朝鲜半岛中南部三叠纪岩浆岩的分布、系列与成因浅析  

A preliminary study on the distribution,magma series and petrogenesis of the Triassic igneous rocks in middle-southern Korean Peninsula

作　　者：彭澎[1,2] 杨书艳[1,2] 王欣平[1,2] 

机构地区：[1]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,北京100029 [2]中国科学院大学地球科学学院,北京100049

出　　处：《岩石学报》2016年第10期3083-3097,共15页Acta Petrologica Sinica

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

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。There are many Triassic plutons in Korean Peninsula,mainly in the middle-southern,which constitutes a NE-trending corridor zone.Based on lithology,this corridor can be divided into two subzones along the Hongseong-Koseong line,the north subzone（syenite zone/alkaline rocks zone） covers the southern part of the Rangnim massif and the northern part of the Kimggi（ Gyeonggi）massif and is composed of alkaline series,mainly syenites; while the southern sub-zone（ monzonite zone） lies in the southern part of Kimggi massif and the Yongnam massif and is composed of subalkaline series, mainly monzonites, with some diorite to gabbro components,and a few A-type granites to the south.These plutons formed at ca.230 ~ 220 Ma,e.g.,a 228.7 ± 0.8 Ma U-Pb zircon concordia age is obtained for the Kangbuk biotite syenite from the north sub-zone.These Triassic plutons are coeval with the regional high-grade metamorphism and distribute in consistent but slightly bigger areas,which indicates a cogenetic relationship.These plutons are depleted in high field strengthen elements but enriched in light rare earth elements and large ion lithophile elements,a typical feature of continental lithosphere.Compared between the two subzones,the north sub-zone has systematically lower SiO_2 and Na_2O contents,but higher K_2O,Sr,Ba,La,Eu,Y,Cr and rare earth elements and stronger fractionation between the light and heavy rare earth element（ represented by higher（ La/Yb）N）.Spatially,the K_2O/Na_2O and SiO_2 values changes oppositely,i.e.,the K_2O/Na_2O increases while the SiO_2 decreases from south to north in both sub-zones.However,the variations in K_2O ＋ Na_2O and Sr/Y change in a similar trend,i.e.,they both decrease from south to north in the south sub-zone and from north to south in the north subzone.We think the boundary of the two sub-zones is close to the suture between the basements of the North and South China blocks,and the rocks were products of a syn-to post-collision process.And subduction of the South China block（

关 键 词：华北古陆 华南古陆 朝鲜半岛 三叠纪 正长岩 (纹长)二长岩 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]