VEIN AND SKARN FORMATION AT THE CANNINGTON Ag Pb Zn DEPOSIT, NORTHEASTERN AUSTRALIA

Abstract

Synchronous deformation and metamorphism at the Cannington Ag-Pb-Zn deposit, in northeastern Australia, involved a phase of Ca and Mn mobilization that accounts for the distribution of pyroxene-and garnet-bearing rocks, which were preferentially overprinted by sulfide mineralization. Garnet composition and its textural association in relation to three generations of planar fabric (S 1 to S 3 ) show that skarn-related grossular-rich garnet formed in the last garnet-stable event, D 3 . The D 3 Cl-rich biotite in the gneiss is intergrown with garnet in veins, and within skarn rocks is continuous along strike with veins of garnet ± pyroxmangite, hedenbergite or amphibole, which indicates a period of anhydrous through to hydrous metasomatism. Compositional maps show that infiltration extended from alteration fronts through fractures, which indicates the high permeability of S 3 ; these maps and X Grt profiles across skarn-gneiss contacts show that there was large-scale transport of mass by infiltration and varying degrees of hydrodynamic dispersion. Precipitation of oscillatory Ca-and Mn-zoned grossular-rich garnet in veins parallel to veins filled with Cl-rich biotite, in conjunction with the distribution of biotite-filled veins across the deposit, suggest that the mass transfer during D 3 may be responsible for deposit-scale Ca-Mn skarn-like zoning.Keywords: garnet, zoning, metasomatism, skarn, shear zones, veins, Cannington, Australia. SOMMAIREUne déformation et une recristallisation métamorphique synchrones dans le gisement à Ag-Pb-Zn de Cannington, dans le nord-est de l'Australie, a impliqué une mobilisation de Ca et de Mn qui rend compte de la distribution de roches à pyroxène et grenat, qui sont devenues par la suite les hôtes ciblés d'une minéralisation en sulfures. La composition et l'association texturale du grenat aux trois générations de foliation (S 1 à S 3 ) montrent que le grenat lié à la formation du skarn, riche en grossulaire, s'est formé lors du dernier épisode de déformation où le grenat était stable, D 3 . La biotite de la génération D 3 dans le gneiss, riche en Cl, montre une intercroissance avec le grenat en veines, et dans les roches du skarn, montre une continuité le long de la gneissosité avec des veines à grenat ± pyroxmangite, hedenbergite ou amphibole, indications d'une période de métasomatose anhydre à aqueuse. Des cartes de répartition d'éléments montrent que l'infiltration s'est propagée à partir de fronts d'altération le long de fissures, indication d'une grande perméabilité le long de S 3 ; ces cartes et les profils de X Grt perpendiculaires aux contacts skarngneiss montrent qu'il y a eu transfert important de masse par infiltration et par dispersion hydrodynamique à divers degrés. D'après la précipitation de cristaux de grenat à zonation oscillatoire en Ca et Mn dans des veines parallèles aux veines remplies de biotite riche en chlore, ainsi que la distribution de telles veines de biotite de part et d'autre du gisement, le tranfert de masse au cours de l'événement D 3 aurait...

A classification of Broken Hill-type deposits: A critical review

“…Ore models for Cannington include the zone refining model of Walters and Bailey (1998), Bodon (1998), Marshall and Spry (2000), and Large et al (2005), in which Pb-Zn-Ag mineralization is syngenetic and later remobilized during metamorphism, deformation, and high-salinity metasomatism. This model contrasts to epigenetic models proposed by Williams et al (1996), Chapman and Williams (1998), Roache (2004), Roache et al (2005), and Kim and Bell (2005) who suggested the introduction of ore metals during the protracted metamorphic and deformation history. Walters (1996), Walters (1998) suggested that the high silver content was related to zone refining as a result of the addition of an external post-metamorphic fluid.…”

Integration by design: Driving mineral system knowledge using multi modal, collocated, scale-consistent characterization

“…It has undergone a protracted structural and metasomatic history (e.g., Rubenach, 2013). Whilst there is much conjecture as to the genesis of deposits and timing of different styles of mineralisation (e.g., Groves et al, 2010;Hitzman et al, 1992;Hitzman and Porter, 2000;Williams et al, 2005), there is general agreement on the broad timing of major structural, metamorphic, magmatic, metasomatic and mineralisation events (Figure 4). The Cloncurry district is very diverse in terms of the types and styles of mineralisation present.…”

“…Various studies have recognised a continuum between different mineralisation styles in different deposits (e.g., Austin and Blenkinsop, 2009;Little, 2019), and the Cloncurry deposits contain mixtures of iron-apatite (Kiruna style), magnetite-dominant IOCG, pyrrhotite-dominant iron sulphide copper-gold (ISCG), and hematite-dominant IOCG assemblages. There is also an array of skarn-like assemblages (Williams and Heinemann, 1993;Williams and Baker, 1995;Roache, T. J., et al, 2005). These include dolomite-magnetite-chalcopyrite (e.g., Starra-276;Patterson et al, 2016), to calcite-pyrrhotite-sphalerite-chalcopyrite assemblages (e.g., Artemis: Austin et al, 2016a;Knorsch et al, 2020), calcitepyrrhotite-chalcopyrite assemblages (e.g., Canteen; Austin et al, 2016b), calcite-pyrrhotite-galena (Maronan; Austin et al, 2016c), calcite-barite-fluorite-magnetite-chalcopyrite (e.g., Monakoff; Austin et al, 2016d).…”

Genesis of the Supergiant Shuangjianzishan Ag–Pb–Zn Deposit in the Southern Great Xing’an Range, NE China: Constraints from Geochronology, Isotope Geochemistry, and Fluid Inclusion

“…Silver (Ag), lead (Pb), and zinc (Zn) are widely developed in different genetic types of deposits [1][2][3]. The Ag-Pb-Zn deposits in the world can be divided into the following genetic types: (1) volcanic-hosted massive sulfide (VHMS or VMS) deposit [4][5][6]; (2) sedimentary exhalative (SEDEX) deposit [7][8][9]; (3) carbonate-hosted Mississippi Valley type (MVT) deposit [10]; (4) skarn-type deposit [11][12][13]; (5) magmatic-hydrothermal vein-type deposit [14,15]; and (6) epithermal deposit [16][17][18]. In addition, a few researchers have identified porphyry-type Ag-Pb-Zn deposits [19].…”