首页|The Hera orebody: A complex distal (Au-Zn-Pb-Ag-Cu) skarn in the Cobar Basin of central New South Wales, Australia

The Hera orebody: A complex distal (Au-Zn-Pb-Ag-Cu) skarn in the Cobar Basin of central New South Wales, Australia

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The Hera Au-Pb-Zn-Ag deposit in the southeastern Cobar Basin of central New South Wales preserves calc-silicate veins and remnant sandstone/carbonate-hosted skarn within a reduced anchizonal Siluro-Devonian turbidite sequence. The skarn orebody distribution is controlled by a long-lived, basin margin fault system, that has intersected a sedimentary horizon dominated by siliciclastic turbidite, with lesser gritstone and thick sandstone intervals, and rare carbonate-bearing stratigraphy. Foliation (S1) envelopes the orebody and is crosscut by a series of late-stage east-west and north-south trending faults. Skarn at Hera displays mineralogical zonation along strike, from southern spessartine-grossular-biotite-actinolite-rich associations, to central diopside-rich-zoisite-actinolite/tremolite-grossular-bearing associations, through to the northern most tremolite-anorthite-rich (garnet-absent) association in remnant carbonate-bearing lithologies and sandstone horizons; the northern lodes also display zonation down dip to garnet present associations. High-T, prograde skarn assemblages rich in pyroxene and garnet are pervasively replaced by actinolite/tremolite-biotite-rich retrograde skarn which coincides with the main pulse of sulfide mineralization. The dominant sulfides are high-Fe-Mn sphalerite-galena-non-magnetic high-Fe pyrrhotite-chalcopyrite; pyrite, arsenopyrite; scheelite (low Mo) is locally abundant. The distribution of metals in part mimics the changing gangue mineralogy, with Au concentrated in the southern and lower northern lode systems and broadly inverse concentrations for Ag-Pb-Zn. Stable isotope data (O-H-S) from skarn amphiboles and associated sulfides are consistent with magmatic (or metamorphic) water and sulfur input during the retrograde skarn phase, while hydrosilicates and sulfides from the wall rocks display comparatively elevated delta D and mixed delta S-34 consistent with progressive mixing or dilution of original magmatic (or metamorphic) waters within the Hera deposit by unexchanged waters typical of low latitude (tropical) meteoritic waters. High precision titanite (U-Pb) and biotite (Ar-Ar) geochronology reveals a manifold orebody commencing with high-T skarn and retrograde Pb-Zn-rich skarn formation at >= 403 Ma, Au-low-Fe sphalerite mineralization at 403.4 +/- 1.1 Ma, foliation development remobilization or new mineralization at 390 +/- 0.2 Ma followed by thrusting, orebody dismemberment at 384.8 +/- 1.1 Ma and remobilization or new mineralization at 381.0 +/- 2.2 Ma. The polymetallic nature of the Hera orebody is a result of multiple mineralization events during extension and compression and involving both magmatic and likely formational metal sources.

Ar-Ar geochronologyCobar Basinmineral chemistryskarnstable isotopesU-Pb geochronology

Matchan, Erin、Huang, Huiqing、Fitzherbert, Joel A.、McKinnon, Adam R.、Blevin, Phillip L.、Waltenberg, Kathryn、Downes, Peter M.、Wall, Corey

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Univ Melbourne, Sch Earth Sci, Melbourne, Vic, Australia

James Cook Univ, Geosci Div Trop Environm & Soc, Townsville, Qld, Australia

Geol Survey New South Wales, Maitland, NSW 2320, Australia

Aurelia Met Ltd, Brisbane, Qld, Australia

Geosci Australia, Symonston, ACT, Australia

Boise State Univ, Dept Geosci, Boise, ID 83725 USA

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2021

10.1111/rge.12262

Resource Geology

Resource Geology

SCI
ISSN：1344-1698
年,卷(期)：2021.71(4)
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