Drilling collaborations report Plenty River project

Abstract

The Plenty River Project is a greenfields exploration project located in central south-eastern Northern Territory and is targeting base metal mineralisation below the Cretaceous (Eromanga Basin) sediments. Previous exploration work has been limited to loam sampling and near surface drilling for kimberlite pipes undertaken under a Joint Venture between AusQuest and Rio Tinto Exploration Ltd from 2005 - 2006. Recently AusQuest acquired further detailed geophysical data (gravity) that suggested a coincident gravity /magnetic target below the Cretaceous sediments may have potential for IOCG style mineralisation. The original exploration model for the Plenty River Project was based on comparisons with the Prominent Hill style deposit located in South Australia which is characterised by a low tenor gravity response and a semi-coincident magnetic anomaly reflecting the presence of significant quantities of hematite mineralisation (alteration). Drilling in 2009 under the first NTG Drilling Collaboration Program (Sherington et al 2009) did not confirm haematite alteration, but did locate a sedimentary basin with interlayered mafic sills. A second phase of ground EM surveys was completed in 2010 and this indicated a potential conductive geophysical target at depth and offset from the 2009 drilling target. A possible basin (base metal) style mineralisation model was inferred and 3 holes were planned to test the target. AusQuest applied for additional funding under the Northern Territory Government Drilling Collaborations Programme in May 2011 and received approval July 2011. The drilling programme at the Caroline prospect commenced in October 2011 and was completed in November 2011. A total of two pre-collared diamond holes (11CPD004 and 005) totalling 1305.5m of drilling (comprising 280.9m of mud rotary pre collars and 1024.6m NQ diamond core) were completed. Drilling intersected a thick sequence of sulphidic (pyrrhotite) laminated sediments with interbedded felsic volcanoclastics and interlayered mafic sills. Physical property measurements on core confirmed the magnetic anomaly is caused by the pyrrhotite mineralisation and the gravity response is due to a thick section of gabbro/dolerite in the core of a synclinal structure. The presence of graphite in the laminated sediments is the most likely cause of the conductive response. Weakly elevated base metal values were encountered within the sedimentary package but no ore grade intersections were reported.