西昆仑北缘库斯拉甫一带中元古代岩浆活动及地质意义

西昆仑北缘库斯拉甫一带侵入前寒武纪结晶基底(Ch)的中元古代两期岩体,早期以喀特列克岩体为代表,年龄为1 567 Ma,晚期以阿孜巴勒迪尔岩体为代表,年龄为1 423 Ma。早期岩体(δoPt)具有贫硅、高钙、中碱和准铝质等特征; 岩性主要为钙碱性石英闪长岩,岩石稀土总量为168.4×10^-6～374.38×10^-6、轻重稀土比值为9.3～18.23,中等负铕异常(δEu=0.53～0.82)。晚期岩体(ηγPt)具有富硅、高碱、富钾、强过铝质和全铁含量高等特征; 岩性主要为碱性二长花岗岩,岩石具高的10⁴*Ga/Al比值(3.01～3.5),很高的REE含量(375.68×10^-6～1 075.46×10^-6),高LREE/HREE(7.07～16.87)和高(La_N/Yb_N)(8.32～25.2)及强烈负Eu异常(δEu=0.25～0.31)。通过对两期岩体(δoPt和ηγPt)同位素年龄、矿物学、岩石化学、微量元素及稀土元素等特征系统地研究,认为西昆仑北缘在中元古代发生两次明显的岩浆-构造事件,早期事件(δoPt的侵位)与兴地运动(Ⅰ幕)有关; 晚期事件(ηγPt的侵位)在时间及区域上与兴地运动(Ⅱ幕)比较吻合; 早期岩浆(δoPt)可能存在部分幔源物质的加入,显示Ⅰ型花岗岩的特征,可能属于造山期后花岗岩类; 晚期岩浆(ηγPt)可能经历过下地壳的部分熔融或较高程度的分异演化过程,属于A2型花岗岩的范畴。两期岩浆活动可能为古塔里木板块的固结-裂解提供了新的证据及裂解模式的补充。

Mesoproterozoic magmatic activities and its geological significance in Kusilafu area of the northern margin of western Kunlun

There are two period Mesoproterozoic rock-masses intruding in the Precambrian crystalline basement in Kusilafu area of the northern margin of western Kunlun.The early rock-mass is Kateleke,and age is 1 567 Ma.The late is Azibaledier,and age is 1 423 Ma.Kateleke is characterized by SiO₂-poor,Ca-high,alkaline-middle,metaluminous,and generally belongs to calc-alkaline quartz-tonalite.Its REE is high(∑ REE=168.4×10^-6～374.38×10^-6),enrichment in light rare elements(LREE/HREE=9.3～18.23)and moderate negative Eu anomaly(δEu=0.53～0.82); Azibaledier is characterized by SiO₂-rich,alkaline-high,K-high,strongly peraluminous,FeO^T-rich,and generally belongs to monzonitic granite.Its REE is very high(∑ REE=375.68×10^-6～1 075.46×10^-6)and high 10⁴*Ga/Al(3.01～3.5),enrichment in light rare elements(LREE/HREE=7.07～16.87)and strong negative Eu anomaly(δEu=0.25～0.31),high La_N/Yb_N(8.32～25.2).By systematic study of two rock-mass's Isotopic age,Mineralogy,Petrochemistry,Trace elements and REE,we think that there are two obvious Mesoproterozoic magma-tectonic events in northern margin of western Kunlun.The early event(δoPt emplacement)may be associated with the Xindi Movement(the first episode); the late event(ηγPt emplacement)is good agreement with the Xindi Movement(the second episode)in time and regional aspects.The early magma(δoPt)may exist part of the mantle-source substances,shows Ⅰ-type granite's features and may belong to postorogenic granitoids.The late magma(ηγPt)may be experienced partial melting of the lower crust or higher degree of differentiation-evolution process,belong to the A2-type granite.Two magmatic activities may provide new evidences of the ancient Tarim Plate's consolidation-cracking and its cracking mode's supplementary.