Antimony in rutile as a pathfinder for orogenic gold deposits

Andrea Agangi, Steven M. Reddy, Diana Plavsa, Denis Fougerouse, Chris Clark, Malcolm Roberts, Tim E. Johnson

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

In our study we explore the applicability of rutile as a pathfinder for orogenic gold deposits, which are an important source of this metal worldwide. We analysed rutile associated with orogenic Au deposits from three different Precambrian terranes, the Capricorn Orogen, the Barberton Greenstone Belt and the Ashanti Belt, all of which formed under greenschist conditions and share similarities in the style of mineralisation. Microtextural evidence from scanning electron microscopy and electron back-scatter diffraction indicates that rutile formed during the main deformation and alteration stage in these rocks, and is therefore related to mineralisation. We used electron microprobe and laser ablation ICP-MS to investigate the trace element compositions of rutile and we compared our results to other gold deposits. We find that hydrothermal rutile from gold deposits contains certain trace element characteristics, in particular high Sb concentrations (up to similar to 1500 ppm in Au deposits of the Capricorn Orogen), that are distinct from rutile from non-mineralised rocks of various petrogenetic origin. Other elements, such as W and Sn, are found to be more enriched in rutile from other rock types, namely felsic magmatic rocks and hydrothermal veins, and are therefore not diagnostic of Au mineralisation in this type of deposits. We also find that the presence of sub-pm-scale inclusions - in particular Zr-(Si, Th)-bearing phases, sulfide minerals and native Au - can severely affect analyses of this type of rutile and compromise the applicability of Zr-in-rutile geothermometry.

Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalOre Geology Reviews
Volume106
DOIs
Publication statusPublished - Mar 2019

Cite this

Agangi, A., Reddy, S. M., Plavsa, D., Fougerouse, D., Clark, C., Roberts, M., & Johnson, T. E. (2019). Antimony in rutile as a pathfinder for orogenic gold deposits. Ore Geology Reviews, 106, 1-11. https://doi.org/10.1016/j.oregeorev.2019.01.018
Agangi, Andrea ; Reddy, Steven M. ; Plavsa, Diana ; Fougerouse, Denis ; Clark, Chris ; Roberts, Malcolm ; Johnson, Tim E. / Antimony in rutile as a pathfinder for orogenic gold deposits. In: Ore Geology Reviews. 2019 ; Vol. 106. pp. 1-11.
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abstract = "In our study we explore the applicability of rutile as a pathfinder for orogenic gold deposits, which are an important source of this metal worldwide. We analysed rutile associated with orogenic Au deposits from three different Precambrian terranes, the Capricorn Orogen, the Barberton Greenstone Belt and the Ashanti Belt, all of which formed under greenschist conditions and share similarities in the style of mineralisation. Microtextural evidence from scanning electron microscopy and electron back-scatter diffraction indicates that rutile formed during the main deformation and alteration stage in these rocks, and is therefore related to mineralisation. We used electron microprobe and laser ablation ICP-MS to investigate the trace element compositions of rutile and we compared our results to other gold deposits. We find that hydrothermal rutile from gold deposits contains certain trace element characteristics, in particular high Sb concentrations (up to similar to 1500 ppm in Au deposits of the Capricorn Orogen), that are distinct from rutile from non-mineralised rocks of various petrogenetic origin. Other elements, such as W and Sn, are found to be more enriched in rutile from other rock types, namely felsic magmatic rocks and hydrothermal veins, and are therefore not diagnostic of Au mineralisation in this type of deposits. We also find that the presence of sub-pm-scale inclusions - in particular Zr-(Si, Th)-bearing phases, sulfide minerals and native Au - can severely affect analyses of this type of rutile and compromise the applicability of Zr-in-rutile geothermometry.",
keywords = "Gold, Antimony, Orogenic gold deposit, Indicator mineral, Exploration, BARBERTON GREENSTONE-BELT, TRACE-ELEMENT COMPOSITIONS, ASHANTI BELT, SOUTH-AFRICA, CAPRICORN OROGEN, MINING DISTRICT, DETRITAL RUTILE, EVOLUTION, FLUID, MINERALIZATION",
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Agangi, A, Reddy, SM, Plavsa, D, Fougerouse, D, Clark, C, Roberts, M & Johnson, TE 2019, 'Antimony in rutile as a pathfinder for orogenic gold deposits' Ore Geology Reviews, vol. 106, pp. 1-11. https://doi.org/10.1016/j.oregeorev.2019.01.018

Antimony in rutile as a pathfinder for orogenic gold deposits. / Agangi, Andrea; Reddy, Steven M.; Plavsa, Diana; Fougerouse, Denis; Clark, Chris; Roberts, Malcolm; Johnson, Tim E.

