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West Perth, Australia

Hodkinson I.P.,Murrumbo Ltd | Dunn C.E.,Consulting Inc. | Waldron H.M.,Xenocryst Pty Ltd | Scarlett R.,Tanami Gold NL | Vose C.P.,Murrumbo Ltd
Geochemistry: Exploration, Environment, Analysis

 The Palaeoproterozoic Granites–Tanami Province in Western Australia and the Northern Territory contains numerous significant gold deposits, but recent exploration for additional deposits has been hampered by deep weathering of the basement and extensive Tertiary and Quaternary cover. Biogeochemical exploration has rarely been attempted in this environment, with soil sampling and drilling being the principal exploration methods. This paper outlines the methodology and results of a biogeochemical exploration programme utilizing Triodia pungens (soft spinifex), a perennial, hummockforming grass, widely found throughout much of arid and semi-arid Australia. The species possesses several attributes which make it suitable for biogeochemical exploration, being ubiquitous in the area, readily harvested and capable of the uptake of trace elements useful in geochemistry. Systematic sampling has been undertaken at 50 m intervals on widely spaced lines over several prospect areas. Collection of large samples from several plants at each sample station is desirable to try to obtain a representative sample. Initial multi-element analytical work utilizing small samples (c. 2.5 g) of dried and shredded vegetation did not allow sufficient resolution of anomalies, with most results for Au and Pt being below detection levels. However, preconcentration by ashing of substantially larger samples (c. 30 g) has allowed anomaly thresholds for those elements to be more readily defined. The species displays extensive geochemical variability for precious metals, pathfinders, base metals and major cations suggesting it offers much promise as a sampling medium. Test sampling traverses across known gold occurrences confirm the effectiveness of the technique in areas of thick cover sequences. © 2015 AAG/The Geological Society of London. Source

Bagas L.,University of Western Australia | Boucher R.,ABM Resources NL | Li B.,University of Western Australia | Miller J.,University of Western Australia | And 4 more authors.
Australian Journal of Earth Sciences

The Granites-Tanami Orogen (GTO) is a significant auriferous province located in the poorly exposed southwestern part of the North Australian Craton. The stratigraphic succession of the Paleoproterozoic Tanami Group in the orogen is hard to define conclusively, owing to the general lack of outcrop, and is best understood by studying orientated diamond drill holes, such as those at the Dead Bullock Soak and Tanami goldfields, and the Groundrush and Coyote gold deposits. The group is broadly a succession of turbiditic sedimentary rocks included in the Killi Killi Formation conformably overlying shale, mafic volcanic units associated with abundant dolerite and diorite sills, and chert nodules and bands in the Stubbins and Dead Bullock formations. The Mount Charles Formation, previously inferred to be younger than the Killi Killi Formation, is lithologically similar to the Stubbins Formation and also overlain by the Killi Killi Formation. Based on whole-rock and trace-element geochemistry, geochronology, lithostratigraphy and the principles of superposition, the ca 1864 Ma Stubbins, Dead Bullock and Mount Charles formations are here correlated and assigned to the Dead Bullock Formation of the Tanami Group. The deposition of the now extended Dead Bullock Formation was in a back-arc basin setting to the east of the Halls Creek Orogen. Deposition in the basin changed with the introduction of sand-dominated turbiditic successions forming the Killi Killi Formation before ca 1850 Ma when collisional tectonics between the GTO and Halls Creek Orogen resulted in the development of northerly trending isoclinal (FGTO1) folds and associated layer-parallel faults. A second (DGTO2) major collisional event followed at ca 1795 Ma, which is associated with orogenic lode-gold deposits at Callie, Groundrush, Old Pirate and Coyote, and the intrusion-hosted Buccaneer gold deposit in the GTO. This was a period in the history of the GTO when granitic rocks were emplaced shortly before or synchronously with gold mineralisation at ca 1795 Ma. © 2014 Geological Society of Australia. Source

Bagas L.,University of Western Australia | Bierlein F.P.,University of Western Australia | Bierlein F.P.,Afmeco Mining and Exploration Pty Ltd | Anderson J.A.C.,Tanami Gold NL | Maas R.,University of Melbourne
Precambrian Research

The Palaeoproterozoic Granites-Tanami Orogen (GTO) is a significant auriferous province located in the poorly exposed southwestern part of the North Australian Craton (NAC). U-Pb data from Sensitive High Mass Resolution Ion Microprobe (SHRIMP) studies, Sm-Nd isotopic data, geochemistry and petrological studies all suggest that granitic rocks in the Western Australian portion of the GTO were emplaced around ca. 1795 Ma broadly synchronous with gold mineralization. These are variably fractionated, peraluminous, and derived from, or interacted with, ca. 2600 Ma upper crustal material. Deformation, metamorphism and magmatism around 1795 Ma in the GTO were synchronous with the Stafford Orogeny in the Arunta Orogen of central Australia. This deformation was the product of north- to northeast-directed compression within the GTO, and is associated with greenschist facies regional metamorphism. Amphibolite facies metamorphism is restricted to the immediate aureole of certain granitic rocks. This process is clearly a thermal overprint of the regional greenschist facies metamorphism, and indicates that the granitic rocks were emplaced during peak regional metamorphism or soon after. The granitic rocks are inferred to have formed in response to convergence and amalgamation of the GTO and the northern part of the Arunta Orogen along an accretionary margin delineated by the Willowra Lineament, which extends for thousands of kilometres in central and western Australia. Synchronous ca. 1795 Ma orogenic gold mineralization and syn-collisional granitic rocks have been identified across extensive regions throughout the NAC (e.g. the Pine Creek and Halls Creek orogens) suggesting that the Palaeoproterozoic assembly of Australia was marked by a widespread, significant metallogenic event at that time. Crown Copyright © 2009. Source

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