陆相火山沉积岩系非金属矿床的地质特征及控矿条件

为讨论陆相火山岩系中由火山岩与沉积岩交互堆积的火山沉积岩系与非金属矿床成因的关系，采用宏观（野外地质观察研究及东南沿海7省非金属矿床地质调查）与微观（岩矿显微镜研究与相关的测试手段）相结合的方法，综合研究了大量地质详查和勘探成果，总结了陆相火山岩系非金属矿床的主要地质特征及控矿地质条件。研究表明火山沉积类型非金属矿床的主要地质特征为：矿体呈层状、似层状产出；矿体厚度、品位变化较稳定；蚀变微弱；矿区内断裂及浅成侵入岩体均未见矿化；含矿火山沉积岩系的韵律旋回明显，含矿构造与火山机构关系密切；含矿岩石主要为沉火山碎屑岩，它与陆地堆积的“干式”火山碎屑岩在不同碎屑块度中的形态和成分不同，如出现石英晶屑的炸裂、玻屑中的撕裂状构造等，物质成分也有改变；其控矿地质条件为成矿温度在50～100 ℃，低压（1×10⁵～n×10⁵ Pa），由于酸碱度不同，从酸性→碱性可形成明矾石、高岭石、叶蜡石、伊利石（近于中性）至碱性的膨润土和沸石等矿床。

Geological Characteristics and Controlling Conditions of Non-metal Deposits in Continental Volcanic Sedimentary Rock Series

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×10~(5 )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.