Chemical and boron isotope composition of tourmaline from the Kiaka orogenic gold deposit (Burkina Faso, West African Craton) as a proxy for ore-forming processes
Chemical and boron isotope composition of tourmaline from the Kiaka orogenic gold deposit (Burkina Faso, West African Craton) as a proxy for ore-forming processes
The Kiaka orogenic gold deposit (Burkina Faso), located in the Paleoproterozoic domain of the West African Craton, is characterized by a two-stage gold mineralization hosted in volcano-sedimentary metamorphic rocks that was formed during the Eoeburnean (2.20–2.13 Ga) and Eburnean (2.13–2.05 Ga) orogenic cycles. These two stages include an early disseminated low-grade gold mineralization and a late vein-hosted high-grade gold mineralization. Paragenetic studies indicate that the first gold stage was coeval with the deposition of hydrothermal tourmaline. The aim of this paper is twofold: (i) to determine the processes responsible for deposition of the economic disseminated gold mineralization and (ii) to identify the source of the mineralizing fluids. For this purpose, we performed an in situ study on tourmaline by combining electron probe microanalysis and secondary ion mass spectrometry measurements of boron isotopes. Hydrothermal tourmaline hosted in metamafic volcanic rocks and metagreywackes has a dravite composition but shows different δ11B values falling within the two intervals of − 25.1 to − 22.0‰ and − 19.6 to − 15.1‰, respectively. Our results suggest that tourmaline formed from a distal, high-temperature (ca. 400 °C), reduced, and low-salinity hydrothermal fluid that interacted with the local host rocks. Based on the modeling of tourmaline–fluid boron isotope fractionation, we propose a metamorphic fluid origin derived from devolatilization of deeply buried muscovite schists during the regional prograde to peak metamorphism prior ca. 2.13 Ga. This metamorphic fluid–rock interaction model may possibly extend to other orogenic gold deposits in the West African Craton.
Tourmaline, Boron Isotopes, Orogenic gold deposit, West African Craton, Burkina Faso
Gauriau, Judith
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Harlaux, Matthieu
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Andre-Mayer, Anne-Sylvie
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Eglinger, Aurelien
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Richard, Antonin
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Fontaine, Arnaud
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Lefebvre-Desanois, Marie
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Beziat, Didier
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Villeneuve, Johan
e90142af-89f2-45fc-be9b-0db49b1e69ea
Lemarchand, Damien
17801f84-7da0-4511-8ebb-dda7ed7f179f
24 July 2020
Gauriau, Judith
d20dbaba-0387-48a9-b6a2-d7d9fe855c6f
Harlaux, Matthieu
2f37fa79-8198-4d82-abb8-c70185197e29
Andre-Mayer, Anne-Sylvie
5bb66a9e-cc3a-40d7-a766-1adb0c1fd584
Eglinger, Aurelien
504f6103-ee6c-4845-9fdb-d1ffa2de029b
Richard, Antonin
c0ebf47e-421c-4e81-acae-aa3788b2217e
Fontaine, Arnaud
48f10ec7-ed5a-494f-921b-2c51c6e0053f
Lefebvre-Desanois, Marie
b9ca8d27-8ab9-4a72-b4e4-39defc53aa85
Beziat, Didier
50956e00-f730-47ee-9994-b5ff98f87b9f
Villeneuve, Johan
e90142af-89f2-45fc-be9b-0db49b1e69ea
Lemarchand, Damien
17801f84-7da0-4511-8ebb-dda7ed7f179f
Gauriau, Judith, Harlaux, Matthieu, Andre-Mayer, Anne-Sylvie, Eglinger, Aurelien, Richard, Antonin, Fontaine, Arnaud, Lefebvre-Desanois, Marie, Beziat, Didier, Villeneuve, Johan and Lemarchand, Damien
(2020)
Chemical and boron isotope composition of tourmaline from the Kiaka orogenic gold deposit (Burkina Faso, West African Craton) as a proxy for ore-forming processes.
Mineralium Deposita.
(doi:10.1007/s00126-020-01002-7).
Abstract
The Kiaka orogenic gold deposit (Burkina Faso), located in the Paleoproterozoic domain of the West African Craton, is characterized by a two-stage gold mineralization hosted in volcano-sedimentary metamorphic rocks that was formed during the Eoeburnean (2.20–2.13 Ga) and Eburnean (2.13–2.05 Ga) orogenic cycles. These two stages include an early disseminated low-grade gold mineralization and a late vein-hosted high-grade gold mineralization. Paragenetic studies indicate that the first gold stage was coeval with the deposition of hydrothermal tourmaline. The aim of this paper is twofold: (i) to determine the processes responsible for deposition of the economic disseminated gold mineralization and (ii) to identify the source of the mineralizing fluids. For this purpose, we performed an in situ study on tourmaline by combining electron probe microanalysis and secondary ion mass spectrometry measurements of boron isotopes. Hydrothermal tourmaline hosted in metamafic volcanic rocks and metagreywackes has a dravite composition but shows different δ11B values falling within the two intervals of − 25.1 to − 22.0‰ and − 19.6 to − 15.1‰, respectively. Our results suggest that tourmaline formed from a distal, high-temperature (ca. 400 °C), reduced, and low-salinity hydrothermal fluid that interacted with the local host rocks. Based on the modeling of tourmaline–fluid boron isotope fractionation, we propose a metamorphic fluid origin derived from devolatilization of deeply buried muscovite schists during the regional prograde to peak metamorphism prior ca. 2.13 Ga. This metamorphic fluid–rock interaction model may possibly extend to other orogenic gold deposits in the West African Craton.
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Accepted/In Press date: 16 June 2020
Published date: 24 July 2020
Keywords:
Tourmaline, Boron Isotopes, Orogenic gold deposit, West African Craton, Burkina Faso
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Local EPrints ID: 449750
URI: http://eprints.soton.ac.uk/id/eprint/449750
ISSN: 0026-4598
PURE UUID: 7e59d898-a701-4849-b37c-4e5a2bdc2f8b
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Date deposited: 15 Jun 2021 16:32
Last modified: 17 Mar 2024 04:07
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Contributors
Author:
Judith Gauriau
Author:
Matthieu Harlaux
Author:
Anne-Sylvie Andre-Mayer
Author:
Aurelien Eglinger
Author:
Antonin Richard
Author:
Arnaud Fontaine
Author:
Marie Lefebvre-Desanois
Author:
Didier Beziat
Author:
Johan Villeneuve
Author:
Damien Lemarchand
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