Sr, Nd, and Pb isotopic compositions of Hainan basalts (south China): Implications for a subcontinental lithosphere Dupal source
- Univ. of Illinois, Chicago (USA)
- Carnegie Institution of Washington, DC (USA)
- Academia Sinica, Guangzhou (China)
Sr, Nd, and Pb isotopic ratios were determined for postspreading basalts from Hainan Island, erupted in a quasi-oceanic pull-apart trough at the northern edge of the South China Basin. The basalts comprise quartz tholeiite, olivine tholeiite, alkali basalt, and basinite and show oceanic island basalt (OIB)-type trace element distributions relatively enriched in Nb, Ta, and Th. Despite normal OIB-like Sr and Nd isotopic compositions, Hainan lavas have unexpectedly high {sup 208}Pb/{sup 204}Pb and {sup 207}Pb/{sup 204}Pb ratios, resembling those of Southern Hemisphere Dupal OIB and some alkalic arc basalts. The authors propose that the Hainan source comprises a lower lithospheric region of accreted asthenospheric melt (isotopically resembling Central Indian Ridge-type basalt) overprinted by radiogenic melts of subducted sediment. In the absence of a mantle plume, decompression melting of subcontinental lithospheric mantle may result from lithosphere stretching, as a regional response to the Indo-Eurasian collision.
- OSTI ID:
- 5541716
- Journal Information:
- Geology; (USA), Vol. 19:6; ISSN 0091-7613
- Country of Publication:
- United States
- Language:
- English
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580000* - Geosciences