A REVIEW OF THE REGIONAL GEOLOGICAL SURVEYS AND MAIN ACHIEVEMENT IN 1986

Nationwide 1: 1. 000, 000-scale regional geological survey work has been in the main completed except for the geological reports on the Rutog and Gadak Sheets of Xizang （Tibet） that are being compiled. With regard to 1:200, 000- scale regional geological surveys, mapping continues to be conducted at present in Heilongjiang, Nei Monggol （Inner Mongolia）, Xizang, Qinghai and Xinjiang. 55, 900 sq km of mapping was completed in 1986 and thus the total cumulative area mapped in the whole of China reaches 6, 403, 800 sq km, accounting for about 66. 7% of the territory of the country. As to the regioual geological survey work on a scale of 1: 50, 000, 82. 400 sq km of mapping was accomplished in 1986, which was more than double that of 1984. This figure includes 24, 600 sq km of regional surveys in urban areas. The compilation of the "Regional Geology" of various provinces （municipalities or regions） is proceeding rapidly. By the end of 1986, 18 provinces （municipalities or regions） have finished the task of compilation and these monographs. will be published and distributed. In respect of the study of basic geology, a lot of achievements were made in the stratigraphical study in various parts of China in 1986. Many new fossils were for the first time found, thus establishing or revising stratigraphical systems of various regions. A group of new achievements were obtained in aspects of the definition of the Carboniferous-Permian-Triassic boundaries, phenomena of biotic mixing, etc. In sedimentary areas, the data about sedimentary facies and the results of their study increased steadily; in Mesozoic volcanic areas, the study of volcanic edifices was deepened continuously; in metamorphic areas, the study on deformation structures, metamorphism and isotope geology was strengthened daily, which has played an important role in correctly recognizing the strati- graphical sequence and structures, probing mechanisms for ore formation and guiding prospecting and exploration of mineral deposits in metamorphic areas; in granite areas, unit-superunit trial mapping was carried out in selected places. According to the preliminary statistics, 640 new anomalies of various sorts and 150 new ore occurrences （mineralizations） were discovered through regional geological surveys on various scales in 1986. 350 ore deposits and occurrences （mineralizations） were reconnoitered and evaluated and 200 localities of anom- a1ies were checked. The above-mentioned work and achievements bave provided a lot of important information for mineral prospecting and exploration in the future.