Linking Archaean climate change with gold metallogeny
نویسندگان
چکیده
First large-scale concentration of gold to ore grade in Earth’s crust took place at around 2.9 Ga quartz-pebble conglomerates, well before endogenous deposits, such as porphyry and epithermal systems or orogenic-type started play a significant role from ca. 2.75 onwards. The conglomerate-hosted placers, typified by those the Mesoarchaeaen Witwatersrand Basin South Africa, are thought have been sourced leaching background levels Archaean continental crust, promoted deep chemical weathering under reducing acidic atmosphere. Gold dissolved meteoric waters was trapped possibly acidophile microbes, fossil remnants which preserved kerogen layers lower Central Rand Group Supergroup. Mechanical reworking delicate microbial mat-bound led rich placers Well-endowed older than conspicuously missing, although suitable siliciclastic host rocks, even containing relics former known sediment sequences old 3.22 Ga. A review climate-sensitive rock types geochemical data on extent reveals that period 2.96–2.91 cold, with repeated glaciations evidenced glaciogenic diamicite, whereas warmer (or) wetter climates reigned 2.90 2.78 In concert temporal distribution placer accumulation, conclusion is reached rate, dictated climate, key determining factor exogenous binding Au into sedimentary deposits.
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ژورنال
عنوان ژورنال: Canadian Journal of Earth Sciences
سال: 2023
ISSN: ['1480-3313', '0008-4077']
DOI: https://doi.org/10.1139/cjes-2022-0058