Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)

Augustin Dekoninck; Jocelyn Barbarand; Gilles Ruffet; Yves Missenard; Nadine Mattielli; Rémi Leprêtre; Abdellah Mouttaqi; Michèle Verhaert; Omar Saddiqi; Johan Yans

doi:10.1007/s00126-023-01212-9

Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)

Augustin Dekoninck, Jocelyn Barbarand, Gilles Ruffet, Yves Missenard, Nadine Mattielli, Rémi Leprêtre, Abdellah Mouttaqi, Michèle Verhaert, Omar Saddiqi, Johan Yans

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

Abstract

The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. ⁴⁰Ar/³⁹Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O₂-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. Graphical Abstract: [Figure not available: see fulltext.]

Original language	English
Pages (from-to)	453-472
Number of pages	20
Journal	Mineralium Deposita
Volume	59
Issue number	3
DOIs	https://doi.org/10.1007/s00126-023-01212-9
Publication status	Published - 6 Oct 2023

Funding

We are grateful to all those involved in the field missions carried out between 2012 and 2018. We acknowledge the \u201COffice National des Mines et des Hydrocarbures\u201D (ONHYM) for having shared their logistical and scientific support. We are very grateful to the Imini mine (SACEM) for providing field access and assistance in the field. We are thankful to Prof. M. Essalhi (University Moulay Ismail Errachidia), Th. Mortier (UMons), Z. Pirotte (ULB), B. Saint-B\u00E9zar (PSUD), and G. Delpech (PSUD) for field assistance. We appreciate the help of Prof. J. Wouters and Dr. N. Tumanov of the PC2 platform (UNamur) for collecting XRD patterns. We also thank G. Rochez for gathering field pictures and the preparation of sections and sample powders. Co-authors would like to warmly thank Jeroen De Jong for his assistance during the isotopic analyses and the \u201CFonds National de la Recherche Scientifique\u201D (FNRS) for funding support in lab instruments. This research used the resources of the Electron Microscopy Service located at the University of Namur (\u201CPlateforme Technologique Morphologie \u2014 Imagerie\u201D). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. We are very grateful to Prof. M. Bouabdellah and Prof. J. Gutzmer for their careful review of the paper, as well as Prof. G. Beaudoin for editing the final version.

Funders	Funder number
Office National des Mines et des Hydrocarbures
ONHYM
Fonds de la Recherche Scientifique F.R.S.-FNRS
University of Namur
UK Research and Innovation	104831

Keywords

Ar/Ar dating
Geodynamics
K-Mn oxides
Ore deposits
Pb isotopes

Access to Document

10.1007/s00126-023-01212-9

Cite this

@article{836ad192a2434ef0b07a115d18d69549,

title = "Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)",

abstract = "The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. Graphical Abstract: [Figure not available: see fulltext.]",

keywords = "Ar/Ar dating, Geodynamics, K-Mn oxides, Ore deposits, Pb isotopes",

author = "Augustin Dekoninck and Jocelyn Barbarand and Gilles Ruffet and Yves Missenard and Nadine Mattielli and R{\'e}mi Lepr{\^e}tre and Abdellah Mouttaqi and Mich{\`e}le Verhaert and Omar Saddiqi and Johan Yans",

note = "Publisher Copyright: {\textcopyright} The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.",

year = "2023",

month = oct,

day = "6",

doi = "10.1007/s00126-023-01212-9",

language = "English",

volume = "59",

pages = "453--472",

journal = "Mineralium Deposita",

issn = "0026-4598",

publisher = "Springer",

number = "3",

}

TY - JOUR

T1 - Intraplate orogenesis as a driver of multistage karst-hosted mineralization

T2 - the Imini manganese case (Atlas, Morocco)

AU - Dekoninck, Augustin

AU - Barbarand, Jocelyn

AU - Ruffet, Gilles

AU - Missenard, Yves

AU - Mattielli, Nadine

AU - Leprêtre, Rémi

AU - Mouttaqi, Abdellah

AU - Verhaert, Michèle

AU - Saddiqi, Omar

AU - Yans, Johan

N1 - Publisher Copyright: © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.

PY - 2023/10/6

Y1 - 2023/10/6

N2 - The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. Graphical Abstract: [Figure not available: see fulltext.]

AB - The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore. Graphical Abstract: [Figure not available: see fulltext.]

KW - Ar/Ar dating

KW - Geodynamics

KW - K-Mn oxides

KW - Ore deposits

KW - Pb isotopes

UR - http://www.scopus.com/inward/record.url?scp=85173745546&partnerID=8YFLogxK

UR - https://rdcu.be/dqXM5

U2 - 10.1007/s00126-023-01212-9

DO - 10.1007/s00126-023-01212-9

M3 - Article

AN - SCOPUS:85173745546

SN - 0026-4598

VL - 59

SP - 453

EP - 472

JO - Mineralium Deposita

JF - Mineralium Deposita

IS - 3

ER -

Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Morphology - Imaging

Physical Chemistry and characterization(PC2)

Cite this

Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Equipment

Morphology - Imaging

Physical Chemistry and characterization(PC2)

Cite this