气候变化领域集成服务门户(CCPortal): Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence

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DOI	10.1130/B31586.1
	Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence
	Zhang Zeming; Xiang Hua; Ding Huixia; Dong Xin; Gou Zhengbin; Tian Zhulin; Santosh, M.
通讯作者	Zhang, ZM (通讯作者)
发表日期	2017
ISSN	0016-7606
EISSN	1943-2674
起始页码	869
结束页码	885
卷号	129 期号:7-8
英文摘要	The Greater Himalayan Sequence and leucogranite forming the core of the Himalayan orogen provide an excellent natural laboratory in which to study processes related to crustal melting, granitoid formation, and the tectonic evolution of mountain belts. In contrast to most previous studies, which considered the Himalaya-aged granitoids as leucogranites, here we report a Miocene orbicular diorite from the Greater Himalayan Sequence in the east-central Himalaya. The diorite consists of ellipsoidal orbicules in a diorite matrix. The orbicules have a diorite core with or without garnetsillimanite--biotite schist enclaves, an inner shell of tangentially oriented biotite laths, and an outer shell of radial or plumose plagioclase crystals. The diorite is aluminous and calcic, shows a fractionated rare earth element pattern with a strongly positive Eu anomaly, and has elevated Sr concentration. The schist enclaves underwent hightemperature -metamorphism and partial melting under conditions of 9.2-12 kbar and 765-900 degrees C, followed by a retrograde pressure-temperature path of decompression and cooling. The inherited magmatic cores, metamorphic mantles, and magmatic rims of zircon from the diorite yield a protolith age of ca. 494 Ma, metamorphic ages ranging from ca. 26 Ma to 22 Ma, and melt crystallization ages of ca. 18-14 Ma. The inherited magmatic cores of zircon show variable but mostly negative epsilon(Hf) (t) values, whereas the metamorphic mantles and the magmatic rims of zircon yield variable and lower epsilon(Hf) (t) values. Our study shows that the orbicular diorite is a -plagioclase + biotite + cordierite cumulate rock that formed by the fractional crystallization of peraluminous melt, which was generated by mixing of melts derived from the partial melting of both early Paleozoic granitoids and old pelitic rocks. The orbicular diorite and the trapped metapelitic schist have a prolonged high-temperature metamorphic, anatectic, and crystallization history that was initiated at ca. 26 Ma and lasted until ca. 14 Ma. The formation of orbicular structures was probably related to decompression during the ascent of anatectic melt, and subsequent rapid cooling. Melt mixing was also a key factor that aided in the formation of the orbicular structure of the diorite.
关键词	GRENVILLE FRONT ZONE CHANNEL FLOW MODEL U-PB AGES SOUTHERN TIBET NAMCHE-BARWA TECTONIC IMPLICATIONS PHASE-EQUILIBRIA SIKKIM HIMALAYA HIGH-PRESSURE GEOCHEMICAL CONSTRAINTS
语种	英语
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:000405373200007
来源期刊	GEOLOGICAL SOCIETY OF AMERICA BULLETIN
来源机构	中国科学院青藏高原研究所
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/259025
推荐引用方式 GB/T 7714	Zhang Zeming,Xiang Hua,Ding Huixia,et al. Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence[J]. 中国科学院青藏高原研究所,2017,129(7-8).
APA	Zhang Zeming.,Xiang Hua.,Ding Huixia.,Dong Xin.,Gou Zhengbin.,...&Santosh, M..(2017).Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence.GEOLOGICAL SOCIETY OF AMERICA BULLETIN,129(7-8).
MLA	Zhang Zeming,et al."Miocene orbicular diorite in east-central Himalaya: Anatexis, melt mixing, and fractional crystallization of the Greater Himalayan Sequence".GEOLOGICAL SOCIETY OF AMERICA BULLETIN 129.7-8(2017).