冈底斯南缘拉隆地区变形花岗岩地质特征及其构造意义

doi:10.19388/j.zgdzdc.2020.04.11

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Abstract In the Gangdise magmatic arc develops an important ductile shear zone. In order to peer deeper into the genesis of the deformed granite and its deformation and properties, the authors studied the whole rock geochemistry, deformation structure and zircon U-Pb geochronology of the deformed granite in Lalong area in the southern margin of Gangdise. It is found that the deformed granite is distributed in nearly EW direction, the north side contacts with Mesozoic Mamuxia Formation along a fault,and the rest is covered by Quaternary system,after the geological profile measurement and field geological mapping of the deformed granite exposed in Lalong area in the southern margin of Gangdise.The main rock type is tonalite, belonging to high silica calc alkaline series. SiO₂ content ranges from 66.2% to 71.0%, with an average of 68.3%. The content of total alkali (Na₂O + K₂O) is higher,so is the content of Al₂O₃ and MgO.The content of light rare earth elements (∑LREE) is higher than that of heavy rare earth elements (∑HREE). Rb, Th and other large ion lithophile elements are enriched, while Ta, Zr, Nb and other high field-strength elements are depleted. Sr content is high, Y content is low, and Sr/Y value is 73.02~99.05. All shows that the rock has the adakitic rock characteristics. The LA-ICP-MS zircon U-Pb age of the deformed granite is (83.56±0.83) Ma, which is the late Cretaceous and represents the magmatic crystallization age.The deformed granite was mainly formed by partial melting of the thickened lower crust under the background of northward subduction and reduction of Neo-Tethys Ocean. During Miocene 28~13 Ma, the deformed granite underwent nearly EW trending left-lateral shear and northward slip ductile shear deformation.

Key words： deformed granite Adakitic rock Ziron U-Pb shear deformation Neo-Tethys Ocean

Received: 23 June 2019

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	TANG Hua
	CHEN Yongdong
	WEI Long
	LI Ning

Cite this article:

TANG Hua,CHEN Yongdong,WEI Long, et al. Geological characteristics and tectonic implications of the deformed granite in Lalong area in the southern margin of Gangdise[J]. , 2020, 7(4): 85-94.

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http://www.zgdzdcbjb.com/EN/10.19388/j.zgdzdc.2020.04.11 OR http://www.zgdzdcbjb.com/EN/Y2020/V7/I4/85

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