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

利用激光烧蚀电感耦合等离子体质谱(LA-ICPMS)技术研究年轻次大陆岩石圈地幔(SCLM)中硫化物的铂族元素(PGE)系统学。我们的目标是提供大陆岩石圈复兴的亲铁观点：以橄榄石为代价引入辉石的过程。这种返老还童被提议在轻度亏损橄榄岩预期的成分范围内进行，而且似乎比之前预期的更相关。然而，这一返老还童的概念并没有涉及亲铁矿物的演化，因此也没有涉及这种大陆地幔根部的前列腺素E含量。通过使用LAICPMS分析一套特征良好的中Atlas橄榄岩包体中PGE含量的硫化物组分，以及经历了模式恢复的全岩PGE、铜和主要元素系统学的异常良好的关联，我们将能够(A)表征导致全岩PGE组成的硫化物矿物学，(B)识别交代过程中耦合或解偶的硫化物-硅酸盐和氧化物的沉淀和消耗，以及(C)研究SCLM硫化物中PGE的分馏潜力。这一数据采集对于来自克拉通外大陆地幔根部的橄榄岩来说将是独一无二的，从而将进一步得出岩浆过程中经济相关元素的活动性和岩石圈地幔中PGE系统学长期二分法的结论。

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.