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Hellyer Stringer Zone Project. Progress Report No. 1 (CODES publication 17)

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Gemmell, JB (1988) Hellyer Stringer Zone Project. Progress Report No. 1 (CODES publication 17). Technical Report. University of Tasmania, Hobart, Tasmania. (Unpublished)

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Abstract

SUMMARY The alteration zone underlying Hellyer is larger in size and extent than commonly reported for volcanogenic massive sulphide deposits and has consistent alteration mineral zonation with Archean deposits and deposits hosted in mafic volcanics. Alteration within the siliceous core of the feeder system consists of intensive silicification down to a depth of 350 m below the massive sulphide. The silicification is underlain by chloritic alteration to the known extent of the alteration system (555 m). Eight stages of veining have been determined in the alteration zone, these include one stage of pre-mineralisation, three stages of syn-mineralisation, and four stages of post-mineralisation veining. The most abundant veins are related to the mineralising processes and contain significant quantities of base-metal and iron sulphides. The identification of the syn-mineralisation veins within areas of intense alteration is a good exploration target. An analysis of metal zoning in the stringer zone indicates the presence of three feeder systems within the alteration pipe. The central feeder is located in the middle of the deposit (10720 N/l0850 N) with a second feeder system to the south (l0500N) and a third feeder system is weakly developed under the far northern portion of the ore body (10950N). The alignment of the three hydrothermal systems under the massive sulphides is not related to the Jack fault and may be of significance for regional exploration. Fluid inclusion measurements indicate that the fluid responsible for the formation of the syn-mineralisation veining are consistently of high temperature (280-350°C) but of varying salinity. Stage 2A quartz-pyrite-carbonate veins have high salinities (12 - 24 equiv. wt % NaCI) while Stage 2B base-metal-rich sulphide veins have very low salinities (<3 equiv. wt % NaCI). The high temperature-low salinity data are similar to the stockwork siliceous ores of the Kuroko deposits. Carbon and oxygen isotope analyses of carbonate minerals reveal slight differences between the various vein stages and the chlorite-carbonate alteration, but these differences are minor. The carbon and oxygen data suggests, even though there are differences in the time of precipitation of carbonates in the various syn- and post-mineralisation veins and the chlorite-carbonate alteration, a similar source (seawater or modified seawater) for both the carbon and oxygen in carbonate minerals throughout the Hellyer stringer system.

Item Type: Report (Technical Report)
Publisher: University of Tasmania
Date Deposited: 10 Aug 2009 04:32
Last Modified: 18 Nov 2014 04:04
URI: http://eprints.utas.edu.au/id/eprint/9032
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