Garden Well

Summary

Stage	Production
Mine Type	Open pit
Mineralisation	Mixed ultramafic- sediment shear
Plant type	Crush, grind, CIL
Throughput	5mtpa
Reserve grade	0.91g/t gold
Recovery	88%
Mine Life	7 years
Ore Reserves	1.01Moz
Mineral Resources	2.47Moz

History

Garden Well is a shear hosted Archaean orogenic gold deposit located 100 km north of Laverton in the Duketon Greenstone Belt in Western Australia. It is the largest and most recent gold discovery in the Duketon area.

The Garden Well area was first drilled in late 2008 by reconnaissance Aircore drilling, targeting an area with surficial cover along strike of the concealed Moolart Well deposit discovered in 2001. Following the discovery of Moolart Well, Regis developed new empirical exploration techniques by focussing on new geochemical interpretation methods that can be integrated with geophysical data to detect and delineate under cover targets similar to Moolart Well. There are no historical gold workings or previous drilling associated with the deposit making Garden Well a blind virgin discovery. Several historical small workings occur in adjacent tenements and various companies have explored and mined gold throughout the area in the past 40 years.

Two of the first pass 2008 Aircore holes located 160m apart, intersected multiple gold mineralised zones including 4m @ 1.88 g/t, 4m @ 1.78 g/t, 8m @ 1.61 g/t and 10m @ 2.22 g/t gold indicating there is potential for wide zones of mineralization between the two holes. A small follow-up Aircore programme of 18 holes drilled in late 2009 intersected wide zones of anomalous gold in 14 holes including 47m @ 2.58 g/t, 18m @ 11.32 g/t and 19m @ 4.46 g/t indicating a new major gold discovery. Further Aircore, RC and diamond drilling on a 40m x 40m grid commenced in early 2010 and a maiden Reserve was announced in December 2010. Following a revised Reserve in March 2011 a Definitive Feasibility Study was completed in June 2011. Construction of a new 4mtpa gold plant and 250 man village commenced in August 2011 and was completed on time in the September 2012 quarter at a cost of $113 million.

Geology

The Garden Well gold deposit is covered by a Tertiary palaeochannel up to 30m thick and has no surface geochemical response, but does display moderate gold anomalies on the margins of the palaeochannel distal from the deposit. Moderate 8 to 75ppb gold anomalies on the palaeochannel margin were tested with the 2008 Aircore drilling and may represent gold leakage anomalies at the base of the palaeochannel or a truncated surface gold anomaly. Gold mineralisation occurs as oxide ore down to 70m below the base of the palaeochannel and hypogene ore was drilled to a depth of 400m. Gold mineralisation is open at depth. Oxide mineralisation consists of a 70 to 100m wide moderate east dipping gold bearing zone in clay rich residual Archaean saprolite with some sub-horizontal supergene gold developed in the upper part of the saprolite profile. Host rocks are strongly sheared moderately east dipping Archaean ultramafic rocks in contact with overlying moderately east dipping argillaceous sediments. The shear zone continues as primary hypogene mineralisation below the top of fresh rock and is characterised by a 50 to 70m wide strongly altered quartz-dolomite-fuchsite-chlorite-pyrite zone in ultramafic rocks.

Mining is conducted using truck and shovel excavation methods by Mining and Civil Australia Limited who supply the same services at the Moolart Well Gold Mine. The plant design is based on a nominal 4.0mtpa throughput utilising a three stage crushing circuit, a scrubber and a single ball mill followed by gravity and carbon in leach circuits.