辽北地区早石炭世变质火山岩年代学和地球化学特征:对华北板块北缘东段构造演化的启示  

Geochronology and geochemistry of the Early Carboniferous meta-volcanic rocks,northern Liaoning Province:Implications for the tectonic evolution of the eastern segment of the northern margin of the North China Block

作　　者：张丽[1,2] 张超[1] 刘永江[3,4] 李伟民 葛锦涛[1] 冯志强 陈井胜[1] 付俊彧[1] ZHANG Li;ZHANG Chao;LIU YongJiang;LI WeiMin;GE JinTao;FENG ZhiQiang;CHEN JingSheng;FU JunYu(Shenyang Institute of Geology and Mineral Resources,China Geological Survey,Shenyang 110034,China;College of Earth Sciences,Jilin University,Changchun 130061,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,MOE Key Lab of Submarine Geosciences and Prospecting Techniques,and College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266100,China;Department of Earth Science and Engineering,Taiyuan University of Technology,Taiyuan 030024,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]吉林大学地球科学学院,长春130061 [3]深海圈层与地球系统前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,青岛266100 [4]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,青岛266100 [5]太原理工大学地球科学与工程系,太原030024

出　　处：《岩石学报》2020年第8期2394-2412,共19页Acta Petrologica Sinica

基　　金：中国地质调查局项目(DD20190042-03、1212011220435);国家重点研发计划(2017YFC0601300-01);泰山学者计划(ts20190918);青岛市创新领军人才计划(19-3-2-19-zhc)联合资助。

摘　　要：华北板块北缘东段分布的构造混杂岩带为研究古亚洲洋的演化提供了重要的依据,"下二台岩群"作为该构造混杂岩带的重要组成部分,其形成时代和构造属性仍存在争议。详细的研究表明下二台地区变质火山岩原岩包括流纹岩、英安岩、安山岩,为一套钙碱性火山岩,属于准铝质-弱过铝质岩石,根据岩相学和地球化学特征将其分为变质酸性火山岩和变质中性火山岩;二者均相对富集轻稀土元素,亏损重稀土元素,轻重稀土元素分馏明显,Eu负异常不明显,但变质中性火山岩稀土总量低于变质酸性火山岩,变质酸性火山岩明显亏损Sr、P元素,结合野外产出面积和高场强元素相关性特征,认为二者不是同一基性岩浆分异的产物。变质火山岩锆石LA-ICP-MS U-Pb年龄为341~348Ma,代表其原岩结晶年龄。变质酸性火山岩原始岩浆来自于地壳物质的部分熔融,变质中性火山岩原始岩浆来自于俯冲带附近岩石圈地幔,并遭受了地壳物质的混染,二者均形成于活动大陆边缘火山弧环境。最新研究成果表明"下二台岩群"由不同时代、不同构造环境下形成的地质单元叠置混杂而成,称其为"下二台"构造杂岩更为准确。下二台地区变质火山岩表明在早石炭世初,古亚洲洋板块已经南向俯冲,在华北板块北缘形成活动大陆边缘弧环境,早石炭世变质火山岩原岩为这一俯冲阶段的产物。The tectonic mélange belt distributed in the eastern segment of the northern margin of the North China Block provides an important evidence for studying the evolution of the Paleo-Asian Ocean.The"Xia’ertai Group"is located in this belt,its formative age and tectonic properties have also been controversial.The detailed research indicates that the protolith of meta-volcanic rocks in the Xia’ertai area includes rhyolite,dacite and andesite,they are calc-alkaline series and metaluminous-weak peraluminous rocks.The meta-volcanic rocks in the Xia’ertai area can be divided into metamorphic acid volcanic rocks and metamorphic intermediate volcanic rocks according to the petrography and trace element characteristics.The trace elements of them all show that LREEs are relatively enriched,while HREEs are relatively deficient and obvious REEs fractionation,meanwhile,negative Eu anomalies is not obvious,but the total amount of REEs in metamorphic intermediate volcanic rocks is lower than that in metamorphic acidic volcanic rocks,and the metamorphic acid volcanic rocks are depleted in Sr and P,combined with the distribution area and the correlation of HSFEs,we believe that they are not the product of the same basic magma differentiation.The zircon LA-ICP-MS U-Pb ages of the meta-volcanic rocks are341~348 Ma,represents the crystallization age of their protolith.The primordial magma of the metamorphic acidic volcanic rocks came from partial melting of material in the crust,but the primordial magma of the metamorphic intermediate volcanic rocks was originated from the lithospheric mantle near the subduction zone with the mixing of crustal materials,meanwhile,they were all formed in the volcanic arc environment of an active continental margin.The material composition of the"Xia’ertai Group"is characterized by different times and different tectonic backgrounds,we suggest to the"Xia’ertai Group"as a tectonic complex.The meta-volcanic rocks in the Xia’ertai area indicate that the Paleo-Asian Ocean was subducted southward

关 键 词：中亚造山带 华北板块北缘 “下二台岩群” 构造杂岩 早石炭世 

分 类 号：P542[天文地球—构造地质学] P588.14[天文地球—地质学]