个旧锡矿区物理-地质模型及应用效果

PHYSICO-GEOLOGIC MODEL OF THE GEJIU TIN DISTRICT AND ITS APPUCATION

个旧锡矿区,氧化深度一般为200—700m。因此,在找浅部矿和深部矿(400m或更深)时,物探通过找硫化物而达到找锡矿的作法效果不好。为此,根据工作地区的地质及地球物理特点,建立了区域找矿物探异常模式、矿田物探异常模式及在矿田中寻找矿床的物探异常模式。通过解决找矿过程中的地质问题,物探在圈出找浅部矿体的远景区和找深部矿床的远景区等方面,都取得了很好的效果。

The Gejiu tin district is controlled by a complex anticline and a Yanshanian buried granite intrusion, while the ore fields in the district are controlled by secondary folds and faults and small stocks. The depth of oxidation in the district is 200-700 m. In the oxidation zone, no sulfides exist and the geophysical method meets with great difficulty in looking for sulfides and then finding tin deposits.Based on the known geological and geophysical data of this area, a physico-geological model of Gejiu tin deposits, and geophysical anomaly patterns of regional exploration, ore fields and searching for ore bodies in the fields are established also.Good results have been achieved by using the geophysical method in the exploration in the Gejiu area.For example, by means of middle-scale aeromagnetic and ground gravity surveys a buried granite intrusion was delineated in the eastern part of Gejiu and it has been proved that no buried intrusion occurs in the western part of Gejiu. In the eastern part, electric sounding was used to map the top depth of the intrusion (generally over 400 m) and thus delineate the possible areal extent of the ore field (i.e. the deep ore prospect area). Then through drilling a big ore field was found. The average relative error inferred by the geophysical method is about ±12%.To search for shallow ore bodies, the resistance method was used to trace the known faults and then rock samples in the fault zones were taken for a lith-ogeochemical study in order to evaluate the mineralization in the fault zones. According to the statistics, about 500 faults were delineated and about 100 were verified by exploration engineering. The results indicate that the rate of success is about 90%.