| 由深源捕虏体限定的华北克拉通下地壳特征 |
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| 引用本文： | 路凤香,侯青叶.由深源捕虏体限定的华北克拉通下地壳特征[J].地学前缘,2012,19(3):177-187. |
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| 作者姓名： | 路凤香 侯青叶 |
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| 作者单位： | 1. 中国地质大学武汉地球科学学院,湖北武汉,430074
2. 中国地质大学北京地球科学与资源学院,北京,100083 |
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| 基金项目： | 国土资源部行业专项“深部探测技术与实验研究”第四项目第二课题，国土资源部公益性行业科研专项，国家自然科学基金项目(90714008)
成文的过程中翟明国院士、邵济安教授、张宏福研究员和郑建平教授提供了有益的和未发表的资料;两位评审人提出了宝贵的修改意见;在此一并表示感谢 |
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| 摘 要： | 文中收集了新生代、中生代和古生代由喷出/浅成岩携带的下地壳麻粒岩捕虏体及其锆石年龄的资料。结果显示,它们代表了不同时代、不同地区下地壳最下部的组成及年龄。新生代汉诺坝、女山、莒南和青岛等地的玄武岩和其中捕虏体的资料,几乎可以涵盖华北相当一大部分下地壳底部的状态。金伯利岩虽然只能提供500Ma以前的信息,但它们能够检验并确认古老地质事件发生时间的准确性。内蒙古中生代闪长岩中出露的麻粒岩属于同源捕虏体,只能代表该岩浆活动波及地区下地壳的状态。华北克拉通发育了多次以地幔物质添加为主的地质事件(地壳增生),主要有:2.8～3.0Ga,2.5Ga,1.8Ga,140～90Ma及47～45Ma,其中以2.5Ga和140～90Ma最为重要。2.5Ga的地幔岩浆底侵事件在不少地区出现,推测与地幔柱活动有关。中生代(140～90Ma)的底侵作用在克拉通分布相当广泛,包括华北北部,华北东部及东南部都有明显的记录。女山和莒南地区出现了2.3Ga的年龄,是中生代的底侵岩浆与先存的古老基底发生混合与反应的产物。1.9～2.0Ga以及1.8Ga可能与地壳的造山运动和与其伴随的短暂的热扰动造成的锆石再结晶有关。在研究下地壳捕虏体时一个重要的问题是,要注意构造背景。在一级构造单元的交界处,由于该处块体之间的相互作用复杂,需要注意判别捕虏体的块体归属,以便对华北克拉通不同部位的复杂演化历史获得更全面的认识。
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| 关 键 词： | 麻粒岩捕虏体 下地壳最下部 锆石年龄 岩浆底侵作用 华北克拉通 |
The feature of lower crust of North China Craton（NCC） constrained by xenoliths |
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| Lu Fengxiang,Hou Qingye.The feature of lower crust of North China Craton（NCC） constrained by xenoliths[J].Earth Science Frontiers,2012,19(3):177-187. |
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| Authors: | Lu Fengxiang Hou Qingye |
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| Institution: | 1.Faculty of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,China 2.School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing100083,China |
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| Abstract: | The data on lower crustal granulite xenoliths of the Cenozoic,the Mesozoic and the Paleozoic and their zircon ages were collected in this study.The results show that these xenoliths represent the compositions and formation ages of the bottom of lower crust in different domains and different times in NCC.The most useful information is from the Cenozoic basalts and their xenoliths such as from Hannuoba,Nushan,Junan and Qingdao.They may reflect almost the whole bottom of lower crust situations in NCC.Although the data from kimberlites provided the information only before 500Ma,they also can examine and confirm the accuracy of the results from the Cenozoic data.Granulites entrained by Mesozoic diorite in Inner Mongolia are cognate xenoliths,so they merely represent the bottom of lower crust of local area where these kinds of magmas distributed.The multi-stage geological events have occurred in NCC which were dominated by adding the juvenile mantle materials.The major events were happened in 2.8-3.0 Ga,2.5 Ga,1.8 Ga,140-90 Ma and 45-47 Ma and the very important two lower crust growths appeared in ca.2.5 Ga and 140-90 Ma.Basic magma underplating at ca.2.5 Ga was recorded in granulites of the Cenozoic and the Paleozoic from different places and it may relate to the "mantle plum" activity.Magma underplating in 140-90 Ma is widespread in NCC including northern,eastern and southeastern parts.It is possible that the zircon ages of 2.3 Ga reported in granulite xenoliths from Nushan and Junan are the products of Mesozoic underplating magma mixed or/and interacted with the Archean lower crust.Data on the zircon ages of 1.9-2.0 Ga and 1.8 Ga attest it correlated to the tectonic movement at crust and the disturbance of instantaneous thermal event led to recrystallization of zircon.Tectonic background,a very important problem,must be pay attention to when you study the deep-seat xenoliths,especially at the boundary of the first-order tectonic units because of the complicated interaction between adjacent blocks,so it is necessary to distinguish which block be each xenolith derived from.This is helpful to the understanding of the complicated evolution history in different domain of NCC. |
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| Keywords: | granulite xenolith the bottom of lower crust zircon age magma underplating North China Craton |
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