Geologic Structure And Deep Feasibility Study Of Prospection In Xuanhua Dabaiyang Gold Deposit, Northwest Of Hebei

Zhangxuan area located in western marginal arched area of Yanshan platform fold belt,North China platform, and the north of which is Chongli-Chicheng deep fault. In this area Chongli terrain mesometamorphic rock series was exposured widely, and magmatic activities was developed comparatively under the countrol of Chongli-Chicheng deep fault. Zhangxuan area is one of crowded gold deposits area in the north of North China platform, distribute varied scale gold deposits, and is called "gold triangle" of Hebei province.Based on extensive data collection, detailed field geological studies and laboratory investigation, we judged that Hanjiagou gold deposit appears in Chongli terrain second lithodeme, the main structure is Hanjiagou anticlinorium which composed by three anticlines and two synclines, and in the eastern limbs of anticlines （partly were reversed limbs） formed thrust-overlap fault structure easely. Mineral ore all were shaped in shear cracks which were mineralise structure, and then thrust-overlap fault converted to down fault which were host stucture. Later down fault altered mineral ore after mineralization. The main type of mineral ore is auric sulphide quartz vein, the mineralization were pyritization, galenitization and chalcopyritization in the vein ore, and chloritization, sericitization, potassic alteration appeared in the surrounding rock. Three stages hydrothermal activities emerged in Hanjiagou gold deposit after magmatic stage:borengite-granitic vein, auric sulphide quartz vein and veinlet auric quartz vein. In Xiangshuigou gold deposit, metallogenic mother rock of mineral deposit was Xiangshuigou granite mass whose auric abundance is 15ppb, and the mineral ore was mainly generated in the later quartz vein. According to the study of inlusions, we know the inlusions are gas-liquid phase and can descerned three generations, the formational temperature was 245°-365°, the mineralizing fluid was alkalescent and low-to-moderate salinity whose type is Na-K-SO₄-Cl.Based on the studies of auric aboundance in Chongli terrain, surfur isotope, host stucture in this mineral deposit, mineralization period of Au, we generally establish mineralize model of Hanjiagou gold deposit:First, Hanjiagou anticlinorium generated in Archean pressure environment, and strust-overlap fault structure formed in the eastern limbs of anticlines; Second, acid rock mass intruded in Yanshan stage, and then auric thermal fluid unlifted along the progenetic fault after magmatic stage, making Au further concentrated by activating and extracting Au from surrounding rock; Finally, progenetic reverse fault converted down fault, and along with the descent of temperature and pressure, the auric thermal fluid continued uplifted, and then mineralized in down fault at approximate 170Ma.