Reconstructing the Magmatic and Hydrothermal Evolution of the Au-rich, Cu-Poor Dorado Porphyry Deposit, Chile: Implications for Cu/Au Ratios in Porphyry Deposits Worldwide

在全球范围内，与1960年相比，社会每年的铜消费量增加了约300%，黄金消费量增加了100%。今后几十年，铜和黄金的产量必须大幅增加，才能实现联合国可持续发展目标，即为地球上近10亿人提供电力，而缺乏电力是造成经济贫困的原因之一，并在全球建设可再生能源基础设施，以取代化石燃料。为了以人类前所未有的规模和速度满足这一需求，地质学家必须改进用于勘探和定位新的铜和金矿的模型。目前，一种被地质学家称为斑岩铜金矿床的矿藏类型提供了世界上大部分铜和约15%的黄金。该项目将研究世界主要铜生产国智利马里孔加带富含金矿的斑岩矿床的形成。人们对这些富含金矿的斑岩矿床知之甚少，寻找新的矿床需要更好地了解形成它们的地质过程。预期的结果将有助于限制智利富含金矿的矿藏的形成方式，并使地质学家能够改进他们对新的未发现矿藏的勘探策略。形成于俯冲带环境中的斑岩矿床是人类社会最重要的铜来源和金的重要来源。对于解释斑岩矿床形成的一般地质模型，人们达成了共识。然而，对于这些矿床中铜与黄金等金属的比例为何会出现几个数量级的差异，目前还没有达成共识。现有的解释铜/金比值变化的假说包括：1)上地壳源区岩浆侵位深度及其对岩浆-热液成矿流体演化的影响；2)源区岩浆的组成对金属及其可溶于流体的配位体在熔体和岩浆-热液成矿流体之间的分配起一级控制作用；3)参与岩浆系统演化的氧化还原条件，这些条件对铜与金的相对活动性起作用。该项目的成果将有助于阐明Dorado金矿斑岩系统从岩浆侵位到富Au、贫铜斑岩形成的演化。该项目有可能显著改变我们对斑岩矿物系统中铜与金比例变化的理解，并有助于指导富含Au的系统的勘探。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Globally, society consumes about 300 percent more copper and 100 percent more gold every year than in the year 1960. Production of copper and gold over the next several decades must increase significantly to achieve the United Nations Sustainable Development Goals of providing electricity to nearly one billion people on Earth for whom the lack of electricity contributes to economic impoverishment, as well as building renewable energy infrastructure to replace fossil fuels globally. To meet this demand at a scale and speed never before accomplished by humans, geologists must refine the models used to explore for and locate new copper and gold deposits. Currently, one mineral deposit type, referred to by geologists as a porphyry copper gold deposit, supplies the majority of the world's copper and about 15 percent of the world's gold. This project will investigate the formation of gold-rich porphyry deposits in the Maricunga belt of Chile, the world's leading producer of copper. These gold-rich porphyry deposits are poorly understood and finding new deposits requires a better understanding of the geologic processes that form them. The anticipated results will help constrain how the gold-rich deposits in Chile formed and allow geologists to improve their exploration strategies for new, undiscovered deposits. Porphyry-mineral deposits formed in subduction zone environments are society’s most important source of copper and an important source of gold. There is consensus for the general geologic model that explains the formation of porphyry mineral deposits. However, there is no consensus on why the ratio of metals such as copper to gold varies by several orders of magnitude among these deposits. Existing hypotheses to explain the variability of copper to gold ratios invoke: 1) the depth of emplacement of the upper crustal source magma and its impact on the evolution of the magmatic-hydrothermal ore fluid; 2) the composition of the source magma that represents a first order control on the partitioning of ore metals and their fluid-soluble ligands between melt and magmatic-hydrothermal ore fluid; 3) the redox conditions attending the evolution of magmatic systems that play a role in the relative mobility of copper vs. gold. The project outcomes will help clarify the evolution of the Dorado Au-porphyry system from magma emplacement to Au-rich, Cu-poor porphyry formation. This project has the potential to significantly change our understanding of the variability of copper to gold ratios in porphyry mineral systems and help guide exploration for Au-rich systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.