首页|New U—Pb zircon and geochemical constraints on Late Devonian Back-arc basin origin of eclogite protoliths from northeastern Hainan Island, South China
New U—Pb zircon and geochemical constraints on Late Devonian Back-arc basin origin of eclogite protoliths from northeastern Hainan Island, South China
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Geochronological, geochemical, and Sr—Nd isotopic data are used to constrain the age, origin, and tectonic setting of the protoliths of newly discovered eclogites from Chaotanbi, northeastern Hainan Island, South China. New sensitive high-resolution ion microprobe (SHRIMP) U—Pb zircon dating reveals that the protoliths of the Chaotanbi eclogites formed at 364 ± 2 Ma and were metamorphosed at 297 ± 1 Ma. All samples collected from a coherent area of —1.8 km2 in the intertidal and subtidal zones on the island exhibit tholeiitic compositions, with initial ~(87)Sr/~(86)Sr and ε_(Nd) values of 0.705-0.707 and-1.1 to +7.4, respectively. The samples can be further categorized into three groups based on incompatible trace elements. Group #1 samples have a normal mid-ocean ridge basalt (N-MORB) affinity and were originated from relatively high-degree partial melting of a depleted spinel lherzolite mantle source slightly modified by slab-derived fluids. Group #2 samples have an enriched mid-ocean ridge basalt (E-MORB) affinity and were derived from an enriched spinel and spinel-garnet lherzolite transition mantle source at depths greater than that of Group #1. Group #3 samples have an island arc basalt (IAB) affinity and were generated by partial melting of an enriched spinel-garnet lherzolite mantle source modified by fluid-and sediment-related recycled components. The association of these diverse basalt types, with MORB-type samples accounting for —90% of all samples, suggest a Late Devonian mature back-arc basin existed on northeastern Hainan Island, as a part of the Jinshajiang-Ailaoshan-Song Ma-Hainan back-arc basin system. Therefore, the Chaotanbi eclogites are a fingerprint of the opening and closure of the eastern Paleo-Tethyan Ocean.
Late DevonianEclogite protolithMature back-arc basinHainan IslandPaleo-Tethys
Xiaochun Liu、Yi Chen、Mengmeng Xia
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Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
NSTL
