Porphyry Targets

Gold, silver and base metals mineralised systems are evident in the southern sector of the Dart tenement at the Mammoth-Donovan Hill system, and in what the Company refers to as the Northern Sector Porphyries. Gold and base metals mineralisation is associated with the Cravensville Volcanic Arc as reduced intrusive related gold style with similarities to Fort Knox and other major gold and base metal deposites in the Tintina belt of North America.

Dart has achieved substantial progress toward understanding the porphyry style of mineralisation in the Tenements by geological, geophysical, metallogenic and structural synthesis through geological time scales, aided by three-dimensional digital modelling. This led to the development of the Polygonal Vortex Model which assists Dart in identifying porphyry exploration targets.

Regional water geochemistry sampling has continued to build up data for the Polygonal Vortex Model that the Company uses to focus exploration for intrusive related gold mineralisation (in particular reduced intrusive related gold (RIRG) polymetallic mineralisation). A generic cross section through such a system is shown in Figure 5a and illustrates the way in which ground water analysis is able to help locate buried mineralisation. Deep faults and fracture systems associated with the intrusions allow ground water to reach the surface via springs and creeks carrying trace amounts of indicative metals. Tracking this water flow has been proven overseas to be a very useful and well proven tool to determine the occurrence of mineralisation.

The very sensitive analysis method used by the Company is able to detect these metals and will focus exploration as sample density increases. Over 400 samples have been collected and analysed to date with the companies PVD6000 unit.

The program has uncovered anomalous drainages within all ELs, including highly anomalous drainages about the Unicorn Porphyry within the Dart EL, and some gold reef trends in the Buckland EL. The program has both confirmed and highlighted the mineralised environment around the Empress and Zulu Corridor intersection zone, an area which also hosts the Mt Unicorn and Mt Morgan porphyry prospects within the Dart EL.

Dart aims to further resolve the interpretation of Mammoth-Donovans Hill before undertaking limited stratigraphical drilling on the North Mammoth drill target. If warranted, a second phase of geophysically targeted drilling would aim to penetrate the fault silver cap at depth to test for the presence of the Mammoth protolith plug.

At the Northern Sector Porphyries, Dart intends to use geophysical surveys to assist in determining alteration vectors to gold, silver and base metals mineralisation and to refine the interpretation. Drill testing of targets at the Mt Morgan and Mt Unicorn intrusions will follow.

Dart’s interpretation of the systems encourages further exploration of the porphyries within the Dart tenement with the objective of a major gold and base metals discovery. The Polygonal Vortex Model has been the first step in understanding this structurally complex system.

Figure 5a

Click to enlarge

last updated June 2008