Origin of magnetite from the Volcanogenic Massive Sulfide deposits of the Matagami Mining Camp, Abitibi, Canada: implications for exploration

火山成因块状硫化物矿床主要开采锌（来自硫化物矿物闪锌矿- ZnS）和铜（来自硫化物矿物黄铜矿- CuFeS2）。VMS沉积物是由古代海底火山岩中循环的热液形成的（类似于今天海底的黑烟）。然而，一些VMS矿床含有异常高的矿物磁铁矿（Fe3O4），使得大部分矿床不具有经济价值。磁铁矿被认为是由硫化物的置换形成的。然而，这一替换过程的详细机制，以及为什么在某些情况下整个矿床的替换几乎完成，都不是很清楚。因此，该公司的具体问题是更好地了解魁北克Matagami VMS矿床中块状磁铁矿的来源。为了解决这一科学问题，本项目旨在通过对Matagami VMS矿床中磁铁矿和硫化物的岩石学和微量元素化学的综合研究，为VMS矿床中磁铁矿的形成提供新的约束条件。我们将使用创新的激光烧蚀icp - ms技术来获得高质量的原位微量元素数据。这是矿床研究中一个迅速发展的研究领域。该项目的预期成果将有助于：(1)更好地了解磁铁矿的替代过程和形成时间；(2)识别所涉及的热液流体类型及其与矿化新类型的可能关系。目前（也是最后一个）正在运营的Matagami矿山归该公司所有，将仅持续几年，这使得下一个矿山的勘探对这个北方矿业小镇至关重要。能够更好地了解Matagami VMS矿床中磁铁矿的作用将有助于更好地确定勘探标准，这将有助于寻找新的勘探目标。加拿大东部的许多其他VMS矿床也含有类似的块状磁铁矿，因此本研究的结果直接适用于加拿大的其他采矿/勘探公司。

Volcanogenic massive sulfide (VMS) deposits are exploited primarily for Zinc (from the sulfide mineral,sphalerite - ZnS) and Copper (from the sulfide mineral, chalcopyrite - CuFeS2). VMS deposits formed fromhot, hydrothermal fluids circulating through volcanic rocks on ancient seafloor (similar to black smokers on theseafloor today). However, some VMS deposits contain unusually high amounts of the mineral magnetite(Fe3O4), rendering significant parts of the deposits uneconomic. Magnetite is thought to form by replacementof the sulfides. However, the detailed mechanism/s of this replacement process, and why the replacement of theentire deposit is nearly complete, in some cases, are not well understood. Therefore the Company-specificproblem is to understand better the origin of massive magnetite in their VMS deposits at Matagami, Quebec.To address this scientific problem, the proposed project aims to provide new constraints on the formation ofmagnetite in VMS deposits through a combined study of the petrography and trace element chemistry ofmagnetite and sulfides from Matagami VMS deposits. We will use the innovative technique of laser ablationICP-MS to obtain high quality, in-situ trace element data. This is a rapidly expanding field of research withinMineral Deposit studies. The expected outcomes of the project will lead to 1) a better understanding of thereplacement process/es and timing of magnetite formation and 2) identification of the type of hydrothermalfluids involved and their possible relation to new style of mineralization in the Mining Camp. The current (andlast) operating mine of Matagami is owned by the Company and will last only a few years, making explorationfor the next mine critical for this northern mining town. Being able to better understand the role of themagnetite in the VMS deposits of Matagami will help better define exploration criteria that will contribute tofinding new exploration targets. A number of other VMS deposits in Eastern Canada contain similar massivepods of magnetite, and thus the results of this study are directly applicable and beneficial to othermining/exploration companies in Canada.