Tempo of magma degassing and the genesis of porphyry copper deposits.
Tempo of magma degassing and the genesis of porphyry copper deposits.
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DOI：
10.1038/srep40566
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发表时间：
2017-01-12
影响因子：
4.6
通讯作者：
Simpson G
中科院分区：
文献类型：
--
作者：
Chelle-Michou C;Rottier B;Caricchi L;Simpson G
斑岩矿床是富铜矿体，由岩浆侵入体释放的热液中的金属硫化物沉淀形成，这些热液在地壳深处冷却。寻找新的斑岩矿床至关重要，因为它们是我们最大的铜来源，而且它们还含有其他战略金属，包括金和钼。然而，由于缺乏对决定巨型斑岩矿床规模的因素的了解，巨型斑岩矿床的发现受到了阻碍。在这里，我们使用热模拟和统计模拟来量化从冷却的岩浆系统释放的流体的速度和化学成分。我们确认典型的弧状岩浆产生的流体成分与斑岩铜矿相似，岩浆活动的规模和持续时间对经济斑岩铜矿床的赋存(铜的总质量)起一级控制作用。因此，最初的岩浆在铜和硫中的富集度，尽管增加了成矿潜力，但并不一定要形成一个巨大的矿床。我们的结果将从著名的大型矿床到超大型矿床的岩浆和热液活动的持续时间与它们的金属赋存联系起来。这一新方法很容易作为另一种勘探工具加以实施，有助于评估岩浆-热液系统的经济潜力。
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.