Genesis of LCT Pegmatites during Early Paleozoic Orogeny of the North Qinling Orogenic Belt,China:Emplacement Conditions and Structural Control  

作　　者：CEN Jubiao FENG Yonggang LIANG Ting WANG Mengxi ZHANG Jianxin TAN Xijuan ZHANG Jie GAO Jinggang HE Lei 

机构地区：[1]School of Earth Science and Resources,Chang’an University,Xi’an 710054,China [2]Xi’an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Chang’an University,Xi’an 710054,China [3]Northwest Bureau of China Metallurgical Geology Bureau,Xi'an 710119,China [4]The Fourth Geological Exploration Institute,Henan Bureau of Geo-Exploration and Mineral Development,Zhengzhou 450001,China

出　　处：《Acta Geologica Sinica(English Edition)》2024年第5期1226-1243,共18页地质学报（英文版）

基　　金：supported by the National Key R&D Program of China(Grant Nos.2021YFC2901902 and 2019YFC0605202)。

摘　　要：The Guanpo pegmatite field in the North Qinling orogenic belt(NQB),China,hosts the most abundant LCT pegmatites.However,their emplacement conditions and structural control remain unexplored.In this contribution,we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study.The orientations of type A1 pegmatites(P_(f)<σ_(2))are predominantly influenced by P-and T-fractures due to simple shearing in Shiziping dextral thrust shear zone during D_(2)deformation,whereas type A2 pegmatites(contemporaneous with D_(4))are governed by hydraulic fractures aligned with S_(0)and S_(0+1)stemming from fluid pressure(P_(f)<σ_(2)).Additionally,type B pegmatites(P_(f)≤σ_(2))exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones(contemporaneous with D_(3)).The albite-quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites(including types B and A2)suggest that the crystallization P-T for late magmatic and hydrothermal stages are 527.5-559.2℃,320℃,3.1-3.6 kbar and 2.0 kbar,respectively.Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long-term,multi-stage event during early Paleozoic orogeny(including the collision stage)of the NQB,and was facilitated by various local fractures.

关 键 词：LCT pegmatite emplacement mechanism emplacement condition oxygen isotope geothermometry fluid inclusion North Qinling orogenic belt 

分 类 号：P534.4[天文地球—古生物学与地层学] P588.13[天文地球—地质学] P542