对松嫩地块东部小兴安岭和张广才岭地区前寒武纪变质岩系中东风山群亮子河组石榴子石黑云母片岩,以及张广才岭群红光组的蚀变红柱石二云母片岩进行了锆石LA-ICP-MS U-Pb测年.测年结果显示,小兴安岭晨明镇的亮子河组石榴子石黑云母片岩存在3组峰值年龄,分别为757Ma±9Ma、917Ma±10Ma和1709Ma±75Ma；张广才岭钓鱼台地区的红光组蚀变红柱石二云母片岩主要有2组峰值年龄,843Ma± 10Ma和927Ma±6Ma,此外还获得2495～1012Ma分散的古—中元古代锆石年龄.上述结果表明东风山群形成于新元古代.结合区域地层资料,可以判定东风山群为一套具有稳定陆缘沉积建造组合特征的中低级变质岩系,其原岩为一套含硼较高的泥质岩、灰岩、炭质泥岩及砂岩.认为原定张广才岭群需要解体,其中部分具有稳定陆缘沉积建造组合特征的富铝片麻岩类、富铝云母片岩类和强变形的大理岩类岩石应归属于东风山群.碎屑锆石的年龄组合特征指示松嫩地块东部存在与格林维尔期有关的新元古代变质基底.%LA -ICP -MS U -Pb dating was conducted for detrital zircon from Liangzihe Formation of Dongfengshan Group and Hongguang Formation of "Zhangguangcai Ling Group" Precambrian metamorphic rock series in eastern Songnen masiff within Xiao Hinggan Mountains and Zhangguangcai Mountain regions. Three peak ages are shown for the garnet-biotite schist of Liangzihe Formation in Chenming Township, i.e., 757Ma±9Ma,917Ma±10Ma and 1709Ma±75Ma, and two major peak ages are shown for the altered andalusite-two-mica schist of Hongguang Formation in Diaoyutai area, i.e., 843Ma±10Ma and 9271Ma±6Ma. Besides, some dispersed zircon ages from 2495Ma to 1012Ma were also found. These data indicate that the Dongfengshan Group was formed in Neoproterozoic. Combined with regional stratigraphy, the protolith assemblages of Dongfengshan Group should be a set of meso- and epi-metamorphic strata which were composed of mudstone rocks, limestone rocks, carbonaceous mudstones and sandstones with high boron content and formed in the stable continental margin. Based on field investigation, petrography, zircon U-Pb geochronology in combination with recent researches and reports on "Zhangguangcai Ling Group", the authors hold that the originally defined "Zhang-guangcai Ling Group" is not a unified integration but is made up of a series of granitic rocks and moderately to slightly metamorphosed rocks with different ages. A part of Al-rich paragneisses, Al-rich mica-schists and strongly deformed marbles of originally assigned to "Zhangguangcai Ling Group" should belong to Neoproterozoic Dongfengshan Group. The zircon U-Pb dating results indicate that the rocks mainly exposed in the source region of these metamorphic rocks include Grenvifle phrase rocks related to Rodinia supercon-tinent formation.
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