| 其他摘要 | As the only accepted large igneous province in china, Emeishan large igneous province has been accepted by internationalsholas. It has significant meanings to study the substance structure of mantle, content variation, deep process of continental lithosphere, the cause of continental cracking and mineralization.The Emeishan large igneous province (ELIP) was recently interpreted as the production of mantle plume activity in Permian and Triassic period in southewest of China. It probably started erupt in 260Ma, and the eruption period between 259~257Ma, and the acid rock in 251Ma may represent the end. Mantle plumes and associated voluminous eruption of lavas are generally considered to be a potentially important cause for crises in global climate and biological extinction. The high accordance between Emeishan mantle plume activity and mass extinction of biont incident likely imply that they have inherent relationship. Based on the observation in field, late Paleozoic debases in north Guangxi province have been studied and the geodynamic background of northern Guangxi and reflection to Emeishan mantle plume has been considered. New results and progress have been obtained. 1. After analyzing the debated basaltic rocks of Baise and Bama, north of Guangxi in field and laboratory carefully, we conclude that the dykes are intruded into country rocks and the interference is clear with silification. And the rocks are massive structure with diabasic texture. So, we think that they are diabases. 2. Geochronology, petrology and geochemistry were performed systematically on diabases in Baise and Bama, north Guangxi province. Diabases in north Guangxi were homologous with Emeishan basalts and were derived from mantle plume with little contamination. The LA-ICP-MS U-Pb zircon data of diabases yields a concordant age, 255-259Ma, which is in almost accordance with the main eruption time of Emeishan basalts. 3. The range of ELIP has been expanded, and the activity of Emeishan basaltic magmas in Permian has an influence on north of Guangxi. Also, basic rocks, which have similar characteristics in south of Guizhou and east of Yunnan, may be the results of this activity. All of this will supply new constraints on the spatial and temporal distributions of ELIP. The main eruption age of ELIP,which is concentrated in 1~3Ma, has been considered to be 259~257Ma by most scholars. Emeishan large igneous province was production of rapid mantle uplifting. Through the study of this article, diabases of Pingxu, Longchuan, Poyou and Yanna have equal chronology with Emeishan mantle plume. So, they must be the homogeneous interphase product of Emeishan basaltic magama activity. Therefore, we consider that the distribution of Emeishan large igneous province probably has extended to west of Guangxi province. Due to the same eruption time with the mass biological extinction incident, the relationship between the two has further been proved. |
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