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鄂拉山岩浆岩地处东昆仑、西秦岭、南祁连造山带交汇部位,内部结构复杂,是中国西部重要的构造结和矿集区之一。海相火山岩出露广泛,岩石类型主要由杏仁状玄武安山岩、杏仁状安山岩、安山质火山角砾岩、安山质晶屑岩屑凝灰岩、安山质角砾凝灰熔岩及英安岩、流纹岩等组成,以火山地层、夹层状、透镜状等形式赋存于洪水川组索拉曲砂岩、幸福村细浊积岩、河卡山粗浊积岩中,属海相喷发环境的产物。火山岩岩石化学成分与岛弧钙碱性安山岩平均化学成分相似,δEu平均为0.75,显示为弱负异常,(La/Sm)N、(Gd/Yb)N值平均分别为5.09、1.76,轻重稀土元素之间分馏程度显著,轻稀土元素分馏程度较高且富集。Ba、Rb、Th元素强烈富集,Ti、Cr等元素较亏损。Th×Ta/Hf2值在0.029～0.162,平均为0.079,具有陆缘火山弧的特性。由上所述,洪水川组火山岩产于碰撞后的拉伸环境。
Elakon magmatic rocks are located in the intersection of East Kunlun, West Qinling and South Qilian orogenic belts with complicated internal structure and are one of the important tectonic knots and ore-gathering areas in western China. Marine volcanic rocks are widely exposed. The rock types are mainly composed of almond basaltic andesite, almond-shaped andesite, Anshan volcanic breccia, ananitic clastic tuff, andesite breccia tuff, and dacite, Rhyolite and other components of the volcanic strata, disseminated, lenticular and other forms occur in the Hongshuichuan Formation Soraxo sandstone, happiness village turbidite, Hekaoshan coarse turbidite, marine eruption of the environment product. The chemical composition of volcanic rocks is similar to the average chemical composition of island arc calc-alkaline andesite. The δEu average is 0.75 and shows weak negative anomalies. The values of (La / Sm) N and (Gd / Yb) N average 5.09 and 1.76, respectively. Significant fractional distillation between elements, light fractionation of higher levels of rare earth elements and enrichment. Ba, Rb, Th elements strongly enriched, Ti, Cr and other elements more loss. Th × Ta / Hf2 values range from 0.029 to 0.162 with an average of 0.079, which has the characteristics of a continental volcanic arc. As mentioned above, the volcanic rocks of the Hongshichuan Formation are produced after the collision.