大兴安岭中段突泉盆地玛尼吐组火山岩地球化学特征及成因

突泉盆地玛尼吐组安山岩位于内蒙古东部兴安盟突泉县，大地构造位置属华北板块北缘晚古生代陆缘增生带，大兴安岭构造岩浆岩带中段.安山岩样品的SiO₂、Al₂O₃、Na₂O、K₂O含量分别为60.64%~64.36%、15.84%~17.38%、3.76%~5.30%、2.44%~3.81%，为过铝质、高钾钙碱性岩石，轻稀土元素富集，重稀土元素亏损，无Eu异常和Ce异常，富集大离子亲石元素（Rb、K、Ba、LREE）和化学性质活泼的不相容元素（U、Th），相对亏损高场强元素（Nb、Ta、P、Ti）和重稀土元素（如Y、Yb、Lu）.原始岩浆来源于地壳岩石部分熔融源区，是蒙古-鄂霍次克洋闭合后岩石圈伸展环境下的产物.

PETROGEOCHEMISTRY AND GENESIS OF THE VOLCANIC ROCKS OF MANITU FORMATION IN TUQUAN BASIN,MIDDLE DAXINGANLING MOUNTAINS

The andesite of Manitu Formation in the Tuquan Basin, Eastern Inner Mongolia, is tectonically located in the middle section of Daxinganling tectonomagmatic belt, in the Late Mesozoic continental marginal accretion zone on the northern margin of North China Plate. Study of petrogeochemistry indicates that the andesite is characterized by high silica (with SiO₂ of 60.64%-64.36%) and alumina (Al₂O₃ 15.84%-17.38%), and medium alkali (Na₂O 3.76%-5.30%, K₂O 2.44%-3.81%), belonging to peraluminous high potassium calc-alkali rock. The chondrite standard curve of rare earth elements reveals an enrichment of LREE and deficit of HREE, without Eu and Ce anomaly. The andesite is enriched in LILE (such as Rb, K, Ba and LREE), mobile incompatible elements (such as U and Th), relatively depleted in HFSE (such as Nb, Ta, P and Ti) and HREE. The primitive magma of the andesite is derived from the partial melting of the crust, as the result of the closure of Mongolia-Okhotsk Ocean in the extensional environment of the lithosphere.