Juliane Hübert

2D joint inversion of RMT and ERT data versus individual 3D inversion of full tensor RMT data: An example from Trecate site in Italy

Tensor radiomagnetotelluric (RMT) and electrical resistivity tomography (ERT) data were acquired along 10 parallel lines to image electrical resistivity of the vadose and the saturated zone in an a ...

Integrated MagnetoTelluric and Seismic Reflection study: Skellefte Ore District, northern Sweden.

The Skellefte District is a very rich mining area in northern Sweden. The main deposits consist of volcanic-hosted massive sulphides VHMS rich in zinc, copper, lead, gold and silver. Since the area has been mined and explored for over a century, todays challenge is to locate deeper deposits. The VINNOVA 4D modeling project aims to address this challenge by understanding the regional setting of the district and its evolution over time. © 2011 Society of Exploration Geophysicists.

The Electrical Structure of the Central Main Ethiopian Rift as Imaged by Magnetotellurics: Implications for Magma Storage and Pathways

The Main Ethiopian Rift is part of the East African Rift with its unique geological setting as an active continental breakup zone. The Main Ethiopian Rift includes a number of understudied active volcanoes with potentially high risks for this densely populated part of Ethiopia. Using newly recorded (2016) magnetotelluric data along a 110 km long transect crossing the whole rift, we present a regional 2-D model of electrical resistivity of the crust. The derived model endorses a previous study that drew the surprising conclusion that there was no highly conductive region associated with a magma chamber directly under the central rift volcano Aluto. This has implications for the estimation of the amount of magma present, its water content, and the storage conditions, as the volcano is actively deforming and results from seismicity and CO2 degassing studies all indicate magma storage at about 5 km depth. Additionally, the existence of a strong conductor under the Silti Debre Zeyt Fault Zone approximately 40 km to the northwest of the rift center is confirmed. It is located with a slight offset to the Butajira volcanic field, which hosts a number of scoria cones at the boundary between the NW plateau and the rift. The magnetotelluric model reveals different electrical structures below the eastern and western rift shoulders. The western border is characterized by a sharp lateral contrast between the resistive plateau and the more conductive rift bottom, whereas the eastern flank shows a subhorizontal layered sequence of volcanic deposits and a smooth transition toward the shoulder.

3D joint inversion of magnetotelluric and airborne tipper data: a case study from the Morrison porphyry Cu-Au-Mo deposit, British Columbia, Canada: Joint inversion of magnetotelluric and airborne tipper data

Z-axis tipper electromagnetic (ZTEM) and broadband magnetotelluric (MT) data were used to determine three-dimensional (3-D) electrical resistivity models of the Morrison porphyry Cu-Au-Mo deposit in British Columbia. ZTEM data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground-based MT surveys can achieve a greater exploration depth than ZTEM, but data collection is slower and can be limited by difficult terrain. The airborne ZTEM tipper data and the ground MT tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling and collection date. Resistivity models derived from individual inversions of the ZTEM tipper data and MT impedance data contain some similar features, but the ZTEM model appears to lack resolution below a depth of 1 km and the MT model suffers from non-uniform and relatively sparse spatial sampling. The joint ZTEM-MT inversion solves these issues by combining the dense spatial sampling of the airborne ZTEM technique and the deeper penetration of the lower frequency MT data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3 % Cu zone have the moderate resistivity that is expected of disseminated sulfides. The joint ZTEM-MT inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared to the individual ZTEM and MT inversions. This case study shows that a joint ZTEM-MT approach effectively images the interpreted mineralized zone at the Morrison deposit and could be beneficial in exploration for disseminated sulfides at other porphyry deposits. This article is protected by copyright. All rights reserved

3-D joint Z-axis tipper electromagnetic and magnetotelluric inversion: A case study from the Morrison porphyry Cu-Au-Mo deposit, British Columbia, Canada

Z-axis tipper electromagnetic (ZTEM) and broadband magnetotelluric (MT) data were used to determine three-dimensional (3-D) electrical resistivity models of the Morrison porphyry Cu-Au-Mo deposit in British Columbia. ZTEM data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground-based MT surveys can achieve a greater exploration depth than ZTEM, but data collection is slower and can be limited by difficult terrain. The airborne ZTEM tipper data and the ground MT tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling and collection date. Resistivity models derived from individual inversions of the ZTEM tipper data and MT impedance data contain some similar features, but the ZTEM model appears to lack resolution below a depth of 1 km and the MT model suffers from non-uniform and relatively sparse spatial sampling. The joint ZTEM-MT inversion solves these issues by combining the dense spatial sampling of the airborne ZTEM technique and the deeper penetration of the lower frequency MT data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3 % Cu zone have the moderate resistivity that is expected of disseminated sulfides. The joint ZTEM-MT inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared to the individual ZTEM and MT inversions. This case study shows that a joint ZTEM-MT approach effectively images the interpreted mineralized zone at the Morrison deposit and could be beneficial in exploration for disseminated sulfides at other porphyry deposits. This article is protected by copyright. All rights reserved