Application Study Of Comprehensive Geophysical Methods In Prospecting Buried Magnetite In Shangqiu Area In Eastern Henan Plain

Shangqiu area in East Henan Plain has better regional metallogenic conditions, itsregional basement construction is composed of presinian period metamorphic rock,contains rich iron. Extensive fault fractures’ movement and differential elevationmake the regional basement to form many secondary swells and cavities, under theconditions of faulting、regional metamorphism and other hydrothermal activities,dispersive Fe element is activated、transferred and enriched to form ore metals. Thereis ordinarily large iron mine especially in the core area of folds. According to theprevious geological and geophysical working results, magnetic and gravity anomaliesin this area are large scale and high strength, they predict more possibility for findinglarge and better iron mine in the area.But Cenozoic stratum in Shangqiu is great thick, there is no any metallogenicinformation in the surface, so common geological prospecting methods can not workin the area. For finding out field source of gravity and magnetic anomaly and exploremagnetite, numerous ground high precision magnetic&gravity surveying andcontrolled source audio-frequency magneto-telluric sounding work has done in thearea. Based on thorough researching on the comprehensive geophysical anomalies, wefound magnetite body or iron mineralized body in the underground between1400-1600m, and prospective resources are estimated iron ore reserves of553milliontons, achieved good prospecting results.Through the ground precision magnetic survey measurements, we found eightmagnetic anomalies named from ShangC-1to ShangC-8, their size and strength is alldifferent. Based on further study on the nature, depth, size, shape and othercharacteristics of their field source, we researched focus on the integrated geophysicalprofiles which contain the ground precision magnetic method, precision groundgravity, controlled source audio magneto-telluric (CSAMT) sounding method, andarranged ZK01and ZK02hole to be drilled and supplemented by integrated loggingverification according to the results of inference and interpretation of the integratedprofile anomalies. Finally, we found thick mineralized magnetic layer in the ZK01hole (ShangC-6) and9magnetite ore bodes or mineralized iron bodes in the ZK02hole (ShangC-1) in Archean Taihua Group. by measuring physical parameters of thedrill core, we consider that the criteria for determining Sedimentary metamorphic rocktype buried magnetite is the is high magnetism, high-density, low-resistancecharacteristicsThe combination of comprehensive geophysical methods consists of the precisionground magnetic&gravity survey, CSAMT sounding method and integrated loggingis better than the single magnetic prospecting in exploring buried magnetite mine inthis area, and worthy of promotion.