摘要
东昆仑早石炭世火山岩主要沿昆中缝合带及其旁侧分布,岩性以玄武岩为主,之后亦有安山岩和英安岩产出,先后形成于洋脊、洋岛和岛弧构造环境。洋脊玄武岩K2O、P2O5、SiO2、REE含量和FeO/MgO比值低,钙、铁、镁高,轻重稀土元素分馏差。岛弧玄武岩硅、碱、铝和REE含量以及LREE/HREE比值高,镁、铁质低。洋岛玄武岩TiO2和P2O5高,K2O低,REE和LREE/HREE介于前二者之间。火山岩的构造背景表明,早石炭世昆中断裂带以“开”为主,形成洋脊玄武岩和洋岛玄武岩;早石炭世末转为“合”,形成岛弧型玄武岩、安山岩和英安岩。洋脊玄武岩的识别,对于研究区域构造及其演化甚为重要。
Early Carboniferous volcanic rocks in East Kunlun Mountains are distributed along Mid_Kunlun deep fault zone and consist mainly of basalts overlain by andesites and dactite. They were formed sequentially in setting of mid_ocean ridge, ocean island and island arc. The mid_ocean ridge basalt has lower K 2O, P 2O 5,SiO 2, REE, FeO */MgO and LREE/HREE values, and higher CaO, FeO * and MgO contents than the island_arc basalt. The ocean island basalt is characterized by highest TiO 2 and lowest K 2O contents, but its REE and LREE/HREE values are between values of the other two sorts of basalts. The study on the tectonic setting of the volcanic rocks shows that the Mid_Kunlun suture was dominantly in “spreading” state in Early Carboniferous, resulting in the formation of mid_ocean ridge basalt and ocean island basalt, and then evolved into “closing” state, giving birth to island_arc basalt, andesite and dacite at the end of Early Carboniferous. The identification of the ocean_ridge basalt is important to the understanding regional tectonics and its evolution.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
1998年第4期289-295,共7页
Acta Petrologica et Mineralogica
关键词
岩石分布
火山岩
地球化学
构造背景
tectonic setting
tectonic geochemistry
volcanic rocks
tectonomagmatism
Eastern Kunlun Mountains.