The project consists of 16 exploration license applications within Aurora’s large Capricorn Project located in the southern Pilbara Region of central Western Australia. The manganese potential mineralized horizons strike for about 95kms along the southern margin of one of a series of sub-basins comprising the northwestern arm of the mid-Proterozoic aged Bangemall Basin. The area has been sub-divided into West-Of-Road, East-Of-Road, Far East and Even-Further-East Areas for prospecting purposes.
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Regional scale exploration by the Geological Survey of Western Australia (GSWA) had identified anomalous manganese values in stream sediment samples over a 30km strike and this led Aurora to explore this rugged part of the Bangemall Basin.
Reconnaissance prospecting by Aurora in late 2008 to investigate these anomalous manganese stream sediment values discovered significant zones of outcropping manganese mineralization with rock-chip samples assaying up to 47% Mn.
These initial results were received in January 2009 and announced to the ASX. Results and updates of Aurora’s subsequent prospecting campaigns have been released as a series of announcements to the ASX progressively throughout 2009.
Follow-up field investigations in April-May this year identified more high-grade massive manganese oxide outcrops over a 15km strike east of the main Mount Augustus to Dooley Downs road. Detailed surface sampling across the Mango 9 prospect averaged 40.4% Mn over a 16m section, including 6m averaging 51.8% Mn, and at the Mango 4 prospect averaged 33.5% Mn over a 10m section.
Reconnaissance sampling in May-June was designed to prospect the approximately 19kms strike of the favorable horizon west of the road, and to test for parallel mineralized zones within the sedimentary sequence. Aurora’s results identified many high-grade massive manganese oxide occurrences within three parallel sedimentary sequences, with rock-chip samples assaying up to 56.5% Mn.
Continued prospecting in July and August extended the zone of high-grade mineralization for another 19kms to the east in the Far East Area. Fortysix of 262 rock-chip samples collected assay over 40%Mn with a high of 55.1% Mn. Prospecting also discovered a fourth manganese mineralized horizon 100m to 200m north of the original mineralized horizons. Eight samples from a 2.4km long section ranged from 22.9 to 47.1% Mn, averaging 37% Mn.
Published geologic mapping and Aurora’s prospecting has identified a thick sequence of shales, siltstones and cherts of the mid-Proterozoic Ullawarra Formation, intruded by laterally persistent dolerite sills which split the sediments into three sequences, each 50 to 300m wide, and informally termed Lower, Middle and Upper.
In the Far East Area a fourth mineralized horizon has been discovered lying 100m to 200m north of the Upper sequence at Mango 116 prospect. So far this has been found to be present over the entire 8kms between Mango 116 and Mango 111 prospects, and may extend throughout the 95km long Project.
In the West-Of-Road Area the sediments are folded about NW-SE axes, but overall the beds dip 400 to the northeast.
In East-Of-Road and Far East Areas the sequence is more linear, striking around NW-SE with dips varying from 600 to 300 to the NE. The strike changes to more East-West in Far East and Even-Further-East Areas.
Massive to semi-massive manganese oxide mineralization occurs as a series of semi-continuous parallel bands or horizons, individually from a few centimeters up to 5m wide and may be several hundred meters in strike length, and locally as pods and lenses up to tens of meters wide on surface, often within wider zones of manganese-bearing host siltstones and shales.