Geochemical characteristics and geologic implications of Cenozoic basalts, east Altai, Xinjiang.

The K-Ar dating indicates that Cenozoic Basahs in Halaqiaola area,eastern Ahai in north Xinjiang,were emplaced at 10 ～20Ma.And the Basalts are belonging to shoshonite,which have high concentration of TiO_2,high K and alkali,and characterized by enrichment in light rare earth elements and compatible elements,indicating an enriched mantle source.Their geochemical characters and Sr-Nd isotopic composition are similar to those of oceanic island basalts(OIB),which has the isotopic results of(~(87)Sr/~(86)Sr)i= 0.704432～0.704538,(~(143)Nd/~(144)Nd)i=0.512641～0.512779,e_(Nd)(t)=0.29～1.03.The ratios of La/Nb(0.765～0.823 )and Nb/U(35.02～52.01 )shows that some recycled ernst material might be interfused into the enriched source.Analyzing integrally with the Cenozoic basahs in the adjacent areas such as Tuoyun basin,we find that the Cenozoic volcanic rocks in central Asia are scatteredly distributed and developed along the major strike slip faults,which cannot be the results of typical plumes.So this article,combining with the ernst evolution in Central Asia,points out that the Cenozoic basalts similar to OIB were originated from the modified enriched mantle which were derived from subducted oceanic crusts during Late Paleozoic.