Sediments Grain-size Characteristics And Depositional System Research Of Dishui Sandstone-hosted Copper Ore In Xinjiang

Many sandstone-type coppers had been developed in fragmentary roek in Neogene in Kuqa Basin, especially Baicheng Dishui small copper, has been exploited from Qing dynasty. Dishui copper ore beds in the north rim of Kuqa basin, and copper mining anticline north wing, high in whole west and lower in the east, the deposit is a typical sandstone type copper deposits.Papers treat clastic sediments as the main research object of Neogene Kangcun group. Guided by sedimentology, stratigraphy, faeies palaeogeography, clastic rocks and other theories, combining with a large number of data of outcrop observing, rock core, drill and palaeobios material, and adopting many testing and analytic techniques, the thesis carries a thorough and detailed research of sediments in the diggings. Partition Neogene strata, analyses the sediments grain-size characteristics and depositional system of study area, to research depositional environments, lithofacies palaeogeography.According to the mark of sedimentary facies and combined with geology data, this paper divided the type of sedimentology system into alluvial fan-fan deltasfacies and lake facies. Discusses the characteristics of sedimentary facies, sedimentary subfacies and sedimentary microfacies of these depositional systems, and establishes the studied area sedimentary models of the settings of Neogene of, based on which discussed the characteristics of the evolution of depositional systems. The basin was shallow and distributed to a large area, and nearly all the basin accepted lake sedimentation, featured by gypsum lake sedimentation at Jidike group. Kangcun period basically inherited the Jidike sedimentary framework, provenance supply mainly from north of the south Tianshan and western WenSu embossment, from the piedmont to basin center, development fan delta and lake sedimentary.From the research of depositional system and sedimentary facies in the study area, chiefly of ore-bearing bed originate in the overlying lacustrine facies (marl) fan delta front subfacies. Thereinto underwater distributary channel microfacies is medium-grained and fine-grained sandstone enrichment period of copper. Fan delta front is part of fan delta underwater, and fan delta sedimentation fairly active part, is a weak oxidation weak reduction environment. In this sedimentary environment is good for the handling of copper materials to deposit. In underwater distributary channel deposition medium-thick graind sandstone and fine-grained sandstone primary pore has good penetration, favorable for the migration of ore-forming fluid. Overlying the marl is an excellent water-resisting layer, effectively ensure the copper material in the process of diagenesis concentration in the lower part of sandstone.