排序方式: 共有1条查询结果,搜索用时 390 毫秒
1
1.
Cenozoic Volcanism in Tibet: Evidence for a Transition from Oceanic to Continental Subduction 总被引:93,自引:2,他引:93
Geochronological (KAr or 40Ar/39Ar), major and traceelement, SrNdPb isotopic and mineral chemicaldata are presented for newly discovered Cenozoic volcanic rocksin the western Qiangtang and central Lhasa terranes of Tibet.Alkali basalts of 6545 Ma occur in the western Qiangtangterrane and represent primitive mantle melts as indicated byhigh mg-numbers [100 x Mg/(Mg + Fe)] (5465), Cr (204839ppm) and Ni (94218 ppm) contents, and relatively lowratios of 87Sr/86Sr (0·70460·7061), 206Pb/204Pb(18·2118·89), 207Pb/204Pb (15·4915·61)and 208Pb/204Pb (38·4238·89), and highratios of 143Nd/144Nd (0·51240·5127). Incontrast, younger volcanic rocks in the western Qiangtang terrane( 相似文献
1