DOI: 10.26186/145260
title: Solid Geology map of the East Tennant region

description: New multidisciplinary data collected as part of the Exploring for the Future (EFTF) Program has changed our understanding of the basement geology of the East Tennant region in the Northern Territory, and its potential to host mineralisation. To ensure this understanding is accurately reflected in geological maps, we undertake a multidisciplinary interpretation of the basement geology in East Tennant. For the purposes of this product, basement comprises polydeformed and variably metamorphosed rocks of the pre-1800 Ma Warramunga Province, which are exposed in outcrop around Tennant Creek, to the west. In the East Tennant region, these rocks are entirely covered by younger flat-lying strata of the Georgina Basin, and locally covered by the Kalkarindji Suite, and South Nicholson Basin (Ahmad 2000). The data from this solid geology map are designed to be included in mineral potential models and future updates to Geoscience Australia’s chronostratigraphic solid geology maps. This interpretation comprises a Geographic Information System (GIS) dataset containing basement geology polygons, faults and contacts. Geological units are consistent with the Australian Stratigraphic Units Database and faults utilise existing conventions followed by Geoscience Australia’s chronostratigraphic solid geology products (Stewart et al. 2020). To aid in understanding the data, we have added a three-stage fault hierarchy. Basement geology was interpreted at 1:100000 scale (but is intended for display at 1:250000 scale) using geophysical imagery, namely total magnetic intensity and vertical derivatives of these data, and gravity. The interpretation makes use of numerous new datasets collected as part of the EFTF program. These include a new 2-km spaced gravity grid over most of East Tennant, drill-core lithology from new boreholes drilled as part of the MinEx CRC National Drilling Initiative, airborne electromagnetic data collected under the AusAEM program, new active seismic data, and geochronology from legacy boreholes. These data are available to view and download from the Geoscience Australia portal (https://portal.ga.gov.au). We interpret that basement in the East Tennant region does represent the eastern continuation of the Warramunga Province. There is no obvious geophysical or geological boundary between Tennant Creek and East Tennant. However, the East Tennant region mostly lacks stratigraphy equivalent to the Ooradidgee Group, which overlies and postdates mineralisation in turbiditic rocks of the Warramunga Formation at Tennant Creek. Instead, East Tennant is underlain by a widespread succession of clastic metapelitic rocks that bear many lithological and geochronological similarities to the Warramunga Formation (Cross et al. 2020). Other important outcomes of this work include the documentation of significant regional faults and shear zones and abundant intrusive rocks at East Tennant. Geophysical and geochronological data suggest that this deformation and magmatism is the eastern continuation of ~1850 Ma tectonism preserved at Tennant Creek (e.g. Cross et al. 2020). NOTE: Specialised (GIS) software is required to view this data. References: Ahmad M, 2000. Geological map of the Northern Territory. 1:2 500 000 scale. Northern Territory Geological Survey, Darwin. Cross AJ, Clark AD, Schofield A and Kositcin N, 2020. New SHRIMP U-Pb zircon and monazite geochronology of the East Tennant region: a possible undercover extension of the Warramunga Province, Tennant Creek. In: Czarnota K, Roach I, Abbott S, Haynes M, Kositcin N, Ray A and Slatter E (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4. Stewart AJ, Liu SF, Bonnardot M-A, Highet LM, Woods M, Brown C, Czarnota K and Connors K, 2020. Seamless chronostratigraphic solid geology of the North Australian Craton. In: Czarnota K, Roach I, Abbott S, Haynes M, Kositcin N, Ray A and Slatter E (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.