Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance
文献类型：期刊论文
| 作者 | Pang, Kwan-Nang4; Teng, Fang-Zhen5; Sun, Yang1,4; Chung, Sun-Lin3,4; Zarrinkoub, Mohammad Hossein2 |
| 刊名 | GEOCHIMICA ET COSMOCHIMICA ACTA
 |
| 出版日期 | 2020-06-01 |
| 卷号 | 278页码:110-121 |
| 关键词 | Makran arc Continental crust Magnesium isotopes Iran Carbonates |
| ISSN号 | 0016-7037 |
| DOI | 10.1016/j.gca.2019.10.005 |
| 英文摘要 | Continental crust loses Mg by lower crustal foundering and chemical weathering to become its intermediate-silicic composition. Both processes should preferentially retain heavy Mg isotopes in the crust, yet the estimated Mg isotopic ratio for the bulk continental crust is indistinguishable from that for unmodified mantle. This can be elucidated by two notions that are not mutually exclusive: (i) the basaltic parent to the crust has Mg isotopes lighter than the mantle and has since become mantle-like as a result of Mg loss by igneous and weathering fractionation, and (ii) heavy Mg isotopes in the continental crust are constantly balanced by a hidden input of light Mg isotopes. Arc magmas are arguably building blocks of the continental crust and their Mg isotopic signature could be used to place limits on the above views. Here, we conducted a Mg isotopic study of the Makran arc, a rare continental arc in Iran within the Alpine-Himalayan orogenic belt. The measured Mg isotopic ratios for most mafic and intermediate samples are mantle-like with delta Mg-26 values ranging from -0.32 parts per thousand to -0.20 parts per thousand. After excluding dubious samples affected by alteration, the silicic samples span a broad range of isotopic ratios with delta Mg-26 values ranging from -0.32 parts per thousand to +0.32 parts per thousand, beyond that of unmodified mantle (delta Mg-26 = -0.25 +/- 0.04 parts per thousand). The isotopic data form a trend from mantle-like delta Mg-26 at relatively high MgO towards elevated delta Mg-26 at low MgO, requiring the isotopic variability be related to differentiation in an open system involving assimilation of high-delta Mg-26 crustal rocks. Our results are generally consistent with Mg isotopic data compiled for global arcs where magmas have Mg isotopic ratios ranging from mantlelike to similar to 0.7 per mil above the mantle range, and compositions substantially below that range are rare. Thus, heavy Mg isotopes in the continents predicted by igneous and weathering fractionation might have been compensated by a hidden input of light Mg isotopes, which is presumably in the form of carbonates, leading to a bulk crustal Mg isotopic composition that is mantle-like. (C) 2019 Elsevier Ltd. All rights reserved. |
| 资助项目 | Ministry of Science and Technology, Taiwan, Republic of China[MOST 104-2116-M-001-001-MY2] ; Ministry of Science and Technology, Taiwan, Republic of China[105-2628-M001-002-MY4] ; National Science Foundation[EAR-1747706] |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:000596123600009 |
| 出版者 | PERGAMON-ELSEVIER SCIENCE LTD |
| 资助机构 | Ministry of Science and Technology, Taiwan, Republic of China ; Ministry of Science and Technology, Taiwan, Republic of China ; National Science Foundation ; National Science Foundation ; Ministry of Science and Technology, Taiwan, Republic of China ; Ministry of Science and Technology, Taiwan, Republic of China ; National Science Foundation ; National Science Foundation ; Ministry of Science and Technology, Taiwan, Republic of China ; Ministry of Science and Technology, Taiwan, Republic of China ; National Science Foundation ; National Science Foundation ; Ministry of Science and Technology, Taiwan, Republic of China ; Ministry of Science and Technology, Taiwan, Republic of China ; National Science Foundation ; National Science Foundation |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/99907]  |
| 专题 | 地质与地球物理研究所_岩石圈演化国家重点实验室 |
| 通讯作者 | Pang, Kwan-Nang |
| 作者单位 | 1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Univ Birjand, Dept Geol, Birjand, Iran 3.Natl Taiwan Univ, Dept Geosci, Taipei 10617, Taiwan 4.Acad Sinica, Inst Earth Sci, Taipei 11529, Taiwan 5.Univ Washington, Dept Earth & Space Sci, Isotope Lab, Seattle, WA 98195 USA |
| 推荐引用方式 GB/T 7714 | Pang, Kwan-Nang,Teng, Fang-Zhen,Sun, Yang,et al. Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance[J]. GEOCHIMICA ET COSMOCHIMICA ACTA,2020,278:110-121. |
| APA | Pang, Kwan-Nang,Teng, Fang-Zhen,Sun, Yang,Chung, Sun-Lin,&Zarrinkoub, Mohammad Hossein.(2020).Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance.GEOCHIMICA ET COSMOCHIMICA ACTA,278,110-121. |
| MLA | Pang, Kwan-Nang,et al."Magnesium isotopic systematics of the Makran arc magmas, Iran: Implications for crust-mantle Mg isotopic balance".GEOCHIMICA ET COSMOCHIMICA ACTA 278(2020):110-121. |
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来源：地质与地球物理研究所
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