• journal_title：Geology
• Contributor：Kan Tu ; Martin F. J. Flower ; Richard W. Carlson ; Ming Zhang ; Guanghong Xie
• Publisher：Geological Society of America
• Date：1991-
• Format：text/html
• Language：en
• Identifier：10.1130/0091-7613(1991)019<0567:SNAPIC>2.3.CO;2
• journal_abbrev：Geology
• issn：0091-7613
• volume：19
• issue：6
• firstpage：567

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 basanite 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 ²⁰⁸Pb/²⁰⁴Pb and ²⁰⁷pb/²⁰⁴Pb ratios, resembling those of Southern Hemisphere Dupal OIB and some alkalic arc basalts. We 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.