Age and origin of Mid-Pleistocene volcanic rocks from Qushi in Tengchong area, western Yunnan Province: SHREMP zircon U-Pb dating and constraint from Hf-in-zircon isotopes

作者：Li LinLin^*; Wang ShuBing; Liu JianHui; Shi YuRuo

来源：Acta Petrologica Sinica, 2015, 31(9): 2609-2619.

• Cenozoic volcanic rock
• SHRIMP zircon U-Pb age
• Hf isotope
• Mid-Pleistocene
• Magmatic origin
• Qushi in Tengchong

This paper reports U-Pb age and the geochemical characteristics of volcanic rocks from Qushi in Tengchong area. Mid-Pleistocene age (0. 41 +/- 0. 01 Ma) of zircons in dacite (TC7) is yielded using SHRIMP in Beijing SHRIMP Center, which is the youngest high sensitive zircon U-Pb age in China by now. Whole rock analyses of major, trace elements for these rocks indicate they are high-K calc-alkaline series rocks including trachybasalt, basaltic trachyandesite, trachyandensite, trachyte and basalt, andesite, dacite. These rocks are enriched in LILE, LREE and low HFSE relatively, such as Nb, Ta, Ti. They have high Th/Nb values normalized by the primitive mantle and low Nb/La (< 1) and Nb/U (3 similar to 13). They are rich in Zr and have high Zr/Y values relatively, which are different from those of typical island arc volcanic rocks. Hf analyses carried out on zircons in TC7 yield epsilon(Hf)(t) values ranging from -11. 0 to -1. 5 and t(DM2) modal age of 951 similar to 1437 Ma, which is much larger than its real age. These geochemical features of the Tengchong volcanic rocks show an affinity with contaminated continental basaltic rocks. The volcanoes in Tengchong area erupted in an intraplate tectonic setting and their magma sources may have been strongly contaminated by large-scale crustal materials.

• 出版日期2015-9
• 单位中国地质科学院; 中国地质科学院地质力学研究所