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北秦岭新元古代后碰撞花岗岩的确定及其构造意义
引用本文:张成立,刘良,张国伟,王涛,陈丹玲,袁洪林,柳小明,晏云翔.北秦岭新元古代后碰撞花岗岩的确定及其构造意义[J].地学前缘,2004,11(3):33-42.
作者姓名:张成立  刘良  张国伟  王涛  陈丹玲  袁洪林  柳小明  晏云翔
作者单位:1. 西北大学,大陆动力学教育部重点实验室,陕西,西安,710069;南京大学,内生矿床国家重点实验室,江苏,南京,210093
2. 西北大学,大陆动力学教育部重点实验室,陕西,西安,710069
3. 中国地质科学院,地质研究所,北京,100037
基金项目:国家自然科学基金资助项目 (4 0 0 32 0 1 0 C,40 0 72 0 6 5,40 372 0 39),西部高校高级访问学者资助项目
摘    要:应用LA ICPMS获得北秦岭蔡凹花岗岩体锆石U Pb年龄 ( 889± 1 0 )Ma ,代表岩体的形成时代。该岩体富集LILE、贫化HFSE ,显示活动陆缘俯冲带I型花岗岩体地球化学特征。同时岩体又具有富铝、高钾和锶、明显亏损Nb、Ti、P等元素的大陆造山带后碰撞演化阶段花岗岩特征。根据区域构造资料并结合岩体的变形特征分析 ,蔡凹岩体为碰撞造山过程地壳增厚背景下 ,在后碰撞拉张阶段由卷入有消减带物质的下部地壳部分熔融所形成 ,指示了秦岭在该时期已进入由主碰撞挤压转向后碰撞伸展演化阶段 ,为进一步精细确定北秦岭新元古代陆块汇聚碰撞造山过程提供了新的依据

关 键 词:后碰撞花岗岩  LA-ICPMS  锆石U-Pb定年  地球化学  北秦岭
文章编号:1005-2321(2004)03-0033-10
修稿时间:2004年5月18日

Determination of Neoproterozoic post-collisional granites in the north Qinling Mountains and its tectonic significance
ZHANG Cheng-li.Determination of Neoproterozoic post-collisional granites in the north Qinling Mountains and its tectonic significance[J].Earth Science Frontiers,2004,11(3):33-42.
Authors:ZHANG Cheng-li
Institution:ZHANG Cheng-li~
Abstract:A new age of 889±10 Ma has been obtained from the Caiwa granitic pluton. This age represents the formation age of the pluton. The pluton is enriched in LILE and poor in HFSE, geochemically similar to those of I-type granitoids formed in subduction zone on the active margin. However, the granite has high Al_2O_3, K_2O and Sr and evidently depleted in Nb, Ti and P, showing a characteristics of post-collisional granite developed in continental orogeny. Furthermore, the Cawai granite, based on the regional structural analyses and its weakly deformation, were formed by partial melting of lower crustal materials, including subducted materials, under the thickening crust during the post-collisional extension, suggesting that it entered into transformation period from compression to extension during the Neoproterozoic in the Qinling Mountains, which provide us a new evidence to determine the Neoproterozoic continental collision process in the north Qinling Mountains in detail.
Keywords:post-collisional granite  LA-ICPMS  zircon U-Pb dating  geochemistry  north Qinling
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