In: Ore Geology Reviews, Vol. 106, 03.2019, p. 1-11.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Antimony in rutile as a pathfinder for orogenic gold deposits

AU - Agangi, Andrea

AU - Reddy, Steven M.

AU - Plavsa, Diana

AU - Fougerouse, Denis

AU - Clark, Chris

AU - Roberts, Malcolm

AU - Johnson, Tim E.

PY - 2019/3

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N2 - In our study we explore the applicability of rutile as a pathfinder for orogenic gold deposits, which are an important source of this metal worldwide. We analysed rutile associated with orogenic Au deposits from three different Precambrian terranes, the Capricorn Orogen, the Barberton Greenstone Belt and the Ashanti Belt, all of which formed under greenschist conditions and share similarities in the style of mineralisation. Microtextural evidence from scanning electron microscopy and electron back-scatter diffraction indicates that rutile formed during the main deformation and alteration stage in these rocks, and is therefore related to mineralisation. We used electron microprobe and laser ablation ICP-MS to investigate the trace element compositions of rutile and we compared our results to other gold deposits. We find that hydrothermal rutile from gold deposits contains certain trace element characteristics, in particular high Sb concentrations (up to similar to 1500 ppm in Au deposits of the Capricorn Orogen), that are distinct from rutile from non-mineralised rocks of various petrogenetic origin. Other elements, such as W and Sn, are found to be more enriched in rutile from other rock types, namely felsic magmatic rocks and hydrothermal veins, and are therefore not diagnostic of Au mineralisation in this type of deposits. We also find that the presence of sub-pm-scale inclusions - in particular Zr-(Si, Th)-bearing phases, sulfide minerals and native Au - can severely affect analyses of this type of rutile and compromise the applicability of Zr-in-rutile geothermometry.

AB - In our study we explore the applicability of rutile as a pathfinder for orogenic gold deposits, which are an important source of this metal worldwide. We analysed rutile associated with orogenic Au deposits from three different Precambrian terranes, the Capricorn Orogen, the Barberton Greenstone Belt and the Ashanti Belt, all of which formed under greenschist conditions and share similarities in the style of mineralisation. Microtextural evidence from scanning electron microscopy and electron back-scatter diffraction indicates that rutile formed during the main deformation and alteration stage in these rocks, and is therefore related to mineralisation. We used electron microprobe and laser ablation ICP-MS to investigate the trace element compositions of rutile and we compared our results to other gold deposits. We find that hydrothermal rutile from gold deposits contains certain trace element characteristics, in particular high Sb concentrations (up to similar to 1500 ppm in Au deposits of the Capricorn Orogen), that are distinct from rutile from non-mineralised rocks of various petrogenetic origin. Other elements, such as W and Sn, are found to be more enriched in rutile from other rock types, namely felsic magmatic rocks and hydrothermal veins, and are therefore not diagnostic of Au mineralisation in this type of deposits. We also find that the presence of sub-pm-scale inclusions - in particular Zr-(Si, Th)-bearing phases, sulfide minerals and native Au - can severely affect analyses of this type of rutile and compromise the applicability of Zr-in-rutile geothermometry.

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KW - Orogenic gold deposit

KW - Indicator mineral

KW - Exploration

KW - BARBERTON GREENSTONE-BELT

KW - TRACE-ELEMENT COMPOSITIONS

KW - ASHANTI BELT

KW - SOUTH-AFRICA

KW - CAPRICORN OROGEN

KW - MINING DISTRICT

KW - DETRITAL RUTILE

KW - EVOLUTION

KW - FLUID

KW - MINERALIZATION

U2 - 10.1016/j.oregeorev.2019.01.018

DO - 10.1016/j.oregeorev.2019.01.018

M3 - Article

VL - 106

SP - 1

EP - 11

JO - Ore Geology Reviews

JF - Ore Geology Reviews

SN - 0169-1368

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