Young orogenic gold mineralisation in active collisional mountains, Taiwan

Craw, Dave; Upton, Phædra; Yu, Biao; Horton, Travis W.; Chen, Yue‐Gau

doi:10.1007/s00126-010-0297-4

Cited by 43 publications

(15 citation statements)

References 40 publications

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“…The penny finally dropped in the light of integrated petrology and geochronology carried out by Craw et al (2010) on mineralisation in Taiwan. This study demonstrated that the gold-quartz veins formed during rapid uplift at the end of the metamorphic cycle.…”

Section: Orogenic Gold Depositsmentioning

confidence: 99%

Fluids in the Continental Crust

Yardley¹,

Bodnar²

2014

GeochemPersp

221

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Section: Orogenic Gold Depositsmentioning

confidence: 99%

Fluids in the Continental Crust

Yardley¹,

Bodnar²

2014

GeochemPersp

221

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“…Phanerozoic orogenic gold deposits in metasedimentary terranes rarely display epithermallike textures (e.g. Nesbitt et al, 1986;Dowling and Morrison, 1990;Herrington and Wilkinson;1993;Bierlein and Crow, 2000;Craw et al, 2010). However, it may be significant that vuggy vein textures interpreted as indicative of open space growth are reported from the later quartz generations in the Caledonian age Curraghinalt gold deposit in Northern Ireland (Wilkinson et al, 1999).…”

Section: Orogenic Goldmentioning

confidence: 99%

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

et al. 2011

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The Bohaun gold deposit in County Galway, western Ireland is located in the Caledonian orogenic belt, proximal to a major accretionary boundary. The mineralization is hosted in a normal extensional fault, representing a zone of repeated extension and vein infilling of open cavities, within clastic sedimentary rocks, which have only reached the late diagenetic zone of low-grade metamorphism.The mineralization consists of undeformed veins, stockworks and breccias. Quartz dominates all the veins and commonly displays multiple growth stages and a variety of classic epithermal textures, including comb, plumose and banded, indicative of low confining pressures. The veins have a simple mineralogy comprising quartz-sericite-chlorite with minor sulfides, hematite, rare visible gold, with a high silver content (up to 41 wt %), and late barite and dolomite.Vein quartz is associated with two fluids compositions: Type I with moderate to high salinity (8.0-23.6 wt % NaCl equiv) and Type II with low to moderate salinity (0.0-7.8 wt % NaCl equiv). CO 2 contents in both fluid types are <3.5 wt percent. The majority of fluid inclusion homogenization temperatures range from 126 to 257 o C and geologically constrained depth estimates (≤5 km) indicate maximum fluid inclusion trapping temperatures between 175 and 245°C.The geodynamic setting of Bohaun, which comprises a deformed continental margin of an allochthonous terrane, is typical of orogenic gold deposits. However, an orogenic association for the Bohaun mineralization is discounted on the basis of fluid inclusion evidence, atypical vein textures, gold grain composition and undeformed veins. While vein textures locally resemble those found in epithermal quartz-adularia mineralization, there is no obvious magmatic association and alteration is restricted to the veins and immediate host rocks. The origin of the gold at Bohaun remains enigmatic. However, we favor an association with widespread Carboniferous or later mineralizing fluids and a model which involves transport and deposition of gold from a basinal brine type fluid, in a similar fashion to red-bed Au-Pd mineralization. Bohaun provides further evidence that low temperature brines may be capable of generating economic grade gold mineralization, independent of other fluids.3

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“…Studies such as the work of Craw et al (2010) appear to demonstrate beyond reasonable doubt that some vein deposits of Au hosted by metamorphic rocks do indeed derive from the passage of fluids released during metamorphism. This is not to say that all 'orogenic gold deposits' have formed in the same way, however.…”

Section: Mineralizing Potential 3: Flow Considerationsmentioning

confidence: 98%

“…On the other hand, an origin during uplift at the end of the orogenic cycle (Pettke et al 2000) not only fits better with field relationships in many cases, but it is also compatible with a short duration for the ore-forming event. Craw et al (2010) have presented detailed petrology and geochronology for the formation and subsequent uplift of young orogenic gold veins in Taiwan. They argue that the metamorphic fluid release that gave rise to Au mineralization took place in a short-lived event bracketed by greenschist facies metamorphism below 10 km depth at 5 Ma and late veining at a depth of c. 4 km, dated to 2 Ma.…”

Section: Mineralizing Potential 3: Flow Considerationsmentioning

confidence: 99%

The role of metamorphic fluids in the formation of ore deposits

Yardley

Cleverley

2013

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Many ore deposits are hosted by metamorphic rocks, and metamorphic fluids have been invoked as a source for various deposits, especially gold deposits. Metamorphic fluid compositions reflect original sedimentary environment: continental shelf sequences yield saline metamorphic fluids with little dissolved gas while metasediments from accretionary and oceanic settings host less saline fluids with significant CO 2 contents.The principal difficulty in reconciling ore deposits with a metamorphic origin is that many form quickly (c. 1 Ma), whereas metamorphic heating is slow (c. 10-208/Ma). Gravitational instability means that fluid cannot be retained. Metamorphic ores may nevertheless form by: (a) segregation leading to enrichment of pre-existing concentrations; (b) infiltration of water-rich fluids from schists into marbles at high temperature overstepping decarbonation reactions and allowing fast reaction that locally draws down temperature; and (c) rapid uplift driving dehydration reactions owing to pressure drop.Some orogenic lode gold deposits fit well with a purely metamorphic origin during rapid uplift, but others are problematic. At Sunrise Dam, Western Australia, anomalies in Sr-isotope ratios and in apatite compositions indicate a partial mantle/magmatic source. Low salinity, H 2 O-CO 2 fluids commonly associated with hydrothermal gold reflect the effect of salt on gas solubility, not the origin of the fluid.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.Many hydrothermal ore deposits are hosted by metamorphic rocks, and so the possibility that ore deposits may form from metamorphic fluids has been discussed for many years. In this paper we will review what is known about metamorphic fluids from a chemical perspective, and the implications that this may have for their ore-forming potential, and then put this in the context of the history of regional metamorphism and the physical supply of fluid to possible ore systems. Possible natural examples of metamorphic fluids giving rise to ore deposits are also discussed with an emphasis on gold mineralization, because this is the type of mineralization for which metamorphic fluids have been most widely invoked.The term metamorphic fluid is used here in the strict sense to denote fluids present during prograde metamorphism. They will commonly include a component of pre-metamorphic formation waters as well as fluid released by breakdown of volatilebearing minerals, all modified by ongoing interactions with host rock. This definition is much more restrictive than that often used in stable isotope studies, which embraces all fluids that have isotopically equilibrated with metamorphic rocks, irrespective of their origin.Despite some clear evidence to the contrary (e.g. Roedder 1972), until recently crustal fluids were generally assumed to carry only small amounts of potential ore metal in solution. Thus the problem of understanding ore deposits was seen as one of accounting for extensive focussing of fluid flow. With the ...

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Young orogenic gold mineralisation in active collisional mountains, Taiwan

Cited by 43 publications

References 40 publications

Fluids in the Continental Crust

Fluids in the Continental Crust

Atypical Gold Mineralization in an Orogenic Setting--The Bohaun Deposit, Western Irish Caledonides

The role of metamorphic fluids in the formation of ore deposits

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