Evolution of inorganic and organic carbon in the slab during subduction indicated by continental volcanic rock

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-09-13 DOI:10.1016/j.chemgeo.2025.123055

Zheng Xu

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引用次数: 0

Abstract

Continental volcanic rocks provide critical insights into carbon recycling processes within the mantle transition zone. Here I present the carbon isotope compositions of carbonates in the Cenozoic continental volcanic rocks from Eastern China. δ¹³C of carbonates in these rocks, which represent carbon isotope composition of the involved magma before carbonate precipitation, vary from −15.0 ‰ to −2.4 ‰. After the correction of magma degassing assuming the initial CO₂ content of the magma is 1500 ppm, the initial δ¹³C of the magma is between −13.6 ‰ to +6.2 ‰. Combining with degassing corrected carbon isotope compositions and whole rock trace element and SrNd isotope compositions, these rocks can be divided into two groups, which includes samples with δ¹³C higher than DM and within or lower than DM. The distinction of carbon isotope compositions for the two groups can be attributed to the different proportions of high δ¹³C inorganic carbon and low δ¹³C organic carbon in the mantle sources. δ¹³C of these continental volcanic rocks are lower than arc emissions. This marks the consumption of inorganic carbon in the slab during decarbonation at sub-arc depth. The petrogenesis of continental volcanic rocks is related to the decarbonation in the mantle transition zone. However, δ¹³C of these rocks are comparable with OIB. This observation indicates the proportions of inorganic and organic carbon in the slab may not be significantly changed after decarbonation in the mantle transition zone.

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陆相火山岩指示俯冲期板块内无机碳和有机碳的演化

大陆火山岩为地幔过渡带内的碳循环过程提供了重要的见解。本文介绍了中国东部新生代陆相火山岩中碳酸盐的碳同位素组成。碳酸盐岩δ13C变化范围为- 15.0‰~ - 2.4‰，代表了碳酸盐岩沉淀前岩浆的碳同位素组成。假设岩浆初始CO2含量为1500 ppm，经过岩浆脱气校正后，岩浆的初始δ13C值在−13.6‰~ +6.2‰之间。结合脱气校正后的碳同位素组成及全岩微量元素和SrNd同位素组成，将这些岩石分为δ13C高于DM和低于DM的两组，两组岩石碳同位素组成的差异可归因于地幔源中高δ13C无机碳和低δ13C有机碳的比例不同。这些陆相火山岩的δ13C低于弧辐射。这标志着在次弧深度脱碳过程中板坯中无机碳的消耗。陆相火山岩的成岩作用与地幔过渡带的脱碳作用有关。然而，这些岩石的δ13C与OIB相当。这一观测结果表明，在地幔过渡带脱碳后，陆块中无机碳和有机碳的比例可能没有明显变化。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Chemical Geology 地学-地球化学与地球物理

CiteScore

7.20

自引率

10.30%

发文量

374

审稿时长

3.6 months

期刊介绍： Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry. The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry. Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry. The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.