ISSN 1006-3021 CN11-3474/P
Published bimonthly started in 1979
投稿时间:2022-01-20  修订日期:2022-03-01
关键词:southern margin of the Lhasa Terrane  Sangri area  Late Cretaceous  Neo-Tethys ocean  Volcanic rocks
杨同山 成都理工大学 地球科学学院 610059
郎兴海 成都理工大学 地球科学学院 
王旭辉 成都理工大学 地球科学学院 
邓煜霖 成都理工大学 地球科学学院 
吕娜 成都理工大学 地球科学学院 
董咪 成都理工大学 地球科学学院 
何青 成都理工大学 地球科学学院 
梁海辉 成都理工大学 地球科学学院 
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Chronology, geochemical characteristics, and genesis of Late Cretaceous volcanic rocks in Sangri area, southern margin of the Lhasa Terrane
      Intermediate-acid volcanic rocks are widely exposed in Sangri area of the southern margin of Lhasa terrane. The superposition of multiple magmatic activities makes the magmatic rocks in the area complex in composition and large span in age. In order to study the formation age,tectonic setting and genetic mechanism of volcanic rocks in this area,we selected the intermediate-acid volcanic rocks near Tamu Village in the west of Sangri County as the research object,and carried out zircon U-Pb dating,whole rock major and trace elements, and Sr-Nd isotope analysis. The contents of SiO2 and MgO in Late Cretaceous volcanic rocks in Sangri area are 55.79%-74.26% and 1.31%-4.34%,respectively. They also have high Sr (average 779×10-6),low Y (8.36×10-6 ~ 15.8×10-6),Yb (0.92×10-6 ~ 1.38×10-6) and high Sr/Y ratio (36.28 ~ 105.59). Geochemical characteristics show that the Late Cretaceous volcanic rocks in Sangri area are adakite rocks. At the same time,the Late Cretaceous Sangri volcanic rocks in Sangri area are enriched in LILE elements of Rb,Sr and Pb,and depleted in HFSE of Nb,Ta and Ti,with low initial values of 87Sr/86Sr (0.704152 ~ 0.704515) and high initial values of 143Nd/144Nd (0.512676 ~ 0.512750). Based on petrogeochemical characteristics and regional geological data,the Late Cretaceous volcanic rocks in Sangri area were formed in an active continental margin related to the northward subduction of the Neo-Tethyan oceanic crust,and were the products of partial melting of the Neo-Tethyan oceanic crust. During the rising process of ocean crust melt, the material of mantle wedge was added and underwent separation crystallization.
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