安徽中部燕山期富钾岩浆岩系的成因及其对成矿作用的制约

Genesis of Yanshanian K-rich magmatic rock series in central Anhui and its constraints on mineralization

安徽中部大别山地区和下扬子地区燕山期岩浆岩富K、大离子亲石元素,亏损高场强元素Nb、Ta岩浆从早到晚的演化趋势为:高钾钙碱性—钾玄岩系列→钾玄岩系列→双峰式岩浆岩或者A型花岗岩,表明大别造山带和下扬子地区在燕山期处于同一个构造-岩浆活动区。大别地区富K岩系的源区与富集地幔密切相关,下扬子地区的则与下地壳有更多亲缘关系。岩浆源区的不同是造成大别地区和下扬子地区成矿作用重大差别的根本原因。

Yanshanian magmatic rocks in the Dabie area and lower Yangtze Valley area in central Anhui are enriched in large-ion lithophile elements and depleted in the high-field strength elements Nb and Ta. The magma exhibits an evolutionary trend from the high-K calc-alkaline-shoshonitic series in the early Yanshanian→shoshonitic series→bimodal magmatic rocks or A-type granite in the late Yanshanian, which suggests the Dabie orogen and the lower Yangtze Valley area were located in the same tectonomagmatic area in the Yanshanian. The source area of K-rich magmatic rocks in the Dabie area is closely related to the enriched mantle, while the rocks in the lower Yangtze Valley area are more affined to the lower crust. The difference in magma source area is the fundamental cause for the appreciable difference in mineralization between the Dabie area and the lower Yangtze Valley area in the Yanshanian.