Annual report on EL 27335 Coppock and EL 27336 Connor for year ended 30 November 2010 Burt Plain Project

Abstract

A full GIS review of all three Burt Plain tenements (EL 27335, EL 27336 and EL 27337) was completed using digital terrain model, geology, Landsat 321, Ternary radiometrics, gravity and RTP magnetic data, results are summarized in Dow (2010). Ternary radiometric data confirm Landsat and 1:250,000 scale geological mapping showing almost complete cover over EL 27335 and EL 27336 (speckled light blue-green colours). There is a subtle, discrete, circular, deep blue, low radiometric anomaly that covers Mount Burne, possibly one of the only outcrop areas in the two tenements. Depth to basement of the Burt Plain project tenements was assessed by evaluating water bores. Twenty six water bores have been drilled within and in close proximity to Arafura's Burt Plain tenements. Water bore use is mainly for stock on the Aileron Station but have also been drilled by railway and road companies, the BMR and the Army. Lithological logs have only been completed for 18 of the 26 bores, but this is enough to get a rough guide to depth of cover sequences (average of 38.9m) and basement characteristics (mostly granite with subordinate gneiss and schist). Water bore lithological data is effectively restricted to the southern half of EL 27336 and holes within and to the east of EL 27335. Where information has been recorded, basement depths are variable over short distances. Depths to basement are typically shallow (0-20m) or relatively deep (50-100m) and so the average of 38.9m is possibly not representative. There doesn't appear to be any relationship between depth to basement and basement lithology. The Burt Plain tenements are located on the northern boundary of a substantial gravity high, thought to represent a major crustal feature, possibly a deep-seated mafic- to ultramafic intrusive complex. The abrupt northern edge to this anomaly is marked by the Hann Range that outcrops in the northern part of EL 27337 and extends east to just north of EL 27336. Analysis of airborne magnetic data indicates that two major structural systems (northwest- and east-northeast-trending) cut through several terrains indicating extensive development and probable old and deep origins of these structures. It is possible that these structures are reactivated normal and transverse structures active during extension to form the Irindina Basin (northwest and east-northeast-trending respectively). The northwest-trending system that defines the eastern edge of the gravity anomaly extends northwest into the Reynolds Range and is thought to be the primary structural control on the possible carbonatite intrusive thought to be responsible for the Nolan's Bore deposit. This structural zone possible extends through the northeast quarter of EL 27336 and the central half of EL 27335. The appearance of carbonatites along this structural zone indicates that it has sampled the upper mantle / lithospheric mantle (i.e. very deep). Two other northwest-trending structures are identified west of Nolan's, however, these are not as well-developed and are not laterally continuous (they appear to be cut by the east-and east-northeast-trending structures). At this stage it is unclear if these structures have the potential to host carbonatites (i.e. tapped the upper mantle). Field activities included two days of reconnaissance field work and the collection of 2 rock chip samples. GIS review indicated that the only basement outcropping zone on both EL 27335 and EL 27336 is the Mount Burne area. Mount Burne was also described by CRA geologists in 1971 as showing several annular features that might represent kimberlite or carbonatite and so assessing this area became the top field priority. A day was spent on the combined tenements identifying all access tracks, assessing the distribution of potential calcrete outcrops and the relative density of vegetation. Both the Old Sandover track and the Plenty Highway were driven as were all station tracks. Several, extensive calcrete zones were identified and it was clear that dense vegetation covers most of the two tenements, significantly restricting 4WD vehicle access. A day was spent walking around the hills at Mount Burne. Mount Burne is characterized by three extensive, north-trending, milky quartz veins (up to 50 metres wide and several hundred metres long) that cut variably deformed orthogneiss. A single rock chip was collected near the Trig Point at Mount Burne, however, assay results indicated no anomalous geochemistry. There appears to be a vegetation anomaly at the break in slope surrounding the base of Mount Burne and the hills immediately to the north, possibly reflecting nutrient deficient soils. A series of minor pegmatites, to the north near the break of slope, were sampled because of the presence of moderate sericite alteration, however, these rocks were also devoid of anomalism (total of two rock chips on EL 27335).