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| Gold Cycle | |
|---|---|
| Name | Gold Cycle |
| Element | Gold |
| Atomic number | 79 |
Gold Cycle
The Gold Cycle describes the pathways, transformations, and fluxes of elemental Gold across Earth's lithosphere, hydrosphere, atmosphere, and biosphere as influenced by geological, biological, and anthropogenic processes. It links processes studied in geochemistry, mineralogy, economic geology, and environmental science while intersecting with historical episodes such as the California Gold Rush, the Klondike Gold Rush, and modern industrial developments in South Africa and Australia. Understanding the cycle informs resource management, metallurgical technology, and remediation efforts related to mining in regions like Nevada and the Yukon.
The Gold Cycle integrates sources such as magmatic processes in mid-ocean ridge and subduction zone settings, concentrations via hydrothermal systems studied at sites like Witwatersrand Basin and Carlin Trend, redistribution through weathering in terrains exemplified by Sierra Nevada, transport in river systems including the Amazon River and the Mekong River, and anthropogenic fluxes from mining districts in Ghana, Peru, and Indonesia. Important conceptual frameworks derive from work by researchers affiliated with institutions like United States Geological Survey and Geological Survey of Canada, and are applied in policy contexts involving agencies such as the Environmental Protection Agency and the International Maritime Organization when addressing contamination and trade. The cycle also overlaps with economic episodes involving the Gold Standard, central banks like the Federal Reserve System, and markets on exchanges such as the London Stock Exchange and the New York Stock Exchange.
Gold originates in part from nucleosynthetic processes traced through studies of meteoritic material and is concentrated in the crust via processes including magmatic differentiation, sulfide segregation at mid-ocean ridges, and volatile-rich fluids in subduction zones. Hydrothermal transport is mediated by ligands such as chloride and bisulfide, producing lode deposits typified by vein systems in the Mother Lode (California) and disseminated deposits in provinces like the Yukon and Nevada. Supergene enrichment in weathering profiles at localities such as Kalgoorlie and Johannesburg creates placer deposits exploited historically in Klondike and Gold Rush episodes. Secondary sinks include seawater in basins like the Atlantic Ocean, sediments in the Gulf of Mexico, and anthropogenic reservoirs such as vaults held by institutions like the Bank of England and central banks in Switzerland.
Although chemically inert compared with many trace metals, particulate and nanoparticulate forms of gold interact with organisms in freshwater systems like the Mekong River and marine environments such as the Great Barrier Reef. Research by laboratories at Smithsonian Institution and universities including Harvard University and University of Cape Town documents uptake by bacteria, algae, and macroinvertebrates with implications for trophic transfer in food webs studied in ecosystems like the Amazon Basin and Lake Victoria. Biomagnification is limited relative to elements like mercury but occurs in association with mining-derived colloids and complexed species observed in surveys by World Health Organization and Food and Agriculture Organization in regions affected by artisanal mining in Indonesia and Peru.
Extraction pathways include hard-rock mining at operations run by corporations such as Barrick Gold Corporation, Newmont Corporation, and AngloGold Ashanti, placer mining by artisanal miners in Ghana and the Amazon, and secondary recovery from electronic waste in recycling facilities in China and Germany. Techniques range from open-pit mining in districts like Yanacocha to underground methods in the Witwatersrand Basin, with metallurgical processes including cyanidation, amalgamation historically using techniques associated with the Gold Rush eras, and modern hydrometallurgy developed in industrial research labs at institutions like Massachusetts Institute of Technology. Technological innovations in sensors, nanomaterials, and biotechnology at companies and centers such as CSIRO and Fraunhofer Society affect recovery efficiencies and environmental footprints.
Gold functions as a monetary asset in systems linked to the Gold Standard legacy, as reserves held by central banks including the Federal Reserve System and European Central Bank, and as traded commodity on markets such as the London Bullion Market Association and the COMEX. Industrial demand from electronics manufacturers in South Korea, Japan, and Taiwan and jewelry industries centered in India and China drives recycling streams. Urban mining and e-waste recovery conducted by firms in Singapore and Sweden recycle notable fractions of annual supply, complementing primary production from mines in Russia and Australia.
Gold mining has generated environmental impacts at sites like Mercury contamination hotspots associated with historical artisanal and small-scale mining districts in Peru and Indonesia, tailings failures recorded in cases such as incidents investigated by International Commission on Large Dams, and landscape alteration in regions like Nevada and Western Australia. Remediation strategies employ phytoremediation trials in collaboration with institutions like University of Queensland and engineered tailings management used by companies under guidance from regulators such as the Environmental Protection Agency and European Environment Agency. Emerging approaches include passive treatment wetlands modeled after projects in the Danube River basin and in situ stabilization techniques piloted in former mining districts in Cornwall.
Quantifying gold across reservoirs uses analytical techniques developed at laboratories within National Institute of Standards and Technology, universities, and commercial facilities: fire assay and atomic absorption spectroscopy for ore-grade assays at operations in Nevada; inductively coupled plasma mass spectrometry for trace-level determinations in environmental samples collected from the Amazon Basin; transmission electron microscopy and synchrotron-based X-ray absorption spectroscopy at facilities like Argonne National Laboratory and European Synchrotron Radiation Facility for nanoparticle speciation studies; and isotope dilution methods applied in geochronology labs at Columbia University and ETH Zurich to trace provenance of placer and lode gold. Quality assurance follows standards from organizations such as International Organization for Standardization.
Category:Biogeochemical cycles