Authors / CoAuthors
Fitzherbert, J.A. | McKinnon, A.R. | Blevin, P.L. | Waltenberg, K. | Downes, P.M. | Wall, C. | Matchan, E. | Huang, H.
Abstract
The Hera Au–Pb–Zn–Ag deposit in the southeastern Cobar Basin of central New South Wales preserves calc-silicate veins/skarn and remnant carbonate/sandstone-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-rich lithologies and sandstone horizons; the northern lodes also display zonation down dip to garnet present associations at depth. High-T skarn assemblages are pervasively retrogressed to actinolite/tremolite–biotite-rich skarn and this retrograde phase is associated with the main pulse of sulfide mineralisation. The dominant sulfides are high-Fe-Mn sphalerite–galena–non-magnetic high-Fe pyrrhotite–chalcopyrite; pyrite, arsenopyrite and scheelite are 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/basinal water and magmatic sulfur inputs, while hydrosilicates and sulfides from the wall rocks display elevated δD and mixed δ34S consistent with progressive mixing or dilution of original basinal/magmatic 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 mineralisation at 403.4 ± 1.1 Ma, foliation development remobilisation or new mineralisation at 390 ± 0.2 Ma followed by thrusting, orebody dismemberment at (384.8 ± 1.1 Ma) and remobilization or new mineralisation at 381.0 ± 2.2 Ma. The polymetallic nature of the Hera orebody is a result of multiple mineralizing events during extension and compression and involving both magmatic and likely basinal fluid/metal sources. <b>Citation:</b> Fitzherbert, Joel A., McKinnon, Adam R., Blevin, Phillip L., Waltenberg, Kathryn., Downes, Peter M., Wall, Corey., Matchan, Erin., Huang Huiqin., The Hera orebody: A complex distal (Au–Zn–Pb–Ag–Cu) skarn in the Cobar Basin of central New South Wales, Australia <i>Resource Geology,</i> Vol 71, Iss 4, pp296-319 <b>2021</b>. DOI: https://doi.org/10.1111/rge.12262
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document
eCat Id
144158
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Keywords
- theme.ANZRC Fields of Research.rdf
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- Mineralogy and CrystallographyGeochronologyOre Deposit PetrologyEARTH SCIENCESIsotope Geochemistry
- ( Stratum )
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- Cobar Basin
- ( Theme )
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- skarn
- ( Discipline )
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- mineral chemistry
- ( Discipline )
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- stable isotopes
- ( Discipline )
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- U-Pb geochronology
- ( Discipline )
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- Ar/Ar geochronology
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- Published_External
Publication Date
2023-08-23T04:15:33
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Describes new time and chemistry constraints for the Hera deposit in the Cobar Basin, New South Wales
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notPlanned
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geoscientificInformation
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Resource Geology Volume 71, Issue 4, October 2021 296-319
Lineage
Contains U-Pb SHRIMP analyses conducted at Geoscience Australia, U-Pb LA-ICPMS analyses conducted at James Cook University, U-Pb TIMS analyses conducted at Boise State University Isotope Geology Laboratory in Idaho USA, Ar/Ar analyses conducted at the University of Melbourne, stable isotopes analysed at Nevada Stable Isotope Laboratory in Reno USA. Two of the U-Pb SHRIMP results are also published in Waltenberg et al GA Record http://dx.doi.org/10.11636/Record.2019.005
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[-33.2761780019999, -30.6560400029999, 144.016326006, 146.705596987]
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GDA94 / Geoscience Australia Lambert (EPSG:3112)
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