内蒙古德言其庙斜长角闪岩系年代学、地球化学特征及其地质意义

Geochronological,Geochemical Characteristics and Geological Significance of Deyanqimiao Amphibolite Series in Inner Mongolia

德言其庙斜长角闪岩系位于内蒙古中部温都尔庙地区以东，构造位置处于华北板块北缘温都尔庙俯冲-增生杂岩带内。对德言其庙斜长角闪岩系进行了地球化学分析和锆石SHRIMPU—Pb定年。结果表明：斜长角闪岩系SiO2质量分数为51．62％～55．60％，Al2O3为16．45％～17．78％，全碱质量分数（4．5％-5．12％）较低；斜长角闪岩系具有钙碱性系列岩石地球化学特征，原岩为辉长质和辉长闪长质侵入岩；锆石n（206Pb）／n（238U）年龄加权平均值为（490．3±4．6）Ma；岩石富集轻稀土元素，轻、重稀土元素质量分数比值为5．93～7．73，Eu异常（0．84～1．05）不明显，具有明显的Nb、Ta负异常及Ti、P亏损，显示出其原岩具有消减带岩浆的特征，形成于岛弧构造环境。

Deyanqimiao amphibolite series is located in the eastern of Ondor Sum area, the central of Inner Mongolia. The structural location is in Ondor Sum subduction-accretionary complex zone, the northern margin of North China Plate. Geochemical characteristics and SHRIMP zircon U-Pb dating of Deyanqimiao amphibolite series were analyzed. The results show that mass fractions of SiOz of amphibolite series are 51.62%-55.60%, those of A12O3 are 16.45%-17.78%, total alkali mass fractions are low, reaching 4.50%-5.12% amphibolite series has the alc- alkaline series geochemical characteristics, and the original rock is gabbroic and gabbro-dioritic intrusive zircon n （206 Pb）/n （238 U） weighted average age is （490.3± 4.6） Ma light rare earth element is rich in amphibolite with on Eu anomaly （0.84-1.05）, the ratios of mass fractions oflight and heavy rare earth elements are 5.93-7.73%amphibolite has Nb, Ta obvious negative anomaly and Ti, P loss, so that the original rock has the characteristics of subduction belt magma, and forms in island arc tectonic environment.