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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613086
• 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.

我未来五年研究计划的总体目标是更好地了解形成通常所说的经济级氧化铁磷灰石 (IOA) 矿床的地质过程，其中包括最初的侵位和形成。结晶、随后的母岩交代蚀变、矿化以及任何后矿化蚀变这些矿床是世界各地许多著名地点的铁的主要来源。我们目前对 IOA 存款的理解尚未解决的问题。 首先是这些沉积物在自然界中是如何形成的？它们是岩浆沉积、热液沉积还是沿着这两个端元地质过程之间的连续体形成？与此相关的是，IOA 之间存在什么关系？ - 称为氧化铁铜金 (IOCG) 和铜斑岩矿床？ 为什么 IOA 矿床缺乏铜和金的经济富集度？铜斑岩矿床是否与 IOA 矿床相似，但形成水平不同？地壳中形成的铜斑岩矿床和 IOA 和 IOCG 矿床与铜斑岩矿床有一些共同的特性，包括它们与钙碱性到弱碱性岩浆作用的联系，但也有一些明显的区别，包括 IOA 和矿床磁铁矿丰富，S 贫乏？ 智利北部的阿塔卡马沙漠地区是研究此类矿床和在地质有趣且相关的地点培训学生的理想场所，该地区的暴露条件非常好，并且已经可以进入要采集样品的矿山。该研究计划将在智利安第斯山脉中部的两个地区的选定矿床中进行。首先，IOCG 和 IOA 矿床聚集在晚约 1000 公里长的狭窄地带。侏罗纪-早白垩世，位于沿海科迪勒拉山脉，与阿塔卡马断层系统有关，由于其特殊重要性，该项目还将包括安第斯山脉高地的全新世矿床，特别是埃尔拉科矿床和附近的小型矿床。可能代表中生代带的浅层。 将使用各种原位和批量样品分析方法对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进行研究，以解决上述未解决的问题，其中包括磷灰石、锆石、磁铁矿和熔体包裹体、磷灰石中的 Nd-Sm 同位素、锆石中的 Lu-Hf 和 O 同位素以及熔体中的 Pb-Pb 同位素包裹体，以更好地了解锆石的铀-铅地质年代学和尖晶石的 40Ar/39Ar 地质年代学，也将用于约束母岩（后来的热液）的侵位时间。蚀变和铁矿化。