Phase equilibria modelling and zircon U-Pb ages of the Paleoproterozoic high-pressure mafic granulites in the Jianping Complex and tectonic implications
Phase equilibria modelling and zircon U-Pb ages of the Paleoproterozoic high-pressure mafic granulites in the Jianping Complex and tectonic implications
复制标题
建平杂岩古元古代高压镁铁质麻粒岩相平衡模拟、锆石U-Pb年龄及构造意义
DOI：
10.1016/j.precamres.2021.106460
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发表时间：
2021-12
影响因子：
3.8
通讯作者：
Jinlong Yao
中科院分区：
文献类型：
--
作者：
Nanqing Xu;GuochunZhao;Hui C.G. Zhang;Chao Wang;Jinlong Yao
华北陆壳晚古元古代变质演化一直是一个有争议的问题，并对华北陆壳的最终变质作用具有重要意义。建平杂岩位于古元古代华北造山带与东部陆块的边界，是研究华北造山带构造演化的理想场所。岩石学研究表明，沿着JPC西缘出露的镁铁质麻粒岩具有峰期矿物组合石榴石+斜长石+单斜辉石+角闪石+钛铁矿+石英和峰后矿物组合斜方辉石/角闪石+斜长石+磁铁矿+石英的特征。选择两个有代表性的镁铁质麻粒岩样品，使用THERMOCALC 3.45进行相平衡建模。模拟结果结合岩相学观察表明，这些镁铁质麻粒岩记录顺时针P-T路径，涉及近等温减压（ITD）过程或减压与热松弛。角闪石中Ti含量和斜长石中XAn含量的等值线确定了峰期变质的P-T条件为13.0-13.5 kbar/850-900 °C。样品19 JP 7和19 JP 32的峰后最终固相线组合分别在7.5-8.0 kbar/750-800 °C和10.5-11.5 kbar/880-920 °C的条件下稳定。样品19 JP 7变质锆石的变质年龄为1.82Ga，样品19 JP 32的岩浆年龄为1.21Ga，变质年龄为1.85Ga，代表了侵位和高压变质作用的时间。通过变质作用研究和锆石U-Pb年龄分析，认为华北造山带古元古代高压变质作用是沿着华北造山带东西陆块碰撞的产物，其时间为1.85 Ga。
The late Paleoproterozoic metamorphic evolution of the North China Craton (NCC) has been a controversial issue, and bears significant implications for the final cratonization of the NCC. The Jianping Complex (JPC) is located at the boundary between the Paleoproterozoic Trans-North China Orogen and the Eastern Block, and thus is an ideal site for studying the tectonic evolution of the NCC. Petrographic study reveals that mafic granulites exposed along the western margin of the JPC are characterized by the peak stage mineral assemblage of garnet + plagioclase + clinopyroxene + amphibole + ilmenite + quartz and post-peak growth of orthopyroxene/amphibole + plagioclase + magnetite + quartz around peak-stage garnet. Two representative mafic granulite samples were selected for phase equilibria modelling using THERMOCALC 3.45. The modelling results, combined with petrographic observations, indicate that these mafic granulites recorded clockwise P-T paths involving near isothermal decompression (ITD) process or decompression with thermal relaxation. Isopleths of Ti content in amphibole and XAn in plagioclase define the peak metamorphic P-T condition as 13.0–13.5 kbar/850–900 °C. The post-peak final solidus assemblages of samples 19JP7 and 19JP32 were stable at the conditions of 7.5–8.0 kbar/750–800 °C and 10.5–11.5 kbar/880–920 °C, respectively. Metamorphic zircons from sample 19JP7 yield a metamorphic age of ∼1.82 Ga, while zircons from sample 19JP32 yield magmatic age of ∼2.1 Ga and metamorphic age of ∼1.85 Ga, representing the timing of emplacement and high-pressure metamorphism. Based on the metamorphic study and zircon U-Pb ages, we conclude that the Paleoproterozoic high-pressure metamorphism of the JPC resulted from the collision of the Eastern and Western Blocks along the Trans-North China Orogen at ∼1.85 Ga.
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影响因子：
6.1
作者：
Guochun Zhao;M. Zhai
通讯作者：
Guochun Zhao;M. Zhai
影响因子：
1.8
作者：
L. Fu
通讯作者：
L. Fu
DOI：
10.18654/1000-0569/2021.01.04
发表时间：
2021
期刊：
岩石学报
影响因子：
--
作者：
魏春景;张媛媛;董杰
通讯作者：
董杰
影响因子：
3.8
作者：
Guochun Zhao;Peter A. Cawood;San-zhong Li;S. Wilde;M. Sun;Jian Zhang;Yanhong He;C. Yin
通讯作者：
Guochun Zhao;Peter A. Cawood;San-zhong Li;S. Wilde;M. Sun;Jian Zhang;Yanhong He;C. Yin
影响因子：
3.8
作者：
Zhanzhan Duan;C. Wei;H. Rehman
通讯作者：
Zhanzhan Duan;C. Wei;H. Rehman