Scale reduction using magnetotellurics – a mineral exploration example from the Olympic Domain, South Australia
0
Citation
6
Reference
10
Related Paper
Abstract:
SummaryWe present results of 334 ultra-wide band MT stations across an area of 100 km × 100 km in the prospective eastern Gawler Craton. The survey area is situated ~100 km south of the supergiant Olympic Dam IOCG deposit, across an area of several IOCG deposits and prospects, including Carrapateena, Oak Dam, and Khamsin. Station spacing varies between 5 km and reduces to 1.5 km around areas of known IOCG prospects. The 3D resistivity models show a north-south oriented conductor in the upper crust. Known IOCG prospects are situated along its margins. These results expand the previously only 2D defined signatures of IOCG deposits, such as Olympic Dam to the full 3D domain. Together with the wider-spacedAusLAMP deployment and a 1.5km to 3 km spaced AEM survey, the survey is unique for imaging the whole-oflithosphere footprint of IOCG deposits under cover.Keywords:
Magnetotellurics
Geophysical survey
Cite
Citations (0)
The tectonic setting of Hiltaba Suite (1595–1575 Ma) magmatism within the Gawler Craton has long been regarded as anorogenic, accompanied by mild extension (Flint et al. 1993; Creaser 1995). This evaluation was largely based on the apparently limited deformation recorded within the Hiltaba Suite and Gawler Range Volcanics, their enriched geochemical signature and the high-temperature nature of magmatism. However, there is now growing evidence that contractional fault reactivation, metamorphism and locally pervasive deformation were associated with the emplacement of the Hiltaba Suite and the associated iron oxide – copper–gold (IOCG) ± uranium and gold mineral systems, suggesting the existence of a compressional regime in the early Mesoproterozoic Gawler Craton. In this contribution, we briefly summarise evidence for crustal-scale early Mesoproterozoic deformation in the Gawler Craton and suggest it forms part of a broader system that incorporates the Olarian Orogeny of the Curnamona Province. In the light of the new data on the spatial nature of early Mesoproterozoic deformation and metamorphism across southern Australian Proterozoic terranes (Fig. 1), we suggest that the Gawler Range and Benagerie volcanics are an unusual volcanic-fill within a foreland basin that formed within a broadly NW–SE-directed compressional regime.Several lines of evidence suggest that the Gawler Craton and the Curnamona Province were part of a coherent and likely contiguous, crustal system by the late Palaeoproterozoic to early Mesoproterozoic. In brief, these are: (1) likely correlation of the Gawler Range and Benagerie volcanics; (2) similarities in timing of early Mesoproterozoic granitic magmatism; and (3) growing evidence in the Gawler
Orogeny
Cite
Citations (0)
Prospecting
Iron ore
Ore genesis
Gold ore
Cite
Citations (20)
Abstract The link between mineral resources and crustal‐rooted structures has been proposed for many of the world's most significant mineral provinces. Here we utilize a new approach by interpreting potential field data, including satellite gravity data, and high‐resolution continental‐scale magnetotelluric data, constrained with aeromagnetic, and seismic tomography and reflection data, to determine the distribution of crustal‐scale faults in the Archean to Proterozoic Gawler Craton (South Australia). The eastern flank of the craton hosts the supergiant Olympic Dam iron oxide‐copper‐gold (IOCG) deposit within a larger Olympic IOCG province. The central part of the craton contains gold‐only deposits, which define the Central Gawler Gold province. Both of these provinces are part of a Mesoproterozoic mineral system with an extensive hydrothermal alteration footprint, which formed during complicated tectonic mode switches. We show that both types of mineralization are located in proximity to crustal‐scale structures that appear to connect deep crustal fragments, which likely record the amalgamation of the Archean nucleus of the craton during the Neoarchean with subsequent reworking during the Mesoproterozoic. Many of these structures do not have a surface expression but coincide with gradients in magnetism, gravity, and electric resistivity anomalies, the latter data set suggesting they acted as fluid pathways extending to the lower crust. The results indicate that the first‐order controls on the distribution of IOCG and Central Gawler Gold metallogenic provinces are inherited from earlier tectonic events, which formed major crustal boundaries and related structures that are prone to reworking during later tectonism.
Prospectivity mapping
Metallogeny
Basement
Mineral exploration
Cite
Citations (23)
Cite
Citations (21)
The Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) has the goal of mapping the electrical resistivity of the Australian lithosphere to constrain the geodynamic framework of the continent. Between August 2014 and May 2015, 125 long-period magnetotelluric (MT) data will be collected across the Gawler Craton and the south-eastern part of South Australia at intervals of 50 km. Results will be compared to existing 3D models highlighting enhanced conductivity in the sub-lithospheric mantle of the Gawler Craton. Initial results of 1D depth transformations show a significant change in resistivity at mantle lithosphere depths (100 km). The results will also be tied to the newly acquired Eucla MT line and a new 1000 km NS MT profile extending north from the central Gawler Craton into the Arunta Province, NT.
Magnetotellurics
Cite
Citations (0)
Cite
Citations (2)
Deep seismic reflection data acquired in the eastern Gawler Craton show the crustal architecture and Palaeoproterozoic crustal-scale thrusts controlling the locus of fluid-flow leading to Fe oxide Cu-Au mineralisation. They define a northwest-trending exploration fairway.The thrusts are temporally related to the 1.6 Ga Olarian Orogeny of the adjacent Curnamona Province, hut a causal link is yet to be established.The crust below the Adelaide Rift System, at the northern end of the north-south seismic line, may be allochthonous; docking with the proto-Gawler Craton, as a separate terrane prior to final amalgamation of the craton, or it could be part of the Curnamona Province.
Orogeny
Cite
Citations (0)