天然火山作用探测华北下地壳组成、结构及其形成过程  

Detecting the composition, structure and formation processes of the lower crust beneath North China Craton by natural volcanism

作　　者：郑建平[1,2] 平先权[1] 苏玉平[1] 汤华云[1] 马强[1] 魏颖 ZHENG Jianping;PING Xianquan;SU Yuping;TANG Huayun;MA Qiang;WEI Ying(School of Earth Sciences,China University of Geosciences,Wuhan,Hubei 430074,China;State Key Laboratory of Geological Processesand Mineral Resources,China University of Geosciences,Wuhan,Hubei 430074,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangxi 330013,China)

机构地区：[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(武汉)地质过程与矿产资源国家重点实验室,湖北武汉430074 [3]东华理工大学核资源与环境国家重点实验室,江西南昌330013

出　　处：《地质学报》2022年第9期2998-3011,共14页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41930215和41873038)资助的成果。

摘　　要：与中上地壳相比,对下地壳组成、结构的认识受限于样品的获取,然而天然火山作用携带的下地壳捕虏体可以为了解下地壳提供关键样品。华北克拉通是世界上最古老的克拉通之一,显生宙以来的火山作用携带有丰富的下地壳捕虏体,为探测华北下地壳组成、结构及其形成过程提供了可能。通过对这些捕虏体定深、定性及定年的综合研究,构建了以信阳,莒南,汉诺坝和女山等典型地区为代表的下地壳组成、结构剖面模型。这些剖面表明,华北克拉通下地壳具有分层的特点,且上老下新,暗示可能与底侵作用有关。其中捕虏体的锆石U-Pb年龄和Hf同位素的研究,揭示了该克拉通下地壳复杂的形成与演化过程:最古老的组成部分可能老至~4.0 Ga冥古宙,此后经历了3.80~3.65 Ga古太古代的再造作用,2.8~2.5 Ga新太古代和2.3~1.8 Ga古元古代的增生与再造共存,同时还经历了显生宙以来包括462~220 Ma,140~90 Ma和47~45 Ma的增生与再造事件。Compared with the middle and upper crust, the understanding of the composition and structure of the lower crust is limited by the availability of samples. However, lower crustal xenoliths captured by natural volcanism can provide key samples. The North China Craton is one of the oldest cratons in the world, and volcanism in this craton since Phanerozoic had carried abundant lower crustal xenoliths, which provide a possibility to explore the composition, structure and formation processes of the lower crust beneath North China Craton. Based on the comprehensive study of the determinations on the depths, nature and ages of these xenoliths, the composition and structural profiles of the lower crust represented by Xinyang, Junan, Hannuoba and Nushan areas are constructed. These profiles indicate that the lower crust beneath North China Craton is stratified with vertical architecture with old upper part and young lower part, which may be related to magma underplating. Zircon U-Pb ages and Hf isotopes of those xenoliths revealed the complex formation and evolution processes of the lower crust of the craton. The oldest component may have formed in Hadean(~4.0 Ga), and then experienced Eoarchean(3.80~3.65 Ga) reworking. During Neoarchean(2.8~2.5 Ga) and Paleoproterozoic(2.3~1.8 Ga) periods, crustal accretion and reworking coexisted. Since Phanerozoic(462~220 Ma, 140~90 Ma and 47~45 Ma), the lower crust has also experienced multistage accretion and reworking events.

关 键 词：捕虏体 火山作用 下地壳 结构与组成 华北克拉通 

分 类 号：P317[天文地球—固体地球物理学] P548[天文地球—地球物理学]