The behavior of gold in unaltered island arc tholeiitic rocks from Izu-Oshima, Fuji, and Osoreyama volcanic areas, Japan

Togashi, S.; Terashima, Shigeru

doi:10.1016/s0016-7037(96)00369-9

Cited by 48 publications

(14 citation statements)

References 29 publications

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“…The global upper mantle contains 1.5 ppb Au (e.g., Mitchell and Keays, 1981;Lorand et al, 1999;McInnes et al, 1999;Borisov and Palme, 2000), but in Archean greenstones and modern oceanic basalts, typical background Au contents are 0.7-2 ppb (Meyer and Saager, 1985;Greenough and Fryer, 1990;Togashi and Terashima, 1997). Loucks and Mavrogenes (1999) report solubility values of 29 and 167 ppm Au at 0.37 GPa and 625°C in supercritical hydrothermal brines equilibrated with pyrrhotite + magnetite.…”

Section: Implications For the Gold Budget Of Arc Magmasmentioning

confidence: 99%

Gold solubility in arc magmas: Experimental determination of the effect of sulfur at 1000 °C and 0.4 GPa

Jégo

Pichavant

2012

Geochimica et Cosmochimica Acta

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To investigate the behaviour of gold in sulfur-bearing hydrous intermediate calc-alkaline melts under different redox states typical of subduction-zone settings, we have determined the solubility of Au at 0.4 GPa and 1000°C for three dacitic magmas (two adakites and one calc-alkaline composition) from the North-Luzon Arc (Philippines). The experiments were performed over an oxygen fugacity (fO 2 ) range corresponding to reducing ($NNOÀ1), moderately oxidizing ($NNO+1.5) and strongly oxidizing (PNNO+3) conditions as measured by solid Ni-Pd-O sensors. They were carried out in gold containers, serving also as the source of gold, in presence of variable amounts of H 2 O and $1 wt.% of elemental sulfur (S). Concentrations of Au in glasses were determined by laser-ablation inductively-coupled plasma mass spectrometry (LA-ICPMS). Gold solubility in S-bearing melts is drastically enhanced compared to S-free melts, by up to two orders of magnitude. In addition, very high gold solubilities are reached under reducing conditions (

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Section: Implications For the Gold Budget Of Arc Magmasmentioning

confidence: 99%

Gold solubility in arc magmas: Experimental determination of the effect of sulfur at 1000 °C and 0.4 GPa

Jégo

Pichavant

2012

Geochimica et Cosmochimica Acta

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“…In the other models of adakite petrogenesis, as well as in the case of calc-alkaline magma genesis, sources of gold and other metals are mainly mantle protoliths from the wedge (Mungall, 2002), the latter containing on average up to 1.5 ppb Au (e.g., [Mitchell and Keays, 1981], [Lorand et al, 1999], [McInnes et al, 1999] and [Borisov and Palme, 2000]). In comparison, amphibolitic rocks (i.e., archean greentones and modern oceanic metabasalts) generally contain <2 ppb Au ( [Greenough and Fryer, 1990] and [Togashi and Terashima, 1997]). Borisova et al (2006) estimated that a bulk slab composed of 90 wt% fresh MORB + 5 wt% altered MORB + 5 wt% sediment has Au concentrations up to 5 ppb Au.…”

Section: Slab Melting As Source Of Metals?mentioning

confidence: 99%

Controls on gold solubility in arc magmas: An experimental study at 1000°C and 4kbar

Jégo

Pichavant

Mavrogenes

2010

Geochimica et Cosmochimica Acta

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In order to (1) explain the worldwide association between epithermal gold-coppermolybdenum deposits and arc magmas and (2) test the hypothesis that adakitic magmas would be Au-specialized, we have determined the solubility of Au at 4 kbar and 1000 °C for three intermediate magmas (two adakites and one calc-alkaline composition) from the Philippines. The experiments were performed over a fO 2 range corresponding to reducing ( NNO−1), moderately oxidizing ( NNO+1.5) and strongly oxidizing ( NNO+3) conditions as measured by solid Ni-Pd-O sensors. They were carried out in gold containers, the latter serving also as the source of gold, in presence of variable amounts of H 2 O and, in a few additional experiments, of S. Concentrations of Au in glasses were determined by LA-ICPMS. Gold solubility in melt is very low (30-240 ppb) but increases with fO 2 in a way consistent with the dissolution of gold as both Au 1+ and Au 3+ species. In the S-bearing experiments performed at NNO−1, gold solubility reaches much higher values, from 1200 to 4300 ppb, and seems to correlate with melt S content. No systematic difference in gold solubility is observed between the adakitic and the non-adakitic compositions investigated. Oxygen fugacity and the sulfur concentration in melt are the main parameters controlling the incorporation and concentration of gold in magmas. Certain adakitic and non-adakitic magmas have high fO 2 and magmatic S concentrations favorable to the incorporation and transport of gold. Therefore, the cause of a particular association between some arc magmas and Au-Cu-Mo deposits needs to be searched in the origin of those specialized magmas by involvement of Au-and S-rich protoliths. The subducted slab, which contains metal-rich massive sulfides, may constitute a potentially favorable protolith for the genesis of magmas specialized with respect to gold.

