The Devonian Hera metaturbidite-hosted polymetallic Au–Zn–Pb–Ag deposit of central NSW, Australia, contained a total undepleted resource of 3.6 Mt @ 3.3 g/t Au, 25 g/t Ag, 2.6% Pb and 3.8% Zn. The deposit comprises a number of distinctive lodes with each containing a distinctive ore and alteration/gangue mineralogy, though generally the sulfide ore comprises various mixtures of sphalerite, galena, chalcopyrite, pyrrhotite and relatively common visible gold–electrum. The North Pod and Far West lodes are distinctly Sb rich and contain a more diverse ore mineralogy with arsenopyrite, native silver, native antimony, gudmundite, tetrahedrite-(Fe), argentotetrahedrite-(Fe), acanthite, dyscrasite, nisbite and breithauptite. From analysis of 52,760 assays from across the deposit it was found that there was a very poor correlation between gold and each of Fe, Zn, S, Pb, Cu, As and Ag, whereas Ag correlated reasonably well with both Pb and Zn. Results from EPMA shows that gold varies widely in composition from host-rock associated gold (96 wt.% Au) through more intermediate compositions (88–73 wt.% Au) to electrum (46–27 wt.% Au), commonly associated with Sb-phases and containing significant Sb within the gold itself (1.05–2.58 wt.% Sb). From the Far West lense, aurostibite occurs as distinctive rims around gold. Although aurostibite associated with gold contains no silver, the gold itself contains constant moderate amounts (10.87–12.27 wt.% Ag). We suggest that the aurostibite and other Sb phases formed from a late-stage Sb-rich hydrothermal during low-temperature retrograde skarn alteration. There is abundant evidence for both chemical and physical remobilisation at Hera and this remobilisation is largely responsible for the spectrum of gold compositions observed. The source for these fluids may be an underlying magmatic body, evidence for which occurs as granite pegmatite dykes in various locations throughout the deposit. Furthermore, gold with a moderate to high Sb content may be indicative of a low temperature of formation.

Graphite bodies of economic importance occur in the Eastern Ghats migmatite complex of Orissa, India, which consists of sillimanite-rich gneiss (khondalite), calc-silicate granulite, basic (pyroxene) granulite and acidic gneiss palaeosomes and a variety of quartzofeldspathic neosomes and pegmatite veins. There is more graphite in migmatised khondalite and calc-silicate granulite than in their unmigmatised counterparts and it is common at pegmatite-country rock margins. Lodes of graphite are structurally controlled by fold hinge zones, necks of boudins and along the dominant foliation in rocks that show the effects of polyphase deformation. Faults, fractures and joints also act as structural controls. The richest lodes are located where there is the coincidence of several lithological and structural features.

The graphite occurs in graphite-rich schists and gneisses, as veins and as disseminated flakes along grain boundaries and in microfractures and cleavages. It is present in all rock types except pegmatites emplaced after the D4 deformational phase, and is localised in structures developed during the D1, D2, D3 and D4 phases. Most of the bodies of graphite are lenticular and show pinch and swell characters. Fourteen textural and microstructural habits have been recognised and are described with many of the features of fabric, such as intergrowths, inclusions and kinks being particularly well shown under reflected light.

Methanation of carbonate minerals is considered the most likely initial stage in the formation of the carbon with subsequent pyrolysis of the methane being the process of graphitisation. While the possibility of the carbon being either of sedimentary derivation orfrom igneous-derived CO2 cannot be ruled out, there is no convincing evidence for such sources. Remobilisation of graphite following its formation by pyrolysis of methane in structurally controlled low pressure zones is the dominant mechanism of concentration. Thefabric features point to the graphite having moved as a solid phase along open spaces inthe gangue minerals while still maintaining its crystallinity, and having been deformed in the process. The effects of remobilisation apparently have obliterated evidence relating to other methods of concentration.