Sulfide evolution in komatiite-hosted nickel deposits

在这个项目中有两个主要问题需要回答：1)科马铁矿硫化物矿床的形成涉及什么过程？ 2)Kambalda矿床中矿石形成的S的来源是什么？将研究的过程包括科马提岩熔岩流的早期阶段，以科马提岩溶入火山口的就位机制为代表，以及后期阶段，以形成基质矿的机制为代表。最近在Kambalda相交的科马提岩岩脉可以帮助识别和描述这些过程。这项研究还可以将该喷口与地层学中较高的已知熔岩流之一联系起来。为了形成基质硫化物，目前最受欢迎的调整后的“台球模型”无法解释观察到的多层基质矿石。它也与以下理论不一致：由于基质硫化物形成的硫化物高度增加而形成的针尖，其中硫化物被来自下方和上方的旧岩石束缚，因此表明基底硫化物层没有同时凝固。这里要测试的假设是，在莫兰观察到的两个基质硫化物层，都是由两种不同的机制形成的。最初提出的由橄榄石沉入硫化物熔池形成的基底均匀基质硫化物层，但在计算中包括了硫化物熔体压力的变化。相反，上面的不均匀层状基质硫化物堆可能是由橄榄石的沉淀和硫化物在动态熔岩流系统中的共同堆积形成的，根据硫化物的供应形成富硫化物和贫硫化物层。Kamblada镍矿床的硫来源可能是被科马铁矿侵蚀的沉积物，但之前的多次S同位素研究（由于样本覆盖率低）既不能证明也不能推翻这一假设，尽管它对其他矿床有效。第二层基质矿层形成时，熔岩通道已经形成，没有含硫化物的沉积物，指向另一个来源（如地幔或更古老的玄武岩中的沉积成分）。现有的矿石前、早期、主阶段和矿石后阶段的样品套件将允许研究具有可变“R”因子的样品，这应该反映在多种S同位素中。这两个目标都是研究一种马马岩质矿床类型，但研究结果将讨论它们在岩浆硫化物矿床中的一般应用。

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.