| Tongchang copper deposit is a represent deposit which located in Yimen cooper-belt between the North-South Yimen fault and Lvzhijiang fault zone of the western margin of Yimen fault basin.Its prospecting reserves are above the large-scale size.Cu = 0.2-0.4%amount of ore grades account for 93.91%of the total amount of ore.However,the previous geologists research very little involve the ore texture and material composition,which restricted the thorough understanding of ore genesis,metallogenic regularity and prospecting potential.Through the field investigation research the result shows that the ore genesis of copper orebody includes sedimentary diagenesis type and late-stage volcanogenic hydrothermal type.In addition,this paper studied the ore fabric,and the achievement as follows:(1)These two kinds of copper ore-body have different characteristics of production.The sedimentary diagenesis copper ore(Tongchang type)have occurred in dolomite of second group Luoxue Formation and characterized by strata bound type.Main mineral is bornite and chalcopyrite,and the gangue mineral is dolomite and a bit of microcrystalline quartz.The hydrothermal copper ore has mainly characterized by trans-layer,and the occurrence are mainly chalcopyrite(bornite)—calcite(quartz,barite)vein and chalcopyrite—quartz vein.(2)The sedimentation-diagenesis mineralization distributed mainly in the southern segment of 15 exploration line,30 exploration line section of Dajianshan-Tongchang ore section and the Xiaomashan ore section.Besides,the superposed mineralization area distributed mainly between the 30 exploration line and 15 exploration line.The research of three kinds of mineralization have different characteristics about metallogenic regularity and occurrence of ore-body.(3)The study of ore structure showed that the mineral granularity of bornite is very fine,which occurred in sedimentary-diagenesis ore,and the mineral granularity were concentrated in the range above 0.01-0.15mm,and the ore texture mainly includes powder-fine crystalline structure and interstitial structure.The ore structure was mainly includes laminar structure and stylolite structure.In addition,the mineral granularity of chalcopyrite is relatively coarse,the mineral granularity of chalcopyrite were concentrated in the range above 0.05-0.25mm.The ore texture of hydrothermal ore was mainly includes metasomatic texture and Solid solution separation structure.And the ore structure was mainly includes vein structure,anastomosing structure and dissemination structure.(4)The gangue mineral(dolomite)of sedimentary diagenesis has characterized by the enrichment of Cu?Pb?Zn?Ba?Bi?Sb?Ga?Ag and the loss of Mo?Cr?Ni?Co?V.The REE distribution pattern was and marine sedimentary.The metallogenic material has obvious feature of crustal source.Besides,the gangue mineral(calcite and quartz)of hydrothermal-vein type has characterized by the loss of chalcophile elements(Cu?Pb?Zn)incompatible elements(Ba?Be?Rb?Nb?Ta?Zr?Hf?Th?U and so on and enrichment ofV?Co?Ni.Its REE distribution pattern was characterized by accumulation in the light REE which the individual sample showing the REE earth enrichment feature and hydrothermal mineralization characteristic.(5)The value of ?18OSMOW indolomitewas in the range above 16.7‰?21.6‰,and the value of ?13CPDB were in the range above-3.7‰?1.0‰.The dosage point results of sample showed that the ?18OSMOW-?13CPDB were close to the unilateral marine carbonate,which characterized by marine depositional genesis.In addition,the?18OSMOW of calcite in hydrothermal-vein ore were in the range above 11.9‰?O17.0‰,and the value of ?13CPDB were in the range above-3.7‰?0.1‰.The dosage point results of sample showed that the ?18OSMOW-?13CPDB were concentrated between the magic-carbonatite and marine-carbonatite,which showed the close association between the hydrothermal-vein ore and deep magmatism.(6)Because of the aplasia about fluid inclusion in gangue mineral of sedimentary diagenetic ore,this research cannot obtained the homogenization temperature.On the contrary,the fluid inclusion in gangue mineral of hydrothermal-vein ore had being well-developed.Its homogenization temperature has concentrated in the range above 60?290?,and the average temperature(131.6?)showed the characteristic of low-middle hydrothermal deposit. |
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