Aileron Project EL 26375 Chianina Partial relinquishment report for the period ending 15 April 2010

Abstract

This is the first Partial Relinquishment Report for Chianina tenement EL 26375 that was granted to NuPower on 16 April 2008. There are no known mineral occurrences in the area, or within 20km of the tenement. The area covered by EL 26375 was selected by NuPower Resources Limited because of the potential for secondary uranium mineralisation, derived by erosion of adjacent uraniferous basement granites and gneisses, in unconsolidated Tertiary basin sediments of the Ti-Tree Basin. There is little primary uranium potential. Highly weathered basement rocks that outcrop sparsely in the eastern part of the area exhibit no airborne uranium radiometric anomalies and only subtle thorium anomalies. The basement of the Aileron region comprises rocks of the Arunta Region, a complex basement inlier in central Australia that has undergone a prolonged history of sedimentation, magmatism, and tectonism extending from the Palaeoproterozoic to the Palaeozoic that is subdivided into three, largely fault bounded terranes with distinct geological histories; the Aileron, Warumpi and Irindina Provinces. The basement geology of Chianina area is assumed to comprise units of the Aileron Province that consists of greenschist to granulite facies metamorphic rocks with protolith ages in the range 1865-1710 Ma. It forms part of the North Australian Craton and is geologically continuous with the gold-bearing Tanami and Tennant Regions to the North. Because of the high grade of metamorphism and the relative paucity of continuous outcrop across the Arunta Province, a reliable stratigraphy has not yet been constructed for the metasedimentary sequences. Instead, the Early-Mid Proterozoic metamorphosed rocks of the area have been subdivided by Stewart (1981) into three 'Divisions', intruded by granites, on the basis of 'broad lithological correlations', Division 1 being regarded as the oldest and Division 3 as the youngest. The rock units within each division may be chronostratigraphic correlatives but there is no evidence yet to support this. The Arunta Block is traversed by a series of WNE-NW trending faults that locally widen into extensive zones of shearing and retrogression comprising muscovite-quartz schist with extensive quartz veins and epidote-bearing rocks. There is evidence for these here in the regional airborne magnetic data. Basement rocks of probable Division 1 group are limited to areas of highly weathered rocks in the eastern part of the tenement Pre-Cambrian rocks outcrop east of the tenement and include the Delny Gneiss comprising biotite-microcline-muscovite-quartz gneiss, biotite-muscovite schist, metapsammite, amphibolite and minor calc-silicate gneiss and the Chiripee Gneiss of the Strangways Metamorphic complex consisting of migmatitic garnet-biotite-feldspar gneiss, amphibolite, calc-silicates and quartzite. These are intruded by Proterozoic gneissic biotite and hornblende granite of the Crooked Hole Granite and porphyritic biotite gneissic granite, biotite and hornblende adamellite, and garnet-bearing granite of the Woodgreen Granite Complex. To the west of Chianina outcrop includes Proterozoic undifferentiated granite, diorite and tonalite and Woolla Gneiss comprising quartz-biotite-feldspar gneiss, muscovite-biotite-quartz schist and garnet-biotite-quartz-feldspar gneiss. Northeast of Chianina the Arunta Inlier is stratigraphically unconformably overlain by Neoproterozoic and early Palaeozoic sediments of the Georgina Basin and outliers may underlie Chianina. The stratigraphy if this basin comprises basal quartz sandstones, quartzites and conglomerates of the Grant Bluff Formation overlain by transitional marine/continental and glacial red and white sandstones and siltstones, quartzite, arkose, shale, conglomerate with basal tillites, boulder beds and ferruginous pebbly sandstones of the Central Mount Stuart Formation. These in turn are unconformably overlain by Cambrian and Ordovician sandstones, siltstones dolomite and chert of the Tomahawk Beds. The youngest rocks in the basin are of Devonian age and consist of cross-bedded sandstone, siltstone and conglomerate of the Dulcie Sandstone. The southern NT forms a 'basin and range' province in which Proterozoic and Palaeozoic rocks form prominent ranges separated by broad valleys in which at least twenty major Cainozoic sedimentary basins have developed, of which the Ti Tree Basin underlies the western two thirds of the license area. The stratigraphy of these basins is generally poorly known due to a lack of outcrop, strong weathering overprints, the paucity of drillholes and a lack of attention paid to the 'cover' overlaying crystalline basement. Limited stratigraphic drilling by both the BMR and the NTGS during the 1960's and 1970's provides much of the regional stratigraphic