SusChEM: Geochemical and Mineralogical Constraints on the Genesis of Country Rock-hosted Massive Sulfide Mineralization Associated with Mafic Rock-related Cu-Ni-PGE Deposits

SusChEM：与镁铁岩相关的 Cu-Ni-PGE 矿床伴生的围岩中大量硫化物矿化成因的地球化学和矿物学约束

• 批准号: 1522926
• 负责人: Edward Ripley
• 金额: $ 38万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1522926&HistoricalAwards=false
• 关键词: SusChEM; Geochemical; Mineralogical; Constraints; Genesis

Nickel (Ni), copper (Cu) and platinum-group elements (PGEs: platinum (Pt), palladium (Pd), rhodium, iridium, ruthenium, and osmium (Os)) are vital to the economic growth of the United States. Ni and PGEs are found almost exclusively in igneous rocks that are rich in iron and magnesium. Copper may occur in a variety of rock types but is also found in association with Ni and PGEs. The ore elements typically occur bonded to sulfur in sulfide minerals, or in some cases PGEs may be found bonded to arsenic (As), tellurium (Te) or antimony (Sb). Although most of these deposits are found within igneous rock bodies, there is a category of mineralization that is composed of nearly pure sulfide minerals that is located outside of the igneous rocks and within enclosing sedimentary rocks. The grade of these occurrences may be high and they represent a poorly understood resource that will be of national importance as our global need for raw materials increases and we strive to maintain a sustainable earth. Because the ore is massive the mineable dimensions are relatively small and hence the environmental footprint is correspondingly small; any necessary reclamation is readily accomplished. Nickel is a strategic ferro-alloy which is essential to the manufacture of stainless steel. Both Pt and Pd are used as active metals within catalytic converters. The United States has only one actively producing Ni mine and only two mines that produce Pt and Pd (both within the same igneous body). The work that will be undertaken as part of this project will increase our understanding of how massive sulfide occurrences form outside of the spatially associated igneous rocks. In order for the project to be successful a collaborative effort between company geologists and scientists at academic institutions is required. A key broader implication of the research is that students from the IU Department of Education frequently undertake research projects in our lab; the experience is beneficial as teachers are prepared to promote student training in science, mathematics and sustainability.Although massive sulfide mineralization associated with igneous can often be explained via gravitational accumulation of immiscible sulfide liquid in a magmatic system, some occurrences of massive sulfide mineralization associated with Ni-Cu-PGE deposits are more difficult to explain by this mechanism. Mineralization such as that found at Voisey's Bay (Labrador), Eagle (Michigan) and the newly discovered Tamarack deposit (Minnesota) are associated with magma conduits; massive sulfides may have accumulated where magma velocity decreased as the conduit widened, and perhaps flattened. However, discoveries at each of these localities of massive sulfide hosted by metamorphosed sedimentary country rocks are not easily accounted for by such a mechanism. Cu-Ni-(PGE) massive sulfide mineralization hosted by country rocks is also found in association with larger, sheet-like layered intrusions, including intrusions of the Duluth Complex (Minnesota) and the Stillwater Complex (Montana). In both of these localities massive sulfides are found in pelitic rocks of the contact aureoles, with limited or no connectivity with the igneous rocks. Preliminary geochemical data from the massive sulfide mineralization in the Virginia Formation near the contact with the Duluth Complex show strong signatures for partial crustal derivation of S, Os, Cu and lead (Pb). In many localities the country rock-hosted massive sulfides penetrate and crosscut disseminated sulfide-bearing igneous rocks. The origin of the country rock-hosted massive sulfide occurrences is poorly understood; clearly a better understanding is essential for future development of limited natural resources. We plan to undertake a detailed study of the physical and textural form of three such deposits in the Midcontinent region (Eagle, Tamarack, and the Mesaba (Babbitt) deposit of the Duluth Complex, and at the Stillwater Complex), along with a determination of key geochemical characteristics (variations of Ni/Co, S/Se, PGE, Sb and As concentrations and ratios, and Os, Pb, Cu, Ni and S isotopic compositions), that will shed light on the interpretation of whether mantle-derived melts, crustal melts, or hydrothermal fluids have controlled their formation. The well-known Noril'sk Ni-Cu-PGE deposits in Siberia also contain massive sulfide mineralization that occurs in the sedimentary country rocks, separated by several meters from sulfide-bearing igneous rocks. Our Russian colleagues are in the midst of a detailed study of the mineralization at Noril'sk, including the country rock - hosted type which is of particular economic significance. Their study parallels our proposed work and provides an opportunity for comparative evaluation of a poorly understood ore type.This project is supported in part via the NSF FY15 Sustainable Chemistry, Engineering, and Materials (SusChEM) initiative.

