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，社会每年消耗的铜和黄金分别增加了约300%和100%。未来几十年，铜和黄金的产量必须大幅增加，以实现联合国可持续发展目标，即为地球上近10亿因缺电而导致经济贫困的人口提供电力，并在全球范围内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种需求，地质学家必须改进用于勘探和定位新铜矿和金矿的模型。目前，一种被地质学家称为斑岩铜金矿床的矿床类型提供了世界上大部分的铜和约15%的黄金。该项目将调查智利Maricunga带富金斑岩矿床的形成，智利是世界主要的铜生产国。人们对这些富含金矿的斑岩矿床了解甚少，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了解智利富含金矿的矿床是如何形成的，并允许地质学家改进他们的勘探策略，以寻找新的、未发现的矿床。在俯冲带环境中形成的斑岩矿床是社会上最重要的铜来源和重要的金来源。对于解释斑岩矿床形成的一般地质模型已达成共识。然而，在这些矿床中，铜与金等金属的比例为何会有好几个数量级的差异，目前还没有达成共识。现有的解释铜金比变异性的假说包括：1)上地壳源岩浆侵位深度及其对岩浆热液成矿流体演化的影响；2)源岩浆的组成对矿石金属及其流溶配体在熔体和岩浆热液之间的分配具有一级控制作用；3)岩浆系统演化过程中的氧化还原条件对铜与金的相对迁移率有重要影响。该项目成果将有助于厘清Dorado金斑岩系统从岩浆侵位到富、贫金斑岩形成的演化过程。该项目有可能显著改变我们对斑岩矿物系统中铜金比变异性的理解，并有助于指导富金系统的勘探。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.