摘要
通过对藏南隆子-古堆一带广泛发育近东西走向的中基性脉岩较系统的地质年代学和岩石地球化学研究,3个基性脉岩的SHRIMP锆石U-Pb年龄为133～140.9Ma,代表了辉长岩的结晶年龄,而中性脉岩的SHRIMP锆石U-Pb年龄130±1.7Ma代表了闪长岩的结晶年龄。表明中基性脉岩属于钙碱性-碱性系列,总体富Ti O2,平均含量为3.08,LREE富集,轻重稀土分异较为明显,LILE略为富集,HFSE亏损不明显,属被动大陆边缘构造环境,可能代表了早白垩世新特提斯洋扩张引起喜马拉雅被动大陆边缘一侧裂解的产物。
Geochronoloical study for intermediate-basic dyke in the Gudui region, south Tibet indicates that SHRIMP U-Pb dating for zircons from three basic samples yields an age of 133-140.9Ma, representing the crystallization age of gabbro, while the SHRIMP U-Pb dating for zircons from the intermediate sample yields an age of 130±1.7Ma, representing the crystallization age of diorite. Petrochemical study indicates that the intermediate-basic rocks are calc-alkaline and alkaline series with high TiO2 of the average content of 3.08%. They are characterized by enrichment in LREE and high ratios of LREE/HREE, and slight enrichment in LILE, and less loss of HFSE. All these prove that the tectonic setting is WPB. The intermediate-basic rocks may be regarded as the products of the splitting of the Himalayan passive margin which caused the large-scale spreading of the Late Neo-Tethys ocean during the Late Jurassic-Early Cretaceous.
出处
《四川地质学报》
2014年第4期496-500,共5页
Acta Geologica Sichuan
