Crystallization, alteration, and ore-forming processes, of iron oxide apatite (IOA) ores and related host rocks in the Atacama Desert of northern Chile

未来五年我的研究计划的总体目标是更好地了解导致通常被称为经济级氧化铁磷灰石（IOA）矿床形成的地质过程。 这包括最初的侵位和结晶，随后的交代蚀变的寄主岩石，矿化，和任何矿化后的蚀变。 这些矿床是来自世界各地许多著名地区的铁的主要来源。 我们目前对IOA存款的理解至少有两个主要的悬而未决的问题。 ** 首先，这些存款是如何形成的？ 它们是岩浆的、热液的，还是沿着这两种端元地质作用之间的连续体形成的？ 与此相关，IOA，即所谓的氧化铁铜金（IOCG）和斑岩铜矿之间的关系是什么？ 为什么IOA矿床缺乏Cu和Au的经济浓度？ 铜斑岩矿床是否与IOA矿床相似，但在地壳中形成于不同的水平，而IOCG矿床是否介于两者之间？铜斑岩矿床和IOA和IOCG矿床与铜斑岩有一些共同的性质，包括它们与钙碱性至弱碱性岩浆活动的关系，但也有一些明显的差异，包括IOA和矿床富磁铁矿和贫S。 ** 智利北方的阿塔卡马沙漠地区是研究这类矿床和在地质学上有趣和相关的地方培训学生的理想实地区域。 暴露条件极佳，而且已经安排好了前往采集样本的矿井的通道。 这项研究计划将在智利中部安第斯山脉的两个地区进行。 首先，IOCG和IOA矿床聚集在一个狭窄的带约1000公里长的晚侏罗世-早白垩世的年龄，在沿海科迪勒拉，有关的阿塔卡马断层系统。 由于其特殊的重要性，该项目还将包括高安第斯山脉的全新世沉积，特别是El Laco存款和附近的小的前景，可能代表浅的中生代带。** 将使用各种现场和批量样品分析方法对选定矿物和熔融包裹体以及整个岩石样品的微量元素、示踪同位素和地质年代学进行调查，以解决上述未解决的问题。 其中包括磷灰石、锆石、磁铁矿和熔融包裹体中的微量元素，磷灰石中的Nd-Sm同位素，锆石中的Lu-Hf和O同位素，熔融包裹体中的Pb-Pb同位素，以更好地了解磁铁矿的源区。锆石U-Pb年代学和透长石40 Ar/39 Ar年代学也将用于控制容矿岩石的侵位、后期热液蚀变和铁矿化的时间。**

The overarching objective of my research program for the next five years is to gain a better understanding of the geologic processes that lead to the formation of what are commonly referred to as economic grade iron oxide apatite (IOA) deposits. This includes the initial emplacement and crystallization, the subsequent metasomatic alteration of the host rocks, the mineralization, and any post mineralization alteration. These deposits are a major source of iron from many well-known localities around the world. There are at least two major unresolved issues with our current understanding of IOA deposits. ******The first is how do these deposits form in nature? Are they magmatic, hydrothermal, or do they form along a continuum between those two end-member geologic processes? Related to that, what is the relationship(s) if any between IOA, so-called iron oxide copper gold (IOCG), and Cu porphyry deposits? Why are IOA deposits devoid of economic concentrations of Cu and Au? Are Cu-porphyry deposits similar to IOA deposits but form at a different level in the crust with IOCG deposits forming somewhere in between? Cu porphyry deposits and IOA and IOCG deposits share some common properties with Cu-porphyries including their association with calc-alkaline to mildly alkaline magmatism but there are also some distinct differences including IOA and deposits being magnetite rich and S poor? ******The Atacama Desert region of northern Chile is an ideal field area for studying these kinds of deposits and for training students in a geologically interesting and relevant locality. The exposure is excellent and the access to the mines where the samples are to be collected has already been arranged. This research program will be carried out on a selected group of deposits of the Chilean Central Andes in two areas. In the first, IOCG and IOA deposits are clustered in a narrow belt approximately 1000 km long of Late Jurassic-Early Cretaceous age, in the Coastal Cordillera, related to the Atacama Fault System. The project also will include - due to its special importance - the Holocene deposits of the High Andes, and in particular the El Laco deposit and minor nearby prospects that likely represent the shallow equivalent of the Mesozoic belt. ******The trace element, tracer isotope, and geochronology of selected minerals and melt inclusions, and whole rock samples will be investigated using a variety of in situ and bulk sample analytical methods to address the unresolved issues above. These include trace elements in apatite, zircon, magnetite, and melt inclusions, Nd-Sm isotopes in apatite, Lu-Hf and O isotopes in zircon, and Pb-Pb isotopes in melt inclusions, to gain a better understanding of the source region of the magnetite ores. Uranium-Pb geochronology of zircon, and 40Ar/39Ar geochronology of sanidine feldspar will also be used to constrain the timing of the emplacement of the host rocks, the later hydrothermal alteration, and the Fe mineralization. **