小兴安岭西北部达音河岩体主要由碱长花岗岩、正长花岗岩组成.碱长花岗岩的锆石LA-ICP-MS U-Pb定年结果为304.4±1.3 Ma,时代属于晚石炭世,而不是过去认为的晚侏罗世.该岩体化学组成以高硅、钾、钠,低钙为特征,富集Rb、La、Th等大离子亲石元素,亏损Ba、Sr、Eu等大离子亲石元素和Nb、Ta、Zr高场强元素,反映斜长石作为源区残留相对岩浆地球化学特征的控制.该岩体同区域上十二站、新开岭、龙镇、扎兰屯等岩体构成晚石炭世造山后伸展背景下形成的I型和A型花岗岩带,反映了兴安、松嫩块体在晚石炭世结束块体碰撞造山,转入造山后伸展环境.%The Dayinhe intrusion, located in the northwest of the Xiao Hinggan Mountains, is mainly composed of alkali-feldspar granite and syenogranite. Zircon U-Pb age obtained by LA-ICP-MS analysis of the alkali-feldspar granite is 304.4 ±1.3 Ma, suggesting that it intruded in the Late Carboniferous period rather than the Late Jurassic period as proposed before. Petrochemically, the Dayinhe intrusion is characterized by high Si, Na, K and low Ca. It is enriched in Rb, La, Th and depleted in Ba, Sr. Nb, Ta, Zr, implying the effect of plagio-clase as the stable residual phase in the magma source. Regionally, the Dayinhe intrusion, together with the Shierzhan, Xinkailin, Longzhen and Zhalantun granites that share the same petrologic and geochemical characteristics, forms the Late Carboniferous post-orogenic I-type and A-type granite belt in the Da Hinggan Mountains, implying the end of the collision and orogen between the Hinggan block and the Songnen block and the beginning of post-orogeic extension in this region.
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