Granitoid emplacement during syn-convergent transtension:An example from the Huamenlou pluton in North Qinling,central China  

作　　者：Yang Li Wentian Liang Guowei Zhang Yazhou Ran Qi Shen Jingli Wang Chunsheng Jin 

机构地区：[1]State Key Laboratory of Continental Dynamics,Northwest University,Xi’an 710069,China [2]Collaborative Innovation Centre of Continental Tectonics,Northwest University,Xi’an 710069,China [3]Earthquake Administration of Shaanxi Province,Xi’an 710068,China [4]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

出　　处：《Geoscience Frontiers》2018年第1期191-205,共15页地学前缘（英文版）

基　　金：Financial support for this study was jointly provided by the NSFC(Nos.41672200 and 41002070);Fund from the State Key Laboratory of Continental Dynamics(BJ081331 and BJ14257);Innovation Fund for Graduate students of Northwest University(YZZ14016)

摘　　要：The Huamenlou pluton,is an elongated granite intrusion with high aspect ratio,emplaced within the southern margin of the North Qinling(central China).Here we investigate this pluton through multiple techniques including the fabric study,microstructural observation and zircon geochronology.Our zircon U-Pb data confirm that the granite crystallized at ca.462 Ma which is consistent with the ages of other linear plutons in North Qinling.Microstructural observations of the Huamenlou granites illustrate that the pluton has undergone superimposed deformation during its emplacement,from magmatic to hightemperature solid state conditions.The internal fabric obtained by anisotropy of magnetic susceptibility(AMS)and shape preferred orientation(SPO)show similar results.The fabrics are relatively concordant and generally vary from NE-SW to NEE-SWW which are roughly oblique to the trend of the pluton elongation and the regional structures.Meanwhile,scalar parameters reflect two completely different strain regimes for the pluton and its host rocks,i.e.,the fabrics within host rocks are mainly oblate while the central part of the intrusion displays mainly prolate fabrics.It is inferred that the structural pattern recorded in this pluton was caused by local dextral transtension in consequence of oblique convergence between the South and North China Blocks.We propose that the local transtension in convergence setting probably evolved from vertical extrusion tectonics that provided room for the magma emplacement and imparted prolate fabrics in the Huamenlou pluton.The Huamenlou pluton, is an elongated granite intrusion with high aspect ratio, emplaced within the southern margin of the North Qinling(central China). Here we investigate this pluton through multiple techniques including the fabric study, microstructural observation and zircon geochronology. Our zircon U-Pb data confirm that the granite crystallized at ca. 462 Ma which is consistent with the ages of other linear plutons in North Qinling. Microstructural observations of the Huamenlou granites illustrate that the pluton has undergone superimposed deformation during its emplacement, from magmatic to hightemperature solid state conditions. The internal fabric obtained by anisotropy of magnetic susceptibility(AMS) and shape preferred orientation(SPO) show similar results. The fabrics are relatively concordant and generally vary from NE-SW to NEE-SWW which are roughly oblique to the trend of the pluton elongation and the regional structures. Meanwhile, scalar parameters reflect two completely different strain regimes for the pluton and its host rocks, i.e., the fabrics within host rocks are mainly oblate while the central part of the intrusion displays mainly prolate fabrics. It is inferred that the structural pattern recorded in this pluton was caused by local dextral transtension in consequence of oblique convergence between the South and North China Blocks. We propose that the local transtension in convergence setting probably evolved from vertical extrusion tectonics that provided room for the magma emplacement and imparted prolate fabrics in the Huamenlou pluton.

关 键 词：Zircon U-Pb dating Magnetic fabric Shape preferred orientation Linear PLUTON QINLING OROGEN 

分 类 号：P[天文地球]