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首页> 外文期刊>Contributions to Mineralogy and Petrology >Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland
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Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

机译：硫化铜微滴中Se，Te，PGE和Au的极度富集：来自格陵兰东部Skaergaard入侵中硫化物的LA-ICP-MS分析的证据

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摘要

The Platinova Reef, in the Skaergaard Intrusion, east Greenland, is an example of a magmatic Cu-PGE-Au sulfide deposit formed in the latter stages of magmatic differentiation. As is characteristic with such deposits, it contains a low volume of sulfide, displays peak metal offsets and is Cu rich but Ni poor. However, even for such deposits, the Platinova Reef contains extremely low volumes of sulfide and the highest Pd and Au tenor sulfides of any magmatic ore deposit. Here, we present the first LA-ICP-MS analyses of sulfide microdroplets from the Platinova Reef, which show that they have the highest Se concentrations (up to 1200 ppm) and lowest S/Se ratios (190-700) of any known magmatic sulfide deposit and have significant Te enrichment. In addition, where sulfide volume increases, there is a change from high Pd-tenor microdroplets trapped in situ to larger, low tenor sulfides. The transition between these two sulfide regimes is marked by sharp peaks in Au, and then Te concentration, followed by a wider peak in Se, which gradually decreases with height. Mineralogical evidence implies that there is no significant post-magmatic hydrothermal S loss and that the metal profiles are essentially a function of magmatic processes. We propose that to generate these extreme precious and semimetal contents, the sulfides must have formed from an anomalously metal-rich package of magma, possibly formed via the dissolution of a previously PGE-enriched sulfide. Other processes such as kinetic diffusion may have also occurred alongside this to produce the ultra-high tenors. The characteristic metal offset pattern observed is largely controlled by partitioning effects, producing offset peaks in the order Pt+Pd>Au>Te>Se>Cu that are entirely consistent with published D values. This study confirms that extreme enrichment in sulfide droplets can occur in closed-system layered intrusions in situ, but this will characteristically form ore deposits that are so low in sulfide that they do not conform to conventional deposit models for Cu-Ni-PGE sulfides which require very high R factors, and settling of sulfide liquids.
机译：位于格陵兰东部Skaergaard侵入体的Platinova礁岩是在岩浆分化后期形成的岩浆Cu-PGE-Au硫化物矿床的一个例子。这类沉积物的特征是，它含有少量硫化物，显示出峰值的金属偏移，并且富含Cu但缺乏Ni。但是，即使对于此类矿床，普拉蒂诺瓦礁石也含有极少量的硫化物，以及任何岩浆矿床中最高的Pd和Au次生硫化物。在这里，我们展示了来自普拉蒂诺瓦礁的硫化物微滴的首次LA-ICP-MS分析，结果表明它们在任何已知岩浆中都具有最高的Se浓度（最高1200 ppm）和最低的S / Se比（190-700）。硫化物沉积并有明显的Te富集。另外，在硫化物体积增加的情况下，从原位捕获的高Pd-男高音微滴变为较大的低男高硫化物。这两个硫化物形态之间的过渡以Au的尖峰和随后的Te浓度为特征，然后是Se的宽峰，随着高度的升高而逐渐减小。矿物学证据表明，岩浆后热液没有明显的S损失，而且金属剖面基本上是岩浆作用的函数。我们建议，要生成这些极端的贵金属和半金属，硫化物必须由异常富含金属的岩浆包裹形成，可能是通过溶解先前富含PGE的硫化物而形成的。与此同时，还可能发生其他过程，例如动力学扩散，以产生超高男高音。观察到的特征性金属偏移图案在很大程度上受到分配效应的控制，产生的偏移峰的顺序为Pt + Pd> Au> Te> Se> Cu，与发布的D值完全一致。这项研究证实，在封闭系统分层侵入中原位可能会发生硫化物液滴的极度富集，但这会形成特征性的矿床，其硫化物含量极低，以致与常规的Cu-Ni-PGE硫化物矿床模型不符。需要非常高的R因子，并且会沉淀出硫化物液体。

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