Abstract:

Non-metal deposits are commonly found in continental volcanic sedimentary rock series in the coastal area of China, which were formed during Jurassic and Cretaceous. They usually occurred as stratiform orebodies or stratiform-like orebodies with relatively stable thickness and grade along volcano-sedimentary sequence, not affected by faults nor by subvolcanic intrusions. In the same area, these are several metallogenetic cycles closely related to ore-bearing structures and volcanic apparatus. Ore-bearing rocks are sedimentary volcanic pyroclastic rocks altered by aqueous or hydrothermal solutions and indicated by typical structures, such as quench-cracks of quartz, ripped vitroclastic in the matrix, as well as change in chemical compositions, so they are different from ‘dry’ volcanic pyroclastic rocks formed on land. The controlling conditions of non-metal deposits are as follows: mineralization temperature is about 50-100 ℃; pressure is below n×10⁵ Pa; pH value varies from one type to another and increases in the following sequence: alunite→kaolinite→pyrophyllite→illite→bentonite →zeolite, from acid to alkali.Bring into and leaching out of rock-forming components can be found. Ore-bearing minerals account for about 30%-50% or above.

Key words: volcanic sedimentary rock series, non-metal deposits, geological characteristic, controlling condition