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新疆阿尔泰苏普特一带中泥盆统阿勒泰组为一套以玄武质岩石为主的双峰式火山岩组合,下部以变质玄武岩为主,夹少量流纹岩,中部以变质玄武岩、玄武质凝灰岩、沉凝灰岩为主,夹少量酸性火山岩及其碎屑岩,上部流纹质岩石有所增加。玄武质岩石往往变质为角闪片岩、绿帘阳起石片岩等,属拉斑玄武岩系列,低SiO2、K2O,高Ti,富Na、Rb、Ba、Th、U等,轻稀土略富集,无明显铕异常,Nb负异常明显,相似于MORB和岛弧型玄武岩的某些特征,与弧后盆地玄武岩的特征基本一致。流纹质岩石属钙碱性系列,高SiO2,低K2O,为钠质型;大离子亲石元素富集,具明显的Nb、P、Ti负异常和弱的Th正异常,Sr含量较低;稀土元素含量较高,∑REE为135.67×10-6～407.71×10-6,轻稀土略富集,(La/Yb)N为2.55～3.73,铕负异常较明显,δEu值为0.34～0.54。流纹质岩石地球化学特征也与典型弧后盆地双峰式火山岩中的流纹岩相似。结合区域资料分析,苏普特双峰式火山岩是阿尔泰南缘俯冲撕裂型裂谷盆地演化晚期局部形成的类似于弧后环境的产物。
The Middle Devonian Aletai Formation in the Altay Supert area, Xinjiang is a bimodal volcanic assemblage dominated by basaltic rocks. The lower part is dominated by metamorphic basalts with a small amount of rhyolite and the middle part is composed of metamorphic basalts, basaltic tuffs, Sedimentary limestone, with a small amount of acidic volcanic rocks and their clastic rocks, the upper rhyolitic rocks have increased. The basaltic rocks are often metamorphosed into hornblende and green glauconitic schist, belonging to tholeiitic basalt series with low SiO2, K2O, high Ti, Na, Rb, Ba, Th and U, There is no obvious europium anomaly, and the negative Nb anomaly is obviously similar to some features of MORB and island arc basalts, which are basically the same as those of the basalt in the back-arc basins. The rhyolitic rocks are calc-alkaline series with high SiO 2, low K 2 O and sodium type. Large ionophilic lithofacies are enriched with obvious negative anomalies of Nb, P and Ti and weak Th positive anomalies with low Sr content ; REE content is high, ΣREE is 135.67 × 10-6 ~ 407.71 × 10-6, light rare earth is slightly enriched, (La / Yb) N is 2.55 ~ 3.73, the negative anomalies of europium are more obvious, the δEu value is 0.34 ~ 0.54. Rhyolite rocks are also geochemically similar to rhyolite in bimodal volcanics of a typical back-arc basin. Combined with regional data analysis, the Supute bimodal volcanic rocks are similar to the post-arc environment in the late evolution of the subduction-prone rift basins in the southern margin of Altay.