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“…It is a moderately incompatible element at the early stage of basic magmatic evolution when sulphur is undersaturated. Namely, the concentration of Au increases with increasing SiO 2 content, with the highest concentration at SiO 2 contents of ∼55-60 wt.%, after which the concentration of Au drops suddenly to concentrations of ∼1-2 ppb (Figure 1) (Togashi and Terashima 1997;Sun et al 2004Sun et al , 2011. The turning point for this transformation is slightly different for different suites of arc volcanic rocks, with overall consistent trends.…”

Section: The Geochemical Behaviour Of Aumentioning

confidence: 68%

“…It is the best source rock for orogenic Au deposits. Data source: Togashi and Terashima (1997) and Sun et al (2004).…”

Section: The Geochemical Behaviour Of Aumentioning

confidence: 99%

Large-scale gold mineralization in eastern China induced by an Early Cretaceous clockwise change in Pacific plate motions

Sun

Yang

et al. 2012

International Geology Review

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Orogenic gold (Au) deposits are the most important type, accounting for more than half of the world's proven Au reserves. They are mainly controlled by three key factors: (1) abundant andesitic rocks (SiO 2 of 55-60 wt.%) at depth, which have systematically higher Au contents than other rock types; (2) a pervasive transition from greenschist facies to amphibolite facies metamorphism within a short period, which releases S 2− -rich fluids that may scavenge Au from host rocks; and (3) deformation and fracturing under a compressive/transpressive tectonic regime. Orogenic belts at convergent margins are the best places for such mineralization because convergent margins are rich in andesites; the transition from greenschist to amphibolite facies recrystallization commonly occurs as a result of collision, compression, and thickening at convergent margins, forming large amounts of Au-rich fluids within a short period of time; and strong deformation and fracturing during orogenic processes provide channels for fluid transportation. Moreover, the overlying plate is injected and enriched by auriferous fluids released during amphibolite facies metamorphism of the subducting plate. The Pacific plate changed course by ∼80• (from SW to NW) at approximately 125-122 Ma, reflecting an altered thermal structure and the elevation of the South Pacific plate attending the appearance of the plume head that formed the Ontong Java large igneous province. Consequently, the tectonic regime changed from extension to compressive/transpressive in eastern China, causing deformation, thickening, and metamorphism of the overriding plate, especially along weak crustal belts (e.g. overlying plates of palaeosutures), which resulted in world-class mineralization of orogenic Au deposits. During this process, pyrite changed to pyrrhotite during the transition from greenschist to amphibolite facies, releasing sulphur. Sulphur mobilized and scavenged Au and other chalcophile elements into metamorphic ore-forming fluids. A series of NE-trending compressive faults were formed at ∼120 Ma as a result of continuous compression of the subducting Pacific plate, releasing these ore-forming fluids. Auriferous carbonate-rich quartz veins and/or metasomatized Au-bearing wall rocks were formed due to the decompression of the ascending ore-forming fluids. Orogenic belts along the margins of the North China craton and the Jiangnan block were the most favourable regions for mineralization. Compared with the former, the latter has much smaller proven Au reserves. However, more exploration is needed along the margins of the Jiangnan block. Promising targets include accessory faults and kink points of large, NE-trending Cretaceous faults that transect greenschist facies metamorphic rocks of the Niuwu and Jingtan Groups, etc.

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The behavior of gold in unaltered island arc tholeiitic rocks from Izu-Oshima, Fuji, and Osoreyama volcanic areas, Japan

Cited by 48 publications

References 29 publications

Gold solubility in arc magmas: Experimental determination of the effect of sulfur at 1000 °C and 0.4 GPa

Gold solubility in arc magmas: Experimental determination of the effect of sulfur at 1000 °C and 0.4 GPa

Controls on gold solubility in arc magmas: An experimental study at 1000°C and 4kbar

Large-scale gold mineralization in eastern China induced by an Early Cretaceous clockwise change in Pacific plate motions

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