Rimfire Pacific Mining NL

Rimfire Pacific Mining NL - A.C.N. 006 911 744


		Bingara - Diamond Project

		Objective: Diamonds in basaltic diatremes

		Location: 150km NNW of Tamworth NSW, see Figure 1.

		The highly prospective Bingara-Copeton district has yielded 100's of thousands of diamonds over the last 130 years. To date, no primary source for these diamonds has been discovered.
		Rimfire's exploration techniques utilize new high-resolution geophysical imagery, supported by detailed field sampling (stream sediment, bulk and loam) and drilling; together with applying geological concepts derived from cutting edge research by geologists from the NSW Department of Mineral Resources, Australian Museum and Macquarie University.
		Rimfire has secured 1100 km2 of highly prospective diamond ground in the Bingara region of New South Wales, near-to the historical alluvial diamond fields, see Figure 3(a) & (b). The exploration target is a economic hard-rock source for diamonds mined from alluvial deposits in the area since 1872. Historical estimates by the NSW Department of Mineral Resources places production in excess of 500,000 ct (1 to 2 million diamonds). The stones are of a high quality with one parcel submitted from bulk sampling at the Monte Christo alluvials in 1995, independently valued as 98% gem quality*1.

		Figure 1: Location Bingara Diamond Project


		The exceptionally large number and high quality of the Bingara diamonds make the primary source a highly attractive exploration target. Previous explorers have included De Beers (Stockdale), CRA and BHP. However without an understanding of the non-kimberlitic origin of the diamonds, or the availability of high-resolution airborne magnetics, their task was formidable and very high risk. The New South Wales Government funded a detailed airborne magnetics program over the region under the Discovery 2000 initiative. This data, combined with the new "Eastern States Subduction Diamond Model", enabled Rimfire to target several prominent circular magnetic anomalies in the region and to secure tenements that cover these features.
		The model proposes that diamonds formed in a subduction setting and were entrained at depth by magmas of the Jurassic - Tertiary basaltic pipes and transported rapidly to the surface. There are many areas in the world where diamonds have been discovered in non-cratonic regions, which are also coincident with subduction zones, see Figure 2(a) & (b).
		Over the years there has been a vigorous debate about the possibility of a primary source of the Bingara-Copeton diamonds. Conventional theorists arguie that such a source cannot exist because the crust is too thin to support temperatures and pressures that could attain the diamond stability field. However, at Penarie, 300 km to the west of Bingara, drilling by RTZ recovered 3 diamonds from a basaltic diatreme*2 which confirmed that in eastern Australia basaltic diatremes are a source rock for diamonds. Furthermore, Rimfire through its exploration efforts has discovered the essential Group 1 eclogite facies garnets and a diamond, more than 20km SW of the alluvial fields, in a stream draining a prominent magnetic anomaly.
		Rimfire has secured tenements over several pipes which were previously unidentified on the old, 1 mile flight line, data. The contrast in quality of the data sets can be clearly viewed in Figure 2. The identification of these pipes in proximity to the alluvial diamond fields is considered highly encouraging; see Figures 3(a), (b) & (c).
		Rimfire has sampled some of the streams draining the identified anomalies. The physical analysis of the grains Rimfire has discovered high sodium eclogitic garnets in streams draining Back Creek and Tom and Jerry Anomalies. In addition, Rimfire has discovered a 0.265ct diamond in a stream draining the Tom and Jerry Anomaly, see Figure 4.
		The high sodium garnets are shattered, with sharp conchoidal fractures, confirming the material has travelled only a short distance. The occurrence of these obviously locally derived indicator minerals; together with the discovery by Rimfire of a diamond outside the alluvial fields in drainage derived from a magnetic anomaly, proves the [local] source rock contains mantle material which was subject to a temperature and pressure regime required to support the formation of diamonds ("The Diamond Stability Field")
		The recent work undertaken by Rimfire, since it secured the tenements, give it encouragement to continue with programs designed to locate likely drilling targets. In 2002, the company plans in the first part of the year to further define these targets and to commence drilling later in the year.

		Figure 2(a):
		Non-Cratonic World Diamonds & Subduction Zones

		Non-Cratonic Diamonds Australia

		Figure 2 (b): Diamond Subduction Model

		Figures 3(a): Bingara Tenements, Diamond Fields & Magnetic Anomalies

		Figures 3(b): Bingara Tenements, Diamond Fields & Magnetic Anomalies

		Figures 3(c): Back Creek and Tom & Jerry Anomalies

		Figure 4:
		Rimfire's Garnets Plotted on Shultz's Screen

		Garnet

		References
		*1 Brown, R.E. 1999. Bingara Diamond Field. Minfo. No.63. p. 15.New South Wales Department of Mineral Resources.
		*2 Oxiania Resources NL. 1999. The Bokhara Diamond Project, Northern NSW. Unpublished.