利用重力水平梯度△gx计算深度的方法及地质效果

AN APPROACH OF CALCULATING THE DEPTH FROM HORIZONTAL GRAVITY GRADIENT (△gx) ANDITS GEOLOGSCAL REASONING

地质矿产部航空物探大队

利用重力水平梯度(△gx)计算深度是一种新方法,它是根据参考文献[1]中提出的原理进行的。1978年我们选择济黄地区进行了大面积实践,证明此方法是可行的。计算深度和勾绘深度图的方法完全借用航空磁测的解释方法。这就为今后重磁资料的综合解释提供了新途径,为利用重力资料进行定量解释提出了一种新方法。此项工作,大致有两个重点环节:一个是如何绘制△g连续剖面,并在此基础上制作△gx剖面;另一个是如何分出背景场和不同的密度界面。实践表明,在有高质量的连续性好的△g剖面时,分出两个乃至三个重力密度界面是可能的,并可在此基础上绘制主重力界面深度图。本文介绍了如何利用重力水平梯度异常(△gx)计算深度和剩余密度的方法、实例及体会,指出利用重力水平梯度图可以提供更直观的断裂信息,可以寻找与油气有关的古潜山构造。

It's a new approach to calculate the depth from horizontal gravity gradient (△gx) in the light of the principle proposed in reference 〔1〕. In 1978, tests were made on large scale with the data obtained from Ji-huang region. The approach of depth calculation and depth contour mapping are quoted from those used in aeromagnetics and it is proved feasible. This makes it possible for us to conduct an integrated interpretation of gravity and magnetic data and the quantitative interpretation by using gravity imformation.Generally, there are two major points in the procedure: one of them is how to map the continuous sections of △g, and on the basis of it to construct the △gx sections, the other is how to distinguish the interfaces with different density from the background field. Experience tells that two, sometimes even three, density interfaces could be identified and the map of interfacial depth could also be constructed if the sections are in high quality and have good continuity.In this paper, the approach of calculating the depth and residual density from the horizontal gradient anomaly (△gx) has been described. Examples in this connection are given. With the aid of the horizontal gravity gradient map, the appearance of rifts could be seen audio-visually and searching for old latent mountains related to hydrocarbons could also be made. Besides, experience gained in this respect is recounted in this paper.