Ascertainment and Environment of the OIB-Type Basalts from the Dongbo Ophiolite in the Western Part of Yarlung Zangbo Suture Zone
详细信息
- 责任者：Liu Fei (State Key Laboratory for Continental Tectonic and Dynamics ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Yang Jingsui
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(6)
- 关键词：玄武岩 ; basalts ; 雅鲁藏布江 ; Yarlung Zangbo River
- 页码：p.1909-1932
- 图表：illus., 6 tables, 119 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The western part of the Yarlung Zangbo Suture Zone ( YZSZ) is divided into two sub-belts; the genesis of the south plays a crucial role in the interpretation of the geological setting,magmatic and tectonic processes of the Neo-Tethyan 0cean. Previous research about the Dongbo ophiolite was poor,due to harsh natural environment and traffic inconvenience. This paper reports the data on petrography and geochemistry of 0IB-type basalts and associated sedimentary rocks in the Dongbo ophiolite and discusses their source characteristics and geological significance. Dongbo ophiolite consists of peridotite ( including harzburgite,minor Cpx enriched harzburgite and dunite) ,mafic dikes and submarine volcanic-sendimentary rock sequences,no typical cumulates and pillow lavas. The stable marine volcanic-sedimentary sequences mainly composed of siliceous limestone,red chert,shale interbedded sandstone,basalt and basaltic volcaniclastic rocks.0IB-type basalts are characterized by low SiO2 and MgO,high TiO2 ,P205 and ( K20 + Na20) content,enrichment of Nb,Ta and REE,depletion of Th,K,Pb,Sr. Trace elements and Sr,Nd,Pb isotopedata show that these basaltic lavas were derived from 2% to 5% partial melting of garnet spinel lherzolite. Siliceous rocks are of biogenic origin,and show a close relation to terrigenous component and seamount or island arc basalts. Above evidences indicate that the Dongbo volcano-sedimentary sequences have the typical seamount features,and the Dongbo ophiolite probably is related to a plume hotspot. Therefore, it can be considered,the plume hotspot underplating and interacting with the subcontinental lithospheric mantle of the Gondwana northern margin not only promoted opening the Daba-Xiugugabu Tethyanoceanic basin,but also prompted diamonds and other abnormal mantle minerals to be migrated upper mantle and wrapped in peridotite and chromite.
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