The Ore-Forming Geological Conditions And Prospecting Orientation Of Yanghuidongzi Cu Deposit,Heilongjiang Province

The research area，at an intersection of Taiping range uplift and Laoheishan riftof Zhangguangcai range-Taiping range margin active belt，is located in the northern ofJilin-Heilongjiang fold belt and in the eastern end of the Xing-Meng orogenic belt(eastern part of the Central Asian orogenic belt). It belongs to overlapping area of thePaleo-Asia Tectonic Domain and the Marginal Pacific Tectonic Domain. Multi-stagetectonic transformation and magmatic-hydrothermal events provide favorableconditions for mineralization. Based on the systematic collection of predecessor’sdata and field geological investigation and research，This thesis，strating from regionalgeological setting，sufficiently studies on typical deposit geological characteristics，ore-forming fluid characteristics，ore-forming materials sources，diagenetic andmetallogenic ages，and discusses the genesis and geodynamic. By means of the studyon ore-forming geological conditions，exploration geophysical and geochemical dataof region and mining area，this thesis ascertained the indicators of prospecting，summarized the prospecting orientation in deep and Periphery of deposit.Yanghuidongzi copper deposit’s ore bodies are mainly hosted in granodioriteporphyry and tectonic breccia. The main ores is Primary sulfide ores. The mainmetallic mineral of ores are pyrite，chalcopyrite，sphalerite，galena，molybdenite andpyrrhotite，etc. The main texture of ores are allotriomorphic-hypidiomorphic granulartexture，metasomatic texture，exsolution texture，etc. The main structure of ores areveinlet structure and brecciated structure，etc. Deposit has a planar alteration features and zones distinct. According to the fabric characteristics of ores，mineral interspersedrelationship，temperature range of fluid inclusions，Hydrothermal period of deposit isdivided into following four mineralization stages，（Ⅰ）pyrite-quartz stage，（Ⅱ）pyrrhotite-molybdenite-quartz stage，（Ⅲ）quartz-chalcopyrite stage，and（Ⅳ）quartz-carbonate stage.（Ⅲ）quartz-chalcopyrite stage is the main mineralizationstage.Application of Fluid Inclusions shows the type of fluid inclusions ofquartz-chalcopyrite stage in Yanghuidongzi deposit is the gas-liquid inclusions whichthe ore-forming fluid is NaCl-H2O system，homogenization temperatures vary from190.3to308.8℃with an average of245.8℃，the salinity range is2.23to12.99wt%（NaCleqv），density range is0.76to0.95g/cm3，homogenization pressures vary from15.55to30.51MPa and the mineralization depth is0.52to1.02km with an averageof0.75km. The ore forming fluid in quartz-chalcopyrite stage has the characteristicsof high-middle hydrothermal solution，rich water and low salinity，which is forminglower metallogenic pressure and shallow setting.Research on LA-ICP-MS zircon U-Pb dating indicates that the weight average206Pb/238U ages of zircon grains from granodiorite porphyry are204.4±2.8Ma and201.2±1.7Ma. The diagenesis and mineralization age of the Yanghuidongzi porphyrycopper deposit is Late Triassic to Early Jurassic. Locating in overlapping area of thePaleo-Asia Tectonic Domain and the Marginal Pacific Tectonic Domain， theYanghuidongzi deposit originated from granite magmatism of partial melting of thethickened lower crust occurred in continental collision orogeny regime after theclosure of Paleo-Asia Ocean. Differentiation of some magmatic hydrothermal withthe majority of metallogenic elements， mixed the formation of atmosphericprecipitation and little formation water，forming convection with heating，beingore-bearing hydrothermal solution by extracting some of the minority of metallogenicelements from surrounding rock，deposit from weak point of contact zone and tectonicfracture zone and forming Porphyry copper deposit finally.Ore-forming geological conditions imply that：Yanwangdian anticline is theintrusive rock-controlling and ore-hosting structure. NNW direction faults are the intrusive rock-controlling，NE direction interlaminar fracture zone is the ore-hostingstructure，and NE direction faults are the most important intrusive rock-controllingand ore-hosting and ore-controlling structure. Granodiorite is evolved to peraluminouscalc-alkalic rock series，being rich in LREE and relatively depleted in HREE，theseparation between HREE and LREE is significant. The δEu contents show weaknegative or positive Eu anomalies，the enrichment of large-ion lithophile elements（LILE）and the absence of high field strength elements（HFSE）. The granodioriteporphyry which has characteristics of adakitic rock originated from the partial meltingof the thicken lower crust.According to condition of metallogenic geology，prospecting direction in deep isNo.Ⅰgranodiorite-porphyry continue deepening towards SE-trending，and line of13th should proceed to drilling engineering vertification. The prospecting direction inperiphery of the mining area is hinge of the Yanwangdian antiline extend towardSW-trending，we should find concealed orebody or rock boundary in the position ofstructural join. Small scale of granite porphyry is exposed around granodiorite-porphyry in the SE-trending of the mining area，and diagenesis age of graniteporphyry and whether or not ore-bearing should be proved. Combining that regionalgravity，line and ring type structure interpreted by aeromagnetic anomaly andgeochemical combination of abnormal， the Yanghuidongzi HS-52， LujiaolingHS-66，Xilinhe HS-57and HS-60combination of abnormal is good and should beused as metallogenic predicting area. Combine pedogeochemistry survey，naturalpotential anomalies， apparent resistivity anomalies and apparent chargeabilityanomalies，I delineate two better metallogenic target areas.