A study on the geochemical characteristics and petrogenesis of Holocene volcanic rocks in the Tengchong volcanic eruption field, Yunnan Province, SW China
云南腾冲全新世火山岩地球化学特征及其成因

Studies of major element,trace element and Sr-Nd-Pb isotopic compositions of the Holocene volcanic rocks in the Tengchong volcanic eruption field,including Heikongshan,Dayingshan and Maanshan volcanic rocks,indicate they are high potassium calc-alkaline series rocks including trachybasalt,basaltic trachyandesite,trachyandensite,and dacite.These rocks are enriched in LILE and LREE,and depleted in Nb-Ta-Ti in mantle-normalized incompatible trace element patterns.They have relatively high 87Sr/86 Sr(0.705862 ～ 0.710614),low 143 Nd/144 Nd(0.511941 ～ 0.512526) and relatively high radiogenic Pb isotopes(208 Pb/204 Pb = 38.962 ～39.155,207Pb/204Pb =15.620 ～15.659 and,206Pb/204Pb =17.872 ～18.269).The geochemical characteristics of the Holocene volcanic rocks in the Tengchong volcanic eruptive field indicate that the magma sources of Heikongshan,Dayingshan,Maanshan are from enriched mantle which possibly resulted from palaeo-oceanic crust subduction.The magma sources of these three volcanoes are same but with different evolution stage.The magma evolution of Dayingshan is higher than that of Heikongshan and Maanshan.The comparison with geochemical characteristics of post-collisional K-rich rocks in South Tibet shows that the magma sources of Holocene volcanic rocks in the Tengchong volcanic eruption field and post-collisional K-rich rocks in South Tibet are different.