The Application Of Constrained 3D Gravity Stochastic Inversion In Jiujiang-ruichang Ore Concentration Area

Gravity and magnetic 3D inversion is an effective way to get 3D subsurface geological structure. However, because of the non-uniqueness of the inversion,it is difficult to build an reliably 3D geological model; So it has become an research hotspot on how to decrease the multiple solutions of gravity and magnetic inversion by multiple-property constraints. We can calculate a most probability density and the spatial correlation of the properties to simulate a set of equal probability models. Therefore, this paper attempt to the study constrained gravity 3D stochastic inversion based on the geological data and physical properties. The features of deep structure of Jiurui ore district was studied using this method.And the study provides evidence and reference for the further research of the deeper exploration and deeper geological structure in the area.This paper begins with the stochastic inversion theory, and introduces the prior probability density function, likelihood function and the posterior probability density function. And then discussed the spatial correlation of the properties,global probability densities,and simulation in stochastic inversion. Finally, introduced the gravity and magnetic 3D stochastic inversion workflow. This paper using two models to verify the feasibility and applicability of the method, a layered undulation model and a model containing a intrusive rocks, and then compared the results of gravity only inversion, induce magnetic inversion, and joint magnetic and gravity inversion. The results shows that the constrained gravity and magnetic 3D stochastic inversion can recover the true geological model effectively. Compared with gravity inversion and magnetic inversion, joint magnetic and gravity inversion can decrease the multiple solutions more effectively. As the quantity of constraint conditions increasing, the result of inversion are more realistic. The physical property statistical laws is an important party of 3D stochastic inversion. Therefore provide an reliable physical statistical law are more important.A 3D geologic model of Jiujiang-Ruichang ore, extends to depth of 3km, has been build by the gravity 3D stochastic inversion. Firstly,comprehensive analysis the geological and density information of the build the geological framework model,and based on properties and its spatial relations,build a set of equal probability 3D geological models.Then calculating the most probability 3D geological model, accordingly, to reveal the 3D spatial distribution of the main formations,intrusive rocks and faults.