| Rhenium（Re）is an irreplaceable key raw material in the fields of petrochemical,electronic industry and aerospace,and is a strategic key mineral resource.However,rhenium is a rare element that is extremely abundant in the earth’s crust,and its extraordinary enrichment often requires extremely harsh conditions.With the rapid development of strategic emerging industries,the shortage of rhenium supply has become a very serious problem,and China’s domestic rhenium is also in short supply,and the degree of external dependence is extremely high.Therefore,it is an urgent need of the national resource strategy to carry out research on the law of extraordinary enrichment of rhenium element and find new mineral resources.The Mesozoic terrestrial basin of Mishi,Xichang,Sichuan Province is located at the western edge of the Yangtze Platform,and rhenium associated with sandstone-type copper ore was found in the lower Cretaceous Feitianshan Formation（K1f）in the basin,and the rhenium-copper ore body was deposited in the fragmented and lenticular sandstone of the Feitianshan Formation,and a large number of fine-veined,impregnated asphalt distribution was seen in the ore.In order to find out the extraordinary rich factors of rhenium-copper deposits（points）in Mishi Basin and the effect of organic matter（bitumen）on rhenium and copper mineralization,this paper analyzes ore（rock）stones such as mineralography,scanning electron microscopy-energy spectroscopy（SEM-EDS）,micro-area LA-ICP-MS,S isotopes,and infrared spectroscopy,carbon isotopes and Re-Os isotopes on asphalt on the basis of field geological characteristics investigation and chemical analysis of ore（points）in this paper,so as to reveal its geological characteristics,genesis and mineralization process.The following understandings were mainly obtained:1.A total of six sandstone-type rhenium-copper deposits（points）were found in the Mishi Basin,including Red Moida,Baimiaozi,Bori Nibao,Erhu Village,Jiedingshan,and Laji Township.The ore body is deposited in the light-colored thick sandstone in the middle and lower part of the Cretaceous Feitian Mountain Formation（K1f）,which is produced in layer-like and lensicular forms,with a length of 120～1000m and a thickness of 0.30～1.0m.The ore type is fragmented,lenticular sandstone with bitumen bands（some impregnated）.The metal minerals in the ore are mainly chalcocite and bornite,as well as a small amount of molybdenite,pyrite,blue pyrocite,hematite and malachite.2.The analysis results of 78 samples of rhenium-copper deposits（points）showed that the Re content changed greatly,0.01 g/t～131.49 g/t,of which the Re element content of 29samples was greater than that of rhenium industrial index in the associated copper and molybdenum deposits by 2g/t,which was 2.76 g/t～131.49 g/t,with an average of 24.70 g/t,a mineralization coefficient of 0.00～65.74,and a mineralization rate of 37%.3.Correlation analysis showed that there was a significant positive correlation between Re-Cu and Re-Mo（R=0.817,p<0.01,n=78;R=0.628,p）.<0.01,n=78);The electron microscopy-energy spectroscopy（SEM-EDS）element surface scan showed that Cu,Re,Mo,Fe and other elements were concentrated and uniformly distributed,and Re and other elements were uniformly distributed in the Cu element distribution area.The results of LA-ICP-MS micro-region showed that Re in bitumen was 164.83～4818.15×10-6,with an average of1431.48×10-6,and the Re content in copper-containing minerals was 87.60～17795.62×10-6,with an average of 4676.04×10-6.Therefore,it is preliminarily believed that Re is mainly present in copper-containing minerals in the form of homogeneous or supermicromechanical mixing in the rhenium-copper deposit（point）in the Mishi Basin,and some of it is deposited in black bitumen in the form of ion adsorption.4.All ore bodies of rhenium-copper deposits（points）in the Mishi Basin are accompanied by a large number of black fine-veined,impregnated asphalt development,and copper minerals are produced in asphalt-filled fractures,and the two are closely symbiotic in space.From the perspective of the symbiotic combination of minerals,chalcocite and bornite formed an alternating structure with asphalt,indicating the existence of asphalt when copper minerals were formed.Bitumen that is closely related to mineralization has high Cu and Re content,indicating that with the progress of mineralization,organic matter contains and adsorbs some mineralizing elements.These characteristics show that bitumen and copper minerals are products of the same metallogenic stage,and the two have a close genesis relationship,and the genesis of rhenium-copper deposits is closely related to the organic matter（bitumen）of oil and gas evolution.5.The value of bitumen organic carbon isotopeδ13Corg was-21.7‰～-23.3‰,and the average value was-22.68‰,indicating that asphalt was the product of oil and gas migration evolution of the Triassic Baiguowan Formation（T3bg）in the underground part of the basin,and Cu,Re and other minerals may come from the late Baiguowan Formation（T3bg）,which became the"source"of ore deposit formation to a certain extent.In the process of buried diagenesis of sediments rich in metal and organic matter,metal elements and oil and gas can be discharged at the same time,and the pore fluid carries a large number of metal elements,and the metal mineralizing elements migrate to the formation favorable strata in the form of adsorption,dissolution and chelation,that is,"transportation"in the mineralization process.The thick sandstone of the Feitian Mountain Formation（K1f）can provide good reservoirs,and in the later structural deformation,sliding and shearing occur along the sandstone layer,so that the sandstone is broken between layers,which provides a good storage space for oil and gas containing mineralizing elements,and constitutes the"reserve"of the mineralization process.During the Himalayan period,the earth’s crust rose,oil and gas reservoirs were damaged,and metal elements were precipitated and enriched to form ore deposits. |
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