Identifying clinopyroxene-sulphide co-precipitation, rejuvenation mechanisms and platinum-group element fractionation processes in young continental mantle roots

应用激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）技术研究年轻的次大陆岩石圈地幔（SCLM）中硫化物的铂族元素（PGE）系统学。我们的目的是提供一个亲铁的大陆岩石圈复兴的观点：辉石的引入过程中的橄榄石的代价。这种复兴已被提议在轻度亏损橄榄岩预期的成分范围内运作，似乎比以前预期的更相关。然而，这种复兴的概念并没有解决亲铁矿物的演变，从而PGE含量的大陆地幔根。通过使用LAICP-MS从一套充分表征的中阿特拉斯橄榄岩捕虏体中分析硫化物部分的PGE含量，该捕虏体具有异常良好相关的全岩PGE、Cu和主要元素系统，其经历了模态再生，我们将能够（a）表征负责全岩PGE组成的硫化物矿物学，（B）确定交代作用期间硫化物-硅酸盐和氧化物沉淀和消耗的耦合或解耦，以及（c）研究SCLM硫化物中铂族元素分馏的潜力。这一数据采集将是独特的橄榄岩从off-duponic大陆地幔根，从而将允许进一步的结论，在岩浆过程中的流动性的经济相关的元素和长期的岩石圈地幔中的铂族元素系统的二分法。

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) techniques shall be utilized to investigate platinum-group elements (PGE) systematics of sulphides in young subcontinental lithospheric mantle (SCLM). We aim at providing a siderophile perspective on continental lithosphere rejuvenation: a process of pyroxene introduction at the expense of olivine. This rejuvenation has been proposed to operate within the compositional range anticipated for mildly depleted peridotite and appears to be more relevant than previously anticipated. However, this rejuvenation concept does not address the evolution of siderophile minerals and thus the PGE content of such continental mantle roots. By analyzing the sulphide fraction for the PGE content using LAICP- MS from a suite of well-characterized Middle Atlas peridotite xenoliths with unusually well correlated whole-rock PGE, Cu and major element systematics that has experienced modal rejuvenation we will be able to (a) characterize the sulphide mineralogy responsible for the whole rock PGE composition, (b) identify coupled or decoupled sulphide-silicate and –oxide precipitation and consumption during metasomatism and (c) study the potential for PGE fractionation in sulphides from SCLM. This data acquisition will be unique for peridotites from off-cratonic continental mantle roots and thus will allow further conclusion on the mobility of economically relevant elements during magmatic processes and the secular dichotomy of PGE systematics in the lithospheric mantle.