内蒙古额济纳旗乱石山北地区中二叠世花岗闪长岩体地球化学特征和LA-ICP-MS锆石U-Pb定年

乱石山北地区中二叠世花岗闪长岩位于塔里木板块东北缘,敦煌微板块北部。岩石地球化学特征显示其呈富铝、富钠、低钾、低镁、准铝质,属钙碱性系列,具I型花岗岩特征;稀土曲线呈右倾; Eu负异常不明显,微量元素富集Rb、K、Ba、La等大离子亲石元素,亏损Nb、Ti、P、Y等高场强元素;构造环境判别显示其为火山弧、岛弧花岗岩,岩浆源区为下地壳基性岩部分熔融的产物。LA-ICP-MS锆石U-Pb定年结果表明岩体形成于264. 8±1. 9Ma,为中二叠世。结合区域地质调查背景分析,乱石山北地区中二叠世时尚未发生板块的碰撞拼合,处于俯冲阶段的岛弧环境。

Geochemical characteristics and LA-ICP-MS Zircon U-Pb dating of the Middle Permian Granodiorite in Luanshishanbei, Ejina Banner,Inner Mongolia

The Middle Permian granodiorite in the northern part of the Quarry Mountain is located in the northeastern margin of the Tarim plate and north of the Dunhuang microplate. The geochemical characteristics of the rock indicate that it is rich in aluminum, rich in sodium, low in potassium, low in magnesium and quasi-aluminum. It is a calc-alkaline series with characteristics of type I granite. Light rare earth enrichment, light and heavy rare earth fractionation is obvious, and Eu negative anomaly is not obvious. The rare earth curve is right-dip; the trace elements are enriched with large ion lithophile elements such as Rb, K, Ba, La, etc., and depleted Nb, Ti, P, Y and other high field strength elements; the tectonic environment discriminates that it is volcanic arc, island arc granite The magma source area is a product of partial melting of the lower crust base rock. The LA-ICP-MS zircon U-Pb dating results show that the rock mass is formed at 264.8±1.9 Ma, which is the Middle Permian. Combined with the background analysis of the regional geological survey, the plated collision of the plate has not occurred in the Middle Permian of the North of the Quarry Mountain, and it is in the island arc environment of the subduction stage.