高精度重力测量在河南某铝土矿区调查评价中的应用

豫某铝土矿勘查中重力异常显示,区域重力异常反映深部奥陶系顶面呈自西向东缓斜坡状起伏分布;对浅表干扰异常,通过上延过滤后,可以发现奥陶系顶界面的隆、凹起伏分布特征;虽铝土矿密度大于奥陶系灰岩密度,有较大密度差,但由于评价区似层状铝土矿厚度薄,斗状铝土矿虽厚度大,但体积小,重力异常不能直接反映铝土矿。含铝岩系厚度与铝土矿厚度总体上成正比,因此寻找厚大含铝岩系分布区可间接起到找矿的作用。比较含铝岩系密度值与奥陶系灰岩密度值可知,含铝岩系与奥陶系地层有一定的密度差,奥陶系灰岩密度相对较大,因此,局部重力高异常对应奥陶系隆起;对比己知见铝土矿钻井资料和上延后重力异常分布关系,发现铝土矿床大多分布在局部重力高异常以外的区域;通过上述分析,圈定了2个铝土矿找矿靶区,从而对铝土矿的调查评价有重要指导作用。

Application of high precision gravity survey in geological survey and evaluation of a certain bauxite mining area in Henan

According to the gravity anomalies revealed by exploration of a certain bauxite deposit in Henan, the regional gravity anomalies indicate that the Ordovician top surface in the deep part is distributed in the form of gentle slope with ups and downs from west to east.The characteristics of uplifts and depressions of the Ordovician top surface become evident after upward extending filtration of superficial interference anoma-lies.Although the density of bauxite is much larger than that of Ordovician limestone,the gravity anomalies cannot directly reflect bauxite ores,because the bauxite occurred as stratoid in form in the appraisal area is thin and that occurred as bucket in form is thick enough but small in size.The thickness of aluminiferous rock system is generally proportional to that of bauxite deposit,so thick and large aluminiferous rock system area can be helpful clues of prospecting for bauxite deposits.By comparing the densities of aluminiferous rock system and Ordovician limestone,it is obvious that there is a density difference between aluminiferous rock system and Ordovician strata,and the density of Ordovician limestone is higher.Therefore,the local high gravity anomalies correspond to Ordovician uplifts.By comparing the data of known drilling boreholes in which bauxite ores do occur and the distribution of gravity anomalies after upward extending,we can see that most of the bauxite deposits distribute outside of the area with local high gravity anomalies.According to the analysis mentioned above,2 bauxite prospecting targets are blocked out,and the paper has important implications for guiding the geological survey and evaluation of bauxite deposits.