Abstract:
The weathered crust of bedrock, including granite, metamorphic rock, volcanic rock, and clastic rock, exhibits distinct tectonic zoning characteristics vertically. However, scholars have not reached a consensus on the division scheme of the weathered crust structures, which leads to confusion in understanding the development regularity of such type of buried hill weathered crust reservoirs. Based on field survey and existing findings, it is believed that granite, metamorphic rock, volcanic rock, and clastic rock are all aluminosilicate-rich rocks, and their weathering processes and weathered crust structural characteristics are consistent. A unified scheme for dividing weathered crust structures has been proposed based on the development process and mechanism of weathered crust, i.e., fractured bedrock zone, disintegration zone, and leaching zone. The fractured bedrock zone is mainly characterized with the development of structural fractures formed by multiple tectonic movements; the feature of the disintegration zone is that physical weathered fractures and tectonic fractures are superposed to form network fractures, and the dense fractures lead to disintegration and fragmentation of rocks, as well as enhancement of leaching efficiency; the leaching zone is mainly characterized by chemical alteration of aluminosilicate minerals. From the bottom of the leaching zone to the surface of the weathered crust, the chemical alteration of aluminosilicate minerals along various fractures is enhanced continuously, forming clay minerals and corrosion pores, and the rocks become loose and sandy. Due to the change of intensity caused by erosion, physical weathering, and chemical weathering, the weathered crust of aluminosilicate-rich rock has different models such as fractured bedrock type, disintegration type, disintegration-leaching type, and leaching type. The structures of weathered crust of various aluminosilicate-rich rocks were divided uniformly according to the weathering mechanism, which is helpful to further study and understand the development law of buried hill reservoirs of aluminosilicate-rich rocks.