Multistage gold mineralization events in the Archean Tati greenstone Belt, northeast Botswana: Constraints from integrative white mica Ar/Ar, garnet U-Pb and sulfides Pb/Pb geochronology

Betsi, Thierry Bineli; Mokane, Lebogang; McFarlane, Christopher R.M.; Phili, Kelebogile; Kelepile, Tebogo

doi:10.1016/j.precamres.2020.105623

Cited by 6 publications

(3 citation statements)

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“…The first Limpopo‐Liberian cycle is associated with the collision between the Zimbabwe and Kaapvaal Cratons. Another regional event associated with the TGB is the second, Paleoproterozoic Limpopo‐Liberian cycle event (2.05–1.95 Ga), which was characterized by prograde amphibolite facies metamorphic mostly in the central zone of the Limpopo Belt (Barton et al, 1994; Betsi et al, 2020; Carney et al, 1994; Holzer et al, 1998; McCourt et al, 2004; Tombale, 1992). The TGB is a host to numerous gold occurrences in Botswana including the Mupane, Signal Hill, Golden Eagle, Map Nora, and Monarch deposits (Figure 1c).…”

Section: Geologic Setting and Gold Mineralizationmentioning

confidence: 99%

Nature and conditions of gold mineralization at the Tau deposit, Mupane mine, Tati Greenstone Belt, Botswana: Evidence from fluid inclusion and arsenopyrite geothermometer

Seaba,

Imai,

Yonezu

et al. 2023

Resource Geology

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The gold mineralization at the Tau deposit in northeastern Botswana can be distinguished into two stages. The first stage of mineralization consists of invisible gold associated with early, sulfur‐rich arsenopyrite (Apy1). The second stage is characterized by native gold associated with late, sulfur‐poor arsenopyrite (Apy2). This study aims to constrain the nature of the ore‐forming fluid at the Tau deposit on the basis of fluid inclusion microthermometry and arsenopyrite geothermometry. Quartz crystals closely associated with gold‐bearing sulfides (Apy1) from the host rock host three types of fluid inclusions occurring in the same assemblages: Type I, two‐phase aqueous fluid inclusions, Type II three‐phase aqueous‐carbonic fluid inclusions and Type III one‐ or two‐phase CO2‐rich fluid inclusions. Microthermometric and Raman spectroscopic studies revealed the dominance of coexisting H2O+NaCl (Type I) and CO2N2CH4 (Type III) fluid inclusions. The coexisting Type I and Type III fluid inclusions could represent products of the immiscibility of a homogenous H2OCO2NaClN2CH4 primary ore fluid. The salinity of Type I (calculated from melting temperature of ice) and Type II (calculated from dissolution temperature of clathrate) fluid inclusions vary from 3.4 to 9.2 wt% NaCl equiv. and 5.8 to 9.8 wt% NaCl equiv., respectively. The overall fluid inclusion salinity range (<10 wt% NaCl equiv.) and gas compositions of fluids suggest that the primary ore‐forming fluid at the Tau deposit was of low salinity and H2OCO2N2CH4NaCl composition. Integration of fluid inclusion microthermometry and arsenopyrite geothermometer results suggest that the first stage and second stages of gold mineralization and the associated alteration at the Tau deposit occurred at pressure and temperature conditions of 75–145 MPa and 290–370°C and 85–160 MPa and 330–370°C, respectively. These results suggest that there was an increase in temperature from the first stage to the second stage of mineralization, resulting in the recrystallization of invisible gold‐bearing arsenopyrite in the first stage to form native gold‐bearing arsenopyrite in the second stage. Fluid composition and the estimated physico‐chemical conditions at the Tau deposit confirm that gold was transported as reduced bisulfide complexes and initial gold deposition was likely caused by a reduction in sulfur contents as a result of sulfidation reactions and pressure‐induced phase separation (fluid immiscibility).

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Section: Geologic Setting and Gold Mineralizationmentioning

confidence: 99%

Nature and conditions of gold mineralization at the Tau deposit, Mupane mine, Tati Greenstone Belt, Botswana: Evidence from fluid inclusion and arsenopyrite geothermometer

Seaba,

Imai,

Yonezu

et al. 2023

Resource Geology

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“…Although the geology of the Mupane gold deposits is well documented, the genesis of gold mineralization is poorly understood and insufficiently documented in peer‐reviewed works. Betsi et al (2020) evaluated the multiple stages of gold mineralization events in the TGB using integrative white mica Ar/Ar, garnet U–Pb, and whole‐rock sulfides Pb/Pb geochronology to track the sources and time frames of gold mineralization events. To our knowledge, there was no documented data on sulfides, chemistry and sulfur isotope compositions for the Tau deposit prior to this study.…”

