东天山晚古生代构造转折:红山南-天木东地区岩浆岩年代学与地球化学的约束  

Late Paleozoic tectonic transition of the East Tianshan:Constraints from geochronology and geochemistry of the igneous rocks in the Hongshannan-Tianmudong area

作　　者：袁修财 吴艳爽[1,2,3,4] 吴昌志 陈衍景 YUAN XiuCai;WU YanShuang;WU ChangZhi;CHEN YanJing(State Key Laboratory of Desert and Oasis Ecology,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,China;Xinjiang Key Laboratory of Mineral Resources and Digital Geology,Urumqi 830011,China;Xinjiang Research Centre for Mineral Resources,Chinese Academy of Sciences,Urumqi 830011,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Earth Science and Resources,Chang an University,Xi an 710054,China;MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Peking University,Beijing 100871,China)

机构地区：[1]中国科学院新疆生态与地理研究所,荒漠与绿洲生态国家重点实验室,乌鲁木齐830011 [2]新疆矿产资源与数字地质实验室,乌鲁木齐830011 [3]中国科学院新疆矿产资源研究中心,乌鲁木齐830011 [4]中国科学院大学,北京100049 [5]长安大学地球科学与资源学院,西安710054 [6]北京大学,造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2023年第9期2651-2678,共28页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42072106);新疆维吾尔自治区自然科学基金项目(2022D01A344);长安大学中央高校基本科研业务费专项资金领军人才项目(300102271302)联合资助.

摘　　要：东天山是中亚造山带的重要组成部分,区内晚古生代岩浆活动与成矿作用强烈,是理解中亚造山带构造演化与成矿作用的关键地区。然而,前人对东天山构造带由俯冲向碰撞转变的时间和过程仍存在较大争议。本文对东天山红山南-天木东地区广泛出露的晚古生代岩浆岩开展了野外考察和岩相学鉴定,进行了年代学和岩石地球化学分析,以限定其形成时代、岩石成因和构造背景,进而探讨晚古生代构造演化过程。红山南-天木东地区岩浆岩主要为早石炭世火山岩和侵入岩,次为早二叠世侵入岩。早石炭世火山岩主要为安山岩(328.8±2.0Ma)和英安岩,侵入岩主要为辉长闪长岩(328.7±1.8Ma);早二叠世侵入岩为黑云母二长花岗岩(290.3±2.1Ma)和石英闪长岩(290.0±1.6Ma)。早石炭世岩浆岩富含角闪石和斜长石,为钙碱性,准铝质系列,富Rb、Ba、Th、U和Pb等大离子亲石元素,亏损Nb、Ta和Ti等高场强元素和Sr-Nd-Hf同位素,具有岛弧岩浆岩特征,是交代地幔楔部分熔融的产物。相对于早石炭世岩浆岩,早二叠世侵入岩富含黑云母和碱性长石,富集SiO_(2)、Na_(2)O和K 2O,贫Al_(2)O_(3)、MgO、Fe_(2)O T_(3)及CaO,同位素更亏损,为碰撞后背景下新生加厚地壳部分熔融的产物。总之,红山南-天木东地区的早石炭世与早二叠世岩浆岩地球化学差异显著,指示东天山构造背景从早石炭世大洋俯冲体制转变为早二叠世碰撞后造山体制,即其构造转折时间为晚石炭世-早二叠世。The East Tianshan,as an important part of the Central Asian Orogenic Belt(CAOB),is characterized by its extensive Late Paleozoic magmatism and metallogeny,and thus serves as a critical area for understanding the tectonic evolution and metallogeny of the southern CAOB.Nevertheless,the time and process of tectonic transition from subduction to collision of the East Tianshan remain debate.In this contribution,detailed field investigation,petrographic observation,geochronological and geochemical analysis have been conducted to constrain the ages,genesis and tectonic settings of the Late Paleozoic igneous rocks in the Hongshannan-Tianmudong area.Petrological and zircon U-Pb dating results indicate that the Early Carboniferous volcanic rocks are mainly composed of andesite(328.8±2.0Ma)and dacite,while the intrusive rocks are gabbro-diorites(328.7±1.8Ma);the Early Permian intrusive rocks are biotite monzogranite(290.3±2.1Ma)and quartz diorite(290.0±1.6Ma).The Early Carboniferous igneous rocks are rich in amphibole and plagioclase,belonging to the calc-alkaline,meta-aluminous series.They are enriched in large ion lithophile elements such as Rb,Ba,Th,U and Pb,and depleted in high field strength elements(e.g.,Nb,Ta and Ti),and exhibit relatively depleted Sr,Nd and Hf isotopic compositions,i.e.,they are resemble to the island arc magmatic rocks derived from partial melting of metasomatic mantle wedge.Compared with the Early Carboniferous igneous rocks,the Early Permian intrusive rocks are composed of plenty of biotite and alkali feldspar,which are enriched in SiO_(2)、Na_(2)o and K_(2)O,and depleted in Al_(2)O_(3),MgO,Fe_(2)O T_(3)and CaO,and Sr,Nd and Hf isotopic compositions,indicating that their magmas were originated from partial melting of a thickened juvenile crust under the post-collisional setting.Hence the Early Carboniferous and the Early Permian magmatic rocks show significant petrological and geochemical differences,which is indicative of a tectonic setting transition from the Early Carboniferous oceanic su

关 键 词：岩浆岩 锆石U-Pb年龄 地球化学 SR-ND同位素 HF同位素 构造背景 东天山 中亚造山带 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学]