气候变化领域集成服务门户(CCPortal): Using Zircons to Disentangle Back-Veining and Hybridization of Diorite Dykes: an Example From the Gangdese Arc, Tibet

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DOI	10.1093/petrology/egad010
	Using Zircons to Disentangle Back-Veining and Hybridization of Diorite Dykes: an Example From the Gangdese Arc, Tibet
	Weinberg, Roberto F.; Moyen, Jean-Francois; Yi, Jian-Kang; Zhu, Di-Cheng; Nebel, Oliver; Chen, Shaorong; Wang, Qing
发表日期	2023
ISSN	0022-3530
EISSN	1460-2415
卷号	64 期号:3
英文摘要	Thermo-chemical modeling and chemical data suggest that the genesis of arc melts commonly involves re-melting of older intrusions, triggered by the injection of mantle-derived melts, followed by magma mixing. Remelting and mixing may lead to complex zircon populations, which can be used to gain insights into the conditions of mixing. This paper investigates a case where such processes can be studied through the compositional and thermal record provided by zircons preserved in a diorite dyke swarm that remelted host rock tonalites in the Gangdese Batholith in Tibet. Autocrystic zircons from the diorite yield consistent ages of 46 to 47 Ma even though they can be altered, having highly enriched trace elements, reaching similar to 1 wt % in Fe, Ca, Y, U, Th, and anomalously high values of LREE and Ti. Granitic magmas derived from the tonalite, back-veined the dykes and mixed with the dioritic mush, transferring small quantities of 77-79 Ma zircon xenocrysts. The xenocrysts are euhedral with little evidence for resorption, indicating that they were apparently stable during the process of tonalite anatexis and transfer to the diorite magma. This requires that: (i) tonalite melting occurred at low temperatures with minimal zircon dissolution, and (ii) the diorite either cooled rapidly before significant resorption of the grains or was already saturated in zircon when mixing occurred. Zircon saturation temperatures of the diorite are relatively low, indicating that xenocrystic zircons were transferred to a highly crystalline dioritic mush. This requires either liquefaction by injection of the back-veining felsic magma to allow for mixing, or pervasive throughflow of the diorite mush by the felsic magma leaving behind zircon xenocrysts. The findings suggest that the dykes triggered low-T, water-fluxed melting of the host tonalite and that these anatectic melts invaded the diorite mush initially through the interstices leading to mixing. This may have caused the breakdown of the crystalline framework leading to liquefaction and renewed magma flow. Dyking and assimilation of wall-rock through back-veining as recorded in these rocks could be common in transcrustal arcs. However, this process could be hidden due to a combination of the similarity in the isotopic and chemical nature of arc rocks and resorption of zircon xenocrysts during mixing. This process may explain some complex chemistry of arc magmatic rocks and their minerals that are not easily explained by endmember models, such as pure re-melting of older arc rocks or fractional crystallization of mantle-derived melts.
关键词	zircon saturation temperature zircon chemistry magma hybridization magma mingling geothermometry
英文关键词	TRACE-ELEMENT COMPOSITION; IN-SITU ANALYSIS; U-PB ISOTOPE; LADAKH BATHOLITH; SPIRIT MOUNTAIN; MAGMATIC ARC; HF ISOTOPES; JACK HILLS; LU-HF; ROCKS
WOS研究方向	Geochemistry & Geophysics
WOS记录号	WOS:001010636400002
来源期刊	JOURNAL OF PETROLOGY
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/283319
作者单位	Monash University; China University of Geosciences - Beijing
推荐引用方式 GB/T 7714	Weinberg, Roberto F.,Moyen, Jean-Francois,Yi, Jian-Kang,et al. Using Zircons to Disentangle Back-Veining and Hybridization of Diorite Dykes: an Example From the Gangdese Arc, Tibet[J],2023,64(3).
APA	Weinberg, Roberto F..,Moyen, Jean-Francois.,Yi, Jian-Kang.,Zhu, Di-Cheng.,Nebel, Oliver.,...&Wang, Qing.(2023).Using Zircons to Disentangle Back-Veining and Hybridization of Diorite Dykes: an Example From the Gangdese Arc, Tibet.JOURNAL OF PETROLOGY,64(3).
MLA	Weinberg, Roberto F.,et al."Using Zircons to Disentangle Back-Veining and Hybridization of Diorite Dykes: an Example From the Gangdese Arc, Tibet".JOURNAL OF PETROLOGY 64.3(2023).