Section: Introductionmentioning

confidence: 99%

Mineralogical and sulfur isotopic characteristics of Archean greenstone belt‐hosted gold mineralization at the Tau deposit of the Mupane gold mine, Botswana

et al. 2023

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The Mupane gold deposit, which is one of the numerous gold occurrences in the Tati Greenstone Belt in the northeastern part of Botswana, consists of four orebodies, namely Tau, Tawana, Kwena, and Tholo deposits. The present research, which focuses on the genesis of the Tau deposit, was based on ore petrography, mineral chemistry of sulfides, and sulfur isotope data. Mineralogical characteristics of the host rocks indicate that banded iron formation at the Tau deposit includes iron oxides (magnetite), carbonates (siderite and ankerite), silicates (chlorite and amphibole), and sulfides (arsenopyrite and pyrrhotite). The deposit features arsenopyrite‐rich zones associated with biotite‐chlorite veins, which are indicative of the precipitation of arsenopyrite concomitant with potassic alteration. The replacement of magnetite by pyrrhotite in some samples suggests that sulfidation was likely the dominant gold precipitation mechanism because it is considered to have destabilized gold‐thiocomplexes in the ore‐forming fluids. Based on textural relationships and chemical composition, arsenopyrite is interpreted to reflect two generations. Arsenopyrite 1 is possibly early in origin, sieve textured with abundant inclusions of pyrrhotite. Arsenopyrite 1 was then overgrown by late arsenopyrite 2 with no porous textures and rare inclusions of pyrrhotite. Gold mineralization was initiated by focused fluid flow and sulfidation of the oxide facies banded iron formation, leading to an epigenetic gold mineralization. The mineralogical assemblages, textures, and mineral chemistry data at the Tau gold deposit revealed two‐stage gold mineralizations commencing with the deposition of invisible gold in arsenopyrite 1 followed by the later formation of native gold during hydrothermal alteration and post‐depositional recrystallization of arsenopyrite 1. Laser ablation inductively coupled plasma mass spectrometric analysis of arsenopyrite from the Tau deposit revealed that the hydrothermal event responsible for the formation of late native gold also affected the distribution of other trace elements within the grains as evidenced by varying trace elements contents in arsenopyrite 1 and arsenopyrite 2. The range of δ34S of gold‐bearing assemblages from the Tau deposit is restricted from +1.6 to +3.9‰, which is typical of Archean orogenic gold deposits and indicates that overall reduced hydrothermal conditions prevailed during the gold mineralization process at the Tau deposit. The results from this study suggest that gold mineralization involved multi‐processes such as sulfidation, metamorphism, deformation, hydrothermal alteration, and gold remobilization.

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“…Compared with granular minerals, such as quartz and feldspar, schistose mica minerals, they exhibit different behaviors during migration and deposition [27][28][29]. Moreover, results show that mica 40 Ar/ 39 Ar-dating has important implications for future provenance studies [30,31]. Thus, mica could theoretically be employed as an indicator for sediment transport and diffusion [32].…”

Section: Introductionmentioning

confidence: 99%

Detrital Mica Composition Quantitatively Indicates the Sediment Provenance along the Subei Coast to the Yangtze Estuary

2022

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The influence of large rivers on the Subei littoral plain area requires more research than the results that have been available up to now. Thus, specific diagnostic indices of detrital mica are successfully applied for the first time to identify the detritus of the Yangtze River and the ancient Yellow River and to analyze their influence on the coast in the Subei littoral plain area. Based on field investigation and sample collection, detrital mica minerals within the 0.063–0.125 mm grain size fraction were selected and identified. Their content/ratio differentiations and possible origins were analyzed. Moreover, specific diagnostic indices were evaluated for detritus identification considering these two large rivers in addition to their provenance influences on the Subei littoral plain area. The results indicate that the detrital mica contents in the Yangtze River Estuary differed from those in the ancient Yellow River Estuary. The mass percentage in the former (average value of 32.2%) was much higher than that in the latter (average value of 13.1%). The former contained abundant weathered mica, with a particle percentage of approximately 50.6%, while the latter contained abundant biotite (with a particle percentage of approximately 40.9%). Differences, including but not limited to those above, could be attributed to basic geological, climatic and hydrodynamic conditions. In particular, the mica indices were clearly distinguished between these two river estuaries. These indices constitute specific diagnostic indices for differentiating river detritus and quantitative contribution analysis of detritus provenance in the Subei littoral plain area. Finally, the changes and quantitative contributions of four diagnostic indices demonstrated that in the Subei littoral plain area, northward from the Yangtze River Estuary to sample site SBY11 located in Yangkou town, Rudong County, detrital micas were mainly affected by the Yangtze River, and southward from the ancient Yellow River Estuary to sample site SBY12 located in Bengcha town, Rudong County, detrital micas were largely affected by the ancient Yellow River. The main mixing area should be located between these two towns. This study provides both a good example and an efficient approach to the application of detrital mica in detritus identification, mixed zone determination, sediment provenance analysis and transport tracing.

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Multistage gold mineralization events in the Archean Tati greenstone Belt, northeast Botswana: Constraints from integrative white mica Ar/Ar, garnet U-Pb and sulfides Pb/Pb geochronology

Cited by 6 publications

References 90 publications

Nature and conditions of gold mineralization at the Tau deposit, Mupane mine, Tati Greenstone Belt, Botswana: Evidence from fluid inclusion and arsenopyrite geothermometer

Nature and conditions of gold mineralization at the Tau deposit, Mupane mine, Tati Greenstone Belt, Botswana: Evidence from fluid inclusion and arsenopyrite geothermometer

Mineralogical and sulfur isotopic characteristics of Archean greenstone belt‐hosted gold mineralization at the Tau deposit of the Mupane gold mine, Botswana

Detrital Mica Composition Quantitatively Indicates the Sediment Provenance along the Subei Coast to the Yangtze Estuary

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