^(40)Ar/^(39)Ar chronology and geochemistry of high-K volcanic rocks in the Mangkang basin, Tibet  

作　　者：ZHANG Huihua, HE Huaiyu, WANG Jianghai & XIE Guanghong Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China College of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China 

出　　处：《Science China Earth Sciences》2005年第1期1-12,共12页中国科学（地球科学英文版）

基　　金：This work was jointly supported by the National Natural Science Foundation of China(Grant No.49972026);the Guangdong Natural Science Foundation(Grant No.990531);the project of the ChineseAcademy of Sciences(Grant No.KZCX2-SW-117);the Chinese National Key Project for Basic Research(Grant No.G1998040807)and US NSF.

摘　　要：Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ( 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ( 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. Et al., implying that they were formed in the same tectonic setting.Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5±0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5±0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. et al., implying that they were formed in the same tectonic setting.

关 键 词：Cenozoic HIGH-K volcanic rocks  40AR/39AR chronology  Mangkang basin  Tibet. 

分 类 号：P597.3[天文地球—地球化学] P588.1[天文地球—地质学]