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The origin of the gold within the Witwatersrand Basin is thought to be a combination of placer deposition and hydrothermal processes. Gold deposits are concentrated at the base of fluvial cycles within the Central Rand Group, with ancient microbial activity playing a role in the fixation of organic materials and enhancing gold concentration. [ 4 ]
High-grade gold ore from the Harvard Mine, Jamestown, California, a wide quartz-gold vein in California's Mother Lode. Specimen is 3.2 cm (1.3 in) wide. Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
Orogenic gold deposits are responsible for approximately 75% of the world's gold production at over 1 billion ounces, when accounting that the origin of many gold placer deposits were orogenic in nature. [25] [46] The price of gold at a given time will have an impact on whether a deposit will be economically feasible.
Gold, a chemical element; Genomes OnLine Database; Global-scale Observations of the Limb and Disk, a NASA Explorer Mission of Opportunity; GOLD (parser), an open-source parser-generator of BNF-based grammars; Graduates of the Last Decade, an Institute of Electrical and Electronics Engineers program to garner more university level student members
The lithosphere is the dominant reservoir of gold, containing an estimated 2.6x10 13 Mg. [1] Today, gold exists primarily as electrum, in hard rock deposits like tellurides, and as particles in placers in Earth's crust. Gold cycling starts with the microbial weathering of gold-bearing rocks and minerals which mobilizes gold in the environment ...
In their chronology for Earth, Hazen et al. (2008) separated the changes in mineral abundance into three broad intervals: planetary accretion up to 4.55 Ga (billion years ago); reworking of Earth's crust and mantle between 4.55 Ga and 2.5 Ga; and biological influences after 2.5 Ga. [1] [12] They further divided the ages into 10 intervals, some ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
The earliest recorded metal employed by humans seems to be gold, which can be found free or "native". Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, around 40,000 BC. [5] The earliest gold metallurgy is known from the Varna culture in Bulgaria, dating from c. 4600 BC. [6]