Mesozoic Magmatism And Gold Mineralization In Chifeng Harqin Northeast China

This paper studied Harqin intrusive rock, Anjiayingzi gold deposit, Hydrothermal gold deposit and Chenjiazhangzi gold deposit by the testing methods of element geochemistry, isotope geochemistry, geochronology etc. and analyzed gold deposits’output environment, geological features and their relationship with rock masses. Innovative research results are as follows:(1) From the time perspective, the mineralization time of these mineral deposits was later than the diagenetic time of nearby rock masses,which shows they had coupling relationship in terms of time. The Rb-Sr isotope isochron age of Ore-bearing breccia in Chenjiazhangzi gold deposits is191Ma while the K-Ar age of Karkin granite, to the north of the mining area, is192Ma. The K-Ar age of Luohebao rock mass which is less than5kilometers to the south of Hydrothermal gold deposit is145Ma and the mineralization age of Hydrothermal Gold Mine is142Ma. The age of ore rock porphyritic granite of Anjiayingzi gold mine is130Ma and the mineralization age of it is126.6Ma by dating the rhenium osmium isotope of molybdenite.(2) This paper studied the Major, trace and rare earth elements (REE)of the surrounding rock masses in Chenjiazhangzi, Anjiayingzi and Hydrothermal gold deposits and compared these with the geochemical characteristics of Major, trace, rare earth elements of Harqin rock masses and found that they hadsome similarities especially and REE distribution patterns were consistent in form, slope and tilt direction, which showed that they had a good affinity.(3) Sulphide δ34SV_CDT in rock masses of Chenjiazhangzi Mining Area ranged mainly between3.9‰～4.6‰. Sulphide δ34SV_CDT in rock massed of the Hydrothermal Mining Area ranged mainly between2.1‰～2.5‰. Sulphid δ34SV_CDT in rock massed of the Anjiayingzi Mining Area ranged mainly around0and the average was0.5‰. The statistics showed that the rock masses of these various deposits had one single source of sulfur and formed under the same physical and chemical conditions which illustrated that sulfur was in the deep source, namely, sulfur was mainly from the magma.(4) The μ value of lead isotope in ore sample of Chenjiazhangzi Mining Area was between9.06～9.30. Theμ value of lead isotope in ore sample of the Hydrothermal Mining Area was between9.39～9.40. The μ. value of lead isotope in ore sample of the the Anjiayingzi Mining Area was betwenn9.27-9.28. The μ value of sulphide in various mining areas was less than9.58, which showed it came from the lower crust or upper mantle. Ore samples also falled within the evolution scope of the orogenic belt and mantle and the range between the lower crusts.(5) The εNd range of the breccia samples of Chenjiazhangzi mining area was between-13.5～-15.0and that of the porphyry samples was between-13.5～-15.0, which showed that the breccia and porphyry hade the feature of mixed crust-mantle. The εNd range of the plagioclase amphibolite samples of Hydrothermal Mining Area was between-17.2～-18.9and that of pegmatite granite and diorite was between-17.5～-17.8, which showed that the source region of plagioclase amphibolite, and diorite was between the lower crust and the mantle while pegmatite granite was located in the side of enriched mantle. The εNd range of the porphyritic granite and adamellite samples of Anjiayingzi minging area was between-11.9～-12.5and that of the diorite xenoliths sample was between～-11.2～-12.6,which showed that their source regions had the feature+of mixed crust-mantle and they were cast between the lower crust and mantle but close to EMI type mantle range.(6) The genetic types of the three gold deposits are divided in this paper:they are the oxidation intrution-related deposits in categories and high-sulfur type of mesothermal-epithermal deposits in types.