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The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-delta O-18 zircon

文献类型：期刊论文

作者Xu, Wenjing1,2,3; Xu, Xisheng2; Wang, Yuejun1; Brzozowski, Matthew Jacek2
刊名LITHOS
出版日期2021
卷号380页码:10
关键词Mafic-felsic magma interaction Selective contamination Supercritical fluids Early Paleozoic South China Block
ISSN号0024-4937
DOI10.1016/j.lithos.2020.105854
英文摘要The petrogenesis of continental mafic rocks that are enriched in large-ion lithophile elements (LILE) and that have enriched Sr-Nd-Hf isotope compositions is debated, with some models suggesting an enriched mantle source and others arguing for crustal contamination. Crustal contamination has generally not been favored as numerical models indicate that this would require the addition of significant amounts of crustal materials. Here we present the first detailed study of the oxygen isotope composition of zircons from representative early Paleozoic mafic, intermediate, and felsic magmatic rocks in the South China Block (SCB), and combine this information with available geochemical data to re-examine whether crustal contamination or an enriched mantle source is the principal cause of the crustal geochemical signatures in these rocks. Zircon grains in the high-MgO mafic rocks (MgO 8 wt%) with low epsilon(Nd)(t) values (< -6) have similar, or slightly lower, mean delta O-18(zm) values (e.g., 8.3 +/- 0.1%0 and 8.5 +/- 0.2%0 for zircons in the Fuxi monzonorite and Xinchuan hornblendite, respectively) than those in coeval granitoids (9.2 +/- 0.2%0 and 8.6 +/- 0.3%0 for zircons in the Fuxi granite and Xinchuan quartz monzonite, respectively). Zircon grains in the Yonghe low-MgO olivine-bearing gabbro (epsilon(Nd)(t) = -2.9 to -1.5) and the Guantian quartz diorite (epsilon(Nd)(t) = -3.5 to -3.0) are characterized by relatively low mean delta O-18(zrn) values (7.2 +/- 0.1 parts per thousand and 7.7 +/- 0.1 parts per thousand, respectively). Considering that the early Paleozoic mafic rocks in the SCB have heterogeneous Sr-Nd-Hf isotope signatures (whole-rock initial 87Sr/86Sr = 0.7041-0.7114; eNd(t) = -8.4 to +1.8; weighted mean zircon epsilon(Hf)(t) = -8.7 to +5.2) and crustal Ce/Pb, Nb/U, Rb/Sr, and Th/La ratios (0.59-13.1, 3.3-20.9, 0.05-0.68, and 0.11-0.51, respectively), it is suggested that crustal contamination, rather than an ancient subduction-modified enriched mantle source, was the principal cause of the crustal geochemical signatures in these rocks. A refined model is proposed in which water played a key role in the preferential transfer of fluid mobile elements from crust-derived hydrous felsic magmas to mantle-derived mafic magmas, leading to the enrichment of fluid-mobile elements (e.g., LILE), the fractionation of these elements (e.g., elevated La/Sm, La/Ta, Rb/ Sr, and Th/La, and depressed Ce/Pb, Nb/U, and Sm/Nd), and the enrichment in O-18 in the selectively contaminated mafic magmas. (c) 2020 Elsevier B.V. All rights reserved.
WOS关键词ND-HF ISOTOPES ; U-PB AGE ; CATHAYSIA BLOCK ; CRUSTAL CONTAMINATION ; WORKING REFERENCE ; OXYGEN ISOTOPES ; SR ISOTOPES ; MANTLE ; MAGMA ; ORIGIN
资助项目National Natural Science Foundation of China[41430208] ; National Natural Science Foundation of China[41802050] ; National Natural Science Foundation of China[U1701641] ; Natural Science Foundation of Guangdong Province, China[2018A030310315]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
WOS记录号WOS:000612242300001
出版者ELSEVIER
资助机构National Natural Science Foundation of China ; Natural Science Foundation of Guangdong Province, China
源URL[http://ir.idsse.ac.cn/handle/183446/8502]  
专题深海科学研究部_深海地质与地球化学研究室
通讯作者Xu, Wenjing
作者单位1.Sun Yat Sen Univ, Sch Earth Sci & Engn, Guangdong Prov Key Lab Geodynam & Geohazards, Guangzhou 510275, Peoples R China
2.Nanjing Univ, Sch Earth Sci & Engn, State Key Lab Mineral Deposits Res, Nanjing 210023, Peoples R China
3.Chinese Acad Sci, Inst Deep Sea Sci & Engn, Deep Sea Sci Div, Sanya 572000, Peoples R China
推荐引用方式
GB/T 7714		 Xu, Wenjing,Xu, Xisheng,Wang, Yuejun,et al. The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-delta O-18 zircon[J]. LITHOS,2021,380:10.
APA Xu, Wenjing,Xu, Xisheng,Wang, Yuejun,&Brzozowski, Matthew Jacek.(2021).The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-delta O-18 zircon.LITHOS,380,10.
MLA Xu, Wenjing,et al."The effects of selective contamination on the early Paleozoic intracontinental mafic rocks in the South China Block: New insights from high-delta O-18 zircon".LITHOS 380(2021):10.

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来源：深海科学与工程研究所

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