Research progress of the division and correlation of the Precambrian metamorphic strata in Heilongjiang Province

Precambrian strata in Heilongjiang province are widely distributed with sporadic surface outcrops. Based on the comprehensive analysis of the Precambrian stratigraphic chronology, sedimentary formation and ore deposits hosted in the strata, the division and correlation results of the Precambrian metamorphic strata in this area are summarized. Zircon dating of Precambrian metamorphic rocks and Paleozoic strata in this area yield more Archean and Paleoproterozoic harmonic ages, and that of Paleozoic igneous rocks gives Archean and Paleoproterozoic harmonic ages. In addition, the Precambrian metamorphic basement in Heilongjiang Province is mainly the Meso-Neoproterozoic strata, and typical ferrosilicon formation, khondalite series or graphitic series that can be compared regionally are well developed in the sedimentary metamorphic iron deposits and the medium-large graphite deposits hosted in the strata. Based on the 1:250000 regional geological survey and related scientific research results in recent years, the Paleproterozoic surfaee rocks are demarcated in the Ergun Block. The late Archean Mashan Group, Paleoproterozoic Xingdong Group, Dongfeng Mountain Group and Xinghuadukou Group determined in "the regional geology of Heilongjiang province" are revised as rock groups. According to the regional geological survey, high-precision dating, typical formation types and metamorphic degree, the age is determined as Meso-Neoproterozoic. Meanwhile, based on the formation and characteristics of iron deposits, the Tadong Group is divided in the Ning'an area, which provides stratigraphic data for the study of Precambrian geology in Heilongjiang Province.