| 西昆仑黑伞顶新近纪次火山岩地球化学特征及成因 |
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| 关键词:subvolcanic rock Neogene c-type adakitic rock geochemistry Heisanding area west Kunlun Mountains |
| 基金项目:中国地质调查局地质大调查项目(编号：19991300009051) |
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| Geochemistry and Petrogenesis of the Neogene Subvolcanic Rocks in Heisanding Area of West Kunlun Mountains |
| Located at the juncture between the North China plate, the eastern section of west Kunlun and the South China plate, the subvolcanic rocks in Heisanding area are mainly composed of granite porphyry and have intruded into such strata as the Carboniferous Tuokuzidaban Group, the Permian Shuweimenke Formation and the Paleogene Aketashi Formation. The K-Ar age of the granite porphyry is 13.2Ma, suggesting that it was formed in Miocene. The subvolcanic rocks are characterized by low SiO2 (65.19% to 67.21%), MgO (0.83% to 1.47%), Y (8.38×10?6~18.24×10?6) and Yb (0.73×10?6~1.64×10?6), and high Al2O3 (14.53% to 16.5%), K2O (4.44% to 4.93%), Sr (528×10?6~707×10?6) and Sr/Y (38.2~63) values. K2O/Na2O=1.49~1.69, A/CNK=1.08~1.14, and σ= 2.22~3.03, implying that these rocks belong to the peraluminous high-K calc-alkalic type. The rocks are obviously enriched in LILE such as K, Rb, Th, U, and depleted in HFSE such as Nb, Ta, and Ti, with obvious negative anomalies. The total REE contents range from 307.87×10?6 to 458.20×10?6, and the LREE/HREE ratios range from 24.19 to 34.47, with the enrichment of LREE and weak to medium negative Eu anomalies. These geochemical characteristics show that the Heisanding subvolcanic rocks are high-K calc-alkaline and C-type adakitic rocks, which resulted from partial melting of the thickened continental crust in northern Tibetan plateau and were formed in an intraplate post-collision tectonic setting during Miocene. Fractional crystallization played an important role in magmatic evolution. |
| ZHANG Xiang-xin,CHEN Bi-he.2009.Geochemistry and Petrogenesis of the Neogene Subvolcanic Rocks in Heisanding Area of West Kunlun Mountains[J].Acta Geoscientica Sinica,30(3):354-362. |
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