等值反磁通瞬变电磁和微动法在内蒙古某萤石矿采空区探测中的应用效果浅析

Analysis on the Application Effect of Comprehensive Geophysical Prospecting Method in Goaf Detection of a Fluorite Mine in Inner Mongolia

萤石矿老旧采空区是矿石资源二次开发利用过程中常见的不良地质体,物探是采空区勘查的重要手段,等值反磁通瞬变电磁法和微动勘探在采空区的勘察中应用广泛。本文通过等值反磁通瞬变电磁法和微动勘探两种方法在内蒙古某萤石矿采空区进行探测,结合已知矿体分布情况,建立了研究区200 m以浅的电性结构,划分了采空区顶板、底板和边界范围,推断了采空区的空间展布情况,为矿区现有萤石矿储量计算及资源二次开发利用提供了参考依据。两种方法推测结论基本一致,采空区和断裂异常反映略有不同,钻孔验证结果表明,等值反磁通瞬变电磁法及微动勘探两种方法均能反映采空区形态、厚度、埋深等空间分布特征,为采空区边界的详细划定提供依据。等值反磁通瞬变电磁法仪器轻便,采集时间短,受地形限制小,大大提高了野外的施工效率,是采空区勘查中物探首选方法;不足之处是微动勘探在草原、戈壁等相对震源较少区采集数据较慢。

The old mined-out area of fluorite ore is a common bad geological body in the process of secondary exploitation and utilization of ore resources.Geophysical exploration is an important means for the exploration of mined-out area.the construction efficiency and the economic cost of opposing coils transient electromagnetic(OCTE)method and microtremor survey(MS)are widely used in the exploration of mined-out area.In this paper,two methods of equivalent inverse magnetic flux transient electromagnetic method and fretting exploration are used to detect the mined-out area of a fluorite mine in Inner Mongolia.Combined with the distribution of known ore bodies,a shallow electrical structure of 200m is established in the study area.The roof,floor and boundary range of the mined-out area are divided,and the spatial distribution of the mined-out area is deduced,which provides a reference for the calculation of existing fluorite reserves and the secondary exploitation and utilization of resources in the mining area.The borehole verification results show that the construction efficiency and the economic cost of opposing coils transient electromagnetic(OCTE)method and microtremor survey(MS)can reflect the spatial distribution characteristics of the shape,thickness and buried depth of the goaf,providing a basis for the detailed delineation of the boundary of the goaf.The equivalent anti-magnetic opposing coils transient electromagnetic(OCTE)method has the advantages of portable instrument,short acquisition time and small limitation by terrain,which greatly improves the field construction efficiency and is the preferred method for geophysical prospecting in goaf exploration.Its disadvantage is that acquisition data by fretting exploration in grassland,gobi and other areas are relatively slow.