Cargo

GCR's Cargo project lies 12 km west of the Cadia-Ridgeway copper-gold deposit. It is located within prospective rocks of the Molong Volcanic Belt (MVB), a, sequence of Ordovician calc-alkaline island arc-related volcanics and sediments intruded by calc-alkaline and potassic intrusive complexes.  The MVB is a major component of the Lachlan Fold Belt which contains several porphyry copper-gold style deposits and prospects including Cadia, Northparkes and Copper Hill.

Cargo geology

Modern exploration has been conducted at Cargo since the 1960s.  Calibre Mining's recent joint venture work included six reverse circulation holes planned to drill across the southeast part of the prospect and systematically test the full width of the northwest-striking mineralised corridor through the core of the prospect.  Five of six drill holes intersected significant but low grade porphyry-style copper and gold mineralisation over widths of up to 250m.  The drilling showed that mineralisation extends further southeast than previously thought.  The second phase of four diamond holes.

In addition the Calibre geologists undertook a significant geological mapping program and produced a revised geological interpretation shown in the plan opposite.

Calibre no longer participate in the Joint venture and GCR plan to follow up on known gold mineralisation in what is known as the Gum Flat area.  Previous work by Shell found numerous significant gold intersections including 28m @ 1.0g/t Au including 2m @ 5.4g/t Au, 14m @ 1.7g/t Au including 11m @ 2.0g/t Au, 11m @ 3.5g/t Au including 3m@ 11.0g/t Au, 8m @ 3.3g/t Au, 13m @ 1.7g/t Au. These intersections occur over a strike length of 5km although the continuity between drill holes has not been established.

The gold mineralisation occurs as alluvial accumulations in younger sediments  including difficult to treat clay-rich material.  The gold may have been source from the narrow vein systems to the north and north-east but may have been introduced via a major structure from deeper sources .  The mineralisation lies west of  the large  north-south fault  (black line in figure opposite)  that  has displaced the western third of the Cargo Intrusive Complex.  The distribution of the gold mineralisation suggests this fault may play some role in the localisation of this mineralisation and a drilling program has been designed to test this concept.

Historical Exploration

Cargo was originally a small goldmining centre where gold was won from both alluvial and quartz lodes.  In the 1960s the project, like Cadia to the east and Copper Hill to the north was recognised as a porphyry copper system where copper and gold are associated with intrusive rocks. Analogies were made with the large porphyry copper deposits in the SW of the USA. 

Drilling by a variety of companies at this time produced broad, but low grade mineralised intersections. Cargo attracted more interest during the gold boom of the 1980s through to the mid-1990s, when it was realised that significant gold mineralisation is also hosted in the system.

GCR became involved in the project in 1996 and undertook extensive geological studies which indicated the presence of a large, concentrically zoned hydrothermal and mineralogical system which appeared to be truncated to the west by a large fault. The system is characterised by a core zone of intrusive rocks enriched in copper and molybdenum and an outer arcuate zone of magnetic and pyritic volcanic rocks containing gold and gold-bearing veins. Veins locally contain highly elevated gold grades for example 30m @ 2.6 g/t Au, 8.5m @ 5.6 g/t Au.. The rocks are of a similar age and lie in a similar geological setting to those at Cadia-Ridgeway.
  January 2009
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