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

智利北部阿塔卡马沙漠氧化铁磷灰石 (IOA) 矿石及相关母岩的结晶、蚀变和成矿过程

• 批准号: RGPIN-2015-04649
• 负责人: Hanchar, John
• 金额: $ 1.97万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=652991
• 关键词: Crystallization; alteration; ore; forming; processes

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. **

我未来五年的研究计划的总体目标是更好地了解导致通常所说的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、随后的主岩交代蚀变、矿化和任何矿化后的蚀变。这些矿床是世界上许多知名地区的主要铁来源。我们目前对IOA存款的理解至少有两个主要悬而未决的问题。*第一个问题是，这些矿藏本质上是如何形成的？它们是岩浆、热液，还是沿着这两个末端地质过程之间的连续体形成的？与此相关的是，IOA，也就是所谓的铁氧化物铜金和铜斑岩矿床之间的关系(S)是什么？为什么IOA矿床缺乏铜和金的经济浓缩？铜斑岩矿床是否类似于IOA矿床，但形成于地壳的不同层面，而IOCG矿床则形成于两者之间的某个地方？铜斑岩矿床、IOA和IOCG矿床与铜斑岩有一些共同的性质，包括它们与钙碱性到中碱性岩浆作用有关，但也有一些明显的区别，包括IOA和矿床富含磁铁矿，而S则很贫乏？*智利北部的阿塔卡马沙漠地区是研究这类矿床和培养学生地质兴趣和相关地点的理想场地。曝光率很高，而且已经安排好进入要采集样本的矿场。这项研究计划将在智利中央安第斯山脉两个地区选定的一组矿床上进行。首先，IOCG和IOA矿床聚集在与阿塔卡马断裂系统有关的科迪勒拉海岸晚侏罗世-早白垩世，长约1000公里的狭窄带中。由于其特殊重要性，该项目还将包括--由于其特殊重要性--安第斯山脉的全新世矿藏，特别是El Laco矿藏和附近可能相当于中生代浅部的小矿藏。*将使用各种原位和大样本分析方法研究选定矿物和熔体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，以解决上述悬而未决的问题。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，熔体包裹体中的铅-铅同位素，以更好地了解磁铁矿的源区。锆石的铀-铅年代学和橄榄岩长石的40Ar/39Ar年代学也将被用来限制容矿岩石侵位的时间、后期的热液蚀变和铁矿化。**