Tectonic and climatic controls on porphyry copper enrichment in the Central Andes

斑岩铜矿（PCDs）是世界上主要的铜矿商业来源。它们是由与花岗岩岩基相关的含金属热液形成的，通常在会聚的板块边缘环境中发现，例如安第斯山脉中部的智利北部。尽管这些系统起源于地壳深处几公里处，但侵蚀和构造活动将它们挖掘到地表，在那里它们与含氧地下水相互作用。硫化物矿物和含氧水之间的化学反应产生酸，使铜浸出，并在富集的矿石“表生层”中再沉淀。这一过程可以使矿床的铜含量增加一倍以上，使表生带成为矿产勘探的主要目标。智利北部拥有一些世界上最大和最丰富的表生毯（特别是巨大的丘基卡玛塔和埃斯康迪达矿床），但该地区位于阿塔卡马沙漠，是地球上最干燥的地方之一。这种干燥气候的开始被认为与安第斯山脉的隆起有关，这在其西侧造成了雨影。这就提出了一些基本问题：表生富集是如何以及何时发生的，何时以及为什么会停止，以及构造、气候、沉积和水文的区域变化是如何影响矿化的。本博士项目将研究构造隆升、挖掘和气候对智利北部西安第斯边缘表生富集的影响。在该地区，靠近主要矿化地点的河流砾石的广泛沉积为与PCDs相关的火成岩物质的挖掘、运输和沉积模式提供了空间和时间限制。项目目标包括：(1)利用U-Pb年代学和(U-Th)/He热年代学对砾石进行碎屑物源研究。(2)利用数值模拟方法对岩屑中火成岩碎屑的挖掘历史进行了约束，从深部就位到地表的挖掘和河流搬运。(3)将挖掘和沉积模式与区域构造和气候约束联系起来。(4)确定这些模式如何影响富集的PCDs的形成和保存。

Porphyry copper deposits (PCDs) are the world's principal commercial source of copper. Formed from metal-bearing hydrothermal fluids associated with granitic batholiths, they are typically found in convergent plate margin settings, such as northern Chile in the Central Andes. Although these systems begin their life a few kilometres deep in the crust, erosion and tectonic activity exhume them to the surface, where they interact with oxygenated groundwater. Chemical reactions between sulphide minerals and this oxygenated water create acid that leaches the copper and reprecipitates it in an enriched "supergene blanket" of ore. This process can more than double the copper content of a deposit, making supergene zones a primary target for mineral exploration. Northern Chile hosts some of the largest and richest supergene blankets in the world (notably the huge Chuquicamata and Escondida deposits) and yet the area lies in the Atacama Desert, one of the driest places on Earth. The onset of this dry climate is thought to relate to uplift of the Andes mountains, which created a rain shadow on their western side. This raises fundamental questions about how and when supergene enrichment occurred, when and why it stopped, and how regional changes in tectonics, climate, sedimentation, and hydrology might have affected mineralisation. Project goals and methods This PhD project will investigate the roles of tectonic uplift, exhumation, and climate on supergene enrichment along the western Andean margin in northern Chile. In this area, extensive deposition of fluvial gravels proximal to major sites of mineralisation offers an opportunity to place spatial and temporal constraints on patterns of exhumation, transportation, and deposition of igneous material related to PCDs. Project goals include: (1) Conduct a detrital provenance study of gravels using U-Pb geochronology and (U-Th)/He thermochronometry. (2) Use numerical modelling to constrain the exhumation history of igneous clasts in the gravels, from emplacement at depth to exhumation and fluvial transportation on the surface. (3) Relate patterns of exhumation and deposition to regional tectonic and climatic constraints. (4) Determine how these patterns may affect the formation and preservation of enriched PCDs.