气候变化领域集成服务门户(CCPortal): Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation

CCPortal

DOI	10.1029/2020JB020708
	Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation
	Chen W.; Zhang G.; Ruan M.; Wang S.; Xiong X.
发表日期	2021
ISSN	21699313
卷号	126 期号:3
英文摘要	Resolving the geochemical discrepancies in Nb/Ta between the bulk continental crust and its parental mantle melts can provide insights into the processes by which basaltic magmas differentiated into the felsic crust. Deep-seated garnet pyroxenite cumulates (i.e., arclogite) have high Nb/Ta values due to the presence of high Nb/Ta-rutile. For this reason, rutile-bearing arclogites having Nb-rich composition were proposed to complement the low Nb/Ta nature of the continental crust and evolved arc magmas, that is to say, continental arc magma evolution dominantly occurred in the stability field of garnet. However, this suggestion is challenged by the incomplete understanding of the role of rutile in the Nb/Ta fractionation during arc magma evolution due to insufficient partitioning data at low temperatures (T ≤ 1,000°C). Here, we determined Nb and Ta partitioning ratios in rutile-felsic melt systems at 2.0 GPa, 850–1,000°C and ∼4–20 wt.% H2O. Our results confirm that equilibrium crystallization of rutile with respect to Nb and Ta will not impart lower Nb/Ta values to any derivative liquids, whereas diffusive fractionation of Nb/Ta in siliceous melts during the growth of rutile can reduce Nb/Ta ratios in melts. However, a positive correlation between Nb/Ta and Dy/Yb for mature continental arc magmas, incipient continental arc magmas, island arc magmas, and global arc magmas indicates that amphibole rather than rutile-bearing arclogite was responsible for causing low Nb/Ta ratios of many evolved intermediate rocks. Accordingly, the chemical differentiation from primary basaltic to average andesitic compositions of the continental crust mainly occurred in the stability field of amphibole. © 2021. American Geophysical Union. All Rights Reserved.
英文关键词	amphibole; arc magma; continental crust; Nb/Ta differentiation; rutile
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187258
作者单位	Center of Deep Sea Research & Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China; State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
推荐引用方式 GB/T 7714	Chen W.,Zhang G.,Ruan M.,et al. Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation[J],2021,126(3).
APA	Chen W.,Zhang G.,Ruan M.,Wang S.,&Xiong X..(2021).Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation.Journal of Geophysical Research: Solid Earth,126(3).
MLA	Chen W.,et al."Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation".Journal of Geophysical Research: Solid Earth 126.3(2021).