黑龙江省东部东风山岩群岩石学特征及时代探讨

Discussion on the petrological characteristics and age of Dongfengshan group complex in the eastern part of Heilongjiang Province

采自黑龙东省东部晨明地区亮子河铁矿磁铁石英岩围岩红柱石斑点板岩样品中的锆石大多数呈椭圆状-圆状,多数具岩浆生长环带,具有岩浆成因的特点,部分锆石岩浆生长环带不清晰,可能与后期的变质作用有关。锆石测年结果表明:25颗锆石年龄数值多数位于谐和线上或附近,年龄均大于727 Ma,并获得一组谐和年龄为(739.3±4.8)Ma,该年龄应该是东风山岩群沉积时代的下限。由于该区东风山岩群被下古生界地层西林群角度不整合覆盖,由此基本可以判定东风山岩群形成时代为新元古代。笔者通过对该区东风山岩群的岩石学特征进行了叙述,进而与佳木斯地块兴东岩群进行了对比。对松嫩地块表壳岩的构造属性进行了探讨,为研究松嫩地块及黑龙江省东部大地构造提供了新的资料。

Most zircon from the slate with andalusite spotted of magnetite-quartzite wall rock in Liangzihe iron deposit of Chenming area in the eastern part of Heilongjiang Province are elliptical-circular shape, mostly with magmatic growth zoning, characteristics of magmatic origin, magmatic growth zoning of some zircon is not clear, these may be related to later metamorphism. Zircon dating results show that numerical values of 25 zircons dating are mostly located on or near the concordant curve, the age were more than 727 Ma, there was a set of concordant ages（739.3± 4.8） Ma, the age should be the earliest age of Dongfengshan group complex deposition times. The Dongfengshan group complex formed during the Neoproterozoic era, because Dongfengshan group complex in region was covered by Xilin Group of The lower Paleozoic erathem in the form of angular unconformity. Based on the discussion of petrological characteristics of the Dongfengshan group complex and compared with the Xingdong group complex in Jiamusi diastrophic activity block. Tectonic attribute of Songnen block supracrustal rocks are discussed, provided new data for the study on the Songnen block and Eastern Heilongjiang Province tectonic.