The Ore-Controlling Conditions And Prospecting Target Prognosis Of Liushuhezi-Madida Gold Mineralized District In Hunchun City Of Jilin Province

Study region is golden and polymetallic deposit region of Liushuhezi of Hunchun-Madida. The study region belongs to structural magma mobile belt of the coast-Pacific and is constituent of Late Jura in mideast of Yanbian city- magmatic zone of volcano-subvolcano metallogeny structure of early Cretacic and locates in cross part bewteen volcanic-subvolcanic structural magma zone whose direction is nearly east-west of Tianbo mountain-Tuman -Madida and volcanic structural magma zone whose direction is nearly north-south of Xiaoxinancha-Xiasidaogou. Major placer mine of Sandaogou lies on west of the study region and medium size golden-copper deposit lies to east of the study region. The geographical coordinates is as fellow: east longitude is 130°41′30″～130°45′00″;and north latitude is 42°51′30″～42°55′00″. The width of the study region from east to west is about 4.73km and the length from south to north is about 12km, and total area of the study region is about 56.8km2.The study region locates in east of north margin of the North China Plate that is cross part of extinction movable tectonic zone of ancient Asian ocean and east north tectonic zone controlled by continental margin zone of west Pacific and activity fracture of north south controlled by continental margin zone of west Pacific.Main exposed strata of study region are as follow: Paleozoic stratum is a set of volcano-metamorphosed sedimentary rock series that suffering from regional metamorphism of amphibolite facies-greenschistfacies,and its original rock are mainly medium-acidic and medium-basic volcanic rock, fragmentary rock and carbonate rock; Mesozoic strata are mainly continental volcanic rock and volcaniclastic rock of Jingouling group; Cenozoic strata are alluvial deposit and clay and so on.The study region belongs to east sector of east extended part of regional east-west continental crust fracture of Tumen-Huichun, and overlaps with regional south-north fraction and west north, east north fracture to constitute basic tectonic framework of the study region. The character of Liuhezi mining area is fracture spread direction are mainly west east, north south and later west north and east north, and caldera structure is formed obviously with tectonic evolution, and thereby structure in Liuhezi mining area become the structure that controlling rock and mine and the structure is controlled by palaeovolcanic structure。Late Jura-early Cretacic subvolcanic intrusive rock of mining area that is controlled by caldera structure and filling in parasitic volcanic channel is in shape of small stock. Lithologies are fine particle quartz diorite, quartz diorite porphyrite and granite-porphyry and etc. Through geological survey and combined with abnormal distribution characteristics of geochemistry, it showed diorite rock mainly related with Au mineralization and Au element, and Cu mainly related with granitic rock. The results showed Late Jura-early Cretacic subvolcano was important magmatic rock condition of mining area.Orebody is mainly formed in quartz diorite (porphyrite) of mining ( mineralized ) area and in volcanic rock of Jingouling group, and also reach to plagioclase granite. Changes of Orebody along strike and dip are complex, and orebody have characters of branch recombination and thin-out reappearing. Mineral components of ore are pyrite, pyrrhotite, quartz, chalcopyrite, sphalerite, galena, magnetite and etc, and pyrite is main component; rocky mineral is quartz, feldspar and its altered product-mica, kaolinite and etc; main ore fabric are metasomatic erosion texture, erosion texture and the others is skeletal texture and etc. texture is in shape of impregnation, net and vein and ribbon. Wall-rock alteration is development. Wall-rock alteration closely related with Au mineralization is mainly pyritization, silicitication, tourmalinization, greisenization,sericitization, carbonatittion and etc. Internal-external characters of Orebody (ore) form mark conditions to find orebody (mineralized body).In geochemistry field, mineral deposit locates in abnormal belt of high concentration of minerogenic element and concentration belt of abnormal element. Through rehandling mining zone soil measured data whose scale is 1:10000, the result showed Au element and Cu element matched well in space. Au element distribution was in shape of ring in outside of abnormal belt and was consistent with subvocano diorite-porphyrite small stoke distribution; Cu element distribution was in plane and was consistent with distribution of granite-porphyry small stock in channel of volcanic edifice. Above results once more show relationship between subvolcanic rock and metallization that provide important geochemistry information and indicator to find mineral products for mining zone.Through above study, author concluded general information and indicator of finding mineral products.1) the cross part of two groups regional deep fractures whose spread direction was west east and nearly north south respectively was place that the main crater was in and was zone where mineralization was central development; 2)the cross part of ring type volcano fracture structure and fracture structure of nearly north south direction and east north direction was center of volcanic edifice and formation place for intrusive complex of adventive crater, including fine particle quartz diorite, diorite, quartz diorite porphyrite, granite-porphyry and so on. For the control of cross part, the intrusive complex distribute in stock state surrounding volcanic vent in shape of ring; 3) intersect part of fracture in nearly north south direction and its subfracture and fracture in nearly west east direction controlled structure of explosive breccia structures. Breccia pipe generally distributed in margin of subvolcanic intrusion small stock and was controlled by same structural system; 4) secondary NE,NNE and nearly west east fracture and radial fracture (crack) of NE, NW are places where orebody and mineralized body existed; 5) rock type of medium subvolcanic intrusive complex was the best accompanying mineral and had close relationship with gold ore formation , such as fine particle quartz diorite, quartz diorite porphyrite, diorite-porphyrite; 6) medium-acidic subvolcanic small stock had close relationship with Cu, Mo ore formation; 7) chloritization , sericitization, pyritization: they were alteration type or combination near ore, and their distribution scope is not wide and they mostly developed in medium-acidic subvolcanic small stock and its outside, in outside of breccia pipe, and in fissure of volcanic structure; 8) pyrite sericite-quartz: It was main alteration type near orebody and contained tourmaline (Shangyangshugou, Baihushan); 9) silicification, kaolinization: it was plane alteration outer zone type, and it widely developed in medium-acidic shallow intrusion small stock; 10) synthesis abnormality zone of Au, Ag and Cu of 1:10000 soil measure was place where existed subvolcanic rock and mineralization was development; the place where abnormality was very obvious and concentration center was clear was centralized development section of mineralization, and was coincidence with alteration zone of known bodyore and mineralization; 11)low skip positive magnetic field was intrusion contact zone mark of effusive rock and subvolcanic mixtite, and effusive rock showed positive magnetic field character of higher random skip; 12) abnormal zone of aquo-heavy gold dust and copper was indirect mark for finding ore.On the basis of integration marks for finding ore and building model for finding ore, target region prediction and target region classification were carried through. There were three parts was determined asⅠclass predicting target zone and 4 parts was determined asⅡclass predicting target zone in golden and polymetallic deposit region of Liushuhezi of Hunchun-Madid. Author pointed out direction to find ore and target section of engineering verification.