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

斑岩铜矿(PCD)是世界上主要的铜商业来源。它们由与花岗岩有关的含金属热液形成，通常在会聚的板块边缘环境中找到，例如位于中央安第斯山脉的智利北部。尽管这些系统在地壳深处几公里处开始生存，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了酸，酸浸出铜，并将其重新沉淀在富含铜的“表生岩层”矿石中。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、最丰富的表生岩层(特别是巨大的丘基卡马塔和埃斯孔迪达矿床)，但该地区位于地球上最干燥的地方之一阿塔卡马沙漠。这种干燥气候的开始被认为与安第斯山脉的抬升有关，这在安第斯山脉的西侧形成了一个雨影。这就提出了一些根本的问题，比如表生富集物是如何和何时发生的，何时和为什么停止的，以及构造、气候、沉积和水文的区域变化可能如何影响矿化。项目目标和方法本博士项目将研究智利北部西安第斯边缘的构造抬升、折返和气候对表生丰度的影响。在这一地区，主要矿化地点附近河流砾石的广泛沉积为与PCD相关的火成岩物质的折返、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热计时技术对砾石的碎屑来源进行研究。(2)用数值模拟方法对砾石中火成碎屑的折返历史进行了约束，从深部侵位到地表折返和河流搬运。(3)折返和沉积模式与区域构造和气候制约有关。(4)确定这些模式可能如何影响浓缩的多氯联苯的形成和保存。

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.