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引用本文:杜云,郭爱民,卢友月,田磊,王敬元,周立同,樊晖,罗小亚. 湘西南苗儿山岩体北段加里东期花岗岩成因:来自岩石学、地球化学和锆石U-Pb年代学的证据[J]. 中国地质, 2021, 48(5): 1540-1561.
DU Yun,GUO Aimin,LU Youyue,TIAN Lei,WANG Jingyuan,ZHOU Litong,FAN Hui,LUO Xiaoya. Petrogenesis of the Caledonian granites in the northern part of Miaoershan pluton, southwestern Hunan Province: Evidence from petrology, geochemistry and zircon U-Pb age[J]. Geology in China, 2021, 48(5): 1540-1561(in Chinese with English abstract).
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湘西南苗儿山岩体北段加里东期花岗岩成因:来自岩石学、地球化学和锆石U-Pb年代学的证据
杜云1, 郭爱民1, 卢友月2, 田磊1, 王敬元1, 周立同1, 樊晖1, 罗小亚1
1.湖南省地质调查院, 湖南 长沙 410116;2.中国地质调查局武汉地质调查中心, 湖北 武汉 430205
摘要:
苗儿山岩体位于湘西南与桂北交界处,为由晋宁期、加里东期、印支期和燕山期花岗岩组成的复式岩体。其中,加里东期花岗岩构成该复式岩体的主体,可划分为六个侵入次。本次通过锆石LA-ICP-MS测年,获得第一、第二、第六侵入次的年龄分别为(428.1±3.6)Ma、(420.3±3.4)~(421.3±3.2)Ma和(408.3±3.5)Ma。加里东期花岗岩的(87Sr/86Sr)i为0.71765,εNdt)为-9.7,δ18O值为9.8‰,总体属壳源弱过铝-强过铝质花岗岩,形成于碰撞挤压峰期之后挤压减弱、应力松弛的后碰撞构造环境,其早期和晚期的源区岩石类型和形成温度有所区别:早期花岗岩的上地壳源区成分较为复杂,不仅存在泥岩,还有砂屑岩和/或变质火成岩,其形成温度较高(>875℃);晚期花岗岩的源岩为上地壳泥岩,属典型的S型花岗岩,其形成温度较低(<875℃)。
关键词:  锆石U-Pb测年  地球化学  岩石成因  加里东期  苗儿山岩体  湘西南  地质调查工程  江西省
DOI:10.12029/gc20210517
分类号:P588.12;P597
基金项目:中国地质调查局项目(121201009000150002)资助。
Petrogenesis of the Caledonian granites in the northern part of Miaoershan pluton, southwestern Hunan Province: Evidence from petrology, geochemistry and zircon U-Pb age
DU Yun1, GUO Aimin1, LU Youyue2, TIAN Lei1, WANG Jingyuan1, ZHOU Litong1, FAN Hui1, LUO Xiaoya1
1.Hunan Institute of Geological Survey, Changsha 410116, Hunan, China;2.Wuhan Center of China Geological Survey, Wuhan 430205, Hubei, China
Abstract:
The Miaoershan pluton, located at the junction of southwestern Hunan and Northern Guangxi, is a composite batholith composed of Jinningian, Caledonian, Indosinian and Yanshanian granites. Among them, Caledonian granites constitute the main body of the composite batholith, which can be divided into six intruding episodes. Through zircon LA-ICP-MS dating, the ages of the first, second and sixth episodic granites were measured at (428.1±3.6) Ma, (420.3±3.4)-(421.3±3.2) Ma and (408.3±3.5) Ma, respectively. The average (87Sr/86Sr)i, εNd(t) and the δ18O values of the Caledonian granites are 0.71765, -9.7, and 9.8, respectively. Caledonian granites are generally crust derived weak peraluminous-strong peraluminous granites, formed in post-collisional tectonic environment characterized by weakened compression and relaxed stress after the peak period of collision and extrusion. Their material and heat sources are different in the early and late stages. The early stage granites were derived from upper crustal metamorphic mudstone, psammite and/or metamorphic igneous rocks, and their formation temperature is relatively high(> 875℃). The late stage granites were derived from upper crustal metamorphic mudstone with lower formation temperature (< 875℃), showing the characteristics of typical S-type granites.
Key words:  Zircon U-Pb dating  geochemistry  petrogenesis  Caledonian period  Miaoershan pluton  southwestern Hunan Province  geological survey engineering