内蒙古滴水沟闪长岩体地球化学特征及其地质意义

滴水沟闪长岩体位于华北板块北缘西段狼山构造带。结合前人的锆石U Pb测年资料，可确定其形成于晚石炭世—早二叠世早期。岩石学及地球化学分析显示岩体属钙碱性系列，相对富集Rb、Ba、Th、K、P等大离子亲石元素，亏损Nb、Ta、Ti等高场强元素，具有低Rb/Sr(005～010)值、高Ba/Rb(1145～2216)值，且A/CNK＜11；REE含量显示，滴水沟闪长岩体为轻稀土富集型，轻、重稀土元素高度分异，轻稀土元素发生明显的分馏作用，铕异常不明显(δEu=092～113)，反映了俯冲带岩浆岩的特征，推测其物质来源为幔壳混源型。结合区域构造演化，认为其形成于活动板块边缘(碰撞前)火山弧环境，与晚石炭世晚期古亚洲洋板块向华北板块北缘西段的俯冲有关。

Geochemical Characteristics of Dishuigou Diorite in Inner Mongolia and Its Geological Significance

The Dishuigou dioritic intrusion is located in the Langshan arc at the northern margin of the North China Craton (NCC), Inner Mongolia. It is emplaced in the Late Carboniferous Early Permian according to the previous zircon U Pb dating data. In this paper, the major and trace (including rare earth) elements composition of the Dishuigou diorite are reported. The result shows relatively enriched in large ion lithophile elements (LILE) such as the Rb, Ba, Th, K, and P, and depleted in high field strength elements (HFSE) such as the Nb, Ta, and Ti, and high Rb/Sr (005-010) and Ba/Rb (1145-2216) values, and low A/CNK (<11). In combination with the strong fractionation REE (LREE/HREE=297-331) and LREE (La/Sm=275-357), and insignificant Eu anomalies (δEu=092-113), suggesting the dioritic intrusion formed in an arc environment and derived from mantle melt mixed with crust material during ascending. It is concluded that the southward subduction of the paleo Asian oceanic slab in Late Carboniferous Early Permian resulted in the formation of the Dishuigou dioritic intrusion based on the regional evolution the Langshan arc.