AusMT / surveys / North-Western Tasmania 2016

North-Western Tasmania 2016 BBMT

Magnetotelluric survey · Tasmania · University of Tasmania

A broadband magnetotelluric transect of about 50 km was acquired across north-western Tasmania in February 2016, running south from the northernmost site near Forth on the north coast to Dove Lake at Cradle Mountain, along Wilmot Road and Cradle Mountain Road at a nominal 2 km site spacing.

About this survey

A broadband magnetotelluric transect of about 50 km was acquired across north-western Tasmania in February 2016, running south from the northernmost site near Forth on the north coast to Dove Lake at Cradle Mountain, along Wilmot Road and Cradle Mountain Road at a nominal 2 km site spacing. The line crosses the boundary between Precambrian Tyennan basement and the metalliferous Cambrian to Devonian Dundas-Fossey Trough, and was acquired together with a companion western transect for shallower imaging of the lithosphere beneath western and north-western Tasmania. Crews worked from a Gowrie Park field base and began at the northern end of the line. A remote-reference station about 4 km south of Beulah and 20 km east of the line was established before acquisition on the transect began, and the lodged files name three dated records from it. The work was University of Tasmania PhD fieldwork by Thomas Ostersen, supervised by Anya Reading (University of Tasmania) and Graham Heinson (University of Adelaide), proposed and funded by Mineral Resources Tasmania, with Geoscience Australia, the University of Adelaide and PassiveX Ltd contributing field personnel.

Instruments came from the ANSIR national Earth sounding instrument pool, funded by AuScope and maintained by the University of Adelaide. Each site ran a 24-bit six-channel PR6-24 Earth Data Logger sampling at 1000 Hz for 36 to 48 hours, recording Bx and By on two buried LEMI-120 induction coils and Ex and Ey across three Petiau-type lead chloride non-polarisable electrodes on dipoles of about 30 to 51 m against a nominal 50 m. Transfer functions were estimated with the bounded influence remote reference code BIRRP 5.1, driven from MTpy, in a high-frequency pass over a three-hour window and a low-frequency pass over the whole deployment, the two results then merged into one EDI file per site carrying 37 frequencies from 187.49998 Hz to 0.00061 Hz. The two-pass recipe and the three-hour window are stated by the lodgement's own processing README for this transect.

This package serves the 27 EDI transfer functions that were lodged with Mineral Resources Tasmania. Power line noise at 50 Hz meant most impedance estimates at periods shorter than about 0.03 s could not be recovered, which leaves the recovered responses insensitive to structure above roughly 3 km depth for typical shallow crustal resistivities; on that ground Ostersen (2021) section 5.2.3 removed the line from further modelling in the thesis, and no publication presents it. Mineral Resources Tasmania nonetheless holds an Occam2D inversion of this transect in the same lodgement.

Data origin. The transfer functions served here are the 27 files of ProcessedData/Northern_broadband_transect/processed_data/raw_edi.zip in Mineral Resources Tasmania lodgement GPCR2019_01 (MRT webdoc record id 115522, "Geoelectric Structure of the Tasmanian Lithosphere from Multi-Scale Magnetotelluric Data", Ostersen, T., dated 28 April 2021), released under Creative Commons Attribution 3.0 Australia. The raw time series behind them are held by NCI as 32 packed archives, site_201.zip to site_231.zip plus site_232_remote.zip, 96.0 GB in total, under DOI 10.25914/ekv8-my29 within survey record 10.25914/mrx9-r791.

Data and downloads

Stations (27)

Contributors and organisations

Organisation

University of Tasmania

Licence

CC BY 3.0 AU

Instruments

Earth Data PR6-24
LEMI LEMI-120
SDEC Petiau lead chloride electrode

Processing

BIRRP

Funding

Mineral Resources Tasmania
AuScope
National Collaborative Research Infrastructure Strategy (NCRIS)

Publications

Ostersen T C H (2021). Geoelectric Structure of the Tasmanian Lithosphere from Multi-Scale Magnetotelluric Data. PhD thesis, University of Tasmania. 10.25959/100.00037925

Ostersen T C H, Reading A M, Cracknell M J, Roach M, Duffett M L, Bombardieri D J, McNeill A, Fomin T, Brand K E, Thiel S, Boren G, Heinson G (2024). Resistivity anomalies in the shallow and deep crust beneath West Tasmania from a broadband magnetotelluric 2D transect. Exploration Geophysics. 10.1080/08123985.2024.2392802

Identifiers and provenance

Machine-readable survey record · catalogue schema mtcat 2.0