Appendix: Fluorite as indicator mineral in iron oxide-copper-gold systems: explaining the IOCG deposit diversity Tobias U. Schlegel, Thomas Wagner, and Tobias Fusswinkel Additional petrography constrains Extensive petrographic documentation for samples from the Prominent Hill IOCG deposit is documented in Schlegel and Heinrich (2015), Schlegel et al., (2017) and (2018). Petrographic relations in the Cu feeder veins and breccia matrices from Neptune and Triton show that fluorite is intergrown with early quartz, hematite or magnetite, chalcopyrite, pyrite, red-stained apatite, barite and carbonates that infill the interstices (Figs. A3 and A4A-C). Locally, multiple events of brecciation and chalcopyrite + pyrite mineralization occurred (Fig. A4D) resulting in sulfide mineralization involving entirely magmatic source of sulfur (Schlegel et al., 2017). Amygdales of altered andesite show subhedral quartz and subsequent infill of carbonates. Where chalcopyrite is present in amygdales, it is intergrown with hematite, barite, fluorite and late dolomite and/or calcite (Fig. A3E-G). Samples OlyD1-4 from the Olympic Dam IOCG deposit represent a transition from a relatively fine- Page 1 of 15
Transcript
Appendix: Fluorite as indicator mineral in iron oxide-copper-
gold systems: explaining the IOCG deposit diversity
Tobias U. Schlegel, Thomas Wagner, and Tobias Fusswinkel
Additional petrography constrains
Extensive petrographic documentation for samples from the Prominent Hill IOCG deposit is
documented in Schlegel and Heinrich (2015), Schlegel et al., (2017) and (2018). Petrographic
relations in the Cu feeder veins and breccia matrices from Neptune and Triton show that fluorite
is intergrown with early quartz, hematite or magnetite, chalcopyrite, pyrite, red-stained apatite,
barite and carbonates that infill the interstices (Figs. A3 and A4A-C). Locally, multiple events of
brecciation and chalcopyrite + pyrite mineralization occurred (Fig. A4D) resulting in sulfide
mineralization involving entirely magmatic source of sulfur (Schlegel et al., 2017). Amygdales of
altered andesite show subhedral quartz and subsequent infill of carbonates. Where chalcopyrite is
present in amygdales, it is intergrown with hematite, barite, fluorite and late dolomite and/or
calcite (Fig. A3E-G). Samples OlyD1-4 from the Olympic Dam IOCG deposit represent a
transition from a relatively fine-grained hematite breccia (OlyD1) with 3.7 wt. % Cu, 0.79 g/t Au,
0.11 wt. % U and 0.23 wt. % La showing a hematite + fluorite + chalcopyrite dominated matrix
and only few clasts to a clast-dominated hematite breccia (OlyD3). Finally, a pervasively
later filled with barite, fluorite and chalcopyriteFig. A2H and Schlegel et al., 2018, Fig. 3D
PH346c PH04D100 595.1 Chalcopyrite and white fluorite intergrown in chalcopyrite-bearing, sericite altered bxmx
PH445 PH05D057 188.7 Granular fluorite intergrown with chalcocite and bornite intergrown in bxmx Fig. A2JPH462a PH09D259 179.9 Bxmx showing intensive intergrown patchy hematite, fluorite and chalcopyrite-
earing matrix that is crosscut by siderite + fluorite + chalcopyrite veinFig. 2A, Schlegel et al., 2018, Figs. 3C, 5C
PH475a PH06D119 214.4 Coarser-grained fluorite intergrown with bornite in hematite-rich breccia matrix. Bornite replaces early pyrite in the matrix
Fig. A2B and Schlegel et al., 2018, Fig. 3A
PH491 PH08D359 950.8 Fluorite + chalcopyrite + hematite are intimately intergrown in bxmx. Sulfur isotope values of chalcopyrite are –30‰ ± 3‰, the most negative values determined in rocks from the Prominent Hill deposit
Fig. A2A
PH505a PH04D057 186.1 Chalcopyrite and fluorite partly replace sericite altered sedimentary rock clast Schlegel and Heinrich, 2015, Fig. 10B
PH27a PH07D313 757.0 Fluorite + barite vein cutting the hematite-quartz breccia, near the contact to footwall volcanic rocks
Fig. A2H
PH82a PH05D130 438.3 Calcite + fluorite + chalcopyrite-bearing vein cutting through fine grained hematite + fluorite + barite + chalcopyrite-bearing breccia matrix. The vein shows multiple repetitions of early fluorite intergrown with chalcopyrite and late calcite
10016 RLMagnetite-pyrite skarn-like assemblage intergrown with calcite, fluorite and minor quartz
Fig. A2G
Olympic Dam IOCG depositOLYD1 Level 34
(1989)Fine-grained, porous hematite breccia showing disseminated and patchy chalcopyrite intergrown with fluorite in the breccia matrix. Breccia is crosscut by fluorite-chalcopyrite veinlets. Sample contains 3.8 wt.% Cu, 0.8 g/t Au, 0.1 wt.% U, 18.5 wt.% Fe, 0.23 wt. % La
Fig. A5A
OLYD2 Level 34(1989)
Porous hematite breccia with abundant chalcopyrite intergrown with hematite + fluorite in the breccia matrix. Minor idaite and carbonate are present.
