| 琼中古-中元古代变基性火山岩地球化学特征及其地质意义 |
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| 关键词:Paleo-Mesoproterozoic K-rich meta-basic volcanics geochemistry mantle metasomatism Qiongzhong |
| 基金项目:中国地质调查局国土资源大调查项目(编号:20013900018) |
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| Geochemical Characteristics of the Paleo-Mesoproterozoic Meta-Basic Volcanics in Qiongzhong, Hainan Island, and Their Geological Implications |
| The protoliths of the plagio-amphibolites and plagio-amphibolic gneisses in Baoban Group from Qiongzhong, Hainan island, are K_rich metamorphic basic and medium_basic volcanics. Chemically, they are characterized by the enrichment of potassium (K_2O/Na_2O values higher than 0.6) and aluminum (Al_2O_3 contents higher than 15%), and depletion of titanium (TiO_2 contents lower than 1.3%). They have high LILE (such as K, Rb, Ba, Th, etc.) and LREE concentrations and relatively high LRREE/HREE values, and display clear negative Ta, Nb and Ti anomalies. Geochemical characteristics of trace elements and Sm_Nd isotopes indicate that the magma source areas were somewhat away from the primary mantle, and did not suffered from significant contamination by the evolving continental materials. They were formed by partial melting of the mantle wedge above the subduction zone in the continental arc area that had been subjected to the metasomatism of the fluids and silicic melts released by the subduction oceanic shell. The Hainan block might have suffered a geodynamic shifting from extension" to squeezing" in the Paleo_Mesoproterozoic period, leading to the formation of the oceanic_ridge type and oceanic_arc transitional type tholeiites in western Hainan at the early extension stage and the K_high calc_alkaline basalts in the Qiongzhong area at the middle_late subduction stage. This shifting process was probably related to the splitting of the South China continent and the subsequent subduction of the oceanic shell to Cathaysia. |
| XU De-ming,XIE Cai-fu,ZHANG Ye-ming,FU Tai-an,LI Zhi-hong.2006.Geochemical Characteristics of the Paleo-Mesoproterozoic Meta-Basic Volcanics in Qiongzhong, Hainan Island, and Their Geological Implications[J].Acta Geoscientica Sinica,27(3):227-234. |
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