Gundaroo Project
The Gundaroo project, which initially comprised two distinct, strong geochemical Ag-Pb-Zn-As-Sb anomalies adjacent to the regional Dusty Tank Fault (Figure 1) has been the main focus of CCR's exploration since listing in July 2006. Drilling of the smaller discrete geochemical anomaly for Ag in soils immediately east of the fault resulted in the delineation of the De Nardi stratiform silver resource. A 5km soil anomaly with coincident IP response following a low ridge of outcropping Buckambool Sandstone some 2km west of the fault, known as the Ridge Prospect, has yielded encouraging intersections of both stratiform and vein / breccia base metal mineralisation. The zone of flat-lying strata between the Ridge Anomaly and the Dusty Tank Fault has been named Gundaroo Central. The Central Zone is considered to be highly prospective but drilling to date has been minimal.
Figure 1: Soil geochemistry for Ag and selected drill holes at Gundaroo
De Nardi Silver Deposit
The De Nardi silver deposit is situated over a fault-bound basement high separating the Cobar basin from the Winduck shelf sediment sequence. It has been tested with 24 RC holes totaling 1,831m and 7 diamond drill holes totaling 1,730m.
This work has outlined an inferred resource of 2.7Moz of silver occurring as a thick and consistent easterly-dipping zone extending from the surface to a depth of at least 100m.
Figure 2: De Nardi cross section
Ridge Prospect
Drilling of the Ridge prospect has intersected two styles of mineralisation: stratiform Zn-Ag mineralisation in outcropping fine grained sandstones; and breccia-vein and stringer mineralisation associated with a deeper carbonate-bearing sandstone breccia unit in the anticlinal core (Figure 3).
The stratiform Zn mineralisation dips at about 45 degrees to the west and has only been intersected in two core holes, CCR29 (8.5m @ 1.3% Zn, 0.2% Pb and 19g/t Ag from 48m) and CCR150 (7m @ 2.1Zn and 47g/t Ag from 92m). The geochemical dispersion pattern for Zn, together with a nimber of intersections in shallow holes, suggests a potential aggregate strike length for this style of mineralisation of at least 1,000m on the western flank of the Ridge anticline.
Better intersections of the breccia-vein and stringer mineralisation are as follows:
| CCR30 | 6m @ 1.3% Cu, 6.4% Zn & 170g/t Ag from 228m |
| CCR56 | 1m @ 1.3% Cu, 6.1% Pb & 200g/t Ag from 125m |
| CCR155 | 3m @ 1.6% Cu, 0.4% Pb, 0.3% Zn & 283g/t Ag from 99m |
| CCR166 | 1m @ 0.6% Cu, 2% Zn & 118g/t Ag from 151m |
Although the host sandstone breccia unit does not outcrop, it has been intersected in drilling over a strike length exceeding 800m, and may be present over the entire 5km strike length of the Ridge anomaly.
Figure 3: Ridge cross section (Rohrlach 2007)
Gundaroo Central
Very limited drilling has been completed in this area which is interpreted to be underlain by flat-lying sediments. A number of IP anomalies have been delineated, one of which was tested by CCR14A. Breccia-vein and stringer mineralisation assaying 2.5% Pb, 3.4% Zn and 47 g/t Ag was intersected over 1m from 105m, associated with a limestone unit.
Gundaroo Model
A detailed review of the Gundaroo project was undertaken in late 2007 by a geological consultant, Dr Bruce Rohrlach, to improve understanding of the Gundaroo mineralisation and assist with the planning of future exploration. A composite cross section based on Rohrlach's interpretations is shown in Figure 4.
Figure 4: Gundaroo schematic cross section (Rohrlach 2007) (drill holes are shown in red and target zones in yellow)
Key points to emerge from the review are:
- The system of faults in the area almost certainly channeled the mineralising fluids and the zones in which they occur represent prime targets for discovery.
- The De Nardi mineralisation and the intersection in CCR14A are both likely to have been caused by fluids rising through the Dusty Tank Fault. The fault is known to lie within a concealed zone up to 400 meters in width which is yet to drilled. This zone represents a prime exploration target for blind deposits constrained within the fault structure and in flatly-dipping favourable strata proximal to the fault (T1 in Figure 4).
- An apparent increase in both the gain size of the host sandstones and Zn concentration in westerly direction, suggests a feeder structure to the west of the stratiform mineralisation intersected in CCR29 and CCr150. Further drilling down-dip is warranted, both to test this hypothesis, and to evaluate the economic potential of this mineralisation. The potential structure represents a target (T2 in Figure 4) where it intersects the projected mineralised strata.
- The carbonate-bearing unit which hosts the best intersections of breccia-vein and stringer mineralisation dips to the west and its intersection with the potential western feeder structure would be regarded as a prime exploration target (T3 in Figure 4).
- The mineralisation intersected in the core of the Ridge anticline is thought to represent a loose network of upwardly branching crackle veins rather than discrete veins. this type of mineralisation could account for the observed surface geochemical response. The possibility remains that these crackle veins will coalesce at depth into stronger structures which would represent deep targets (T4 in Figure 4).
