华北陆块南缘熊耳群形成时代讨论  

DISCUSSION ON AGE OF THE XIONG'ER GROUP IN SOUTHERN MARGIN OF NORTH CHINA CRATON

作　　者：赵太平[1] 周美夫[2] 金成伟[1] 关鸿[1] 李惠民[3] 

机构地区：[1]中国科学院地质与地球物理研究所 [2]香港大学地球科学系 [3]天津地质矿产研究所,天津300170

出　　处：《地质科学》2001年第3期326-334,共9页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金(批准号 :4 950 2 0 2 8;4 0 0 72 0 61 );香港RGC研究基金资助

摘　　要：分布于豫、晋、陕 3省的熊耳群火山岩系不整合覆盖于太古界及下元古界结晶基底之上 ,其上被汝阳群、官道口群等陆源碎屑岩 碳酸盐岩地层不整合覆盖。已有的各种熊耳群年龄资料为 1 40～ 1 85Ga,故常认为其形成标志着中元古代的开始 ,并将它与蓟县剖面的长城系对比。豫西熊耳山地区马家河组顶部的流纹斑岩和侵入于鸡蛋坪组的辉石闪长岩的单颗粒锆石U Pb和激光探针等离子体质谱 (LP ICPMS)年龄表明 :熊耳群形成于古元古代1 75～ 1 95Ga ,早于长城系 ;火山喷发开始于 1 95Ga± ,中心可能在豫西的熊耳山或崤山地区 ,形成豫西崤山、熊耳山、外方山地区的许山组和鸡蛋坪组 ;大约在 1 85Ga± ,火山活动可能以崤山地区为中心呈三叉裂谷系分别向西、东和北 3个方向发展 ,形成覆盖全区的马家河组 ;末期 (1 75Ga± )可能仅在豫西地区形成次火山 侵入岩———辉石闪长岩类。The volcanic sequence of Xiong'er Group, distributed in Henan, Shanxi and Shaanxi provinces, overlies unconformably the Archean and Palaeo Proterozoic crystalline basement, and is covered by the Middle Upper Proterozoic terrestrial clastic rocks and carbonate rocks of the Ruyang and Guandaokou Groups The available ages of the Xiong'er Group ranging from 1 85 to 1 40 Ga, so it was generally thought that the Xiong'er Group was formed at the beginning of Meso Proterozoic, corresponding to the Changcheng Group We have obtained the ages of the zircons from the rhyolite porphyry at the top of the Majiahe Formation as well as the pyroxene diorite intruded in the Jidanping Formation, using the conventional zircon U Pb and Lasser Probe Inductively Coupled Plasma Mass Sepectrometry (LP ICPMS) It is proved that the Xiong'er Group was formed in 1 75～1 95 Ga, earlier than the formation of Changcheng Group The earliest eruption of the Xiong'er Group volcanics occurred in the Xiong'er and Xiaoshan Mountains, forming the Xushan and Jidanping Formations At ca 1 85 Ga, the volcanism was developed along a trifurcate rift, that was the Majiahe Formation covering all the aera The latest magmatism, represented by some small intrusive pyroxene diorites, occurred probably at 1 75 Ga and was confined in the Xiong'er and Waifangshan Mountains The forming time of the Yunmengshan Formation, the Ruyang Group, and the Gaoshanhe Formation, the Guandaokou Group overlying the Xiong'er Group, is probably corresponding to that of the Changcheng Group

关 键 词：华北陆块 熊耳群 火山岩 形成时代 LP-ICPMS 铀-铅法年龄测试 

分 类 号：P588.14[天文地球—岩石学] P597[天文地球—地质学]