镍（NI），铜（CU）和铂类元素（PGES：铂（PT），钯（PD），Rhodium，iridium，ruthenium和Osmium（OS））对于美国的经济增长至关重要。 Ni和Pges几乎完全在富含铁和镁的火成岩中发现。铜可能发生在多种岩石类型中，但也与Ni和PGES相关。通常发生在硫化物矿物质中的硫的矿石元素，或者在某些情况下可能会发现PGE与砷（AS），Tellurium（TE）或锑（SB）粘合。尽管这些沉积物中的大多数都在火成岩体内发现，但是矿化类别由位于火成岩岩石外和封闭沉积岩石内的几乎纯硫化物矿物组成。这些事件的等级可能很高，它们代表着一个知之甚少的资源，随着我们的全球原材料需求增加，我们努力维持可持续的地球将具有国家重要性。由于矿石的巨大尺寸相对较小，因此环境足迹相应地很小。任何必要的填海都很容易完成。镍是一种战略性的铁合金，对制造不锈钢至关重要。 PT和PD都用作催化转化器中的活性金。美国只有一个积极生产尼雷，只有两个产生PT和PD的矿山（均在同一火成岩体内）。将作为该项目的一部分进行的工作将增加我们对在空间相关的火成岩之外形成大规模硫化物的理解。为了使该项目取得成功，需要在学术机构的公司地质学家和科学家之间进行协作。该研究的一个主要含义是，IU教育部的学生经常在我们的实验室中进行研究项目。这一经验是有益的，因为教师准备促进科学，数学和可持续性的学生培训。尽管通常可以通过在岩浆系统中不混溶的硫化物液体的重力积累来解释与火成岩相关的大规模硫化物矿化，但与Ni-Cu-Pge沉积相关的大规模硫化物矿化的发生，可以通过这种机制来解释一些与Ni-Cu-pge沉积有关的情况。矿化，例如在Voisey's Bay（Labrador），Eagle（Michigan）和新发现的Tamarack矿床（明尼苏达州）发现的矿化化与岩浆式吊带有关；岩浆速度随着导管的扩大而降低，甚至可能变平时，岩浆速度降低，可能已经积累了大量的硫化物。但是，这种机制不容易考虑到变态乡村岩石托管的大规模硫化物的每个地方的发现。还发现了由国家岩石托管的大量硫化物矿化的大量硫化物矿化，也与较大的薄层样层状侵入物相关联，包括德卢斯复合物（明尼苏达州）和斯蒂尔沃特复合物（蒙大拿州）的侵入。在这两个地方，在接触aureoles的毛岩石中都发现了巨大的硫化物，与火成岩的连通性有限或没有连接。来自与Duluth复合物接触附近的弗吉尼亚州大规模硫化物矿化的初步地球化学数据显示出S，OS，CU和LEAD（PB）的部分地壳衍生物的强大特征。在许多地方，该国岩石托管的巨大硫化物穿透并横切散布了含有硫化物的火成岩。该国的起源是岩石托管的大规模硫化物的发生率很少。显然，更好的理解对于有限自然资源的未来发展至关重要。 We plan to undertake a detailed study of the physical and textural form of three such deposits in the Midcontinent region (Eagle, Tamarack, and the Mesaba (Babbitt) deposit of the Duluth Complex, and at the Stillwater Complex), along with a determination of key geochemical characteristics (variations of Ni/Co, S/Se, PGE, Sb and As concentrations and ratios, and Os, Pb, Cu, Ni and S同位素组合物），它将阐明地幔衍生的熔体，地壳熔体或水热液的解释已经控制了它们的形成。西伯利亚著名的Noril'sk Ni-cu-pge沉积物还含有大量的硫化物矿化，发生在沉积物乡村岩石中，与含硫化物的火成岩岩石相距几米。我们的俄罗斯同事正在Noril'sk的矿化详细研究中，包括该国岩石 - 托管类型，这尤其具有经济意义。他们的研究与我们的拟议工作相似，并为对矿石类型的比较评估提供了一个机会。该项目部分通过NSF FY15可持续化学，工程和材料（SUSCHEM）计划支持。