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Three-Dimensional Audiomagnetotelluric Mapping of Kimberlites over Serra da Canastra Diamondiferous Province of BrazilNormal access

Authors: V. Maurya, E. LA TERRA, S. Fontes and L. Panetto
Event name: 81st EAGE Conference and Exhibition 2019
Session: Near Surface Understanding I
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201900975
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.34Mb )
Price: € 20

Summary:
More than hundreds of kimberlites occur along a 3000-km-long, northwest-southeast trending, major crustal fracture zone of Brazil. This tectonic feature passes over Serra da Canastra Diamondiferous Province, Minas Gerais, Brazil. Kimberlites are main source rocks forming the diamondiferous deposits of Serra da Canastra Province. Kimberlites exhibit low-resistivity anomalies which can easily be mapped by Audiomagnetotellurics (AMT). One-hundred AMT stations were obtained over the Canastra-8 kimberlite pipe, which belongs to a well known Serra da Canastra Diamondiferous Province. All sites were processed to produce the impedance transfer function for frequency ranging between 100 kHz - 10 Hz. Phase tensor analysis parameters, phase skews, maximum and minimum phases overviews the three-dimensionality and low-resistivity of kimberlite pipes and high-resistivity of surrounding host rocks. Three-dimensional robust conductivity model was constructed for C-8 kimberlite pipe after various a priori uniform half-space model tests. Kimberlite pipes mapped by AMT 3-D model, branch out in two pipes below 300 m and seems to be a single pipe for depths between 300 - 700 m. 3D resistivity model shows that the crater phase of kimberlites may branch out in several thin pipes in the region. However, deep diatreme phase of kimberlites thickens out with depth, unlike previous models.


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