学术
北秦岭西段唐藏石英闪长岩岩体的形成时代及其地质意义
陈隽璐[1,2] 徐学义[1] 王洪亮[1,3] 王宗起[4] 曾佐勋[2] 王超[1] 李平[1]
[1]西安地质矿产研究所,陕西西安710054 [2]中国地质大学地球科学学院,湖北武汉430074 [3]西北大学地质学系,陕西西安710069 [4]中国地质科学院地质研究所,北京100037
摘 要:
在对陕西宝鸡一带进行地质大调查时，发现北秦岭造山带西段的唐藏石英闪长岩体具有埃达克岩的特征。利用阴极发光、LA-ICPMS方法对唐藏石英闪长岩的单颗粒锆石进行了U-Pb测年，所选锆石晶体均呈长柱状，振荡环带发育，Th／U=0．33—1．10，为典型的岩浆成因锆石。测试的29个样品的^206Pb／^238U加权平均年龄为（454．0±1．7）Ma，各测点^206Pb／^238U表面年龄与加权平均年龄在误差范围内近于一致，因此，这一数值代表岩浆生成年龄。结合北秦岭造山带西段代表洋壳残片的关子镇、岩湾蛇绿（混杂）岩形成时代，说明早古生代古秦岭丹凤洋沿商丹带一线向北发生俯冲消减作用，（454．0±1．7）Ma可能代表俯冲消减的初始时期。研究结果为北秦岭早古生代造山作用过程、壳幔相互作用及大陆动力学的研究提供了重要的依据。[著者文摘]
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文章出处:
《现代地质》-2008年22卷1期 -45-52页
栏目信息:
文献标识码:
A
文章编号:
1000-8527（2008）01-0045-08
LA-ICPMS Zircon U-Pb Dating of Tangzang Quartz-diorite Pluton in the West Segment of North Qinling Mountains and Its Tectonic Significance
CHEN Jun-lu, XU Xue-yi , WANG Hong-liang , WANG Zong-qi, ZENG Zuo-xun, WANG Chao , LI Ping （ 1. Xi＇an Institute of Geology and Mineral Resources, Xi＇an, Shaanxi 710054, China; 2. Faculty of Earth Science, China University of Geosciences, Wuhan, Hubei 430074, China; 3. Faculty of Geology, Northwest University, Xi＇an, Shaanxi 710069, China; 4. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China）
Abstract:
The Tangzang quartz-diorite pluton which has the characteristics of Adakite was founded in a geological survey in Baoji, Shaanxi. Zircons from the quartz-diorite pluton are generally colorless and long columnar with obvious magmatic zone. The LA-ICPMS zircon U-Pb geochronology of 29 samples from the pluton with Th/U ratios from 0. 33 to 1.10, yielded a weighted mean ^206Pb/^238U age of （454. 0 ± 1.7）Ma as the magmatic crystalline age of the protolith of the quartz diorite. Integrated the formation age of the Guanzizhen and Yanwan ophiolites in the west segment of north Qinling orogenic belt, it is indicated that the subduction process of Danfeng ocean along the Shangdan belt had existed, and the age of （454. 0 ± 1.7 ） Ma is the early period of the subduction process. The result provides an important evidence on the research of orogenic process, mantle crust interaction, and continental dynamics of north Qinling mountains.[著者文摘]
Key words:
zircon; Adakite; LA-ICPMS dating; Tangzang quartz-diorite pluton; west segment of north Qinling orogenic belt
基金资助:
国家科技支撑计划项目（2006BAB01A11）;中国地质调查局国土资源大调查研究项目（1212010610319,1212010611807）.致谢：在成文过程中,得到张维吉教授、冯益民研究员的帮助,在此深表谢意;同时感谢西北大学大陆动力学国家重点实验室第五春荣、张红、柳小明等在LA-ICPMS锆石U-Pb测试中给予的热情指导和帮助!
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