摘要
采用高精度离子探针(SHRIMP)测年方法对西藏念青唐古拉山英云闪长质和石英闪长质正片麻岩中锆石的成因和形成时代进行了研究。在阴极发光图像中,片麻岩中的锆石具有较好的晶形,并显示出清晰的岩浆锆石韵律环带结构。离子探针分析表明,片麻岩中的锆石具有高的Th/U比值。对2颗片麻岩中的锆石进行了离子探针U-Pb测年,测得英云闪长质和石英闪长质片麻岩中的锆石206Pb/238U结晶年龄分别为58.5Ma±0.7Ma和63.5Ma±0.8Ma。这一结果意味着念青唐古拉山正片麻岩形成于安第斯型的冈底斯岩浆作用期间。
Zircons from tonalitic and quartz dioritic orthogneisses in the Nyainqêntanglha Mountains ,Ti-bet,were dated by ion microprobe(SHRIMP )and their origin was studied.In the Cathodoluminescence(CL)images the zircons extracted from the dioritic gneiss show good crystal morphology and clear oscilla-tory zoning,as is the case of magmatic zircon.Ion microprobe analyses revealed that the zircon from the orthogneiss has high Th /U ratios.Ion microprobe U-Pb dating of zircons from the tonalitic gneiss and quartz dioritic orthogneiss yielded statistically distinguishable 206 Pb / 238 U crystallization ages of 58.5±0.7Ma and63.5±0.8Ma ,respectively.The result suggests that the orthogneiss in the Nyainqêntanglha Mountains may have crystallized during Andean-type Gangdise magmatism.
出处
《地质通报》
CAS
CSCD
北大核心
2003年第11期936-940,共5页
Geological Bulletin of China
基金
中国地质调查局1:25万当雄县幅区域地质调查项目(编号:200013000166)成果。
