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Non-metal deposits are commonly found in continental volcanic sedimentary rock series in the coastal area of China, which were formed from late Jurassic to Cretaceous time. They usually occurred as stratiform orebodies or stratiform-like orebodies with relatively stable thickness and tenor along volcano-sedimentary sequence, not affected by faults or 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 changed in chemical compositions, so they are different from 'dry' volcanic pyroclastic rocks formed in land.
The controlling conditions of non-metal deposits are as follows: mineralization temperature was about 50-100°; pressure was below several hundred thousand Pa; pH value varied from one type to another and increased in the following sequence: alunite-kaolinite-pyrophyllite-illite-bentonite-zeolite, from acid to alkali.
The mineralization of the main orebody (stratified orebody) in the continental volcanic sedimentary rock series should be volcanic sedimentary origin. When the hot volcanic pyroclastics fall into lacustrine basin, the pyroclastics were suffered hydrolysis and devitrification, in the last they formed non-metal minerals.
The ore-sources came from volcanic pyroclastic or lava diagenetic materials. However, the hot source and water-source were came from hot volcanic materials and transferred to lake water forming a hydrothermal solution with a temperature in 50-100 ° or higher to evaporation. Diagenesis and mineralization were begun in the same time. If volcanic lava was overflowing directly into basin, rhyolite in spherulite, ball foam and rock foam rhyolite, pearlite would be formed.
This research was financially supported by the National Basic Research Program of China (973 Program) granted No. 2007CB411706.
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