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马家街群分布在黑龙江省东部佳木斯地块桦南隆起的西南缘,主要由一套经历了接触变质作用的富铝、富碳沉积碎屑岩所组成。区域上,这套接触变质岩系具有变质矿物分带特征,由西向东依次出现十字石、红柱石、石榴石和黑云母。红柱石碳质板岩和石榴云母石英片岩2件样品获得的LA-ICP-MS U-Pb碎屑锆石年龄谱均显示有272~310Ma、479~533Ma和>800Ma三组年龄。根据两件样品显示的最小年龄均未小于272Ma,而且二者的最小年龄组(272~310Ma)具有类似的峰值年龄,分别为276Ma和279Ma,这限定了马家街群主体岩石沉积年龄的下限应在中二叠世之前。侵入马家街群的花岗岩的锆石年龄为259Ma,说明其接触变质作用时代为晚二叠世早期,限定了马家街群形成时代的上限。479~533Ma年龄组中,2件样品的峰值年龄分别为499Ma和522Ma,这是佳木斯地块麻山群中最为重要的高级变质和花岗质岩浆作用年龄。>800Ma的年龄组具有多个峰值年龄,说明源区(佳木斯地块)具有前寒武纪-早前寒武纪地壳。上述证据表明,马家街群是晚二叠世早期形成的一套接触变质岩系,而非前寒武纪区域变质岩系。鉴于479~533Ma的麻山群在佳木斯地块中普遍存在,说明以麻山群为代表的早古生代变质结晶岩系既是马家街群沉积的基底,也是重要的物源区;而276~279Ma的早二叠世火山岩在佳木斯地块东缘分布广泛,表明其对马家街群的沉积也具有一定的贡献。
The Majiatan Group is located in the southwestern margin of the Huanan uplift in the Jiamusi block in the east of Heilongjiang Province and is mainly composed of a set of Al-rich and carbon-rich sedimentary clastics that have undergone contact metamorphism. In the area, this metamorphic series of metamorphic rocks have metamorphic mineral zonation characteristics, followed by rubble, andalusite, garnet and biotite from west to east. LA-ICP-MS U-Pb detrital zircon ages obtained from two samples of andalusite and pomegranate mica-quartz schist all showed three ages of 272 ~ 310Ma, 479 ~ 533Ma and> 800Ma. According to the two samples, the minimum ages of all the samples are less than 272Ma, and the minimum age of the two groups (272-310Ma) have similar peak ages of 276Ma and 279Ma, which limits the lower limit of the rock age It should be before the Middle Permian. The granite intruded into Majiatou Group has a zircon age of 259Ma, indicating that the age of contact metamorphism was early Late Permian, which limited the upper limit of the age of formation of Majiatan Group. The peak ages of 2 samples in the 479 ~ 533Ma age group are 499Ma and 522Ma, respectively. This is the most important age of advanced metamorphism and granitic magmatism in the Ma Shan Group in Jiamusi Block. > 800 Ma age group has multiple peak ages, indicating that the source area (Jiamusi block) has the Precambrian-Early Precambrian crust. The above evidence shows that Majiatou Group is a set of contact metamorphic rocks formed in the early Permian, not Precambrian metamorphic rocks. Since the Mashan Group of 479 ~ 533 Ma is widespread in the Jiamusi block, it indicates that the Early Paleozoic metamorphic crystallization rocks represented by the Mashan Group are not only the basement of Majiajie Group deposition but also an important source area. However, the early 276 ~ 279 Ma Permian volcanic rocks are widely distributed on the eastern margin of Jiamusi Block, indicating that they also contribute to the sedimentation of Majiatou Group.