| Eryuan area is located in Garze-Litang suture zone, the southern end, located in Eryuan County West, Great Southern Luoping east slope of the plot and other places, starting from a set of foliated metamorphic rhyolite, green clay schist Yang, shallow metamorphic rocks consisting of mica schist, crystalline limestone, crystalline dolomite. In this paper, bimodal volcanic Eryuan area as a research body, the main trace of rock geochemistry data analysis of volcanic rocks, while taking advantage of zircon U-Pb isotopic dating techniques to get their diagenetic Age. Combined with previous studies on Eryuan area bimodal bimodal volcanic rocks in the area, and to explore the causes and structural features Eryuan bimodal volcanic rocks.(1) The major elements wherein, Al2O3 compared with the range of 0.428～27.24, alkali (K2O+Na2O)=0.49～9.02. By the TAS diagram and Zr/TiO2-SiO2 can be seen in the strong regional tectonic deformation, volcanic rocks of alkalis (including active ingredient such as SiO2) can be more excluded from the formation of metamorphic fluid felsic veins. The presence of bimodal volcanic rocks indicating formed in extensional tectonic setting of.(2) REE characteristics of performance, range acidic volcanic rocks of the total rare earth ΣEE value is 36.73-620.39 REE distribution patterns show LREE enrichment type of right-wing, LREE fractionation clear, light, heavy rare earth elements fractionation factor (La/ Yb)N between 4.31 to 11.49, with an average of 7.034. (La/Sm)N is between 2.1 to 5.23, light rare earth fractionation is not obvious, (Gd/Yb)N is between 0.76 to 2.23, HREE fractionation is not obvious, between 8Eu value from 0.32 to 0.79, rocky strong uranium anomalies negative, indicating that the source area plagioclase residues.The total amount of basic volcanic RE ΣREE low, it is worth in the range of between 38 to 166.07; LREE enriched with a rightist characteristics, and LREE enrichment, and light and heavy rare earths there is a strong inter-fractionation, fractionation coefficient (La/Yb)N is 2.14 to 9.27, the occurrence of light rare earth elements inside a certain fractionation, (La/Sm)N value of 1.34 to 2.84, the HREE fractionation weak (Gd/Yb)N is 1.42 to 2.66, negative Eu anomaly is not obvious 8Eu of 0.82 to 1.29.(3) Trace element characteristics indicate that the study area acidic volcanic trace element distribution in the form of the primitive mantle normalized spider curve similar to the performance of large LILE (LILE) K, Rb and relatively LREE enrichment, Ba, Sr appears strong negative abnormal. Volcanic Sr losses described as the presence of plagioclase melt residual phase or crystalline phase separation. P,Ti loss with ilmenite, apatite fractional crystallization close. Rb/Sr ratios of rock to higher 2.11 to 14.72, with an average of 9.61. Distribution of trace elements in which the performance of Eryuan area mafic volcanic rocks of the curve primitive mantle normalized spider diagram is similar, they are manifested as LIEE relative enrichment characteristics, and relatively depleted in HREE are depleted in high strength elements Nb and plant Ta. Rare earth and trace element characteristics can be seen in the study area two end members bimodal volcanic rocks are not homologous.(4)Falling within the plate basalts and its vicinity, in the Yb-Ta illustration granite slab granite but also most of the region falls on the Zr/Y-Zr diagrams, which show that the continental intraplate basalt.(5)The use of Zircon LA-ICP-MS U-Pb dating of the age data obtained 246.5±1.9Ma, presumably bimodal volcanic rocks in the area formed in the Mesozoic of the Middle Triassic.Mesozoic volcanic rocks on the binding region of the spatial distribution characteristics, Eryuan Mesozoic Triassic Volcanic extruded construction and extension of the Himalayas, and with a strong mylonitized and hydrothermal superimposed suture is Southwest Sanjiang band and stretch window. |
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