攀西古裂谷钠质碱性岩锆石SHRIMP U-Pb年龄及地质意义——以红格、白马和鸡街岩体为例  

SHRIMP DATING OF AGPAITIC ALKALIC ROCKS IN PANXI RIFT ZONE AND ITS GEOLOGICAL IMPLICATIONS— EXAMPLES FOR HONGGE, BAIMA AND JIJIE ROCK BODIES

作　　者：夏斌[1] 刘红英[1] 张玉泉[1] 

机构地区：[1]中国科学院广州地球化学研究所与南海海洋研究所边缘海地质重点实验室,广东广州510640

出　　处：《大地构造与成矿学》2004年第2期149-154,共6页Geotectonica et Metallogenia

基　　金：中国科学院知识创新工程项目 (No.KZCXZ -SW -117);国家自然科学基金项目 (No .40 0 72 0 2 2 )资助

摘　　要：用SHRIMP测定攀西古裂谷内钠质碱性岩锆石的U Pb年龄 :红格酸性碱性岩 (钠闪石花岗岩 )锆石U Pb年龄为 2 39Ma,白马中性碱性岩 (碱长石英正长岩 )锆石U Pb年龄为 2 2 5Ma和鸡街超基性碱性岩 (霞辉岩 )锆石U Pb年龄为 2 0 4Ma等 ,其年龄变化范围在 2 39～ 2 0 4Ma ,相当于中三叠世—晚三叠世 ,属于印支期。在成岩时间上显示先酸性、后基性。结合近期对其裂谷作用有关的镁铁—超镁铁层状侵入体和峨眉山玄武岩等定年的结果 ,暗示其裂谷强烈的张裂时间是在晚二叠世—晚三叠世 (2 5 9～ 2 0 4Ma)。SHRIMP technique is applied to U-Pb dating of the agpaitic alkalic rocks in Panxi rift zone. The results are as follows: 239 Ma for Hongge acid alkalic rock (riebeckite granite), 225 Ma for Baima mid-alkalic rock and 204 Ma for Jijie ultra-basic alkalic rock. Here the ages range from 239 Ma to 204 Ma, which corresponds to the period from mid-Triassic to Upper Triassic in Indo-Sinian epoch. The dating of petrogenesis shows that the acid rock is the first formed while the basic rock is late-formed. Based on the dating results of the mafic-ultramafic layered intrusions and the Emeishan basalts related to the rift, it is suggested in this paper that the intense extension occurs in the period from late Permian to Late Triassic.

关 键 词：SHRIMP U-PB 钠质碱性岩 红格 白马和鸡街岩体 四川省和云南省 

分 类 号：P597[天文地球—地球化学]