内蒙古中部大青山—乌拉山地区早前寒武系研究的重要进展及对高级变质区开展地层工作的几点建议

Major progress in Early Precamhrian research in the Daqing Shan-Wula Shan region, central Inner Mongolia, China, and some suggestions for stratigraphic work in high-grade meta-morphic areas.

介绍了1996—2003年期间,通过内蒙古大青山—乌拉山地区1∶5万和1∶25万区域地质调查,在本区早前寒武纪地层尤其是高级变质地层研究方面取得的重要进展。这些进展是:重建了一个由4个岩群12个岩组构成的早前寒武纪地层系统;发现了枣儿沟角度不整合面和新建了古元古代的美岱召岩群;提出了适合高级变质地层发育区地层工作的“构造-岩层-事件法”的工作思路和方法。在这一思路和方法指导下,明确了本区构造样式演化与高级区地层系统重建的关系,提出了主期构造决定岩石地层现今展布特征,早期构造造成地层组成、结构特征、空间叠置及接触关系性质,后期构造导致区内高级变质地层局部复杂化和再造的基本规律性的认识。最后对高级区开展地层研究提出4点建议。

Some progress has been made in the study of Early Precambrian strata, especially high-grade metamorphic strata, in the Daqing Shan-Wula Shan region, Inner Mongolia, through 1：50000 and 1：250000 regional geological surveys from 1996 to 2003. The progress may be summarized as follows： an Early Precambrian stratigraphic system composed of 4 group-complexes and 12 formation-complexes has been re-established; the Zao＇ergou unconformity has been found and the Paleoproterozoic Meidaizhao Group-complex newly established; and a work idea and method of the ＂tectono-lithostradgraphic-event＂ suitable for the stratigraphic work in areas of high-grade metamorphic strata have been proposed. Under the guidance of the work idea and method, the authors ascertain the relationship between the evolution of the tectonic styles and reconstruction of the stratigraphic system in high-grade areas and propose the ideas that the tectonics in the main phase controlled the present distribution characteristics of the lithostratigraphic units, that the early-phase tectonics formed the present composition, structural characters, spatial superimposition and contact relationships of the lithostratigraphic units and that the late-phase tectonics locally complicated and reconstructed the high-grade metamorphic strata in the region. At last, four suggestions about how to carry out the lithostratigraphic research in high-grade areas are put forward.