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Sediment-hosted base metal deposits. CODES/AMIRA Project P.834A. Report No. 2, October 1996

Bull, SW, Keele, RA, Duffett, ML, Cooke, DR, Large, RR, Winefield, PR and McGoldrick, PJ 1996 , Sediment-hosted base metal deposits. CODES/AMIRA Project P.834A. Report No. 2, October 1996.

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This is the second progress report for AMIRA Project P384A and covers work carried out during the six months April to October 1996 to be presented at the October meeting, and two outstanding reports from the first meeting. Good progress has been made to date and much of the material covered here results from fieldwork undertaken earlier this year. The reports by Bull, Keele et al. and Duffett distinguish structures that controlled sedimentation on the Lawn Hill Platform during early McNamara Group times, from later (usually more obvious) structures. This early "grain" was an important control on deformation intensity during later orogeny. Their work has implications for understanding the location of deposits that lack obvious proximal syn-sedimentary structures such as Lady Loretta and Century, and more fundamental implications for understanding the controls on basin scale fluid flow.

The halo studies work at McArthur River has been extended to drill hole Homestead 6 which is 2 km along strike from the HYC orebody. The report by Large and Bull combines this new geochemical and C/O isotope data with results from AMlRA Project P384 to complete the HYC halo model. New C/O isotope data show that C and O isotopes are a powerful method for discriminating MnOD and AI3 halos directly related to ore from those that indicate a favourable horizon for Pb-Zn mineralisation.

Geochemical studies of the upper greenschist to lower amphibolite grade metasedimentary hosts to the Mt Novit pyritic mineralisation are described in the report by McGoldrick. This work shows that Mt Novit has a (relatively) weak lithogeochemical vector signature (SedexAI, AI3, MnOD and Tl) that is preserved during moderate to high grade metamorphism.

The report by Cooke and Large documents computer modelling of Mn transport in hydrothermal fluids presented at the last meeting, and discusses implications for differences in the genesis of McArthur-type and Broken Hill-type Zn-Pb deposits.

The report by Winefield is a detailed outline of work to be included in his PhD. The PhD entitled "Sedimentology and diagenetic history of late Palaeoproterozoic sequences within the southern McArthur Basin, northern Australia" has logistic support from AMIRA Project P384A.

Also to be presented at the meeting, but not reported here, are a description of the Grevillea prospect and recent sampling for halo studies (McGoldrick and Bull). Cooke will present results of preliminary geochemical modelling of Cu and Fe in hydrothermal solutions. The sampling strategy for illite crystallinity studies of lower McNamara group rocks will be discussed by Keele. Bull and McGoldrick will discuss the outcomes from a recent visit to the Belt Basin and visits to the Sullivan mine (B.C.) and the Sheep Creek prospect in Montana and plans for halo studies on these deposits.
Peter McGoldrick
Project Manager

Item Type: Report (Technical Report)
Authors/Creators:Bull, SW and Keele, RA and Duffett, ML and Cooke, DR and Large, RR and Winefield, PR and McGoldrick, PJ
Publisher: CODES/AMIRA
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