Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)

Augustin Dekoninck; Béchir Moussi; Torsten Vennemann; Fakher Jamoussi; Nadine Mattielli; Sophie Decrée; Hédi-Ridha Chaftar; Nouri Hatira; Johan Yans

doi:10.1016/j.clay.2018.07.007

Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)

Augustin Dekoninck, Béchir Moussi, Torsten Vennemann, Fakher Jamoussi, Nadine Mattielli, Sophie Decrée, Hédi-Ridha Chaftar, Nouri Hatira, Johan Yans

Research output: Contribution to journal › Article › peer-review

Abstract

The iron mine of Tamra (Nefza District, NW Tunisia) is a 50 m thick Upper Mio-Pliocene sedimentary series impregnated by Fe-Mn oxides associated with white clay lenses with high halloysite and kaolinite content. This mineralization results from i) synsedimentary weathering/pedogenesis, and ii) mixing surface water and regional hydrothermal fluids. The oxygen and hydrogen isotope composition of halloysite-kaolinite and goethite-hematite is examined in order to provide new insights into the ore formation. This study concludes that halloysite-kaolinite was not equilibrated only with meteoric fluids: the δ ¹⁸O values have a range towards high values that are not consistent with weathering conditions for their formation and/or during their subsequent alteration. The δD and δ ¹⁸O values of goethite lead to the same conclusion. The stable isotope compositions could be related to fluid-rock interaction with the underlying marls (and/or skarns), providing relatively high δ ¹⁸O values to the fluids responsible for the white clay formation. This model also shows that the Pb-isotope compositions of halloysite-kaolinite are explained by a felsic and a carbonated end-member, similar to other ore deposits (IOCG and Sedex) of the vicinity. Several factors should be considered for the precipitation of halloysite-kaolinite and/or destabilization of primary clays in the Tamra ore, i.e. mixing of deep hot saline fluids, related to a thermally driven circulation, and meteoric waters. This hydrothermal contribution postdates the main synsedimentary weathering/pedogenetic Fe-enrichment and may be related to late Fe, Mn, Pb, Zn and As inputs of the Fe-Mn oxides.

Original language	English
Article number	10.1016/j.clay.2018.07.007
Pages (from-to)	33-45
Number of pages	13
Journal	Applied Clay Science
Volume	163
DOIs	https://doi.org/10.1016/j.clay.2018.07.007
Publication status	Published - 17 Jul 2018

Keywords

Halloysite
Iron-manganese ore
Nefza district
stable isotopes
lead isotopes
Tunisia
Stable isotopes
Lead isotopes

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10.1016/j.clay.2018.07.007

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Dekoninck, A., Moussi, B., Vennemann, T., Jamoussi, F., Mattielli, N., Decrée, S., Chaftar, H.-R., Hatira, N., & Yans, J. (2018). Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia). Applied Clay Science, 163, 33-45. Article 10.1016/j.clay.2018.07.007. https://doi.org/10.1016/j.clay.2018.07.007

@article{240f90964b2b413794fd4fb9abc87222,

title = "Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)",

abstract = "The iron mine of Tamra (Nefza District, NW Tunisia) is a 50 m thick Upper Mio-Pliocene sedimentary series impregnated by Fe-Mn oxides associated with white clay lenses with high halloysite and kaolinite content. This mineralization results from i) synsedimentary weathering/pedogenesis, and ii) mixing surface water and regional hydrothermal fluids. The oxygen and hydrogen isotope composition of halloysite-kaolinite and goethite-hematite is examined in order to provide new insights into the ore formation. This study concludes that halloysite-kaolinite was not equilibrated only with meteoric fluids: the δ 18O values have a range towards high values that are not consistent with weathering conditions for their formation and/or during their subsequent alteration. The δD and δ 18O values of goethite lead to the same conclusion. The stable isotope compositions could be related to fluid-rock interaction with the underlying marls (and/or skarns), providing relatively high δ 18O values to the fluids responsible for the white clay formation. This model also shows that the Pb-isotope compositions of halloysite-kaolinite are explained by a felsic and a carbonated end-member, similar to other ore deposits (IOCG and Sedex) of the vicinity. Several factors should be considered for the precipitation of halloysite-kaolinite and/or destabilization of primary clays in the Tamra ore, i.e. mixing of deep hot saline fluids, related to a thermally driven circulation, and meteoric waters. This hydrothermal contribution postdates the main synsedimentary weathering/pedogenetic Fe-enrichment and may be related to late Fe, Mn, Pb, Zn and As inputs of the Fe-Mn oxides. ",

