成岩-极低级变质-低级变质作用及有关矿产

介于成岩作用与低级变质作用之间的极低级变质作用是一个重要过程 ,对于全面认识地球浅层动力学与成矿作用有重要意义。文中简要地回顾了国内外极低级变质研究的历史与现状 ,在大量资料的基础上提出了关于成岩—极低级变质—低级变质带划分的改进方案 ,应用许多研究实例讨论了成岩—极低级变质—低级变质作用研究在化石能源及固体矿产勘查、评价与成矿研究方面的意义 ,指出煤、石油、天然气形成于高级成岩—极低级变质条件 ,很多非金属矿产的成因及质量直接受到变质程度的控制 ,大量低温—低中温铜、铅、锌、金、银、锑、汞等金属矿床分布在高级成岩—极低级变质—低级变质区中。为了获得准确的伊利石K Ar同位素测年数据 ,文中建议应保证所测粘土样品中自生K型伊利石的含量 >90 % ,并且不含钾长石 ,还要根据变质程度的高低来确定分析样品的合适粒度。

TRANSITION FROM DIAGENESIS TO LOW-GRADE METAMORPHISM AND RELATED MINERALS AND ENERGY RESOURCES

Studies on the process between diagenesis and low-grade metamorphism is important for better understanding geodynamics and mineralization in shallow level of the Earth. This paper overviewed the recent progress of the studies on very low-grade metamorphism and presented a new frame for the division of diagenetic-very low grade metamorphic-low grade metamorphic zones based on a quantity of data. It discussed the relationship between diagenesis - very low- to low-grade metamorphism and the formation of fossil energy resources and mineral resources, and the significance of the study in this field for exploration and assessment of coal, oil and gas, metal and non-metal minerals. The conditions from high-grade diagenesis to very low-grade metamorphism are favorable to the formation of coal, oil and gas. The qualities of many non-metal minerals are controlled by metamorphic degree. Lots of low- and low-middle temperature hydrothermal deposits of copper, lead, zinc, gold, silver, antimony, mercury and so on occur in high-grade diagenetic, very low-grade and low-grade metamorphic regions. It was pointed out that in order to make accurate illite K-Ar isotopic dating, more than 90% of authigenic K-illites in clay minerals and proper grain size for analytical samples were required.