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INTRODUCTION
The 132 North deposit is one of a number of small komatiite (ultramafic)-hosted nickel sulfide deposits in the Widgiemooltha district (McQueen, 1981; Marston et al., 1981). It is located 5 km north-northwest of the small community of Widgiemooltha and about 80 km south of the city of Kalgoorlie-Boulder (Fig. 1).(Figure 1 omitted) The deposit gossan was discovered in 1968 by International Nickel Australia Limited during extensive geological mapping, gossan search and geochemical sampling of the Widgiemooltha district. The deposit was purchased by Western Mining Corporation in 1981, and subsequent percussion drilling in 1989 located a small sulfide nickel orebody (approximately 900 metric tons of contained Ni) that was economical to mine.
Western Mining Corporation (WMC) commenced a small opencut on the deposit in 1990. During excavation, a series of five horizontal channel samples was collected (by JFMC) across the ore zone at 10-meter-depth intervals from the surface down to a depth of 40 meters. Samples were also collected from drill core and percussion holes. Following completion of the opencut, one of us (BJG) was granted permission by WMC to collect specimens from the excavated material. Over a thousand specimens were collected, of which over a hundred have been subjected to detailed examination in the CSIRO(2) laboratories.
The specimens required careful examination with the aid of a binocular microscope, and small particles of the minerals to be identified were transferred onto adhesive plates for examination under the scanning electron microscope (SEM). Compositional spectra were obtained under the SEM by means of energy-dispersive spectrometry (EDS). Initially the particles for which compositional spectra were obtained were subjected to X-ray diffraction (XRD) analysis, which enabled the minerals to be positively identified. Subsequent identifications were based largely on the EDS spectra, supplemented by XRD patterns in cases of doubt.
For ease of reference, the mineral descriptions in this paper are arranged in alphabetical order of mineral name.
GEOLOGY
The 132 North deposit is located on a relatively high relief-etch surface that is part of a ridge extending 20 km north-northwest from Widgiemooltha (Finkl, 1979; Clarke, 1991). The surface expression of the deposit is characterized by rubbley outcrops of fresh to slightly weathered metabasalt and more strongly weathered ultramafic rock. Weathering of the metabasalt is typically best developed along joint...