Archaean carbon reservoirs and their relevance to the fluid source for gold deposits

Groves, David; Golding, S. D.; Rock, N. M. S.; Barley, M. E.; McNaughton, Neal J.

doi:10.1038/331254a0

Cited by 71 publications

(36 citation statements)

References 16 publications

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“…In contrast, fluids related to barren quartz veins are NaCl-H 2 O system . The CO 2 -rich fluid in the mesothermal or orogenic gold deposit as recently defined by Groves et al (1998) and is genetically related to deep lithosphere process (Groves et al, 1988;Kerrich, 1990).…”

Section: O H O Vs Nacl (A B) and Homogenization Temperature (Th; Cmentioning

confidence: 99%

High 3He/4He ratios in the Wangu gold deposit, Hunan province, China: Implications for mantle fluids along the Tanlu deep fault zone.

Mao

Kerrich

et al. 2002

Geochem. J.

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The Wangu shear zone hosting gold deposit is located on splay faults of the regional scale Tanlu Tao et al., 1996).During the lithosphere extension and decompressional melting of asthenosphere, noble gases and CO 2 exsolved from basalt melts, advected up to the Tanlu fault zone into splay faults where gold mineralization developed, and through sedimentary basin. There was mixing with isotopically and compositionally evolved meteoric water.

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Section: O H O Vs Nacl (A B) and Homogenization Temperature (Th; Cmentioning

confidence: 99%

High 3He/4He ratios in the Wangu gold deposit, Hunan province, China: Implications for mantle fluids along the Tanlu deep fault zone.

Mao

Kerrich

et al. 2002

Geochem. J.

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“…The δ 13 C values of the carbonate minerals are nearly 0 ‰, indicating that these carbonate minerals are comparable to marine carbonates. Therefore, it is generally considered that this carbonatization was due to seafloor hydrothermal activity Groves et al, 1988). Hickman (1983) found a carbonatized greenstone unit in the Talga Talga Subgroup.…”

Section: Carbonate Minerals In Altered Volcanic Rocksmentioning

confidence: 99%

“…This carbonatization has been classified into two types, fault-related and regional carbonatization, on the basis of geological, mineralogical, and carbon isotopic features (e.g., Barley and Groves, 1987;Groves et al, 1988;Veizer et al, 1989a). The distribution of the fault-related carbonatization is restricted to some areas along large faults and shear zones.…”

Section: Carbonate Minerals In Altered Volcanic Rocksmentioning

confidence: 99%

Carbonate Minerals in the Warrawoona Group, Pilbara Craton: Implications for Continental Crust, Life, and Global Carbon Cycle in the Early Archean

Nakamura¹,

Kato²

2002

Resource Geology

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Abstract:The occurrences of the Early Archean carbonate minerals are compiled and their precipitation processes are investigated for the Warrawoona Group, Pilbara Craton. Sedimentary carbonate rocks such as limestone and dolostone are very rare, and only a small amount of sedimentary carbonate minerals are sometimes contained in the hydrothermal bedded chert, implying that a sink of CO 2 was minor in the Early Archean sediments. Moreover, it is very likely that the activity of cyanobacteria forming stromatolites was considerably low in the Early Archean. Microfossils and carbonaceous matter in the hydrothermal cherts are probably derived from a non-photosynthetic microorganisms related to the seafloor hydrothermal activity. Their preservation in sediments may play a very minor role in carbon sink of the Earth's surface.On the other hand, carbonatized volcanic rocks subjected to seafloor hydrothermal alteration occur ubiquitously in the Early Archean greenstone belts such as the Warrawoona Group, suggesting that the hydrothermally altered oceanic crust had large amounts of CO 2 as carbonate minerals. Global carbon cycle in the Early Archean is considered to have been controlled by the intense seafloor hydrothermal alteration. Large amounts of CO 2 were sunk into the oceanic crust by the alteration. The carbonatized oceanic crust was partly accreted to the continents and/or island-arcs, and partly subducted into the mantle without decomposition. Significant amounts of carbonate minerals in the carbonatized oceanic crust were very likely to store in the accretionary prisms and mantle, consequently giving rise to a decrease of atmospheric and oceanic CO 2 .Keywords: hydrothermal, carbonatization, carbonate, carbon dioxide, oceanic crust, stromatolite, global carbon cycle, Early Archean, Warrawoona Group carbonate displaying a stromatolite texture deposited in the ocean (Fig. 2b;Walter and Heys, 1985;Awramik, 1992;Semikhatov and Raaben, 1996). This geological evidence suggests that biological activity of cyanobacteria was mostly responsible for carbonate precipitation in the Proterozoic (Grotzinger and Knoll, 1999;Riding, 2000). In contrast, sedimentary carbonates were much less in the Archean than the Proterozoic and Phanerozoic (Fig. 2a;Ronov, 1964;Veizer et al., 1989a). Although more than 20 of stromatolite occurrences are now known worldwide in the Archean (Martin et al., 1980;Walter, 1983;Beukes and Lowe, 1989), the true fossil record such as a stromatolite texture and microfossils is sparse in the Archean compared to the Proterozoic (Hofmann, 1999). In particular, the occurrences of the stromatolites older than 3.2 Ga are rare ( Fig. 2b; Hofmann, 1999), and the biogenesis of the stromatolite-like textures has been questioned (Walter et al., 1980;Lowe, 1980bLowe, , 1994Lowe, , 1995Buick et al., 1995). It is assured that the carbonate sediment was significantly minor in the Archean. However, several researchers have believed that the carbonate precipitation is essentially the same throughout the Earth's history ...

