Microchemical signature of alluvial gold from two contrasting terrains in Cameroon

Omang, Benjamin Odey; Suh, Cheo Emmanuel; Lehmann, Bernd; Vishiti, Akumbom; Chombong, N. N.; Fon, Albert Nih; Egbe, J.A.; Shemang, Elisha

doi:10.1016/j.jafrearsci.2015.09.004

Cited by 43 publications

(35 citation statements)

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“…The technique of microchemical classification of the placer gold grains (Chapman et al, ; Chapman, Leake, & Styles, ; Chapman, Mortensen, Crawford, & LeBarge, , ; Chapman et al, ; Chapman, Shaw, Leake, & Jackson, ; Lalomov et al, ; Leake et al, ; Moles et al, ; Omang et al, ) has been applied to illustrate the types of placer gold and their relations to the source mineralization, even in the cases, the lode source remains unknown. This technique provides important clues to predict the mode of source mineralization by comparing the microchemical signature of a population of placer gold grains with the generic characteristics of different modes of gold mineralization (Chapman & Mortensen, ).…”

Section: Discussionmentioning

confidence: 99%

“…Some grains contain both groves and cavities (Figure 3c) which show that the source is within 1,000 m. Grains in Figures 2d and 3d in our study contain neither groves nor cavities which indicate that the source mineralization is farther than 1,000 m. The polished rounded outline of grain in Figure 2b indicates greater than 1,000 m distance from the source mineralization. Leake, & Jackson, 2005;Lalomov et al, 2016;Leake et al, 1998;Moles et al, 2013;Omang et al, 2015) has been applied to illustrate the types of placer gold and their relations to the source mineralization, even in the cases, the lode source remains unknown. This technique provides important clues to predict the mode of source mineralization by comparing the microchemical signature of a population of placer gold grains with the generic characteristics of different modes of gold mineralization (Chapman & Mortensen, 2006).…”

Section: Morphology As Indicator Of Proximity To Gold Sourcementioning

confidence: 99%

“…The morphology and chemistry of alluvial gold grains and their inclusions are potential indicators of characterizing the primary gold mineralization, mineralization style, and the potential host rock (e.g., Chapman, Leake, Bond, Stedra, & Fairgrieve, ; Chapman, Mortensen, & LeBarge, ; Lalomov et al, ; Moles, Chapman, & Warner, ; Omang et al, ; Townley et al, ). The textures of placer gold grains have been used to evaluate authigenic gold precipitation in supergene environments and their distinction from gold grains liberated from lode sources (Youngson & Craw, ).…”

Section: Introductionmentioning

confidence: 99%

“…The Gilgit Baltistan province, dominated by dry temperate climate and glacial environment having steep geomorphology, precluding any significant supergene processes such as silver leaching and addition of authigenic gold on detrital gold grains. The morphology and chemistry of alluvial gold grains and their inclusions are potential indicators of characterizing the primary gold mineralization, mineralization style, and the potential host rock (e.g., Chapman, Leake, Bond, Stedra, & Fairgrieve, 2009;Chapman, Mortensen, & LeBarge, 2011;Lalomov et al, 2016;Moles, Chapman, & Warner, 2013;Omang et al, 2015;Townley et al, 2003). The textures of placer gold grains have been used to evaluate authigenic gold precipitation in supergene environments and their distinction from gold grains liberated from lode sources (Youngson & Craw, 1993).…”

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confidence: 99%

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Morphology and chemistry of placer gold in the Bagrote and Dainter streams, northern Pakistan: Implications for provenance and exploration

