| Xiong'ershan area,which is located in the southern margin of the North China Craton,is an important part of the Fe-Al-Mo-Pb-Zn-Au metallogenic belt in western Henan Province.In this study,the gold deposits in Xiong'ershan area are investigated.Based on existing data,the gold mineralization is mainly studied through comprehensive geological observation,geophysical survey,geochemical data collecting and detailed case studies on several ore deposits in the region.During the processes,major ore controlling factors,regional prospecting criteria and model are discussed and established.The main achievements are as follows:1.The zircon U-Pb age of meta-diabase,which intruded into the Taihua Group,is provided.The age is 2303±30 Ma,which is consistent with gneissic monzogranite that also intruded into the Taihua Group in the region.This result shows that they were formed contemporaneously,thus constitute a suite of bimodal intrusive rocks.The geochemical data of the Majiahe Formation andesite in the Xiong'er Group shows that it was formed in a continental rift environment,which may be related to the extension and segregation of the North China Craton.2.According to the characteristics of gold deposits in the Xiong'ershan area,the gold mineralisation is divided into two groups,four series and six types.To investigate the explosion breccia type,porphyry type,altered fracture zone type and quartz vein type mineralization in this region,the Dianfang gold deposit,the No.189 ore body of Qiyugou gold deposit,Beiling gold deposit and the No.1 vein of Yaogou gold deposit are selected and detailed studies are carried out.3.The results of lead and sulfur isotopic studies indicate that ore-forming materials of the Beiling gold deposit mainly derived from mantle,and may also have experienced minor contamination by crust-derived materials.In the process of mineralization,oxygen fugacity of ore-forming fluids increased due to the addition of meteoric water,which on the other hand caused sulfur isotope fractionation.Trace element composition of ore samples indicates that ore-forming fluid was rich in C1,and the ore-forming environment was relatively reduced.4.The results of sulfur isotope and fluid inclusion studies indicate that the sulfur of sulfide in the Dianfang gold deposit may come from the deep.The ore-forming fluid belongs to H2O-NaCl-CO2 system with medium to low temperature and low salinity signature.The EPMA studies on actinolites,garnet,pyrite,galena and sphalerite in ores show that the main elements of actnolite vary little thus highly consistent.Garnet belongs to almandine species.Pyrite is of magmatic or epithermal origin,and sphalerite is of medium low temperature origin.The minimum age of a single zircon from granite porphyry breccia in breccia pipe is 146 Ma,which may represent the lower limit of its metallogenic age.5.The unconformity plane between the Taihua Group and the Xiong'er Group controls the spatial distribution of gold ore deposits.The main ore controlling factors include regional tectonic regime,Moho surface morphology,crust and mantle material interaction,structures with different properties as well as regional metamorphism together with stratigraphy,and last but not the least,magmatic rocks.Four types of gold prospecting indicators,including geological,geophysical,geochemical and remote sensing,are developed.A comprehensive geological-geophysical-geochemical prospecting model is established.Prospecting and exploration of targeted areas in the region have been carried out,and new gold deposits/propescts are discovered,including but not limited to the Tangmengou pyroclastic type gold deposit,which is considered to be a newly identified type of gold mineralisation in the Xiong'er shan and Waifangshan area. |
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