FellowJan Vozar
Project NameMulti-dimensional integrated geophysical-petrological modelling of the crust, and uppermost mantle for central Europe region by structural joint inversion
Host organisationEarth Science Institute
Duration of the project01.03.2016 - 31.12.2018

Abstract
Geophysical research, particularly using geoelectrical methods, significantly contributes to understanding and exploring processes related to strategic energy and mineral resources. The combination of different geophysical methods in a single inversion scheme reduces the non-uniqueness of inversion problems and the resulting models. Integrated geophysical and petrological modelling, together with inverse problems, represent the most interesting research topics for geophysical studies. In the project a petrologically driven approach with LitMod3D package, which models geophysical observables, constrained by topographic height and heat flow, will be extended by structurally coupled crustal model created by jif3D joint inversion code for gravity, seismic and magnetotelluric data with the new name LitMod3Dic. The original LitMod package derives realistic temperature and pressure distributions within the upper mantle and characterizes mineral assemblages of given bulk chemical compositions as well as water content, what allows us to define a bulk geophysical model of the upper mantle to derive corresponding predicted geophysical observables. The implementation of crustal inversion scheme will be done in two steps: a) the MT inversion code with geoelectrical crustal model will be included, because the MT 3D inversion code is most time consuming for numerical calculation and the necessary modifications of the MT inversion code will be essential; b) the joint inversion framework jif3D approach will be included to add coupled crustal density and seismic velocities models. With final modified code LitMod3Dic will be used to undertake a multi-dimensional, petrologically-driven approach of combining MT, gravity and seismic data in inversion modelling of the upper-most mantle in the Carpatho-Pannonian region. The following studies will focus on the mapping of Neo-vulcanites and sub-basaltic crustal structures and thermal parameters in eastern and central Slovakia.

Project Summary with Interim Results

In the project we proposed a multi-disciplinary geophysical and geological modelling approach with the objectives divided into two thematic subsequent phases of solution: 1) developing a new modelling tool named LitMod3Dic, where the magnetotelluric (MT) method and the joint inversion JIF3D code will be implemented to the thermodynamically self-consistent LitMod3D modelling approach; and 2) application of the new combined LitMod3Dic code aimed to image geological crustal and mantle structures.

In the first phase of the project we focused on methodological development and code modification of compatible 3-D forward and inverse magnetotelluric solver module in order to implement it to the LitMod3D package. This process of implementation led to two main groups of the project outputs.

The first group is connected directly to 3-D MT forward/inverse codes and their assessment for application in small scale and big scale problems. The focus was mainly on resolution and precision of calculated electromagnetic responses obtained by different MT numerical methods, that depends on used gridding scheme. The codes passed through benchmarking of the effective calculating speed and topography effects in final calculated transfer functions. In the second group of outputs we developed the 3-D geoelectric model conversion script with full support of input/output geographical map projection systems. The script allows conversion from four different MT code model formats into LitMod3D package format and reversely. This approach keeps MT module flexibility for future users.

The efficiency of JIF3D joint inversion framework package and its coupling methods has been tested on real geophysical (gravity and MT) data. The modelling results exhibit resolution improvement in both (density and conductivity) models. The spatial positions and determined values of conductivity and density parameters were confirmed by in situ information from boreholes and seismic reflection profiles. The input databases and parameters for integrated modelling planned for the second phase of the project were prepared.