Magnesium isotope fractionation during magmatic differentiation in the lower continental crust
文献类型：期刊论文
| 作者 | Wei, Ying2,3; Huang, Xiao-Long2; Ma, Qiang4; Yang, Fan1; He, Peng-Li2 |
| 刊名 | CHEMICAL GEOLOGY
 |
| 出版日期 | 2024-09-20 |
| 卷号 | 663页码:14 |
| 关键词 | Magnesium isotope Accumulation Granulite xenolith Websterite xenolith Lower continental crust |
| ISSN号 | 0009-2541 |
| DOI | 10.1016/j.chemgeo.2024.122260 |
| 英文摘要 | The Mg isotopic compositions display a significant disparity between the lower continental crust and the mantle. However, due to the limited availability of representative samples from the lower crust, our understanding remains incomplete regarding whether Mg isotope fractionation occurred during its formation and its potential influence on the observed isotopic differences. This study addresses this gap by presenting Mg isotopic data for juvenile lower crustal mafic xenoliths from Daoxian, Southeast China, providing new insights into this poorly understood process. The xenoliths, classified as websterites and two-pyroxene granulites, equilibrated at 818-912 degrees C and 10.6-15.4 kbar. They exhibit high Mg# (77-85), Cr (154-1451 ppm), and Ni (143-312 ppm), as well as trace element patterns resembling those of island arcs and evolved Sr-Nd-Pb isotopic compositions (87Sr/86Sri = 0.7046-0.7071; epsilon Nd(t) = -2.44 to +4.62; 206Pb/204Pbi = 18.26-19.03), indicating their derivation primarily from an enriched mantle source. Despite this, these xenoliths display a diverse range of Mg isotopic compositions. Websterite xenoliths exhibit mantle-like S26Mg values (-0.27%o to -0.29%o), indicating no influence from hybridized mantle source or pyroxene fractional crystallization/accumulation on their Mg isotopes. In contrast, granulite xenoliths show lower and variable S26Mg values (-0.26%o to -0.49%o), which positively correlate with Mg#, Cr, and V, but negatively correlate with Na2O + K2O, indicating that magmatic processes likely influenced Mg isotope fractionation in these samples. Petrological features, coupled with correlations between MgO and CaO/Al2O3, Cr, Co, and Ni, indicate that fractional crystallization and/or accumulation of olivine, spinel, clinopyroxene, orthopyroxene, and plagioclase played crucial roles in the formation of the granulite protoliths. Furthermore, the segregation of spinel during magmatic differentiation could have enriched residual melts in light Mg isotopes inherited by the cumulate Cpx + Opx + Pl (i.e., the granulite protoliths). Overall, the weighted average S26Mg value of the lower crust in South China is estimated to be -0.34 +/- 0.04%o. This finding, together with previous studies on granulite xenoliths in North China and Australia, strongly indicates heterogeneous Mg isotopic compositions in the lower continental crust relative to the mantle. |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:001346677100001 |
| 源URL | [http://ir.gig.ac.cn/handle/344008/82064]  |
| 专题 | 同位素地球化学国家重点实验室 |
| 通讯作者 | Huang, Xiao-Long |
| 作者单位 | 1.Southern Marine Sci & Engn Guangdong Lab Guangzhou, Guangzhou 511458, Peoples R China 2.Chinese Acad Sci, Guangzhou Inst Geochem, State Key Lab Isotope Geochem, Guangzhou 510640, Peoples R China 3.East China Univ Technol, State Key Lab Nucl Resources & Environm, Nanchang 330013, Peoples R China 4.China Univ Geosci, Sch Earth Sci, State Key Lab Geol Proc & Mineral Resources, Wuhan 430074, Peoples R China |
| 推荐引用方式 GB/T 7714 | Wei, Ying,Huang, Xiao-Long,Ma, Qiang,et al. Magnesium isotope fractionation during magmatic differentiation in the lower continental crust[J]. CHEMICAL GEOLOGY,2024,663:14. |
| APA | Wei, Ying,Huang, Xiao-Long,Ma, Qiang,Yang, Fan,&He, Peng-Li.(2024).Magnesium isotope fractionation during magmatic differentiation in the lower continental crust.CHEMICAL GEOLOGY,663,14. |
| MLA | Wei, Ying,et al."Magnesium isotope fractionation during magmatic differentiation in the lower continental crust".CHEMICAL GEOLOGY 663(2024):14. |
入库方式： OAI收割
来源：广州地球化学研究所
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