朝鲜半岛中南部三叠纪岩浆岩的分布、系列与成因浅析

发布时间：2018-06-10 13:57

本文选题：华北古陆 + 华南古陆　；参考：《岩石学报》2016年10期

【摘要】：朝鲜半岛发育大量三叠纪侵入体,主要分布在半岛中部一个北东向走廊地带,该带状区域根据岩性差异,以洪城-高城一线为界分为两个亚带:北亚带(正长岩带/碱性岩带)主要分布在狼林地块南部及京畿地块北部,为碱性系列,以正长岩类为主;南亚带(二长岩带)主要分布在京畿地块南部-岭南地块,多为亚碱性系列,以(纹长)二长岩类为主,部分岩体有闪长岩-辉长岩端元,南部有少量A型花岗岩。这些岩体多形成于ca.230~220Ma,如本文获得的北亚带江北黑云母正长岩228.7±0.8 Ma锆石U-Pb谐和年龄。它们与本区高级变质作用时代接近,分布范围大致对应但稍大,说明它们是同成因的。岩石化学方面,这些岩体均显示高场强元素亏损,轻稀土和大离子亲石元素富集的典型的大陆岩石圈特征。南北亚带相比,北亚带岩体SiO_2和Na_2O等的含量整体上略低,而K_2O、Sr、Ba、La、Eu、Y、Cr等及稀土元素含量略高,轻重稀土分异程度((La/Yb)N)略高。空间上,两个亚带内K_2O/Na_2O和SiO_2有相反的变化趋势:从南向北,两个亚带内K_2O/Na_2O逐渐升高,SiO_2含量逐渐降低;但K_2O+Na_2O和Sr/Y的变化是相似的:南亚带从南向北,北亚带从北向南,两者逐渐降低。我们认为这些岩浆岩为同碰撞或者碰撞后产物,两个亚带之间的界线接近华北和华南古陆缝合带,岩性和成分的空间差异受控于华南古陆(朝鲜半岛南部)向华北古陆(朝鲜半岛北部)之下俯冲所形成的特定壳幔结构。
[Abstract]:A large number of Triassic intrusions were developed on the Korean Peninsula, mainly distributed in a north-eastern corridor in the central part of the peninsula. The Hongcheng-Gaocheng line is divided into two subzones: the northern subzone (syenite / alkaline rock belt) is mainly distributed in the southern part of the Langlin block and the northern part of the Jingji block, which is an alkaline series, mainly composed of syenite; The South Asian belt (Erchangyan belt) is mainly distributed in the southern part of the Jingji block and Lingnan block, mostly of subalkaline series, mainly composed of (plagioclase) monzonite, some of which are diorite and gabbro end elements, and a few A-type granites in the south. Most of these bodies were formed at CA. 230U 220Ma.The zircon U-Pb harmonic age of 228.7 卤0.8Ma zircon from the northern subzone biotite syenite is obtained in this paper. They are close to the age of high grade metamorphism in this area, and the distribution range is about the same but slightly larger, indicating that they are of the same origin. In terms of petrochemistry, these rocks all show typical continental lithospheric characteristics of high field strength element depletion and enrichment of light rare earth and large ion lithophile elements. Compared with the North and South subzones, the contents of SiO2 and NaTi2O in the north subzone are slightly lower, while the contents of K _ 2O _ 2, Sr, Ba, La, La-EU, Ya-Cr and rare earth elements are slightly higher, and the degree of differentiation of heavy and heavy rare earths is slightly higher. In space, the K _ S _ 2O / Na _ 2O and Sio _ S _ 2 in the two subzones have the opposite trend: from south to north, the K _ 2O / Na _ 2O content in the two subzones is gradually increasing and decreasing; but the changes in K _ 2O / Na _ 2O and Sr _ (r / Y) are similar: the South Asia zone goes from south to north, and the north subzone from north to south. Both are decreasing gradually. We think that these magmatic rocks are the product of collision or collision, and the boundary between the two subzones is close to the paleocontinent suture zone in North and South China. The spatial differences in lithology and composition are controlled by the specific crust-mantle structure formed by the subduction of the South China ancient land (south of the Korean peninsula) to the North China ancient land (the northern part of the Korean peninsula).
【作者单位】：中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;中国科学院大学地球科学学院;
【基金】：国家自然科学基金项目(41210003、41322018) 中组部青年拔尖人才项目联合资助
【分类号】：P588.1;P534.51

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