阜平杂岩年龄及其地质意义:兼论前寒武高级变质地体的定年问题  

Zircon U-Pb ages of the Fuping Complex and their implications: some comments on the geochronological study of the Precambrian high-grade metamorphic terranes.

作　　者：孙敏[1] 关鸿[1] 

机构地区：[1]香港大学地球科学系

出　　处：《岩石学报》2001年第1期145-146,共2页Acta Petrologica Sinica

基　　金：国家自然科学基金项目 (编号 :4992 930 1);香港研究资助委员会 ( RGC)项目 ( HKU 7110 / 97P; HKU730 0 / 99P)的部分资助

摘　　要：本文通过对比锆石 TIMS (热电离质谱法 ) ,SHRIMP (高灵敏度离子探针 )及 ICPMS- L P (等离子体质谱 -激光探针 )分析方法对阜平杂岩中主要岩石获得的年龄结果 ,讨论了阜平杂岩中几种主要岩石的形成时代及其地质意义。研究结果表明阜平杂岩是由不同时代、不同成因的各种高级变质岩组成 ,其主体是 2 .5 1Ga的 TTG片麻岩并包裹了少量 2 .7Ga的大陆残片。同时阜平地区还发育一期 2 .0 5 Ga的岩浆活动。阜平杂岩中的湾子表壳岩可能沉积发育于 2 .5 Ga和 2 .1Ga之间。本文还通过比较三种锆石同位素定年方法的特点 ,进而讨论了几种方法在高级变质地体定年上的可行性 ,特别强调了锆石内部结构。Three zircon U-Pb age dating methods have been applied for the Fuping Complex, i.e. Thermal Ionization Mass Spectrometry (TIMS), Sensitive High Resolution Ion MicrProbe (SHRIMP) and Inductively Coupled Plasma Mass Spectrometry - Laser Probe (ICPMS-LP). Based on these results it is suggested that the Fuping Complex is mainly made up of 2.51 Ga TTG gneisses; a small amount of 2.7 Ga hornblende gneisses were developed which may represent the fragments of old continetal materials. One magmatic event of 2.05 Ga was confirmed in the Fuping area. The Wanzi supracrustal rocks were possibly deposited between 2.5 and 2.1 Ga. The characteristics of the three U-Pb dating techniques and their applications on the geochronological study of the Precambrian high-grade metamorphic rocks were also discussed. It is emphasized the significance of the study on the internal structures, chemical characteristics on zircon for its U-Pb geochronology.

关 键 词：阜平杂岩 锆石U-PB年龄 TIMS SHRIMP ICPMS-LP 

分 类 号：P588.34[天文地球—岩石学] P597.3[天文地球—地质学]