Partitioning of chalcophile and highly siderophile elements (HSEs) between sulfide and carbonated melts – Implications for HSE systematics of kimberlites, carbonatites, and melt metasomatized mantle domains
Partitioning of chalcophile and highly siderophile elements (HSEs) between sulfide and carbonated melts – Implications for HSE systematics of kimberlites, carbonatites, and melt metasomatized mantle domains
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DOI：
10.1016/j.gca.2021.05.006
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发表时间：
2021-07
影响因子：
5
通讯作者：
P. Chowdhury;R. Dasgupta;P. Phelps;Cin-Ty A. Lee;Ryan Anselm
中科院分区：
文献类型：
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作者：
P. Chowdhury;R. Dasgupta;P. Phelps;Cin-Ty A. Lee;Ryan Anselm
高亲铁元素（Os、Ru、Ir、Rh、Pt、Pd、Au和Re）及其同位素体系（Re-Os和Pt-Os）是研究幔源岩浆演化和成因的有力工具。考虑到硫化物（副硫化物矿物和/或熔融硫化物）是HSEs在地幔中的主要宿主，并且从大部分地幔体积中提取出低度碳酸化熔体，HSEs在硫化物和碳酸化熔体之间的分配可能在HSEs在地幔和地壳储层之间的分布中发挥关键作用。虽然，HSEs和亲铜元素之间的硫化物熔体和硅酸盐熔体的分区以前已经研究过，硫化物熔体和碳酸盐熔体之间的这些元素的分区没有得到太多的关注。本文利用高PT实验测定了HSEs和亲硫元素（Ni、Co、Mo、Os、Ru、Pd、Pt和Re）在硫化物熔体和碳酸盐硅酸盐熔体（CO2 ~ 17 wt.%）之间的分配硫化物熔体和碳酸盐熔体（CO2 ~> 30 wt.%）在3GPa的压力（P）和1300-1600° C的温度（T）下在石墨胶囊中。所有实验都产生淬火的Fe-硫化物熔体滴+碳酸化硅酸盐熔体基质。用电子探针测量了主量元素的浓度，用LA-ICP-MS测量了HSEs和亲硫元素的含量，发现所有元素在硫化物熔体中均有不同程度的相容性，其D硫化物/碳化物的含量也不同。熔体序列为Mo< Co< Ni< Re< Pt≤ Pd< Ru≤ Os，Mo的熔体序列为10 ~ 10 5。熔体与D硫化物-硅酸盐从以前的研究中，我们表明，硫化物和碳酸盐熔体之间的分配系数HSEs低于这些元素之间的硫化物和硅酸盐熔体的分配系数，表明这些元素在碳酸盐和碳酸盐硅酸盐熔体更大的动员。利用我们实验测量的D值计算碳酸化橄榄岩的体D（D <$），我们使用聚集分数熔融方程模拟地幔来源的低度部分熔体的HSE含量，并将我们模型的原始地幔归一化HSE模式与天然金伯利岩、碳酸岩、洋岛玄武岩和碱性玄武岩进行比较。本文还利用基于原始碳酸盐熔体和SCLM捕虏体中Ru含量的质量平衡计算方法，计算了卡累利阿、卡普瓦尔、加拿大地盾和华北克拉通天然金伯利岩和碳酸盐岩样品中岩石圈下大陆地幔捕虏体碎屑的比例。计算结果表明，天然金伯利岩中碎屑的比例为：卡累利阿岩2-28%，卡普瓦尔岩7-28%，加拿大地盾岩6-16%，这与前人利用各种代用指标的研究结果一致。我们还表明，Re/Os分馏的程度是碳酸盐熔体交代的事件相比，玄武岩熔体交代的类似事件。
Abstract Highly Siderophile Elements (HSEs; Os, Ru, Ir, Rh, Pt, Pd, Au and Re) combined with their isotopic systematics (Re-Os and Pt-Os) are powerful tools for tracking evolution and genesis of mantle derived magmas. Given sulfides (accessory sulfide minerals and/or molten sulfides) are the primary hosts of HSEs in the mantle and low-degree carbonated melts are extracted from large portions of mantle volume, partitioning of HSEs between sulfide and carbonated melt might play a critical role in distributing HSEs between the mantle and crustal reservoirs. Although, partitioning of HSEs and chalcophile elements between sulfide melt and silicate melt has been previously studied, partitioning of these elements between sulfide melt and carbonated melts has not received much attention. Here we use high PT experiments to determine the partitioning of HSEs and chalcophile elements (Ni, Co, Mo, Os, Ru, Pd, Pt and Re) between (i) sulfide melt and carbonated silicate melt (CO 2~ 17 wt.%) and (ii) sulfide melt and carbonatitic melt (CO 2~> 30 wt.%) at a pressure (P) of 3 GPa and temperatures (T) of 1300–1600° C in graphite capsules. All experiments produced quenched Fe-sulfide melt blobs+ carbonated silicate melt matrix. Concentrations of major elements were measured using electron microprobe, and HSEs and chalcophile elements were measured using LA-ICP-MS. We find that all the elements measured are compatible in the sulfide melt to varying degrees and their D sulfide/carb. melt sequence is Mo< Co< Ni< Re< Pt≤ Pd< Ru≤ Os varying from around 10 for Mo to 10 5 for Os. Comparing the D sulfide-carb. melt with D sulfide-silicate from previous studies, we show that the partition coefficients of HSEs between sulfide and carbonated melts are lower than the partition coefficients of these elements between sulfide and silicate melts, indicating greater mobilization of these elements in carbonatites and carbonated silicate melts. Calculating bulk D (D¯) for carbonated peridotite using our experimentally measured D values, we model the HSE contents of mantle derived low-degree partial melts using an aggregate fractional melting equation and compare the primitive mantle normalized HSE patterns of our model with natural kimberlites, carbonatites, ocean island basalts, and alkaline basalts. We also calculate proportions of sub-lithospheric continental mantle (SCLM) xenolith detritus in the natural kimberlite and carbonatite samples from Karelian, Kaapvaal, Canadian shield and North China craton by using mass balance calculations based on Ru concentration in the primary carbonated melt and the SCLM xenoliths. Our calculations show that detritus proportion in natural kimberlites are 2–28% for Karelian, 7–28% for Kaapvaal, and 6–16% for Canadian shield, which are in agreement with previous studies using various other proxies. We also show that the extent of Re/Os fractionation is less for events of carbonate melt metasomatism as compared to similar events of basaltic melt metasomatism.