کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
10119985 1638615 2018 33 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
In-situ lithium isotope geochemistry for a veined jadeitite from the New Idria serpentinite body, California: Constraints on slab-derived fluid and fluid-rock interaction
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
In-situ lithium isotope geochemistry for a veined jadeitite from the New Idria serpentinite body, California: Constraints on slab-derived fluid and fluid-rock interaction
چکیده انگلیسی
Lithium behavior in slab-derived fluids has been constrained using isotope geochemistry of subduction-related metamorphic and volcanic rocks. We investigated a veined jadeitite from the New Idria serpentinite diapir, California, which is regarded as direct precipitates from slab-derived fluids and therefore records slab-derived fluid signatures. We applied an in-situ measurement of Li concentration and δ7Li composition using an ablation volume correction (AVC) LA-MC-ICPMS. This method enabled determinations of millimeter- to submillimeter-scale isotopic variations in the jadeitite veins and host rocks (jadeite matrix), allowing immediate observations on fluid-rock interactions. Multiple-stage jadeite veins and their host rocks showed a wide range of Li concentrations from 4 to 68 μg/g and δ7Li compositions from −11.7 to +6.7‰, with a curvilinear correlation between them. Individual veins formed in different generations also showed wide isotopic variations as large as ~14‰. Those isotopic and compositional variations within/among veins can be readily explained by variable mixing between the matrix and infiltrated fluids. The initial infiltrated fluid compositions were estimated to be between +6.7 and +12.3‰, based on the δ7Li values of jadeites in the veins that were supposed to be unmodified by interactions with their matrices. The estimated fluid composition is mostly consistent with those inferred for slab-derived fluids proposed by previous studies. The New Idria jadeitite provides a line of evidence for the presence of high δ7Li fluids in the mantle wedge at the forearc depth. Our study also demonstrates that the high δ7Li composition of slab-derived fluids can be easily modified by interactions with surrounding rocks along their pathways.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 318–319, October 2018, Pages 376-385
نویسندگان
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