Sulfide evolution in komatiite-hosted nickel deposits

本项目有两个主要问题需要回答：1）科马提岩型硫化物矿床的形成涉及哪些过程; 2）坎巴尔达矿床成矿过程中硫的来源是什么？1.将被调查的过程包括科马提岩熔岩流的早期阶段，代表的科马提岩熔体进入通风口的就位机制，和后期阶段，代表的机制，形成矩阵ore. Komatiite岩浆就位到浅层次的火山喷发现场附近知之甚少。最近在坎巴尔达发现的科马提岩脉有助于识别和描述这些过程。这项研究还可以将喷口与地层中较高的一个已知熔岩流联系起来。为了形成基质硫化物，目前流行的调整后的“台球模型”无法解释观察到的多层基质矿石。这也不同意尖灭的理论，即硫化物从下面和上面被较老的岩石束缚，是由于基质硫化物形成的硫化物高度增加而形成的，因此表明基底硫化物层没有同时固化。这里要检验的假设是，在Moran中观察到的两个基质硫化物层由两种不同的机制形成。如最初提出的那样，由橄榄石沉入硫化物熔体池形成的基底均匀基质硫化物层，但通过将硫化物熔体压力的变化包括在计算中。与此相反，上述不均匀层状基质硫化物堆可能是在动态熔岩流系统中由橄榄石沉淀和硫化物的共同积累形成的，根据硫化物的供应情况形成富硫化物层和贫硫化物层。Kamblada镍矿床的硫源可能是被科马提岩侵蚀的沉积物，但以前的多个S同位素研究（由于样品覆盖率低）既不能证明也不能反驳这一假设，尽管它适用于其他矿床。第二个基质矿石层形成时，熔岩通道已经建立，没有含硫化物的沉积物，指向另一个来源（如地幔或沉积成分在较老的玄武岩）。可用的样品套件的前，早期，主要，和后矿阶段将允许调查样品与变量的“R”的因素，这应该反映在多个S同位素。这两个目标调查科马提质存款类型，但研究成果将讨论他们的应用，岩浆硫化物矿床一般。

There are two main questions to be answered in this project: 1) What processes are involved in the formation of komatiite-hosted sulfide deposits and 2) what are the sources of S for ore formation in the Kambalda deposits?1. Processes that will be investigated include early stages of a komatiite lava flow, represented by emplacement mechanisms of the komatiite melt into the vent, and late stages, represented by mechanisms to form matrix ore.Komatiite-magma emplacement into shallow levels in proximity to the eruption site are poorly understood. The komatiitic dykes recently intersected in Kambalda can help to identify and describe these processes. This study could also link the vent to one of the known lava flows higher in the stratigraphy.To form matrix sulfides, the currently favoured adjusted "billiard-ball-model" is unable to explain observed multiple layers of matrix ore. It is also in disagreement with the theory that the pinchout, where sulfides are bound by older rocks from beneath and above, forms due to an increased sulfide height from the matrix sulfide formation, and hence shows that the basal sulfide layer is not solidified at the same time. The hypothesis to be tested here is, that both matrix sulfide layers, observed in Moran, formed from two distinct mechanisms. The basal homogeneous matrix sulfide layer formed by olivine sinking into a sulfide melt pool as originally proposed, but by including variations of the sulfide melt pressure into the calculation. In contrast, the inhomogeneously layered matrix sulfide pile above could have formed by precipitation of olivine with a co-accumulation of sulfides in a dynamic lava flow system, forming sulfide-rich and sulfide-poor layers depending on the sulfide supply.2. The source of sulfur for the Kamblada Ni deposits is probably the sediments which were eroded by the komatiite, but previous multiple S isotope studies could (due to poor sample coverage) neither prove nor disprove this hypothesis although it worked for other deposits. The second matrix ore layer formed when the lava channel was already established without sulfide-bearing sediments available, pointing to another source (like mantle or sedimentary components in older basalt). The available sample suite of pre-, early-, main-, and post-ore stages will allow to investigate samples with variable 'R' factors, which should be reflected in multiple S isotopes.Both objectives investigate a komatiitic deposit type, but the research outcomes will be discussed in regards to their application to magmatic sulfide deposits in general.