Cenozoic Volcanism in Tibet: Evidence for a Transition from Oceanic to Continental Subduction |
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| Authors: | DING LIN; KAPP PAUL; ZHONG DALAI; DENG WANMING |
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| Institution: | 1 INSTITUTE OF GEOLOGY AND GEOPHYSICS, CHINESE ACADEMY OF SCIENCES, BEIJING 100029, PEOPLE'S REPUBLIC OF CHINA
2 DEPARTMENT OF GEOSCIENCES, UNIVERSITY OF ARIZONA, TUCSON, AZ 85721-0077, USA |
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| Abstract: | Geochronological (K–Ar or 40Ar/39Ar), major and traceelement, Sr–Nd–Pb isotopic and mineral chemicaldata are presented for newly discovered Cenozoic volcanic rocksin the western Qiangtang and central Lhasa terranes of Tibet.Alkali basalts of 65–45 Ma occur in the western Qiangtangterrane and represent primitive mantle melts as indicated byhigh mg-numbers 100 x Mg/(Mg + Fe)] (54–65), Cr (204–839ppm) and Ni (94–218 ppm) contents, and relatively lowratios of 87Sr/86Sr (0·7046–0·7061), 206Pb/204Pb(18·21–18·89), 207Pb/204Pb (15·49–15·61)and 208Pb/204Pb (38·42–38·89), and highratios of 143Nd/144Nd (0·5124–0·5127). Incontrast, younger volcanic rocks in the western Qiangtang terrane( |
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