中天山巴仑台地区花岗质岩石的Hf同位素研究:对构造演化及大陆生长的约束
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NSFC-新疆联合基金重点支持项目(编号U1403291)、中国地质调查局项目(编号1212010611803,1212010811033,12120113096500,12120113094000)、国家科技支撑项目(编号2011BAB06B02-04)和中国地质科学院地质研究所中央级公益性基本业务费专项基金


Zircon Hf Isotopic Characteristics of Granitoids from the Baluntai Region, Central Tianshan: Implications for Tectonic Evolution and Continental Growth
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    摘要:

    中国中天山地块位于天山造山带的核心部位,对研究中亚造山带西南段构造演化、块体起源和陆壳生长等科学问题具有重要意义。本次研究围绕中天山地块西段巴仑台一带出露的古生代花岗质岩石展开,报道了部分代表性岩体的LA ICP MS锆石U Pb年龄和MC ICP MS锆石Lu Hf同位素特征。同时还系统总结前人发表的研究区内花岗质岩石的锆石U Pb年龄和Lu Hf同位素资料。本次研究的7个花岗质侵入体的锆石LA ICP MS年龄分别为435±5 Ma、432±4 Ma、359±4 Ma、312±4 Ma、346±2 Ma、306±5 Ma和362±5 Ma。它们在成因类型上均属于I型花岗岩,起源于深部不同性质地壳物质的部分熔融,部分岩体具有壳幔混合成因。研究表明,巴仑台一带的岩浆事件主要发生在早志留世—早泥盆世(435~408 Ma)、晚泥盆世—早石炭世(370~339 Ma)和晚石炭世—中二叠世(313~263 Ma)三个阶段,第一期岩浆事件是古天山洋闭合形成的后碰撞体制以及古南天山洋俯冲导致的大陆岛弧环境共同作用的结果。而古南天山洋俯冲活动的暂停和新一轮的洋盆扩张是导致区内中、晚泥盆世岩浆活动暂停的原因。第二期花岗质侵入体是古南天山洋第二期北向俯冲所导致的大陆岛弧岩浆作用的产物,而第三期花岗质侵入体形成于古南天山洋最终闭合之后的后碰撞环境中。通过总结区内古生代花岗质岩体的锆石的Hf同位素特征,我们认为巴伦台地区前寒武基底主要形成于三个阶段:①~247 Ga至~226 Ga,为研究区对全球陆核生长事件的响应;②~147 Ga至~125 Ga,对应于哥伦比亚超大陆的裂解;③~120 Ga至~090 Ga,很可能是研究区对导致罗迪尼亚超大陆聚合的“Grenville运动”的响应。

    Abstract:

    Chinese Central Tianshan Block, located in the central part of the Tianshan Orogenic Belt, is of significant importance for understanding the tectonic evolution, origination and continental growth of the Central Asian Orogenic Belt. This paper focuses on petrogenesis and tectonic implications of Paleozoic granitoid intrusions from the Baluntai region in the western part of the Central Tianshan Block. We report zircon LA ICP MS U Pb geochronological and MC ICP MS Lu Hf isotopic results for seven granitoid intrusion from the study area, and their whole rock major and trace element characteristics. The seven intrusions presently studied were respectively emplaced at 435±5 Ma, 432±4 Ma, 359±4 Ma, 312±4 Ma, 346±2 Ma, 306±5 Ma and 362±5 Ma. The petrographic and geochemical features suggest that those Paleozoic granitoid intrusions are typical I type granite in genesis, and were mainly derived from the partial melting of different types of deep crustal sources. Besides, mantle derived magmas played an important role in genesis of some intrusions. Based on present and previous data, three episodic magmatic events are identified in the Baluntai region, i.e., Early Silurian to Early Devonian event (435 to 408 Ma) magmatic event, Late Devonian to Early Carboniferous (370 to 339 Ma) magmatic event and Late Carboniferous to Middle Permian (313 to 263 Ma) magmatic event. The first stage magmatism was not only associated with the final closure of the Paleo Tianshan Ocean, but also a result of the subduction of the South Tianshan Ocean (STO). The magmatic quiescence during Middle to Late Devonican was likely related to the suspension of subduction of the STO. The second stage magmatism was likely related to the northward subduction of the STO, and the third stage magmatism plausibly occurred in post collisional settings after the final closure of the STO. According to the regional scale Hf isotopic mapping of Paleozoic granitoids in the Baluntai region, we suggest that the Precambrian basement rocks were predominately formed at three stages, i.e., (1) ~2.47 to ~2.26 Ga continental growth, responding to the global continental crust growth, (2) ~1.47 to ~1.25 Ga continental growth, associated with the breakup of the Columbia supercontinent and (2) ~1.14 to ~1.02 Ga, overlapping with so called “Grenville ages” of 1300 900 Ma that are thought to be resulted from the assembly of the Rodinia supercontinent.

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黄河,王涛,秦切,侯继尧,童英,郭磊,张磊,王静,梁昭元.2015.中天山巴仑台地区花岗质岩石的Hf同位素研究:对构造演化及大陆生长的约束[J].地质学报,89(12):2286-2313.
HUANG He, WANG Tao, QIN Qie, HOU Jiyao, TONG Ying, GUO Lei, ZHANG Lei, WANG Jing, LIANG Zhaoyuan.2015. Zircon Hf Isotopic Characteristics of Granitoids from the Baluntai Region, Central Tianshan: Implications for Tectonic Evolution and Continental Growth[J]. Acta Geologica Sinica,89(12):2286-2313.

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  • 收稿日期:2015-08-05
  • 最后修改日期:2015-10-04
  • 录用日期:2015-10-10
  • 在线发布日期: 2015-12-23
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