AusMT / surveys / Cariewerloo 2012

Cariewerloo 2012 BBMT

Magnetotelluric survey · South Australia · Adelaide University

A broadband magnetotelluric survey of the Cariewerloo Basin in central South Australia, acquired by the University of Adelaide over ten days in June 2012 as an honours research project.

About this survey

A broadband magnetotelluric survey of the Cariewerloo Basin in central South Australia, acquired by the University of Adelaide over ten days in June 2012 as an honours research project. The survey was designed to investigate the structure and geometry of the basin and its underlying crystalline basement in an area prospective for unconformity-related uranium mineralisation. It complemented an earlier Fugro TEMPEST airborne electromagnetic survey, which mapped the unconformity at the base of the Pandurra Formation but had limited depth penetration beneath highly conductive regolith in the northern and eastern parts of the basin. The MT survey was intended to extend the electrical imaging into the deeper basement, investigate possible fluid pathways, and provide an independent constraint on the AEM interpretation and its influence on MT static shift.

Twenty-nine broadband MT stations were deployed along approximately 110 km of the north-south TEMPEST AEM line 7000201. Most stations were spaced approximately 1 km apart, with six outlying stations at approximately 10 km spacing. Eight AuScope broadband MT systems were used, with sites typically recording for two days at 1000 Hz. Each station measured geomagnetic north and east electric and magnetic field components. Magnetic fields were recorded using orthogonal induction coils, while electric fields were measured with non-polarising Cu-CuSO4 electrodes in an L-shaped arrangement with an average dipole length of 50 m.

Coherent time-series windows were processed using robust remote-reference processing to minimise bias from local electromagnetic noise, with a notch filter applied at 50 Hz and its harmonics. The original processing produced impedance estimates at 46 frequencies between approximately 200 and 0.002 Hz. The MT responses successfully imaged the depth to crystalline basement and provided information on deeper electrical structure, while the TEMPEST data were incorporated as a priori information in regularised MT inversion and used to investigate static-shift effects.

AusMT serves impedance transfer functions for all 29 stations, containing 32 to 58 periods spanning 0.0064 to 2183.4 s.

Data and downloads

Stations (29)

Contributors and organisations

Organisation

Adelaide University

Licence

CC BY 4.0

Instruments

Earth Data Ltd PR6-24
LEMI LEMI-120

Processing

BIRRP

Publications

Millicent Crowe (2012). Magnetotellurics and Airborne Electromagnetics as a combined method for assessing basin structure and geometry. B.Sc Hons Thesis, University of Adelaide. http://hdl.handle.net/2440/92159

Identifiers and provenance

Machine-readable survey record · catalogue schema mtcat 2.0