Study On Contact Zone Tectonic And Deep Exploration In Chengchao Iron Deposit, Hubei Province

Chengchao iron deposit in Hubei province is in the south of lithosome in E town,located in the connecting zones between Yanshanian granite and late Triassic Daye formation(T1dy) carbonatite.The deposit is the important iron deposit in Edong area.The area rarely exposed stratum,only exposed partial Triassic and Jurassic stratum in the southern,and in which Triassic Daye(T1dy)and Puxi(T2+3pq)formation had important space relationship with Chengchao iron deposit.The fracture structure was in NWW and NNE direction,which properly developed before diagenesia and metallogenesis or during diagenesia and metallogenesis,and which controlled spatial distribution and location of lithosome,vein,alteration and mineralization.The magmatic rock in and near this area was biotite-augite-diorite,diorite,quartz monzonite,granite,orthoclase-porphyry,diorite-porphyrite,and so on.The deposit makes up of seven orebodies.Ⅱ,ⅢandⅥorebodies are the largest scale of them,and their storge is 94.8 percentage of the whole ores.The plane projection of ores is like parallel banding distribution of NWW direction.The ores form overlapped echelon shape from head to end in profile chart.The ores are commonly lentoid shape,with dipping south or south-south-west direction and rake angle is 0-57 degrees,with siding NWW direction in 4-18 degrees.The height mark is gradually deepened fromⅠtoⅦ.In the area,main metal mineral is magnetite,hematite,pyrite,chalcopyrite,pyrrhotite,specularite,bornite,and so on.The texture of ores is medium-grained to fine-grained automorphic-hypidiomorphic texture,metasomatic relict texture,brocken texture,intersertal texture,and so on.The structure of ores are mainly blocklike structure,impregnation structure,streaky structure and brecciated structure.The wall-rock alteration in the area is skarnization,chloritization and anhydrization.Chengchao iron deposit in Hubei province is a typical skarn iron ore deposit in Edong area,and the formation and distribution of the main orebody controlled by the intrusion-contact tectonic system.Therefore,strengthening the research on the ore-controlling regularity of contact zone tectonic system is the key scientific problem about deep exploration in Chengchao iron deposit.Combining mineral deposit geology and orefield structure geology with computer technology,we use trend surface analysis for contact zone tectonic of granite lithosome which is closely related to mitallization,so we find its occurrence characteristics,the direction of lithosome invasion and changed abnormal region in vertical direction.In its basis,China University of Geosciences GeoMine 3D system is used to construct three-dimensional visualization models of orebody,contact zone of lithosome and ore-controlled by contact zone of lithosome(the former two superimposed),for contact zone tectonic of granite lithosome and ore body.From the intuitionistic and scientific view,the research analyses contact zone of granite lithosome and the relationship with shape,production and spatial distribution of iron orebody, and summaries ore-controlling regularity of contact zone tectonic for deep metallogenic prognosis.I get the following view points:1.The research studies ore-controlling factors of the iron ore deposit:①Triassic Daye formation dolomitic marble(T1dy),Daye formation(T1dy)and Puxi formation(T2+3pq) carbonate rocks with gypsum and Puxi formation(T2+3pq)pelitic hornstone have close relation with metallization;②The ore fluid move along the succession tectonics fracture of granite surface,and then fill and alternate wall rock for mineralization.The distribution of ore body has been controlled by contact zone tectonic and different fracture in NWW squeezing belt;③The granite and ore deposit genesis,the spatial distribution of ore bodies in the Chengchao iron deposit are extremely close ties.2.According to trend surface analysis with granite contact zone projection in longitudinal direction,we get conclusions as follows:①The granite lithosome contact zone tectonic with NWW to the overall direction,lean to SSW,with rake angle at an average of about 50 degrees, and obviously side to SWW(or west).②The granite invade along the SWW to NEE;③The changing abnormal areas of granite contact zone tectonic in vertical direction and the the distribution of main ore body are closely corresponding.That is,negative altitude abnormal areas correspond with the main location of ore bodies;the line of centres with positive and negative abnormal area is a straight line and alternating appear,and between them is the main site of the orebody.3.GeoMine 3D system is used to construct three-dimensional visualization models of orebody,contact zone of lithosome and ore-controlled by contact zone of lithosome.We summary ore-controlling regularity of the granite lithosome contact zone tectonic:①The major iron orebody locates in external contact surface of the granite,and sides slowly to the W(SWW)in distribution groups.②The side array direction W(SWW)of the orebody groups and the side direction SWW(W)of the lithosome tend to unification.③The top surface of the granite lithosome is sags and crests.The orebodies usually lie in platform or sag of the contact surface.4.On these bases,some preferable sections with potential prospecting are forecast:①FromⅥOrebody 11-exploration section in SEE direction extended to 20-exploration section,the corresponding height mark range is -600～-800m;②FromⅦOrebody 27--exploration section in SEE direction extended to 11-exploration section,the corresponding height mark range is -800～-1000m);③On the bottom betweenⅦorebody 43--exploration section and 55-exploration section,the corresponding height mark range is -900～-1150 m,which is the favorable space of mineralization.