faults : Kirovograd (1), Novokonstantinovka (2), Zvenigorod-Annivka (3), Subotsk-Moshorynsk (4), Central (5)
Cratons
Mobile belts
1
2
3
5
4
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Evolution of quartz content relative to K-feldspar & Na-Ca mineral contents in the granitoids and altered zones associated with U mineralization
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Uranium versus thorium concentration variations in the granitoids and altered zones of Central Ukraine
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Metallogenic model for the genesis of the uranium mineralization associated with Na-metasomatism of Central Ukraine
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE II : HYDROTHERMAL ALBITITES IIb – Vein type
Wall rocks are generally metamorphic rocks
Albitization is variably developed and confined to the wall roks
The uranium mineralization fill veins or breccias
At Beaverlodge the U mineralization is emplaces in the red mylonite which consists of fine grained albitite or quartz albitite
Some pitcheblende veins has albite as a gangue mineral partial overlap between albitization and U deposition
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E.A.G. Trueman, 2009
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E.A.G. Trueman, 2009
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The Rožná U deposit
Czeck Republic
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The Rožná U deposit In plagioclase-biotite paragneisses Hydrothermal U ores related to mylonite, fault breccia Cement = graphite + pyrite, cut by carbonate veinlets. Metasomatic alteration : muscovitization, albitization, chloritization or carbonatization Ores bodies with disseminated U mineralization. U minerals : uraninite + coffinite (rare brannerite & montroseite) with calcite and chlorite. Hexavalent U minerals (liebigite, metaautunite …) Grade : 0.01-0.5% U (0.3 % in average), up to 5% locally
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The Rožná U deposit
Czeck Republic
200
1200
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE II : HYDROTHERMAL ALBITITES IIc – Diagenetic in volcanic rocks
Keratophyres and spillites
Association of basic and acidic volcanic rocks
Abundant carbonates, chlorite, epidote
U ± Zr, if peralkaline tuffs
Ex. Permian from Switzerland Alps
Tokoro Shirmeck (Japan) (Vosges) SIO2 66.10 71.50 Al2O3 16.55 12.97 Fe2O3 5.50 5.12 CaO 3.01 0.46 Na2O 6.19 4.72 K2O 0.01 1.35
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Spillites &
keratophyres in the Quartz/
Feldspar diagram
Trends with decreasing
quartz & increasing
albite contents
K-feldspathisation
silicification
K-FELDSPAR K-(Na+Ca)
Si/3-(Na+K+2Ca/3)
PLAGIOCLASE
Ultrabasic trend
ALKALINE
QUARTZ
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE II : HYDROTHERMAL ALBITITES IIc – Diagenetic at unconformities
Tendancy to dequartzification
Diagenetic saline aqueous fluids (100 – 150°C)
Small intracontinental basins
K-feldspathization also occur
U deposits from Rouergue (Bertholène, )
ALBITITE SIO2 56.11 Al2O3 17.46 Fe2O3 6.00 CaO 4.42 Na2O 6.95 K2O 0.24 Yerle, 1978
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TYPOLOGY OF ALBITITES TYPE I : MAGMATIC ALBITITES Ia – Associated to peraluminous leucogranites Ib – Associated to peralkaline / calc-alkaline granites - Ib1 purely magmatic - Ib2 magmatic-hydrothermal Ic – Associated to ultrabasic complexes TYPE II : HYDROTHERMAL ALBITITES IIa – With dequartzification (episyenite type) IIb – Vein type IIc – Hydrothermal diagenetic in volcanic rocks
IIc – Hydrothermal diagenetic at unconformities IId – IOCG related
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TYPE II : HYDROTHERMAL ALBITITES IIe – IOCG deposit related
3 main types are associated with IOCG deposits: Ca-Na, Fe, K alterations The Na-Ca alteration zones: regional in scale (>1 km wide) range from a strong albitization (± Cpx, titanite), such as in the Cloncurry district, to the CAM assemblage of Skirrow et al. (2002) with calc-silicate (Cpx, amphibole, garnet) - K-feldspar - albite ± Fe-Cu sulphides, ± albite, actinolite, magnetite, apatite, late epidote (Pollard et al, 1998; Wyborn, 1998) In extreme cases it can also result in the formation of albitites Early alterations prepare the ground for subsequent alterations In the Cloncurry district, albitites are extensive, and a spatial & temporal association exists between albitite & U but also between albitite & Cu-Au of IOCG type. But, most albitites in the region are devoid of U, Cu, Au.
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Detailed distribution of two of the major phases of
alteration and mineralization around the
Ernest Henry Cu-Au deposit (Mark et al., 2000)
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Titanite ages for the Cloncurry district suggest a temporal relationship between granite
intrusion & albitization (Mark & Foster, 2000; Pollard, 2001)
C and O isotope data typical for fluids derived from, or equilibrated with, felsic igneous rocks. S isotope values for sulfides from the deposits and albitite-related pyrite at Ernest Henry, point toward an igneous fluid source The regional albitization was most likely
produced by fluids derived at least partly from crystallizing plutons (Mark et al., 2000)
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TYPE II : HYDROTHERMAL ALBITITES IIe –IOCG deposit related (Conclurry district) ALBITIC ABITIC PELITE PELITE Qz Monzonite Qz-Monzonite
SIO2 56.10 65.30 66.50 68.41
Al2O3 21.70 19.50 14.96 15.69
Fe2O3 8.29 0.47 3.81 1.99
CaO 0.35 0.65 2.02 2.47 Na2O 0.53 10.69 4.83 8.94
K2O 6.52 0.38 4.79 0.17
Zr= 130 ppm; Nb= 18 ppm; Rb= 13 ppm Oliver, 2004, Econ. Geol.
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Mark G, Foster DRW 2000 Magmatic hydrothermal albite-actinolite- apatite-rich rocks from the Cloncurry district, NW Queensland, Australia: Lithos, 51, 223-245.
Fluid inclusions in the albitites from the Conclurry district
NaCl-KCl-CaCl2-H2OCO2 ± hematite-gypsum fluids with 2 or more daughter minerals, salinity >50 wt %NaCl eq, NaCl-H2O-CO2 fluids with halite and 20 to 30 wt % NaCl eq. CO2-rich fluids
Pressure corrected entrapment temperatures of inclusions associated both with albitites and with the ores are 300° to 550°C
Albitization stage reached temperatures of 450° to 600°C, determined from calc-silicate mineral equilibria and calcite-dolomite geothermometry (Oliver et al., 1993; Oliver, 1995), & oxygen isotope geothermometry on quartz, magnetite, albite, and amphibole (Mark, 1998a; Mark and Foster, 2000)
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CONCLUSIONS
Extreme diversity of the types of sodium metasomatism : Developped in a wide range of temperature and pressures
Related to a wide variety of fluid types from magmatic to surficial
Only some specific types can be associated with U mineralization processes
Albization envelops exceed largely the U mineralized zones
Dequartzification is generally necessary to create the space necessary for U mineralization precipitation