华北板块北缘中段早中二叠世的构造属性_ 来自花岗岩类锆石U-Pb年代学及地球化学的制约.docVIP

 华北板块北缘中段早中二叠世的构造属性: 来自花岗岩类锆石 U-Pb 年代学及地球化学 的制约# 5 10 15 20 25 30 35 40 王挽琼，刘正宏，徐仲元** （吉林大学地球科学学院，长春 130061） 摘要：内蒙古温都尔庙南—铁沙盖黑云角闪石英闪长岩和角闪黑云花岗闪长岩位于华北板块 北缘中段晚古生代构造岩浆活动带中；锆石 LA-ICP-MS U-Pb 定年结果显示，其形成时代分 别为 271.8±2.4Ma，271.4±1.3Ma、268.7±1.3Ma。主量元素 SiO2 含量为 61.42% ~ 71.73%， K2O 含量为 3.10% ~ 5.11%，K2O/Na2O 值介于 0.93 ~ 1.96 之间，Mg#值为 51.77 ~ 64.58， A/CNK 为 0.90 ~ 1.03；副矿物为锆石、磷灰石和磁铁矿，属亚碱性高钾钙碱性系列、I 型花 岗岩类；富集轻稀土、大离子亲石元素 Cs、Rb 及高场强元素 Th、U，亏损重稀土元素、大 离子亲石元素 Ba、Sr、Eu 及高场强元素 Nb、Ta，弱 Eu 负异常（δEu=0.55 ~ 0.95）。岩体 发育暗色微粒包体。上述特征表明岩体形成于活动大陆边缘弧环境，反映了早中二叠世古亚 洲洋俯冲于华北板块北缘之下及岩浆混合作用的岩浆事件。 关键词：I 型花岗岩；暗色微粒包体；岩浆混合作用；晚古生代；活动大陆边缘弧；索伦缝 合带；内蒙古 中图分类号：P588.121 Early-middle permian tectonic evolution of the middle section of the northern margin of the North China Plate: Constraints from zircon U-Pb geochronology and geochemistry of the granitoid rock Wang Wanqiong, Liu Zhenghong, Xu Zhongyuan (College of Earth Science, Jilin University, ChangChun 130061) Abstract: Biotite-hornblende quartz diorite and hornblende-biotite granodiorite, which are located in the area between the south of Ondor Sum and Tieshagai in Inner Monglia, are the part of the late paleozoic structure magmatism belt in the middle segment of the north margin of the North China Plate; zircon LA-ICP-MS U-Pb dating indicates that weigted mean ages are 271.8±2.4Ma, 271.4±1.3Ma and 268.7±1.3Ma, respectively. Otherwise, they have SiO2=61.42% ~ 71.73%, K2O=3.10% ~ 5.11%, K2O/Na2O=0.93 ~ 1.96, Mg#=51.77 ~ 64.58, A/CNK=0.90 ~ 1.03 and belong to subalkalic high-K calc-alkaline series and I-type granitoid. The accessory minerals are zircon, apatite and magnetite. The rocks are characterized by a strong enrichment in light rare earth, large ion lithophile elements such as Cs and Rb and high field-strength elements such as Th and U; depletion in heavy rare earth, large ion lithophile elements such as Ba, Sr and Eu and high field-strength elements such as Nb, Ta and Ti and weak negative Eu anomalies (δEu = 0.55~0.95). Biotite diorite which are mafi