Geological Characteristics And Genetic Model Of The Laogongshan Phosphate Deposit In Hongya County,Sichuan Province

In this study,the Laogongshan Phosphorus deposit in Hongya County of Sichuan Province was selected as the research object,and the geological data of the deposit have been fully collected.Based on the previous work,the analysis of the geochemical formation of the ore in the study area and the observation of the phosphorus rock mirror Observations,analysis,and analysis of the distribution of sedimentary basins,changes in ore-bearing layers,and sedimentary equivalents can,on the one hand,enrich and refine the theoretical study of the deposit,deepen understanding of the deposit,and accumulate data for later research;On the other hand,the cause of the deposit was initially discussed in order to guide the prospecting work.1.The phosphorus bearing strata in the 1.area are the lower Maidiping formation??₁m?of the lower Cambrian system,which is a set of shallow sea and tidal facies carbonate,mainly dolomite and phosphorite,and the phosphate rock is located in the lower part of the lower miatping formation of the lower Cambrian system.The roof of the ore layer is the grey-light gray medium-thick stratiform pink dolomite in the middle of the Maidiping formation,and the bottom is the gray-gray thick layered siliceous belt dolomite in the bottom of the Maidiping formation.2.Ore minerals are fluorapatite and micro carbonaceous fluorapatite.Gangue minerals consist of siliceous minerals and carbonate minerals.The main chemical compositions of phosphate rock are P₂O₅,MgO,CaO,SiO₂,F and so on,the total content is 95.32%⁹9.82%.The ore structure is mainly composed of sand chip structure,gel sand chip structure,and ore structure has compact block structure,striped strip structure and dissolution structure.3.According to the stable isotopes of C,O and S,it is deduced that the phosphate rock in the study area is formed in the semi confined Bay basin.According to the calculation of oxygen isotope,the formation temperature of phosphate rock in the mining area is 16?to 43?,which is close to the data of the marine phosphorite.According to the sulfur isotope,it is similar to the?³⁴S value of the sulphate in the modern sea water.The sulphur source of the sedimentary medium is derived from seawater sulfate,and its forming environment is dry climate.4.The diagenesis and enrichment of phosphate can be divided into two metallogenic stages.Early diagenetic stage:the sedimentary apatite formed by diagenesis is mainly composed of fibrous aggregate apatite and a small amount of self formed apatite structure.Apatite is clean and bright,with an equal thickness ring structure,showing a"diamond grid"structure.Late diagenetic stage occurs mostly in intergranular dissolved pores and intragranular dissolved pores,and apatite is fibrous,radial,scrub shaped and chrysanthemum shaped.5.The rift basin is the main place for the formation of phosphate rock deposits.Through the study of paleogeography,palaeogeography and sedimentary facies,the formation of phosphorus block deposits in the north section of the Sichuan Yunnan Phosphorus formation belt is controlled strictly by the faulted basin formed by the North-South paleo fault,and the phosphorite is mainly concentrated in the sub-first depression basin in the fault basin.6.The accumulation position of phosphate detritus is related to the sedimentary environment and the energy of water medium,especially the formation of phosphate rich ore is not the product of pure mechanical transformation,but closely related to the biological phosphorus accumulation.It has been studied that there is a broad and flat subtidal flat with a broad and flat subtidal flat with a broad and flat flank,with a broad and flat flank,which is especially favorable for biological phosphorus accumulation,often forming large and high-quality phosphorus block rocks.The old Hsun Shan phosphate deposit is located in the intertidal flat environment.Due to the variable energy of water medium,there are often carbonate impurities mixed into it.Therefore,the intercalated dolomite or dolomite intercalated to reduce the grade of phosphate rock,thus forming medium and low-grade phosphate rock.