内蒙古八道卡石英闪长岩单颗粒锆石U-Pb年龄及其地质意义

UPb AGE OF MONOMINERAL ZIRCON OF BADAOKA QUARTZ-DIORITE IN INNER MONGOLIA AND ITS SIGNIFICANCE

位于黑龙江上游南岸内蒙古八道卡石英闪长岩体,地处蒙古-鄂霍茨克构造带南侧的额尔古纳地块北缘。地球化学分析结果表明,八道卡石英闪长岩为形成于火山弧环境的花岗岩类。八道卡石英闪长岩单颗粒锆石UPb年龄为(254±4)Ma,表明它是晚古生代末期岩浆活动产物。结合区域构造环境认为八道卡石英闪长岩形成于滨南蒙古-鄂霍茨克陆弧环境。

The Badaoka quartzdiorite,located at the southern bank of the upper reach of the Heilongjiang River, northeastern Inner Mongolia, is situated in the northern margin of Ergun massif in the southern part of the Mongol-Okhotsk tectonic belt (collision zone of the Siberian and Mongol-Chinese continents). The results of geochemical analysis of indicates the Badaoka quartzdiorite is a granitoids related to a volcanic arc. UPb isotopic age of monomineral zircon from the Badaoka quartzdiorite is dated at (2 54±4) Ma. It suggests the Badaoka quartzdiorite is a product of late Paleozoic magmatic activity. Based on the data mentioned above and regional tectonic setting, the quartzdiorite under study is considered as being formed in southern continental volcanic arc of the Mongol-Okhotsk Ocean.