| This dissertation was directed by the metallogenic theories of sandstone-type uraniumdeposits. By collecting datum of regional geology，remote sensing，geophysics，hydrology andhydrochemistry，uranium deposits and uranium occurrences systematically，developing fieldgeologic investigation，radioactive geophysics method，drilling validation，inside test andcombination with synthetical studies， and the central studies concentrated on thecharacteristics of depositional systems，sequence stratigraphy，evolvement of sedimentarybasins and basin-mountain coupling，hydrology and hydrochemistry，oxidation zone andUranium mineralization. the author summarized the metallogenic conditions onsandstone-type uranium deposits systematically，and established the metallogenic model ofphreatic interlayer oxidation zone sandstone-type uranium deposits in Northern Sichuan Basin.The author acquired some innovative outcomes and recognitions：On the macro, carry1∶250000Route Geological Survey and Terrestrial gamma-ray spectrometry in the region,1∶50000Route Geological Survey and Terrestrial gamma-ray spectrometry in key regions,1∶10000Route Geological Survey and Terrestrial gamma-ray spectrometry in favorablemetallogenic lot, Combined with common geophysical survey and drilling verification,Broadly identify the sandstone type uranium mineralization uranium mineralizationgeological conditions, uranium mineralization characteristics and control factors in the areas,predict the metallogenic prospect areas; Microscopically, collect some polished and sheetsamples to research the rock geochemistry and enrichment rules of sandstone type uraniumdeposits. The scientific investigation of the sandstone type uranium deposits of northernmargin of the Sichuan Basin show that, tectonic and hydrothermal activity in northernSichuan Basin has a positive role in uranium mineralization within the region, theconstruction intersection site and the underground hydrothermal are mineralizationadvantageous location. In recent years, there are some views that sandstone uraniummineralization in northern Sichuan Basin experienced diagenesis and hydrothermal alterationenrichment, which recognizes the importance of epigenetic mineralization. These provideinformation in the Sichuan Basin sandstone type uranium prospecting work and expand theidea. These new understandings provide new prospecting clues of the Sichuan Basinsandstone-type uranium resources prospect survey. The author acquired some innovativeoutcomes and recognitions∶ 1、Sichuan basin evolution through five main stages: pre-Sinian basement formationstage, Sinian to Middle Triassic cratonic basins stage, Late Triassic foreland basin stage, EarlyJurassic to Late Cretaceous continental sedimentary basins stage, Paleocene to Holocenetectonic basin stage. The base of Sichuan Basin provide material source for the formation ofuranium and other metal minerals; Inland craton stage, Sinian as the important source of orein Cenozoic basins uranium mineralization; Foreland basin stage, and continental sedimentarybasins stage; is the period of prospecting target layer deposition and uranium pre-enrichment,as well as the period of Cangxi formation sedimentary diagenesis and uranium enrichmentmineralization. Structural basin stage is the period of sand interlayer oxidation and uraniumepigenetic enrichment.2、Sichuan Basin devolop double fold, anticline axis mostly Permian Triassic formation,Syncline mostly Cretaceous formation, these formation fold the wings dip gently, typically5°~20°. Uranium mineralization is often produced in the folds of the wings, the shaft portionmineralization rarely, indicating that uranium groundwater in the formation dip gentlymigrate relatively slow, reduction be more fully; Yanshan movement shock strongly, crustalmovements frequent, the fake integration between Jurassic and Cretaceous distributed widely,sedimentary structures such as scour surfaces are well developed. Scour depressions, erosiongroove accumulation of large amounts of carbon-containing organic conglomerate,conglomerate, pebbly sandstone, permeability is better. Containing uranium groundwater,along unconformity surface, erosion surface penetration, continuous cycle, under reducingenvironmental, adsorption precipitated by restore media such as carbonaceous, organicmatter, pyrite, enrichment forming deposits.3、In Wangcang and Tongjiang of Norther Sichuan Basin, the South wing of Xinhuasyncline compare with Longfeng anticline and the West Wing of Nixi syncline, the Cangxigroup having the following characteristics∶ In the first rhythm, conglomerate layerdevelopmented, river diversions frequent, sands developmented,and the303mine thickness of20～40m, Sand grayish black, gray, medium fine-grained, organic-rich, dense cement, erosionstructure particular developmental, shale not developed, have few calcite veins and calcitelumps, Deposits, deposits, mineralization appear banded along the unconformity face ofPenglaizhen group and Cangxi group. Thus, the south wing of the Xinhua syncline is thefavorable lots of uranium mineralization.4、The uranium source of303deposit come from the provenance of Micang mountainand its Ore-bearing, mineralized controlled by horizons, And focused on the bottom of thefirst rhythm of Cangxi group, occur in retention bottom deposition and in the sand of the heartbeach. Ore-bearing rocks are rich in organic matter and low-iron black dark gray lithicsandstone, the sand conten high calcium, rock density, small porosity, groundwater activityweak. Pitchblende, uranium stone and pyrite, hematite and white selenium iron symbiosis,despite the red phenomenon of the rich ore, but the totle conten of iron did not increase, haveno obvious signs of hydrothermal activity. Because of fracture is not development and in theMonoclinic formation zone, structure ore-controlling is not obvious.The factor of Mineralization enrichment are: Organic matter, the reduction gas it produced and absorptionand reduction of the low iron. Mineralization in sedimentary-diagenetic stage as enrichmentmineralization, epigenetic stage have a slight enrichment phenomenon, it is the stratabounduranium deposits mainly of diagenetic enrichment, supplemented by epigenetic overlay. |
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