Abstract:

The Late Mesozoic Chuxiong Basin, located at the southwest margin of the Yangtze Plate, is widely developed with Cretaceous red clastic rock series, hosting copper orebodies in multiple horizons and thus forming the most representative sandstone-type copper ore-concentrated area in China. The lithological assemblage of the Lower Cretaceous Gaofengsi Formation in the Chuxiong Basin shows significant spatial variations, and relevant research remains inadequate, which has restricted studies on the tectono-sedimentary paleogeographic evolution of the Chuxiong Basin during the Early Cretaceous, as well as the evaluation of regional resource potential and the deployment of mineral exploration and reserve increase. Focusing on the Lower Cretaceous Gaofengsi Formation in the central and southern parts of the basin, this study employs methods such as geological profile measurement, observation of rock (assemblage) and sedimentary fabrics, analysis of sandstone component characteristics, measurement of paleocurrent directions, and heavy mineral analysis, combined with regional geological survey data, to clarify the sedimentary sequence, rock (assemblage) characteristics, types of sedimentary facies, and sources of sedimentary materials.The results indicate that:(1) The Gaofengsi Formation in the study area is generally composed of meandering river facies and delta facies. The northeastern part is dominated by meandering river facies with bank subfacies as the main type, while the southwestern part is dominated by delta facies. The sedimentary environment underwent a transition from arid to humid climate from bottom to top;(2) The sediment source area is located in the paleo-highlands in the eastern and northeastern parts of the basin, where sedimentary rocks are mainly exposed, accompanied by a small amount of acidic, basic igneous rocks and metamorphic rocks;(3) The Chuxiong Basin was generally in a tectonically stable period during the Early Cretaceous. Among them, the sandstones of the Gaofengsi Formation with high detrital content and low sorting coefficient are favorable hosting horizons for sandstone-type copper deposits, showing good prospecting potential.Covering the main areas of the central and southern Chuxiong Basin, this study provides new data for regional reconstruction of sedimentary paleogeography and mineral exploration.

Key words: sedimentary facies, sedimentary characteristics, provenance analysis, Lower Cretaceous Gaofengsi Formation, Chuxiong Basin, central Yunnan Province