Geology

Copper in the Crust

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Science  28 Mar 2008:
Vol. 319, Issue 5871, pp. 1737
DOI: 10.1126/science.319.5871.1737c

The concentration of most metals is extremely low in Earth's crust. For copper, the most important ores globally are the porphyry deposits, which form when copper and other metals are concentrated in fluids emanating from and flowing through shallow bodies of magma in the crust. Rapid cooling of these fluids, or a sudden change in their chemistry as they interact with rocks or other fluids, leads to precipitation of copious amounts of metals and metal sulfides. Their formation has been episodic throughout Earth's history, and many ore deposits, as they form at depths, have been eroded. Kesler and Wilkinson account for the formation, uplift, and erosion of porphyry copper deposits to provide a global accounting of these deposits through Earth's history and assess the remaining available resource. They estimate that about 0.25% of the copper in Earth's crust has actually been concentrated in ores, and that about two-thirds of the more than 100,000 ore deposits that have formed over Earth's history have been eroded and recycled. At current consumption rates, they estimate that there is about a 5000-year supply of copper remaining in the Earth. — BH

Geology 36, 255 (2008).

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