Fig. A5B, C
OLYD3 Level 34(1989)
Polymict? hematite breccia showing 1-3cm sized granitic, and completely hematized clasts of unknown protolith. Fluorite replaces granitic clasts and is abundant in the matrix where it is intergrown with hematite + fluorite + chalcopyrite + sericite. Chalcopyrite occurs dominantly as isovolumetric replacement of pyrite.
Fig. A5D, E
OLYD4 Level 34(1989)
Pervasively hematite + sericite altered granite with dark purple fluorite present in the matrix of the altered granite and along a hematite alteration front. Abundant chalcocite, digenite, bornite, and idaite intergrown with fine-grained hematite or fluorite.
Fig. A5F, G
OD3 RWTH collection
(2004)
Hematite-granite breccia with granite clasts showing K-feldspar alteration selvages. Matrix consist of hematite + chlorite + sericite intergrown with idaite + chalcopyrite and minor fluorite. Idaite and chalcopyrite replace pyrite.
Fig. A5H
OD1 RWTH collection
Hematite-sericite breccia with abundant idaite and chalcopyrite intergrown with hematite + sericite + minor fluorite.
Fig. A5I
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Table A1. Continuation
Samplenumber
Drill hole Depth(m) Description Reference to Figures
Ernest Henry IOCG depositErnH1 Ore pile
(2018)(2018) Magnetite breccia showing disseminated chalcopyrite, patchy carbonate and minor
fluorite intergrown with chalcopyrite and carbonateFig. A5J
with rock debris + hematite + fluorite + massive chalcopyrite PH611 DD06NEP001 470.4 Pervasively magnetite + fluorite altered; undifferentiated mafic volcanic rock shows
cavity partly filled with idiomorphic, purple fluorite + chalcopyrite crystals both rimmed by fine-grained hematite
PH613 DD06NEP001 526.3 Porphyritic undifferentiated mafic volcanic rock is magnetite + fluorite altered and shows a cavity partly filled with fluorite + barite + minor chalcopyrite
Triton IOCG prospectAmygdale filled with quartz + hematite + fluorite + chalcopyrite + carbonatePH672 DD09TRI006 434.4 Amygdaloidal, undifferentiated mafic volcanic rock. The amygdales are filled with
chalcopyrite + dolomite. Amygdaloidal andesite is brecciated showing a cavity. The cavity is filled with andesite debris, cemented by fluorite (generation 1) + calcite. The breccia is re-brecciated showing three additional fluorite generations (2, 3, and 4).
