F. Pirajno 1992. Hydrothermal Mineral Deposits. Principles and Fundamental Concepts for the Exploration Geologist. xviii + 709 pp. Berlin, Heidelberg, New York, London, Paris, Tokyo, Hong Kong: Springer-Verlag. Price DM 248.00 (hard covers). ISBN 3 540 52517 3.

Steed, G. M.

doi:10.1017/s0016756800020392

Cited by 3 publications

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“…The fact that gold is not in this paragenesis might also suggest that this paragenesis represents another sulphidation event that is barren with respect to Au. Elements commonly found enriched in mesothermal lode gold deposits in metamorphic terrains include Au, Ag, As, Sb, Hg, W, Bi, and Mo (Pirajno, 1992). Less commonly, Pb, Zn, and Cu may be present.…”

Section: Geochemistrymentioning

confidence: 99%

Statistical evaluation of stream sediment geochemical data from Tchangue-Bikoui drainage system, Southern Cameroon: a regional perspective

Nforba

Egbenchung

Berinyuy

et al. 2020

Geology, Ecology, and Landscapes

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Stream sediments play a significant role in geochemical exploration by identifying possible sources of anomalous element concentration. In this study, we use a multi-element association analysis to investigate the concentration of gold and associated elements in stream sediment samples from the Tchangue-Bikoui drainage area, Southern Cameroon. The main river and its tributaries were sampled, panned for gold grain recovery and the 100 μm size fractions analyzed for Au and associated elements by inductively coupled plasma atomic emission spectrometry (ICP-AES). A total of 50 samples were collected defining an area of~145 km 2 and 20 samples selected for geochemical analysis for a suite of 20 elements. Gold grades estimated by the panning and weighing technique rarely exceed 0.45 g/t and generally erratic while the Au concentrations from chemical analysis range from 0.01ppb to 4.00ppb. R-mode factor analysis produced a five-factor model accounting for 62.4% of the total variance. The Ni-Au-V-Sr association indicated gold mineralization while the others reflect lithologic control. Mo-Cr-Hg-Ag-As-Zr and Pb-Cu show no spatial relationship to Au and point to a typical primary mesothermal sulphide mineralization in the area which can be further investigated. Anomalous gold concentrations clustered mostly in the southeastern part downstream of River Tchangue defining a potential primary gold target.

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Section: Geochemistrymentioning

confidence: 99%

Statistical evaluation of stream sediment geochemical data from Tchangue-Bikoui drainage system, Southern Cameroon: a regional perspective

Nforba

Egbenchung

Berinyuy

et al. 2020

Geology, Ecology, and Landscapes

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Assessment of gold potential in stream sediments around the Neoproterozoic Boyo area, Betare-Oya Gold District, Eastern Cameroon

Jean-Lavenir

Ngomba

Junior

2022

Preprint

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Stream sediment geochemical survey was carried out in Boyo area, samples collected and analyzed for major, trace and rare earth elements using ICP-MS method. Minerals present in concentrates include gold, zircon, muscovite. The grain size of gold varies from 0.125 to 1 mm, their shape ranges from sub-angular to angular. Gold grains are of two categories: the first category includes those that are distal to the source, the second category comprises those that are proximal to the source. Fe2O3, Al2O3 and SO3 are dominant major elements in stream sediment, sediments are depleted in Nb and Mo. Gold (8440 to > 10000 ppb) has the highest concentration, the Au/Ag (av.: 14.16) ratio exhibits unusual value greater than the value of the upper lithosphere. Sediments ranged into low Ag (0.062 to 8.47 ppm) and high Ag (20 to 51.3 ppm) content, and all of this suggests that the Boyo gold grains result from two sources or derived by two geological processes; the sulphidation was the dominant mechanism of gold ore deposition. Ag-Au-Bi-Cu constitutes the mineralization factor and the chalcophile elements Ag, Bi and Cu serve as potential pathfinders for Au in the Boyo area. The presence of these elements in the same factor suggests that gold is associated with sulphide minerals. Ag-Hg-W association is related to the hydrothermal alteration of wall rock. The association Ag-Au-Bi-Cu indicates a typical primary mesothermal sulphide ± gold mineralization paragenesis. The Boyo mature sediments derived from intermediate igneous sources that were deposited in a passive margin environment.

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Shannon Entropy as an Indicator for Sorting Processes in Hydrothermal Systems

Ruitenbeek

Bakker

Hein

2020

Entropy

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Hydrothermal processes modify the chemical and mineralogical composition of rock. We studied and quantified the effects of hydrothermal processes on the composition of volcanic rocks by a novel application of the Shannon entropy, which is a measure of uncertainty and commonly applied in information theory. We show here that the Shannon entropies calculated on major elemental chemical composition data and short-wave infrared (SWIR) reflectance spectra of hydrothermally altered rocks are lower than unaltered rocks with a comparable primary composition. The lowering of the Shannon entropy indicates chemical and spectral sorting during hydrothermal alteration of rocks. The hydrothermal processes described in this study present a natural mechanism for transforming energy from heat to increased order in rock. The increased order is manifest as the increased sorting of chemical elements and SWIR absorption features of the rock, and can be measured and quantified by the Shannon entropy. The results are useful for the study of hydrothermal mineral deposits, early life environments and the effects of hydrothermal processes on rocks.

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F. Pirajno 1992. Hydrothermal Mineral Deposits. Principles and Fundamental Concepts for the Exploration Geologist. xviii + 709 pp. Berlin, Heidelberg, New York, London, Paris, Tokyo, Hong Kong: Springer-Verlag. Price DM 248.00 (hard covers). ISBN 3 540 52517 3.

Cited by 3 publications

References 0 publications

Statistical evaluation of stream sediment geochemical data from Tchangue-Bikoui drainage system, Southern Cameroon: a regional perspective

Statistical evaluation of stream sediment geochemical data from Tchangue-Bikoui drainage system, Southern Cameroon: a regional perspective

Assessment of gold potential in stream sediments around the Neoproterozoic Boyo area, Betare-Oya Gold District, Eastern Cameroon

Shannon Entropy as an Indicator for Sorting Processes in Hydrothermal Systems

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