REGIONAL MINEROGENETIC ANALYSIS OF LOWER CAMBRIAN SEDIMENTARY ORE DEPOSITS IN GANSU

The lower Cambrian ore-bearing sequence in Gansu may be divided into two minerogenetic series: （ 1 ） the multi-element （V, U, P, Mn, REE, Fe, I, Mo, Co, Ni, Zn, Ag, etc.） minerogenetic series in a marine black shale formation, and （ 2 ） the P （and REE） minerogenetic series in a marine mottled terrigenous clastic rock formation and a transitional formation from clastic rocks to carbonate rocks. The former series is distributed in the Beishan Mountains area and the eastern part of the Lunshoushan Mountains area. The rocks in the formation mainly include carbonaceous matter-rich black shale（slate）, black carbonaceous fine sandstone and carbonaceous—pelitic siliceous rocks, which were formed in a relatively stable shallow-sea basin in a warm-humid climatic zone. The latter series is distributed in the Pingliang Mountains area and the eastern part of the Longshoushan Mountains area. The rocks in the formation consist mainly of mottled conglomerate, sandstone, sliltstone and sandy limestone, which were formed in an oxidized （?）nvironment in a dry-hot climatic zone. The sea basin was unstable. The specific ore-controlling characteristics of the ore-bearing sequence are as follows: （ 1 ） P and Mn ores mainly occur on ancient erosion surfaces; （2）black shale plays an active role in the concentration of U, V and their associated usable elements; （ 3 ） ore deposits mainly occur in the ancient near-E-W-trending elliptic ring structure.