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Tempo of magma degassing and the genesis of porphyry copper deposits

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Published in Scientific Reports. 2017, vol. 7, p. 40566
Abstract Porphyry deposits are copper-rich orebodies formed by precipitation of metal sulphides from hydrothermal fluids released from magmatic intrusions that cooled at depth within the Earth’s crust. Finding new porphyry deposits is essential because they are our largest source of copper and they also contain other strategic metals including gold and molybdenum. However, the discovery of giant porphyry deposits is hindered by a lack of understanding of the factors governing their size. Here, we use thermal modelling and statistical simulations to quantify the tempo and the chemistry of fluids released from cooling magmatic systems. We confirm that typical arc magmas produce fluids similar in composition to those that form porphyry deposits and conclude that the volume and duration of magmatic activity exert a first order control on the endowment (total mass of deposited copper) of economic porphyry copper deposits. Therefore, initial magma enrichment in copper and sulphur, although adding to the metallogenic potential, is not necessary to form a giant deposit. Our results link the respective durations of magmatic and hydrothermal activity from well-known large to supergiant deposits to their metal endowment. This novel approach can readily be implemented as an additional exploration tool that can help assess the economic potential of magmatic-hydrothermal systems.
Keywords Porphyry-copperMagma degassing
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Structures
Research groups Petrology and Volcanology
Mineral Resources and Geofluids
Projects FNS: 200020_160071
H2020: FEVER
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CHELLE-MICHOU, Cyril et al. Tempo of magma degassing and the genesis of porphyry copper deposits. In: Scientific Reports, 2017, vol. 7, p. 40566. https://archive-ouverte.unige.ch/unige:91127

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Deposited on : 2017-01-17

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