PH636 DD09TRI007 462.4 Brecciated, weakly magnetite-altered basaltic andesite showing a fine-grained breccia matrix with magnetite + hematite + quartz + fluorite + chalcopyrite + pyrite + barite assemblage and late infill of carbonate in breccia matrix
Fig. A4C
PH584 DD10TRI008 357.0 Replaced and brecciated fine-grained basaltic andesite showing three successive chalcopyrite generations. Early massive chalcopyrite and pyrite altered clasts are rimmed by younger dolomite + barite + hematite + chalcopyrite crusts. This assemblage is then infilled by the youngest mineral generation that comprises calcite + barite + fluorite and late chalcopyrite
XPH621 DD09TRI007 213.2 Chlorite + iron oxide + leucoxene altered andesite breccia crosscut by fluorite + minor chalcopyrite + late calcite vein
Sample contains fluid inclusion assemblages (FIA) analyzed by a) LA-ICP-MS + microthermometry + FIA petrography, b) microthermometry + FIA petrography and c) FIA petrography (Schlegel et al., 2018)
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Figure A1. (A) Geological map of the Prominent Hill area below the cover sequence (modified from Williams et al., 2017) showing the locations of cross-section X: 56050 mE, Y: 55950 mE, and Z: 55650 mE (in mine grid, UTM, zone 53S with easting reduced by 500000 and northing reduced by 6700000). (B-D) Cross-sections X, Y and Z with Cu-grade distribution in the footwall, traces of drill holes and locations of the samples used in this study and in Schlegel et al. (2018).
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Figure A2: Scanned hand specimen images and photomicrographs of representative samples from the Prominent Hill IOCG deposit. (A) Hematite breccia showing matrix of fine-grained, patchy intergrown fluorite, hematite and chalcopyrite; PH491, PH08D359, 950.8 m. (B) Coarse-grained fluorite intergrown with bornite, digenite, and hematite; PH475, PH06D119, 214.4 m. (C) Siderite + fluorite + chalcopyrite + bornite vein crosscutting hematite breccia, PH103, PH04D059, 452.9 m. (D) Part of dm-sized siderite + fluorite + chalcopyrite vein, PH17, Malu pit
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stage 1. (E) Chalcopyrite-bearing hematite-aluminosilicate breccia with fluorite-rich matrix, PH244, PH05D169, 268.4 m. (F) Fluorite intergrown with chalcopyrite + hematite in breccia matrix. Sample contains fluid inclusion assemblages related to mineralization (see Fig. 3A); PH462, PH09D229, 179.9 m. (G) Magnetite + pyrite intergrown with fluorite + carbonate (carb) in magnetite-pyrite skarn-like rock, PH13, Malu pit stage 1. (H) Euhedral fluorite crystals as part of fluorite + barite vein; PH27, PH07D313, 757.0 m. (I) Breccia cavity containing carbonate-cemented Cu sulfide-poor wall-rock debris (bottom left). The remaining cavity space is filled with barite + fluorite + chalcopyrite assemblage; PH251, PH05D169, 219.4 m. (J) Fluorite intergrown with Cu-(Fe) sulfides in hematite-aluminosilicate breccia matrix, PH445, PH05D057, 188.7 m. Mineral abbreviations from Whitney and Evans (2010).
Figure A3: Scanned hand specimen images and photomicrographs of representative samples from the Neptune prospect. (A-B) Magnetite + quartz + apatite + fluorite + pyrite + chalcopyrite + carbonate breccia intervals; PH598, DD06NEP001, 169.4. (A) Magnetite altered andesite clasts (outlined by dashed white lines) in matrix of magnetite + quartz + apatite + chalcopyrite matrix and late infill by dolomite. (B) Early magnetite selvages followed by euhedral quartz + fluorite projecting into the cavity and late infill of dolomite. (C-E) Magnetite + chlorite altered andesite breccia clasts in quartz + magnetite + apatite + fluorite + pyrite + chalcopyrite + dolomite matrix; PH595, DD06NEP001, 164.6 m. (D) Fluorite closely intergrown with chalcopyrite. (E) Fluorite intergrown with chalcopyrite + dolomite. (F) Magnetite altered andesite crosscut by vein showing quartz + chalcopyrite + magnetite + apatite + fluorite assemblage and late infill by dolomite; PH596, DD06NEP001, 165.4m. (G) Quartz + magnetite + fluorite + pyrite + chalcopyrite + carbonate vein crosscutting chlorite + magnetite altered, porphyritic, mafic volcanic rock; PH616, DD06NEP001, 165.4m. Mineral abbreviations from Whitney and Evans (2010).
