浙皖晚中生代仙霞岩体锆石U-Pb年代学、地球化学及成岩地质意义
发布时间：2019-06-06 19:04
【摘要】：仙霞岩体是浙北和皖南交界区域明显受北东向学川-孝丰断裂构造带控制的大岩体,其内部岩性复杂,主要由早期中粒二长花岗岩、巨斑状二长花岗岩和晚期中粗粒正长花岗岩、细粒正长花岗岩组成,后期有大量细晶岩、石英正长岩、闪长玢岩、安山岩、辉绿岩等脉岩侵入。锆石U-Pb年龄数据显示早期二长花岗岩大约侵位于145.1~144.2Ma,晚期正长花岗岩大约侵位于131.7~130.8Ma,后期辉绿岩脉侵位于128.3Ma。两期岩石均具高SiO_2、高K_2O+Na_2O和低P_2O_5特征;早期二长花岗岩为准铝质、高钾钙碱系列岩石,稀土配分曲线强右倾,中等负Eu异常,富集Rb、Th、U、K,亏损Ba、Nb、Sr、P、Ti等特征;晚期正长花岗岩为准铝质-过铝质、钾玄岩系列岩石,稀土配分曲线弱右倾、强负Eu异常,同样富集Rb、Th、U、K,强亏损Sr、P、Ti等特征;均属高分异I型花岗岩类。两期岩石均具有相对高的(86Sr/87Sr)i值(0.70807~0.70988)和εNd(t)值(-8.87~-5.14),Nd二阶段模式年龄为1.36~1.65Ga。成岩可能与古太平洋板块俯冲角度的改变,构造背景由中晚侏罗世(165±5~145±5Ma)的挤压环境向早白垩世早期(145±5~125Ma)的伸展拉张环境转变有关,致使古老江南造山带地壳物质熔融并可能混染扬子岩石圈地幔物质形成的两期岩浆经高程度结晶分离作用先后侵位,也表明浙西北乃至华南地区晚中生代构造转换时间为145Ma左右,且在早白垩世发生了多期次伸展拉张作用。
[Abstract]:Xianxia rock mass is a large rock mass obviously controlled by the northeast Xuechuan-Xiaofeng fault structural belt in the border area between northern Zhejiang and southern Anhui. Its internal lithology is complex, mainly from the early medium-grain monzonitic granite. The macromacular monzonitic granite and the late middle coarse granitic syenite and fine granitic syenite are composed of a large number of fine crystal rocks, quartz syenite, diorite, andesite, diabase and other gangue intrusions in the later stage. Zircon U-Pb age data show that the early monzonitic granite was about 145.1 Ma, the late syenite granite was 131.7 Ma, and the later diabase vein invasion was 128.3 Ma. The rocks of the two stages are characterized by high SiO_2, high K 鈮，
本文编号：2494528
[Abstract]:Xianxia rock mass is a large rock mass obviously controlled by the northeast Xuechuan-Xiaofeng fault structural belt in the border area between northern Zhejiang and southern Anhui. Its internal lithology is complex, mainly from the early medium-grain monzonitic granite. The macromacular monzonitic granite and the late middle coarse granitic syenite and fine granitic syenite are composed of a large number of fine crystal rocks, quartz syenite, diorite, andesite, diabase and other gangue intrusions in the later stage. Zircon U-Pb age data show that the early monzonitic granite was about 145.1 Ma, the late syenite granite was 131.7 Ma, and the later diabase vein invasion was 128.3 Ma. The rocks of the two stages are characterized by high SiO_2, high K 鈮，
本文编号：2494528
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