Characteristics Of The Ancient Weathering Crust Of Carbonatite In Longtou Formation In Huaxi Area,Guiyang

The weathering crust is the product of sedimentary basins exposed, is the important symbol to reveal the crustal evolution history and ancient environment, and build the stratigraphic framework; The weathering crust is an important reservoir of many sedimentary mineral,such as oil and gas; So for the study of weathering crust whether for the basic research or the production practice of prospecting has important scientific significance. The Triassic Longtou formation is an important material of the carbonate weathering crust studying, It provides a favorable conditions to study of weathering crust type, identification, genesis and control factors. There are some ways such the field outcrop, lithofacies combination, microstructure, cathodoluminescence, and geochemical to analysis the features of weathering crust in this paper, excet to improve the research degree of the weathering crust of Longtou formation,and enrich the theory research of carbonate weathering crust.The structure analysis of the Longtou Formation shows that Huaxi Qingyan area carbonate which is located Yangzi carbonate platform margin experienced dozens of submerged and surface exposure process in Middle Triassic; The Stratum experienced a long-term surface exposure in late Latin, causing the weathering crust be saved in the upper Longtou Formation.Karst breccia are a typical feature of the weathering crust of Longtou formation, the percolation beans and miniature stalactites are important petrology characteristics of weathering crust. The cathodoluminescence suggest that weathering crust was transformed in late period of transgression, only partially retained the optical characteristics of calcite. Al and Fe relative enrichment, The O isotpes is aboat-10‰, the C isotpes vary from 1.5‰~3‰, the geochemical characteristics similar to the sediments which are meteoric in origin.,abd they further illustrate the Longtou Formation is karst breccia breccia. The weathering crust of Longtou Formation experienced the formation process of tidal sediments exposed, karst collapse for gravel packing, miniature stalactites cementation diagenesis, Seawater transformation and Further cemented.