Calculation and inversion of two-dimensional gravity in the vicinity of Lake Tuz, Turkey

An example of gravity inversion and interpretation is presented which demon strates how a priori information can be used to derive reliable, though com plex models. In this case, the geometry of the studied model profile has be en constructed on the basis of seismic and geological data. The densities u sed in the forward calculations were obtained from laboratory measurements of drill cores, from density-velocity relationships, and from Nettleton's m ethod of fitting gravity and topography. In the seismic section 21 'formations' are distinguished leading to a very complex gravity model. What is called 'formations' here, are two-dimensiona l bodies which are distinguished from each other seismically and perhaps pa rtly by a priori knowledge. Some of the formations have approximately the s ame densities and could thus be treated as single masses. On the other hand , the same formation may have a complex form and may consist of separate bo dies, e.g. as a consequence of faulting; they are still treated as single b odies. Accordingly, the number of bodies of constant density could be reduc ed to eight. The gravity effect calculated for the model with the initial density assump tions regionally clearly deviated from the observed anomaly. More probable densities were then determined for the formations with inversion calculatio ns in an attempt to optimally fit the calculations to the observations. Alw ays, a better fit could be obtained. In one case about 5 g/cm(3) density wa s calculated for a single small formation. The proposal is to either invest igate whether or not there may exist an ore-body worthwhile for further exp loration or to change the seismic section on a limited scale. If the high d ensity is not accepted, compatibility between observed and calculated gravi ty and plausible densities can be achieved by changing the formation volume (thickness). Other formational densities down to the depth of 32 km have b een found to be between 2 and 2.7 g/cm(3). (C) 1999 Elsevier Science Ltd. A ll rights reserved.