Section 20
Chapter 19,028

Geologic-tectonic evolution and tectonic control of polymetallogenic belt in the northern margin of the northern China Platform

Wang Dongfang

Mineral Deposits = Kuangchuang Dizhi 6(3): 1-9


Accession: 019027505

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The Proterozoic strata in the northern margin of the North China Platform may be divided into three tectonic types. These depsoits were all formed during the period of 1800-1500 Ma, with the stromatolites of the Conophyton and Kussiella association being observed above and beneath the ore bed. They belong to stratiform deposits characterized mainly by layered orebodies, produced at a certain stage of geologic evolution. Observations show that all of these deposits possess similar ore-bearing rock systems. There are clastic rocks, turbidite shale and shale in the lower part which gradually grade into phosphorous-bearing, carbon-bearing formation in the middle part, with polymetallic deposits existing within the transitional part from lutite to chemical sedimentary rocks (dolomites). The great thickness of ore-bearing formation with polycycles seems to have favored the accumulation of ore resources. It is worth noting that this kind of deposit almost always occurs in a fault-depression belt where faults simultaneous with mineralization lead to the formation of ore-controlling basins, of which the second class basins and, especially, the third class ones are the main positions controlling ore deposits. They are distributed along the margin of the ancient uplift. The parallel-grown faults resulted in the condition of reduction and low energy, and caused the heavy brine to flow into them. After the formation of ore deposits, this kind of confined basin is best able to preserve ore-bodies during the long period of geologic-tectonic activities. The study of this sort of fault-depression belt and fault basin on one side of the ancient uplift, therefore, is of key importance in prospecting for polymetallic deposits along the northern margin of the North China Platform.

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