Behaviour of Chalcogens and Highly Siderophile Elements in subduction zones: The mantle wedge perspective

俯冲带在地球地幔和地壳储层的岩石学和化学演化中起着重要作用。虽然在这些构造环境中的亲石元素和它们的同位素特征的行为是很好的理解，硫族元素（S-Se-Te）和高度亲铁元素（HSE）的系统学是不受约束的，仍然是矛盾的。该项目的目的是提供（i）第一个全面的HSE-187 Os-S-Se-Te数据集，以及（ii）第一个详细的堪察加半岛和加拿大科迪勒拉地幔楔橄榄岩捕虏体中硫属元素和HSE寄主矿物的岩相学和地球化学研究，以了解俯冲板片中流体和熔体的蒸发，可能对地幔楔的HSE-187 Os-S-Se-Te体系进行了修正。通过结合HSE-187 Os-S-Se-Te同位素特征，研究目的是：（1）评价这些元素从俯冲板片到地幔楔和从地幔楔到弧熔岩的再循环过程，从而更好地理解HSE-187 Os-S-Se-Te的全球地球循环;（2）更好地理解地幔中小尺度和大尺度~（187）Os-~（186）Os不均匀性的起源，包括洋岛玄武岩和洋中脊玄武岩的特征。

Subduction zones play a major role in the petrological and chemical evolution of the Earth mantle and crustal reservoirs. While the behaviour of lithophile elements and their isotopic signatures in these tectonic settings is well-understood, the systematics of the chalcogens (S-Se-Te) and highly siderophile elements (HSE) is poorly constrained and still contradictory. The aim of this project is to provide (i) the first comprehensive HSE-187Os-S-Se-Te dataset in combination with (ii) the first detailed petrographic and geochemical study of the chalcogens and HSE host minerals in mantle wedge peridotite xenoliths from the Kamchatka Peninsula and the Canadian Cordillera in order to understand how the percolations of fluids and melts, derived from the subducted slab, may modify the HSE-187Os-S-Se-Te systematics of the mantle wedge. By integrating these results with the HSE-187Os-S-Se-Te signatures of paleo-subduction rocks, the goals are (1) to evaluate how and to which extent the recycling of these elements occurs from the subducted slab to the mantle wedge and from the mantle wedge to the arc lavas and consequently provide a better understanding of the global terrestrial cycle of HSE-187Os-S-Se-Te, and (2) to better understand the origin of small and large-scale 187Os-186Os heterogeneities in the Earth mantle, including signatures in oceanic island and mid-oceanic ridge basalts.