The Longshoushan group and Maxianshan group are mainly distributed in the stretches of Mts. Longshoushan and Maxianshan. The Longshoushan group is primarily composed of schists and gneisses partly with migmatization, originated from clastic rock, carbonate and intermediate-basic volcanic rock which were mesometamor-phosed afterwards. And the Maxianshan group which is characterized by the predominance of gneisses seems to be more strongly migmatized. According to iso-topic age determination the calciphyre in the lower part of Longshoushan group has been calculated as 1479 m.y., the Baijiazui gneissic granite intruded in the Longshoushan group has an age of around 1718-1786 m.y., and the pegmatitic granite has been dated at 1740 m.y. Both the two groups are overlain disconformably by the fossili-ferous Sinian rocks and, therefore, can be regarded as Pre-Sinian.
. 1975, 甘肃龙首山区及马衔山区前震旦纪地层简介. 地质科学, 10(1): 56-64.
. A BRIEF INFORMATION ABOUT PRE-SINIAN STRATA OF THE REGIONS MTS. LONGSHOUSHAN AND MAXIANSHAN, KANSU PROVINCE[J]. Chinese Journal of Geology, 1975, 10(1): 56-64.