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Zinc isotopic systematics of the South China Sea basalts and implications for its behavior during plate subduction
Chemical Geology ( IF 3.9 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.chemgeo.2020.119582
Renqiang Liao , Hongli Zhu , Jianghong Deng , Lipeng Zhang , He Li , Congying Li , He Liu , Weidong Sun

Abstract Zinc isotopes is a new tracer for deep materials recycling. However, its behavior during plate subduction remains obscure. To address this issue, here we present high precision Zn isotopic compositions (δ66Zn) of basalts recovered from International Ocean Discovery Program (IODP) Expedition 349 in the South China Sea (SCS), which have been influenced by various amounts of subducted materials. Based on (La/Sm)N values, these basalts are classified into N-MORB ((La/Sm)N The lack of correlations between δ66Zn and geochemical indicators of magma differentiation (e.g., MgO, SiO2, CaO/Al2O3) suggests that crystal fractionation has a limited effect on Zn isotope fractionation. Even though the mantle sources of the SCS basalts are clearly affected by various amounts of subducted materials, there are no correlations between δ66Zn and indicators of subducted components (e.g., Ce/Pb, Nb/U, Ba/La, 87Sr/86Sr). This implies that insignificant amount of Zn was transported from the subducting slab to the mantle sources of the SCS basalts, so that subducted materials have a limited effect on Zn isotopic compositions of the SCS basalts studied here. Therefore, the observed offset of δ66Zn (~0.10‰) between the mantle and the SCS basalts studied here should be primarily controlled by Zn isotope fractionation during mantle partial melting with no need for contributions from subduction materials.

中文翻译:

南海玄武岩锌同位素系统学及其在板块俯冲过程中的作用

摘要 锌同位素是一种新型的深部材料回收示踪剂。然而,它在板块俯冲过程中的行为仍然模糊不清。为了解决这个问题,我们在这里展示了从国际海洋发现计划 (IODP) 南海 (SCS) 远征 349 中回收的玄武岩的高精度锌同位素组成 (δ66Zn),这些玄武岩受到各种俯冲物质的影响。根据 (La/Sm)N 值,这些玄武岩被归类为 N-MORB ((La/Sm)N δ66Zn 与岩浆分异地球化学指标(如 MgO、SiO2、CaO/Al2O3)之间缺乏相关性表明:晶体分馏对 Zn 同位素分馏的影响有限. 尽管南海玄武岩的地幔源明显受到各种俯冲物质的影响, δ66Zn 与俯冲成分指标(如 Ce/Pb、Nb/U、Ba/La、87Sr/86Sr)之间没有相关性。这意味着微量的锌从俯冲板片输送到南海玄武岩的地幔源,因此俯冲物质对这里研究的南海玄武岩的锌同位素组成影响有限。因此,这里研究的地幔和南海玄武岩之间观测到的δ66Zn(~0.10‰)偏移量应主要受地幔部分熔融过程中Zn同位素分馏控制,不需要俯冲物质的贡献。因此,俯冲物质对这里研究的 SCS 玄武岩的 Zn 同位素组成的影响有限。因此,这里研究的地幔和南海玄武岩之间观测到的δ66Zn(~0.10‰)偏移量应主要受地幔部分熔融过程中Zn同位素分馏控制,不需要俯冲物质的贡献。因此,俯冲物质对这里研究的 SCS 玄武岩的 Zn 同位素组成的影响有限。因此,这里研究的地幔和南海玄武岩之间观测到的δ66Zn(~0.10‰)偏移量应主要受地幔部分熔融过程中Zn同位素分馏控制,不需要俯冲物质的贡献。
更新日期:2020-05-01
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