Alam

Santosh

et al. 2018

Geological Journal

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The Bagrote and Dainter valleys in Gilgit Baltistan Pakistan, belonging to the Kohistan island arc and southwestern domain of the Karakorum metamorphic complex, respectively, are a location of regional placer gold mining. However, no in situ hydrothermal gold deposits have been discovered in this region. Here, we report the textural, morphological, and geochemical characteristics of placer gold from the stream sediments of the Bagrote and Dainter valleys with a view to trace the provenance. The morphological features of the studied gold grains indicate proximal source mineralization. The gold grains display a microtexture typical of mechanical abrasion rather than chemical activity. Their chemical composition of most of the grains from each stream falls in a restricted range (minor alloying elements mainly Cu) with high fineness (1,000 Au/(Au + Ag)), suggesting derivation from a homogeneous source or limited number of mineralization types. The high Cu content of the gold grains from the Bagrote stream suggests that the gold here might be associated with previously undiscovered porphyry gold mineralization, whereas the Au–Ag–Hg alloys from the Dainter stream suggest a genetic linkage with undiscovered fault‐controlled auriferous veins of epithermal origin in the southwestern part of the Karakorum metamorphic complex. The chemical composition of both streams placer gold in triangular diagram in terms of Au–Ag–Cu shows all the gold grains from Dainter stream were derived from epithermal type of mineralization, and most of the plots of Bagrote stream fall on the domain of porphyry epithermal type of deposits which are also in consistent with a continental arc setting in the study area. The mechanically developed microtexture, homogeneous chemical composition in individual grains from core to rim, and absence of high fineness rims of the gold grains from both streams, suggest the absence of any supergene regrowth and direct transfer from the primary source through glacier to the fluvial system. The Gilgit Baltistan province, dominated by dry temperate climate and glacial environment having steep geomorphology, precluding any significant supergene processes such as silver leaching and addition of authigenic gold on detrital gold grains.

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Section: Discussionmentioning

confidence: 99%

Section: Morphology As Indicator Of Proximity To Gold Sourcementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Morphology and chemistry of placer gold in the Bagrote and Dainter streams, northern Pakistan: Implications for provenance and exploration

Alam

Santosh

et al. 2018

Geological Journal

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“…The tectonic evolution of this pull-apart basin and hydrothermal alteration around the plutons account for the widespread sulphide-bearing quartz vein gold deposits (Toteu et al 2004). Accordingly, alluvial gold is worked from the streams draining this catchment (Omang et al 2015). Small-scale gold mining constitutes the major industry in the area and dates back to the 1930s (Foumena and Bamenjo 2013).…”

Section: Study Areamentioning

confidence: 99%

Seasonal Hydrological Inputs of Major Ions and Trace Metal Composition in Streams Draining the Mineralized Lom Basin, East Cameroon: Basis for Environmental Studies

et al. 2017

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Purpose The aim of this study is to assess the seasonal variation in major ion distribution patterns and identify the origin and geochemical behavior of some trace metals of streamwaters bathing the mineralized Lom Basin. Methods Eighty-one water samples were collected during the dry and wet seasons and analyzed for major ions using AAS and 12 trace metals (Fe, Mn, V, Cr, Co, Ni, Cu, Zn, As, Cd, Pb, Hg) by ICP-MS. Results All physicochemical parameters besides pH and Cl -varied narrowly between both seasons. No seasonal variability was observed for Cl -given its conservative nature, while NO 3 -levels decreased in the wet period due to the dilution effect. Similarly, SO 4 2-concentrations were low for both seasons reflecting the dissolution of low sulphide minerals associated with gold deposits. In contrast, the concentration of Ca 2? , Mg 2? , Na ? , K ? and HCO 3 -slightly increased during the wet season as they are flushed from the soil layers by rain. Water samples had very low concentrations (\ 1 lg/l) of V, Cr, Co, Cu, Zn, Cd, Pb and significant concentrations of Fe and Mn.Conclusions The seasonal regime of streamwater chemistry is controlled by groundwater supply of major cations and HCO 3 -from chemical weathering, leaching of ions from surface soil layers during precipitation and dilution of nitrate by surface runoff during the wet season. In this tropical basin, low acidity and trace metal loadings revealed lateritic weathering of sulphides, entrapment of trace metals in Fe and Mn oxides and leaching into deep groundwater. Although the streams have not been impacted, these findings may guide policymakers for water chemistry evaluation in Cameroon.

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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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Microchemical signature of alluvial gold from two contrasting terrains in Cameroon

Cited by 43 publications

References 36 publications

Morphology and chemistry of placer gold in the Bagrote and Dainter streams, northern Pakistan: Implications for provenance and exploration

Morphology and chemistry of placer gold in the Bagrote and Dainter streams, northern Pakistan: Implications for provenance and exploration

Seasonal Hydrological Inputs of Major Ions and Trace Metal Composition in Streams Draining the Mineralized Lom Basin, East Cameroon: Basis for Environmental Studies

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

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