MULTIPLE GEOCHEMICAL TRACES OF TWO TYPES OF INTERMEDIATE-BASIC VOLCANIC ROCKS IN XIARUO-TUODING AREAS, JINSHA RIVER COMBINATION ZONE, NORTHWEST OF YUNNAN PROVINCE, CHINA

doi:10.3321/j.issn:1000-2383.2001.01.005

Abstract：When using major and trace elements as a tool to trace tectonicsettings，origins and magma sources of volcanic rocks，we must firstly reconstruct the elements on the bases of macro-regional geology and geochemical investigations，and of various kinds of rock-type assemblages in different geological bodies that occurred at that time. This reconstruction serves as the basis for the identification of the macro-tectonic settings. Secondly，we should adopt the research method characterized by the combination of the multiple geochemical information tracing with the temporal-spatial matching of various kinds of rock types, due to the temporal-spatial complexity of the tectonic settings. Thirdly，we should fully understand the application premises，ranges and conditions, so as to identify correctly the corresponding illustrations. On the basis of the three points mentioned above, this paper focuses on the multiple geochemical tracing of the two types of intermediate-basic volcanic rocks in Xiaruo-Tuoding areas in the Jinsha River combination zone, Northwest of Yunnan Province, China. This research has already brought us the following three relatively excellent effects: (1) The basic volcanic rocks located on the eastern side of the Jingsha River ophiolitic mélange zone occurred in the continental-rift setting. However, the intermediate-basic volcanic rocks are characterized by the island-arc volcanic rocks on the western side of Jingsha River ophiolitic mélange zone. (2) The volcanic lava of the two types of volcanic rocks both originated from the lava-enriched earth mantle. Specifically, the volcanic rock on the eastern side originated from the homogeneous lava-enriched earth mantle, while those on the eastern side originated from the heterogeneous lava-enriched earth mantle. (3) Finally, the structural evolutionary characteristics of these volcanic rocks are discussed.