黑龙江塔溪地区晚古生代后造山花岗岩特征及其地质意义
Characteristics and Geological Implications of the Late Paleozoic Postorogenic Granite in Taxi Area of Heilongjiang

摘要： 摘要：位于兴蒙造山带东端的黑龙江塔溪地区花岗岩主要岩石类型为二长花岗岩和正长花岗岩，锆石UPb( LAICPMS)同位素测年结果为295～285 Ma，表明形成于晚古生代。岩石地球化学以弱过铝质、中—高钾为特征，总体表现为：高钾钙碱性系列，轻稀土元素富集，重稀土元素相对亏损，弱—中等δEu负异常，大离子亲石元素(LILE)Rb、La富集，Ba、Sr亏损，高场强元素(HFSE)Ce、Zr、Hf、Th富集，Nb、Ta亏损。推测花岗质岩浆曾发生壳幔混染作用，有更多壳源物质参与，显示后造山I型花岗岩特征。认为花岗岩形成于挤压向伸展转换的后造山环境，为兴安地块与松嫩地块碰撞拼合的后造山阶段产物。
Abstract: Abstract:The granites in Taxi area, located in the east of the Xingmeng orogenic belt,are mainly composed of syengranite and monzogranite.The zircon UPb( LAICPMS) age analyses from the granites is from 295 to 285 Ma,suggesting that it is the production of Late Paleozoic.According to macroscropical evidences it shows that the studied granite is weakly peraluminous,with middle to high K and the high K calcalkaline series,and that the result of the samples are enriched in light rare earth elements and depleted in heavy rare earth elements with weakly to moderate pronounced Eu anomalies. Evidences of the trace elements show that it is enriched in Rb,La and depleted in Ba,Sr of the LILE and enriched in Ce,Zr,Hf,Th and depleted in Nb,Ta of the HFSE. It is indicated that granitic magma crust and mantle contamination had occurred, with the participation of more crust source material, displaying the characteristics of postorogenic I type granite. We concluded that the granites formed in extruded to stretch conversion postorogenic environment,and that it is the product of postorogenic evolution after the collision of Xingan Block and Songnen Block