The use of microchemical analysis of alluvial gold grains in mineral exploration: experiences in Britain and Ireland

Chapman, Robert J.; Leake, R. C.; Moles, Norman

doi:10.1016/s0375-6742(00)00157-6

Cited by 44 publications

(30 citation statements)

References 6 publications

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“…One assemblage comprised sulphides and sulpharsenides whilst 40% of the inclusions from another were tellurium-bearing minerals. The third population was distinguished both by the presence of molybdenite inclusions and by a mean silver content in the gold alloy 15% higher than recorded for gold from the adjacent rivers (9).…”

Section: Platementioning

confidence: 89%

“…Studies of gold from Britain and Ireland (8,9), North America (5 -7), and New Zealand (41) failed to identify any evidence for augmentation of the alluvial population by authigenic processes, and the internal characteristics of the gold grains were considered consistent with those from the hypogene source. These results give a strong indication that for alluvial gold in temperate climates the contribution of authigenic gold is negligible, although many grains exhibit gold rich rims typically to a thickness of about 10 μm, which have been attributed to a process of silver depletion (22).…”

Section: Platementioning

confidence: 99%

“…The technique is highly reproducible in terms of both sampling and analysis (9). The microchemical signature of gold from an area in the Leadhills district of Southern Scotland is independent of the field sampler, the date of collection and the exact location of the sampling site.…”

Section: Platementioning

confidence: 99%

“…The Search for a Specific Style of Gold Mineralization Alluvial gold is widespread in Northern Ireland and in one part the local geology suggested the presence of skarn mineralization (9). However, interpretation of the microchemical signatures of alluvial gold samples from the area shows that all the gold grains correspond to the two major types of mineralization further south, neither of which is of the skarn type.…”

Section: Applications Of the Technique To Exploration For Gold Mineramentioning

confidence: 99%

“…However, the work of the present authors, which is summarised here (and augmented by previously unpublished data for localities in North America and Australia), represents the first studies to systematically record the mineral inclusion assemblages and to generate classifications of gold grain chemistry which combine this information with that of the gold alloy composition. The resulting 'microchemical signature' provides a more powerful technique for interpreting the origin of alluvial gold than gold alloy composition alone, because the composition of native gold grains can vary from point to point within the same mineralized structure (9). This work has been undertaken for a period of over 15 years during which over 20,000 gold grains from 314 localities in Great Britain and Ireland, together with other sites in North America, South America, southern Africa, Australia, south east Asia, and Fiji, have been studied.…”

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confidence: 99%

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Microchemical Characterization of Alluvial Gold Grains as an Exploration Tool

2002

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There is considerable variation in the composition of native gold and the nature of minerals co-existing with it, and this reflects differences in the geological environment and chemistry of ore-forming processes. In areas where gold-bearing mineralization is subject to active fluvial erosion, especially in temperate climatic regimes, any discrete grains of native gold pass into alluvial sediment with little modification. The chemical characteristics of alluvial grains and the nature of preserved mineral inclusions provide a signature which points back to the type of source mineralization. This signature may be established using electron probe microanalysis and scanning electron microscopy and can be interpreted to provide information about the original bedrock mineralization. Identification of the type of source mineralization using the technique at an early stage in regional exploration can help focus attention on targets with the most potential economic importance.

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Section: Platementioning

confidence: 89%

Section: Platementioning

confidence: 99%

Section: Platementioning

confidence: 99%

Section: Applications Of the Technique To Exploration For Gold Mineramentioning

confidence: 99%

mentioning

confidence: 99%

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Microchemical Characterization of Alluvial Gold Grains as an Exploration Tool

2002

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Mineral chemistry, bulk rock geochemistry, and S‐isotope signature of lode‐gold mineralization in the Bétaré Oya gold district, south‐east Cameroon

et al. 2017

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Lode‐gold mineralization in the Bétaré Oya gold district is related to a series of quartz–sulphide veins that define a steeply dipping NNE–SSW‐trending brittle–ductile shear zone. The veins transect metasedimentary sequences in the vicinity of small granitic intrusions. Quartz veins range from barren (massive quartz) to mineralized with textures that vary from foliated, sheared, vuggy, fractured, and sugary to brecciated with inclusions of altered wall rock. They contain gold, pyrite, and galena in addition to chalcopyrite and both hypogene and supergene haematite and covellite. Parameters that consistently define primary gold mineralization in the area include silicification, sulphidation, sericitization, K‐feldspar alteration, haematitization, and carbonatization. Gold grains recovered from heavy mineral concentrate and grains that occur as inclusions in pyrite were characterized by microchemical methods. The gold grains are zoned and exhibit a simple internal structure of partly deformed and leached rims and high‐purity intragranular veinlets. Gold is alloyed with Ag; gold fineness varies between 859 and 877 in the core and from 958 to 997 in the leached rims. Inclusions of gold in pyrite cluster between 875 and 900. Pyrite has up to 0.59 wt% Au, and other trace elements occur in low quantities but for Pb (0.13 wt%), Ag (1.36 wt%), and Sb (1.63 wt%). The bulk trace element signature of the veins is characterized by Au, Ag, As, Bi, Ba, Cr, Cu, Mn, Pb, Sb, Sr, V, W, Zn, and Zr. This depicts a geochemical association of Au ± Cu ± Bi ± As ± Pb. The occurrence of Au as well as elevated Pb and Zn could suggest a granitic source for the ore‐bearing fluid. The auriferous quartz veins are characterized by a widespread in δ34S from 2.8 to 14.9‰ pointing to multiple sources of sulphur in the system, perhaps a mixture of sulphur from the metasedimentary and the granitic rocks.

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