【摘要】 岩石地球化学分析显示,那更流纹岩SiO₂含量为70.69%～73.21%,全碱（Na₂O+K₂O）含量7.54%～8.38%,且Na₂O>K₂O,Al₂O₃=11.94%～13.11%,A/ANK>1.1,岩石属于高钾钙碱性准铝质系列;岩石轻、重稀土元素存在一定的分馏,负铕异常明显（δEu=0.19～0.34）,相对富集Rb、Ba、Th、U等元素,亏损Sr、Ta、Nb等元素。其与伸展构造背景下地壳物质部分熔融的产物特征一致。²⁰⁶Pb/²⁰⁴Pb=18.182～18.191,²⁰⁷Pb/²⁰⁴Pb=15.572～15.585,²⁰⁸Pb/²⁰⁴Pb=38.451～38.512,表明岩浆来源于下地壳,为地壳下部岩浆经历了早期结晶分异作用的产物。更多还原

【Abstract】 Rock geochemistry shows us that Nageng rhyolite is characterized by SiO₂ content of 70.69%～73.21%, alkali（Na₂O+K₂O） 7.54%～8.38% and Na₂O>K₂O, Al₂O₃ = 11.94%～13.11%, A/ANK>1.1. The rock belongs to the high potassium and calc-alkaline quasi-aluminum series. It is enriched in LREE and Rb, Ba, Th, U and depleted in Sr, Ta, Nb with negative Eu anomalies（δEu=0.19～0.34）. The characteristics is the same as in partially-fused crust of the context of extensional tectonics. We know about ²⁰⁶Pb/²⁰⁴Pb=18.182～18.191, ²⁰⁷Pb/²⁰⁴Pb=15.572～15.585, ²⁰⁸Pb/²⁰⁴Pb=38.451～38.512. All show that magma comes from the lower crust and it experiences the early crystallization differentiation.更多还原