| Abstract: | Studied Volcanic rocks are zonally distributed between Qiangtang and Kunlun landasses, that is in the western part of Lazhulong\|Jinsajiang tectonic belt. It is bounded on the north by Yanghu\|Hohxil deep fult and on the south by Bairabu Co\|Ruolagangri deep fault. As component part of ophiolites in this belt, volcanic rocks mainly occuring within low\|grade metamorphic and thick flysch deposits of Lower Permian and Late Triassic, are associated with gabbro, diabase, ultramafites, radiolarian silicalites and limestones, consisting of basalts, dorgalites, picrites, basaltic\|andesites, andesites and a few pyroclastic rocks. This suit of volcanics\|bearing flysch deposits had been considered as Triassic or Late Triassic stratum and also called as “Ruolagangri Group” before.The basalts in this belt are characterized by having lower SiO\-2, higher TiO\-2(1 74%～4 78%, average 2 94%) and K 2O+Na 2O(mostly 3 50%～5 00%) contents, and usually Na 2O>K 2O. The total REE abundances in basalts which vary from 115 68×10 -6 to 323 66×10 -6 are relatively high, and all of their distribution patterns show moderately or strongly LREE\|enriched. The LREE/HREE ratios range from 8 74 to 14 41, (La/Yb) N from 9 53 to 19 56, and showing faint positive or no Eu anomaly. Incompatible trace elements such as Sr, Rb, Ba, Th, Ta, Nd, P, Zr, Hf etc. are relatively concentrated, whose contents usually are several times to several tens of MORB, while Yb, Y, Sc, Cr are obviously depleted. The characteristics of Petrochemistry and rare elementary geochemistry indicate that the volcanic rocks belong to series of alkaline or subalkaline basalt and show the features of alkaline—transitional basalt under the setting of continental rift or ocean island, and also similar to that of Late Carboniferous basalts in Chabu\|Chasang area of central Qiangtang and that of Permian Emeishang basalts in southwest of China. |