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Figure A4: Scanned hand specimen images and photomicrographs of representative samples from the Triton prospect. (A-B) Hematite + apatite + quartz + phengite + fluorite + pyrite + chalcopyrite + calcite veins (Cu feeder vein). (A) Large apatite grains are intergrown with hematite + quartz + chalcopyrite + pyrite + calcite; PH570, DD10TRI008, 202.8 m. (B) Brecciated, chlorite-altered andesite with matrix composed of hematite + euhedral quartz + apatite + phengite + fluorite + Cu sulfides; PH571, DD10TRI008, 204.6 m. (C) Magnetite altered basaltic
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andesite with magnetite + hematite + quartz + fluorite + chalcopyrite + pyrite + barite assemblage and late infill of carbonate in breccia matrix; PH636, DD09TRI007, 462.4. (D) Replaced and brecciated fine-grained basaltic andesite showing three successive chalcopyrite generations. Early massive chalcopyrite and pyrite altered clasts are rimmed by younger dolomite + barite + hematite + chalcopyrite. This assemblage is then infilled by the youngest mineral generation that comprises calcite + barite + fluorite and late chalcopyrite; sample PH584, DD10TRI008, 356.5 m. (E) Andesite with amygdale filled by euhedral quartz and later infill of dolomite, PH650, DD09TRI007, 198.2 m. (F) Chlorite altered mafic volcanic rock showing dm-sized vein containing deformed fragments of andesite with rims of magnetite + hematite + quartz + calcite + dolomite + fluorite, intergrown with pyrite + chalcopyrite; PH638, DD09TRI007, 475.7 m. (G) Amygdaloidal, mafic volcanic rock. The amygdales are filled with hematite + quartz + chalcopyrite + fluorite + barite + calcite; PH672, DD09TRI006, 434.4 m. (H) Fluorite-rich calcite + barite + chalcopyrite + fluorite vein crosscutting volcanic rock; PH664, DD09TRI006, 310.1 m. Mineral abbreviations from Whitney and Evans (2010).
Figure A5 (next page). Scanned hand specimen images and photomicrographs of ore samples from the (A-I) Olympic Dam and (J) Ernest Henry IOCG deposits. (A) Fine-grained hematite + chalcopyrite + fluorite breccia matrix crosscut by fluorite + chalcopyrite veinlets; OlyD1, mine level 34. (B-C) Porous hematite breccia showing partly by hematite replaced clasts and abundant chalcopyrite intergrown with hematite + fluorite in the breccia matrix; OlyD2, mine level 34. (D-E). Polymict? hematite breccia showing granitic, and hematized clasts. Fluorite replaces granitic clasts and is abundant in the breccia matrix. Chalcopyrite occurs as isovolumetic replacement of pyrite (E); OlyD3, mine level 34. (F-G) Altered granite showing patches of fluorite intergrown with idaite and chalcocite; OlyD4, mine level 34. (H) Fluorite intergrown with hematite, idaite in breccia matrix; OD1, RWTH collection. (I) Hematite-granite breccia with granite clasts showing K-feldspar alteration selvages. Sericite + chlorite replace feldspars and are intergrown with hematite and Cu-(Fe) sulfides; OD3, RWTH collection. (J) Magnetite breccia showing disseminated chalcopyrite. Mineral abbreviations from Whitney and Evans (2010).
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References
Schlegel, T.U., Heinrich, C.A., 2015. Lithology and hydrothermal alteration control the distribution of copper grade in the Prominent Hill iron oxide-copper-gold deposit (Gawler craton, South Australia). Econ. Geol. 110, 1953–1994.
Schlegel, T.U., Wagner, T., Heinrich C.A., Boyce, A.J., 2017. Magmatic-hydrothermal sulfur source for Prominent Hill and other iron oxide-copper-gold mineralisations in the Olympic IOCG province, South Australia. Ore Geol. Rev. 89, 1058–1090.
Schlegel, T.U., Wagner, T., Wälle, M., Heinrich, C.A., 2018. Hematite breccia-hosted iron oxide copper-gold deposits require magmatic fluid components exposed to atmospheric oxidation: Evidence from Prominent Hill, Gawler Craton, South Australia. Econ. Geol. 113, 597–644.
Williams, P.J., Freeman H., Anderson, I., and Holcombe, R., 2017. Prominent Hill copper-gold deposit, in Philips, N.,ed., Australian ore deposits: Carlton Victoria. The Australian Institute of Mining and Metallurgy Monograph 32, 611–614.