keywords = "Halloysite, Iron-manganese ore, Nefza district, stable isotopes, lead isotopes, Tunisia, Stable isotopes, Lead isotopes",

author = "Augustin Dekoninck and B{\'e}chir Moussi and Torsten Vennemann and Fakher Jamoussi and Nadine Mattielli and Sophie Decr{\'e}e and H{\'e}di-Ridha Chaftar and Nouri Hatira and Johan Yans",

note = "Funding Information: The present investigation was carried out with the support of the WBI (Wallonie-Bruxelles International) and the project entitled “Valorisation des argiles tunisiennes”. We warmly thank the team of the “Office National des Mines de Tunisie (ONM)” who have contributed to this study by providing documents, field authorization and by taking part to fruitful discussion about the Nefza area. We are grateful to Wendy Debouge and Jeroen de Jong of the G-TIME laboratories of the “Universit{\'e} Libre de Bruxelles (ULB)” for having performed lead isotope analyzes on halloysite-kaolinite samples. We also thank Johan Wouters and Nikolay Tumanov (Plateforme de Caract{\'e}risation Physico Chimique [PC2]) of the University of Namur for having given access to experimental facilities, especially in collecting XRD patterns. We are grateful to Albert Gilg for sharing his opinion about the origin of these unusual stable isotopes of kaolinite-halloysite. We thank Christian Dupuis for sharing field pictures of white clay lenses. We especially thank Ga{\"e}tan Rochez for having prepared XRD samples and for having taken outstanding pictures in the field. We finally thank three anonymous reviewers who have significantly improved the quality of the manuscript. Publisher Copyright: {\textcopyright} 2018 Elsevier B.V.",

year = "2018",

month = jul,

day = "17",

doi = "10.1016/j.clay.2018.07.007",

language = "English",

volume = "163",

pages = "33--45",

journal = "Applied Clay Science",

issn = "0169-1317",

publisher = "Elsevier",

}

Dekoninck, A, Moussi, B, Vennemann, T, Jamoussi, F, Mattielli, N, Decrée, S, Chaftar, H-R, Hatira, N & Yans, J 2018, 'Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)', Applied Clay Science, vol. 163, 10.1016/j.clay.2018.07.007, pp. 33-45. https://doi.org/10.1016/j.clay.2018.07.007

Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia). / Dekoninck, Augustin; Moussi, Béchir; Vennemann, Torsten et al.
In: Applied Clay Science, Vol. 163, 10.1016/j.clay.2018.07.007, 17.07.2018, p. 33-45.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)

AU - Dekoninck, Augustin

AU - Moussi, Béchir

AU - Vennemann, Torsten

AU - Jamoussi, Fakher

AU - Mattielli, Nadine

AU - Decrée, Sophie

AU - Chaftar, Hédi-Ridha

AU - Hatira, Nouri

AU - Yans, Johan

N1 - Funding Information: The present investigation was carried out with the support of the WBI (Wallonie-Bruxelles International) and the project entitled “Valorisation des argiles tunisiennes”. We warmly thank the team of the “Office National des Mines de Tunisie (ONM)” who have contributed to this study by providing documents, field authorization and by taking part to fruitful discussion about the Nefza area. We are grateful to Wendy Debouge and Jeroen de Jong of the G-TIME laboratories of the “Université Libre de Bruxelles (ULB)” for having performed lead isotope analyzes on halloysite-kaolinite samples. We also thank Johan Wouters and Nikolay Tumanov (Plateforme de Caractérisation Physico Chimique [PC2]) of the University of Namur for having given access to experimental facilities, especially in collecting XRD patterns. We are grateful to Albert Gilg for sharing his opinion about the origin of these unusual stable isotopes of kaolinite-halloysite. We thank Christian Dupuis for sharing field pictures of white clay lenses. We especially thank Gaëtan Rochez for having prepared XRD samples and for having taken outstanding pictures in the field. We finally thank three anonymous reviewers who have significantly improved the quality of the manuscript. Publisher Copyright: © 2018 Elsevier B.V.

