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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Sulfur isotope and PGE systematics of metasomatised mantle wedge
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Sulfur isotope and PGE systematics of metasomatised mantle wedge

机译：硫磺同位素和PGE Systeics of Delasomated Mantle Wedge

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摘要

At convergent margins fluids liberated from subducting slabs metasomatise the overlying mantle wedge, enriching it in volatiles, incompatible elements and possibly ore-forming metals. Despite the genetic link between this process, the genesis of arc magmas, and formation of porphyry Cu-Au deposits, there is currently little understanding of the behaviour of chalcophile and siderophile elements during subduction-related mantle metasomatism. In this study, we report sulfur isotopic compositions and PGE concentrations of sulfides in a suite of garnet peridotites from the Western Gneiss Region of Norway, sampling mantle wedge from similar to 100 to similar to 250 km depth. Sulfides hosted in metasomatised samples have 8345 deviated from typical mantle values, ranging between -10.0 and +5.4 parts per thousand, indicating derivation of sulfur from subducted crust. Sulfides in pervasively metasomatised samples have atypical PGE signatures, with strong enrichment in Os and Ru relative to Ir, whereas channelised fluid flow produced sulfides extremely enriched in Pd, up to 700 times the concentration found in non-metasomatised samples. These signatures are reconcilable with a high oxidation state of the metasomatising agents and demonstrate that subduction can recycle chalcophile and siderophile elements into and within the mantle, along with sulfur. We further show that because the solubility of Os and Ru in fluids is redox sensitive, and Pd is more soluble than the I-PGE, ratios such as Os/Ir, Ru/Ir plotted against Pd/Ir can be used to trace the metasomatic oxidation of mantle samples, mantle-derived magmas and porphyry Cu +/- Au deposits. This geochemical insight is used to show that Au-rich porphyry Cu deposits are derived from more oxidised mantle wedge than Au-poor porphyry deposits. (C) 2018 Elsevier B.V. All rights reserved.
机译：在会聚的边缘流体从俯冲板坯metasomatise覆地幔楔，在挥发物，不相容元素和可能的矿石形成系金属富集它释放出来。尽管这个过程之间的岛弧岩浆的成因形成的斑岩型铜金矿床的成因联系，并且，目前还亲硫和亲铁元素的俯冲地幔有关交代过程中的行为知之甚少。在这项研究中，我们从挪威西部片麻岩区一套石榴石橄榄岩的报告硫化物的硫同位素组成与PGE的浓度，从同样的取样地幔楔100类似250公里深度。硫化物托管metasomatised样品已经从典型地幔值偏离8345中，每千份不等-10.0和5.4之间，指示从俯冲地壳硫的推导。普遍地metasomatised样品中的硫化物具有非典型的PGE签名，与Os和钌相对于铱强烈富集，而信道化的流体流动产生在Pd中极其富含硫化物，高达700倍浓度的非metasomatised样品中发现。这些签名是调和与metasomatising剂的高氧化态和表明俯冲可以回收亲硫和亲铁元素进入和地幔内，与硫一起。进一步的研究表明，因为Os和Ru中的流体中的溶解度为氧化还原敏感性，和Pd比I-PGE更可溶，比率如OS /铱，钌/铱作图的Pd / IR可用于跟踪交代地幔样品，地幔岩浆和斑岩铜+/-金矿床的氧化。这地球化学洞察力用于显示富Au斑岩铜矿床是从多个氧化地幔楔比金匮乏的斑岩型矿床的。 （c）2018年elestvier b.v.保留所有权利。

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