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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=681797
• 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. **

未来五年我研究计划的总体目标是更好地了解导致形成通常称为经济氧化铁磷灰石（IOA）沉积物的地质过程。 这包括最初的扩增和结晶，寄主岩石的随后变质，矿化和任何矿化后改变。 这些沉积物是来自世界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未解决的问题。 ******首先是这些存款在自然界中如何形成？ 它们是岩浆，水热还是在这两个结束成员的地质过程之间沿连续体形成？ 与之相关的是，如果IOA，所谓的氧化铁铜金（IOCG）和Cu斑岩沉积物之间的关系是什么？ 为什么IOA沉积物没有CU和AU的经济浓度？ Cu-perphyry沉积物是否类似于IOA沉积物，但在层中形成IOCG沉积物的地壳中形成不同的水平？ Cu斑岩沉积物和IOA和IOCG沉积物具有一些常见的特性与Cu-porphyries，包括它们与钙碱性与轻度碱性岩浆的关联，但是也存在一些明显的差异，包括IOA和沉积物是磁铁矿富含磁铁矿，较差和较差？ ******智利北部的Atacama沙漠地区是研究这类存款和在地质有趣且相关的地方培训学生的理想场所。 曝光非常好，可以进入要收集样品的矿山。 该研究计划将在两个领域的智利中部安第斯山脉的一组矿床上进行。 首先，IOCG和IOA沉积物聚集在一个狭窄的皮带中，约1000公里长，距侏罗纪晚期的白垩纪，沿海山脉山脉，与Atacama断层系统有关。 该项目还将包括（由于其特殊的重要性），即高安第斯山脉的全新世沉积物，尤其是El Laco矿床和附近的较小潜在客户，可能代表了中生代带的浅层。 ******将使用各种原位和批量样品分析方法研究所选矿物质和融合物的痕量元素，示踪剂同位素以及整个岩石样品，以解决上述未解决的问题。 这些包括磷灰石，锆石，磁铁矿和熔体夹杂物中的痕量元素，氧化磷酸盐，lu-hf和O同位素的ND-SM同位素，以及熔体夹杂物中的PB-PB同位素，以更好地了解磁铁矿矿石的源区域。锆石的铀PB年代学和Sanidine Feldspar的40AR/39AR年代学也将用于限制宿主岩石的扩增时间，后来的热液蚀变和FE矿化的时间。 **