PY - 2018/7/17

Y1 - 2018/7/17

N2 - The iron mine of Tamra (Nefza District, NW Tunisia) is a 50 m thick Upper Mio-Pliocene sedimentary series impregnated by Fe-Mn oxides associated with white clay lenses with high halloysite and kaolinite content. This mineralization results from i) synsedimentary weathering/pedogenesis, and ii) mixing surface water and regional hydrothermal fluids. The oxygen and hydrogen isotope composition of halloysite-kaolinite and goethite-hematite is examined in order to provide new insights into the ore formation. This study concludes that halloysite-kaolinite was not equilibrated only with meteoric fluids: the δ 18O values have a range towards high values that are not consistent with weathering conditions for their formation and/or during their subsequent alteration. The δD and δ 18O values of goethite lead to the same conclusion. The stable isotope compositions could be related to fluid-rock interaction with the underlying marls (and/or skarns), providing relatively high δ 18O values to the fluids responsible for the white clay formation. This model also shows that the Pb-isotope compositions of halloysite-kaolinite are explained by a felsic and a carbonated end-member, similar to other ore deposits (IOCG and Sedex) of the vicinity. Several factors should be considered for the precipitation of halloysite-kaolinite and/or destabilization of primary clays in the Tamra ore, i.e. mixing of deep hot saline fluids, related to a thermally driven circulation, and meteoric waters. This hydrothermal contribution postdates the main synsedimentary weathering/pedogenetic Fe-enrichment and may be related to late Fe, Mn, Pb, Zn and As inputs of the Fe-Mn oxides.

AB - The iron mine of Tamra (Nefza District, NW Tunisia) is a 50 m thick Upper Mio-Pliocene sedimentary series impregnated by Fe-Mn oxides associated with white clay lenses with high halloysite and kaolinite content. This mineralization results from i) synsedimentary weathering/pedogenesis, and ii) mixing surface water and regional hydrothermal fluids. The oxygen and hydrogen isotope composition of halloysite-kaolinite and goethite-hematite is examined in order to provide new insights into the ore formation. This study concludes that halloysite-kaolinite was not equilibrated only with meteoric fluids: the δ 18O values have a range towards high values that are not consistent with weathering conditions for their formation and/or during their subsequent alteration. The δD and δ 18O values of goethite lead to the same conclusion. The stable isotope compositions could be related to fluid-rock interaction with the underlying marls (and/or skarns), providing relatively high δ 18O values to the fluids responsible for the white clay formation. This model also shows that the Pb-isotope compositions of halloysite-kaolinite are explained by a felsic and a carbonated end-member, similar to other ore deposits (IOCG and Sedex) of the vicinity. Several factors should be considered for the precipitation of halloysite-kaolinite and/or destabilization of primary clays in the Tamra ore, i.e. mixing of deep hot saline fluids, related to a thermally driven circulation, and meteoric waters. This hydrothermal contribution postdates the main synsedimentary weathering/pedogenetic Fe-enrichment and may be related to late Fe, Mn, Pb, Zn and As inputs of the Fe-Mn oxides.

KW - Halloysite

KW - Iron-manganese ore

KW - Nefza district

KW - stable isotopes

KW - lead isotopes

KW - Tunisia

KW - Stable isotopes

KW - Lead isotopes

UR - http://www.scopus.com/inward/record.url?scp=85049798857&partnerID=8YFLogxK

U2 - 10.1016/j.clay.2018.07.007

DO - 10.1016/j.clay.2018.07.007

M3 - Article

SN - 0169-1317

VL - 163

SP - 33

EP - 45

JO - Applied Clay Science

JF - Applied Clay Science

M1 - 10.1016/j.clay.2018.07.007

ER -

Mixed hydrothermal and meteoric fluids evidenced by unusual H- and O-isotope compositions of kaolinite-halloysite in the Fe(-Mn) Tamra deposit (Nefza district, NW Tunisia)

Abstract

Keywords

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