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“…Burrows et al. 1986;Groves et al, 1988;Nisbet and Kyser, 1988;Golding et al, 1989;de Ronde et al, 1992). In the Paleoproterozoic Ashanti gold belt, the hydrothermal carbonates have an average value of-14%o (Oberthiïr et al, 1996), whereas the Loulo gold deposit in Mali yielded values ranging between -13.5 and -4.5%o (Fouillac et al, 1993).…”

Section: The Source Of Carbonmentioning

confidence: 99%

Géologie, géochimie et métallogénie du gisement d'or Omai, Bouclier Guyanais, Amérique du Sud =

Voicu¹

1999

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IVdépôt de la minéralisation à Ornai (basse température, pression, salinité, et contenu en CO 2 , pH légèrement acide à neutre, fugacités modérées de l'oxygène et du soufre, fugacité élevée des tellurures), l'implication de l'eau de surface, la présence des structures hôtes de la minéralisation de nature essentiellement cassante et la localisation dans un terrain faiblement métamorphisé sont autant de critères permettant de classer Ornai dans la catégorie des gîtes épithermaux. D'autres caractéristiques majeures tels que: le style d'altération; le cadre géodynamique; l'emplacement tardi-orogénique/syn-à tarditectonique; la présence des fluides d'une source profonde et; de manière moins directe, la paragénèse minéralogique se rattachent à la définition des gîtes mésothermaux plus profonds. La superposition des caractéristiques épi-et mésothermales d'Omai correspond donc à la partie supérieure du "continuum model" proposé pour les gisements archéens de type "gold-only" et définie comme le domaine crustal dit épizonal. Ornai serait donc un premier exemple de gîte orogénique aurifère d'âge paléoprotérozoïque de type épizonal associé aux granitoïdes et aux roches vertes. Il représente un équivalent de ce type de gîte ayant été décrit uniquement dans certains cratons archéens (Yilgarn et Zimbabwe).Mots clé: Guyana, Paléoprotérozoïque, or, géochimie, métallogénie ABSTRACTThe Omai gold mine is located in the Barama-Mazaruni Supergroup, part of the Paleoproterozoic greenstone belt of the north-central Guiana Shield. The lithological sequence consists of mafic volcanic (and genetically related subvolcanic maficultramafic bodies) to felsic volcanic cycles with intercalated sediments. The volcanosedimentary unit was intruded by a quartz monzodiorite plug (the Omai stock) and several irregularly-shaped quartz-feldspar porphyry and rhyolite dikes. Postmineralization mafic dikes and sills were intruded discontinuously from Mesoproterozoic to Triassic. The Barama-Mazaruni volcano-sedimentary sequence has been metamorphosed to lower greenschist faciès. The local structure is relatively simple and consists of two deformational phases (Dl and D2). Dl phase resulted in the ESE-WNW trending/steeply dipping regional scale foliation and ductile shear zones, whereas the D2 event caused brittle± ductile fracturing with moderate dips, oriented perpendicularly to Dl shear zones. D2 structures provided the main pathways for the mineralizing fluids.The Omai deposit consists of two gold mineralized zones exploited in open pit operations referred to as Fennell and Wenot. Fennell mineralization is mainly hosted by the Omai stock and to a lesser extends by the volcanic rocks (tholeiitic basalts and calcalkaline andésites). Wenot mineralization is mainly hosted by tabular quartz-feldspar porphyry dikes as well as by strongly silicified rhyolite dikes, and subordinately by andésites and metapelites.The geological features and geochronological data of these ore zones suggest that they are genetically related and represent a contemporaneous metallo...

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Archaean carbon reservoirs and their relevance to the fluid source for gold deposits

Cited by 71 publications

References 16 publications

High 3He/4He ratios in the Wangu gold deposit, Hunan province, China: Implications for mantle fluids along the Tanlu deep fault zone.

High 3He/4He ratios in the Wangu gold deposit, Hunan province, China: Implications for mantle fluids along the Tanlu deep fault zone.

Carbonate Minerals in the Warrawoona Group, Pilbara Craton: Implications for Continental Crust, Life, and Global Carbon Cycle in the Early Archean

Géologie, géochimie et métallogénie du gisement d'or Omai, Bouclier Guyanais, Amérique du Sud =

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