information of the Cainozoic Basins. During the late 1970's and early 1980's the Hale Basin southeast of Chianina was explored extensively for coal and sedimentary uranium and has therefore become the best known Cainozoic Basin in the NT and although the succession is relatively thin it is considered to represent a generalised Tertiary stratigraphy for the region. Here a broad two-fold stratigraphic subdivision comprises a restricted, fluvial palaeochannel dominated Palaeogene succession (Hale Formation) overlain by a more widespread, dominantly lacustrine Neogene succession (Waite Formation). Although the Cainozoic stratigraphic units were initially defined in separate small and isolated Tertiary Basins, these units are now recognised as components of a much larger Tertiary palaeodrainage system, the extent and size of which has until now been vastly underappreciated. Elsewhere historic and recent drilling results indicate that the basins may contain very thick sedimentary packages. The Cainozoic fill of the Burt Basin exceeds 200m and the Sixteen-Mile Basin contains at least 180m of sediment. Similarly, the Whitcherry Basin and Waite Basins are known to exceed 250m in thickness in some locations, whilst minor tributaries feeding the Ti-Tree Basin contain up to 140m of sediments. The maximum thickness of the Cainozoic sediments in the Ti-Tree Basin is not currently known as exploration drillholes to date by NuPower after drilling though a minimum of 320m of sediment south of Chianina, have locally failed to penetrate to basement and thicknesses of 400-500m of sediments are considered to be likely in the deeper portions of the basin. Deposition of Cainozoic sediments was episodic and punctuated by hiatuses during which prolonged periods of weathering resulted in the formation of well-developed weathered profiles (palaeosols and duricrusts). Deep weathering was an ongoing process during the Tertiary but was enhanced at particular times during this time by the combination of periods of warm, humid climates, non-deposition and surface exposure. Three Palaeogene weathering events affecting the Arunta igneous and metamorphic basement rocks and the overlying Tertiary successions and two weathering events affecting the overlying Neogene successions have been recognised. Sediments of the Waite Formation comprising calcrete, silty sandstone and minor pebble and granule conglomerate and mudstone outcrop extensively in the centre of Chianina. Overlying these sediments are unconsolidated Quaternary sediments including quartz sands, silts, red earths and claying and sandy soils that record a complex history of deposition, erosion and redeposition due to climate changes and gentle tilting. The formation of calcretes, particularly within drainage channels overlying the Waite Formation, was also widespread during the Quaternary. NuPower carried out an airborne electromagnetic (AEM) survey in 2008 during the first year that covered the area, including the relinquishment blocks as part of a larger survey of NuPower's tenements in the Aileron region, designed to explore for buried palaeochannels at the base of and within the Cainozoic sedimentary package as potential hosts for secondary uranium. A total of 457.1line kilometres was flown here at 1km line spacing at a nominal terrain clearance of 120m over the areas relinquished. Concurrently, ground water from 4 station water bores was sampled and assayed for a suite of major and trace elements the results of which were expected to assist with targeting potential sites of uranium accumulation within the palaeochannel systems. The AEM survey results indicated that the technique was very successful, revealing that the Tertiary palaeodrainage system is far more extensive and better developed than previously thought. It indicates that the Ti-Tree Basin infills a deep structural feature developed in two NW-SE trending grabens immediately to the north of the Ti-Tree Fault and that part of these structures lies beneath the southern part of Chianina. The southern part is therefore considered prospective for secondary uranium mineralisation because reduced sediments, required for the precipitation of uranium from groundwater, are likely to be present here. NuPower also contributed to the NTGS Central Australia Gravity Survey (CAGS) over the Central Arunta region that included the relinquished areas from EL26375 to acquire higher quality data for regional basement interpretation. There was no on-ground exploration work during Year 2. As a result of the AEM survey it was shown that much of the northern and eastern parts of EL 26375 are underlain by basement at shallow depths and therefore have little potential for the preservation of substantial thicknesses of reduced Cainozoic sediments required for the formation of secondary sandstone-hosted uranium mineralisation. These areas have therefore been relinquished.