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医巫闾山岩体同伸展侵位的证据及其地质意义 被引量:16
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作者 李刚 刘正宏 +5 位作者 徐仲元 董晓杰 沙茜 王挽琼 王兴安 张超 《吉林大学学报(地球科学版)》 EI CAS CSCD 北大核心 2010年第4期971-978,共8页
医巫闾山岩体是医巫闾变质核杂岩的重要组成部分。根据医巫闾山地区花岗岩变形特征及与周围构造带的相互关系,确定医巫闾山岩体为同伸展侵位的岩体,且以岩床的形式顺层侵入在医巫闾山伸展型韧性剪切带之中,修正了前人挤压环境下岩浆侵... 医巫闾山岩体是医巫闾变质核杂岩的重要组成部分。根据医巫闾山地区花岗岩变形特征及与周围构造带的相互关系,确定医巫闾山岩体为同伸展侵位的岩体,且以岩床的形式顺层侵入在医巫闾山伸展型韧性剪切带之中,修正了前人挤压环境下岩浆侵位的观点。医巫闾山岩体及尖砬子山岩体的侵位时间在160Ma左右,表明医巫闾山地区及燕山地区中侏罗世晚期发生过强烈的地壳伸展运动,华北北部的构造体制在中侏罗世已经改变。区内中生代存在2期伸展作用:早期伸展作用发生在中侏罗世晚期,与医巫闾山岩体的侵位同期;晚期伸展作用发生在早白垩世,形成了瓦子峪拆离断层。 展开更多
关键词 变质核杂 拆离断层 同构造岩体 伸展构造 医巫闾山
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Petrogenesis and tectonic setting of the Queershan composite granitic pluton, eastern Tibetan Plateau: Constraints from geochronology, geochemistry and Hf isotope data 被引量:5
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作者 WU Tao XIAO Long +2 位作者 GAO Rui YANG HaiJun YANG Gang 《Science China Earth Sciences》 SCIE EI CAS 2014年第11期2712-2725,共14页
The Queershan composite granitic pluton is located in the north of the late Paleozoic Yidun arc collision-orogenic belt, eastern Tibetan Plateau. The main rock types are coarse-grained porphyritic alkalic-monzonite gr... The Queershan composite granitic pluton is located in the north of the late Paleozoic Yidun arc collision-orogenic belt, eastern Tibetan Plateau. The main rock types are coarse-grained porphyritic alkalic-monzonite granite with minor fine-grained porphyritic monzogranite and granodiorite distributed in the eastern and southwestern regions. Here we report their zircon U-Pb ages and geo chemical data. The intrusive contact relations indicate that granodiorite was formed earlier than the alkalic-monzonite granite (105.9±1.3 Ma) and monzogranite (102.6±1.1 Ma). These suggest that the Queershan composite granitic pluton was formed through three-stage magmatic events. The alkalic-monzonite granite (105.9±1.3 Ma) and monzogranite (102.6±1.1 Ma) are characterized by high SiO2 (73.5%-77.7%), KzO+Na20 (6.9%-8.5%), Ga/AI ratios (2.6-3.4) and low A1203 (11.8%-14.5%), CaO (0.25%-1.5%), MgO (0.18%-0.69%), negative Ba, Sr and Eu anomalies, showing A-type granite affinities. The granodi- orite exhibits lower SiO2, P205 and K20+Na20 contents, but higher A1203, CaO and MgO contents than alkalic-monzonite granite and monzogranite, showing I-type granite affinity. 176Hff177Hf ratios of the alkalic-monzonite granite and the monzogranite are 0.282692-0.282749 and 0.282685-0.282765, respectively, and with similar cHf(t) values (-0.56 to 1.43 and -0.87 to 1.90 respectively). They also present similar T1-M2 model ages (1.04-1.22 and 1.07-1.2 Ga respectively), indicating they may be sourced from a similar rock source, mostly like Kangding Complex. The homogeneity of the Hf isotopic compositions and the absence of the MMEs demonstrate that little depleted mantle materials have contributed to the source. We propose that the Mesoproterozoic crust materials of the Yangtze Craton exist beneath the Yidun arc terrane and support it was a dismembered part of the Yangtze Craton. The A-type granites of Queershan composite granitic pluton are most probably related to the clo- sure of the Bangong-Nujiang Tethys ocean. 展开更多
关键词 A-type granite GEOCHEMISTRY PETROGENESIS Queershan Yidun arc eastern Tibetan Plateau
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