气候变化领域集成服务门户(CCPortal): A tale of an orbicule in the eastern Gangdese belt of southern Tibet: Petrographic, geochemical, and submagmatic structural perspectives on its formation

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DOI	10.1130/B36607.1
	A tale of an orbicule in the eastern Gangdese belt of southern Tibet: Petrographic, geochemical, and submagmatic structural perspectives on its formation
	Ma, Xuxuan; Xu, Zhiqin; Mao, Xiaohong; Cawood, Tarryn; Yan, Haoyu; Gao, Jianguo; Si, Jialiang; Li, Haibing
发表日期	2024
ISSN	0016-7606
EISSN	1943-2674
起始页码	136
结束页码	1-2
卷号	136 期号:1-2
英文摘要	Owing to their intriguing appearance and unusual occurrence, as well as their significance in addressing magmatic processes, orbicules have attracted attention from geologists all over the world. We discovered an orbicule-bearing boulder in the Linzhi region, near the Eastern Himalayan Syntaxis, which is the first report of orbicules in the Gangdese magmatic belt, southern Tibet. The orbicules are composed of dioritic shells around monzodioritic cores, in a dioritic matrix. They typically have a single shell, composed of elongate and radially oriented hornblendes, with interstitial plagioclase. Zircon laser ablation- inductively coupled plasma-mass spectrometry U-Pb dating yields an indistinguishable age of ca. 28.8 Ma for both the orbicule core and matrix, indicating approximately coeval crystallization. Zircon Lu-Hf and whole -rock Sr-Nd isotopes reveal that the original magmas of both the orbicule matrix and orbicule core were relatively juvenile (sigma Hf(t) = +2.2 to +6.0 for matrix and +1.2 to +3.9 for core; sigma Nd(t) = -1.68 to -1.46 for matrix and -3.65 to -2.52 for core), similar to reported Oligocene- Miocene post-collisional adakites in the Gangdese belt. Zircon and hornblende geochemistry reveals that both the orbicule matrix and cores were generated from highly oxidized, high oxygen fugacity magmas. Hornblende composition further indicates that the original magmas of the matrix and the orbicule cores were water -rich, with H2O contents greater than 4 wt%. In combination with the wholerock geochemistry, these results suggest that the orbicules were formed in a post-collisional setting, from magma generated by partial melting of the juvenile thickened lower crust of the Lhasa terrane triggered by convective removal of the Lhasa lithospheric root. The preferred orientation of euhedral igneous minerals in the matrix and the alignment and compaction of orbicules define a magmatic to submagmatic foliation. This, together with the subsolidus deformation microstructures exhibited by minerals within the orbicules, indicates that some flow or movement of orbicules took place under magmatic to submagmatic conditions, as the subsolidus plastic orbicules were jostled and transported within a hyper solids liquid magma.
语种	英语
WOS研究方向	Geology
WOS类目	Geosciences, Multidisciplinary
WOS记录号	WOS:001169970300003
来源期刊	GEOLOGICAL SOCIETY OF AMERICA BULLETIN
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/291670
作者单位	China Geological Survey; Institute of Geology, Chinese Academy of Geological Sciences; Ministry of Natural Resources of the People's Republic of China; Chinese Academy of Geological Sciences; Southern Marine Science & Engineering Guangdong Laboratory; Southern Marine Science & Engineering Guangdong Laboratory (Guangzhou); Nanjing University; Natural Resources Canada; Lands & Minerals Sector - Natural Resources Canada; Geological Survey of Canada; Chengdu University of Technology
推荐引用方式 GB/T 7714	Ma, Xuxuan,Xu, Zhiqin,Mao, Xiaohong,et al. A tale of an orbicule in the eastern Gangdese belt of southern Tibet: Petrographic, geochemical, and submagmatic structural perspectives on its formation[J],2024,136(1-2).
APA	Ma, Xuxuan.,Xu, Zhiqin.,Mao, Xiaohong.,Cawood, Tarryn.,Yan, Haoyu.,...&Li, Haibing.(2024).A tale of an orbicule in the eastern Gangdese belt of southern Tibet: Petrographic, geochemical, and submagmatic structural perspectives on its formation.GEOLOGICAL SOCIETY OF AMERICA BULLETIN,136(1-2).
MLA	Ma, Xuxuan,et al."A tale of an orbicule in the eastern Gangdese belt of southern Tibet: Petrographic, geochemical, and submagmatic structural perspectives on its formation".GEOLOGICAL SOCIETY OF AMERICA BULLETIN 136.1-2(2024).