Coexistence and Development Model of Multi-Minerals Dominated by Multilayer Magma Intrusion

Abstract

The diversity of coal measure determines the occurrence state and spatial distribution complexity of mineral resources. Abundant resources have become an important part of geological resources and have attracted more and more attention. Coal measure and their overlying and underlying strata often coexist with various mineral resource types, and there is a certain relationship between their genesis and occurrence. In order to further enrich the theory of comprehensive exploration and coordinated development of multi-mineral resources, this paper takes the Huanghebei Coalfield as an example to systematically study the genesis mechanism and occurrence law of coal seam, coalbed methane, and coal-measure shale gas in Late Paleozoic and rich iron ore in Ordovician limestone underlie coal measure. The research is that: 1) The Late Paleozoic Carboniferous-Permian Marine facies, terrestrial facies, and transitional facies all developed in the coal-bearing area in the Huanghebei Coalfield, and the coal seams and mud shales developed well in Shanxi Formation and Taiyuan Formation. 2) Yanshanian magmatic intruded into Ordovician limestone. Contact metasomatism occurred between the ore-bearing hydrothermal fluids and the surrounding rocks, which led to skarn formation. The magnetite mineralization occurred in the metasomatism alteration process, and finally, the contact metasomatic iron deposit was formed; 3) Yanshanian magma intrusion has a significant impact on the generation of coal from coalbed methane and shale gas in the coal measures of Late Paleozoic. The magma carries a lot of heat by baking the coal seam and overlying shale, which is reflected explicitly in the increasing metamorphism degree of coal. Under the action of high temperature, the secondary gas of coal seam and coalbed methane increase sharply. The maturity and thermal evolution of organic matter in shale beds increased, and the shale gas entered a favorable range. The intrusion of magma greatly enhances the thermal evolution of organic matter in coal and shale, forming a variety of coals and promoting the generation and accumulation of coalbed methane and shale gas. At the same time, Mesozoic magmatic intrusion also controlled the formation of rich iron ores. According to the characteristics of mineral development and distribution in the study area, a multi-mineral development and distribution model of “coal - coalbed methane - shale gas - rich iron ore” coexists in the Huanghebei Coalfield, which is referred to as the “Huanghebei model”.