Volcanic rocks from Amensif-Tnirt district in the Western High Atlas (Morocco): Geochemistry, magma features and new age dating

Ilyasse Loudaoued; Ahmed Touil; Namık Aysal; Mohamed Aissa; Mehmet Keskin; İsak Yılmaz; Abdelmalek Ouadjou

doi:10.1016/j.jafrearsci.2023.104975

Volcanic rocks from Amensif-Tnirt district in the Western High Atlas (Morocco): Geochemistry, magma features and new age dating

Ilyasse Loudaoued^*, Ahmed Touil, Namık Aysal, Mohamed Aissa, Mehmet Keskin, İsak Yılmaz, Abdelmalek Ouadjou

^*Corresponding author for this work

Department of Geological Engineering

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

7 Citations (Scopus)

Abstract

The High Atlas Mountains include mafic, intermediate and felsic volcanic-subvolcanic intrusive rocks, representing a result of magmatism related to “Cambrian rift” during the Lower Cambrian. The investigated magmatic rocks in the Amensif-Tnirt area are divided into three main groups as the mafic (SiO₂ 48.31 to 53.06 wt%), intermediate (SiO₂ 59.16 to 67.38 wt%), and felsic (SiO₂ 76.39 to 79.65 wt%) rocks. The mafic rocks correspond to microgabbros with high TiO₂ contents (1.98–2.12 wt%) and FeO_t/MgO ratios (1.65–1.90), La/Yb (9.09–11.60) and Nb/Zr (0.03–0.04) ratios, providing good evidence of extensive intracontinental tholeiite. The Nb/Yb and Zr/Y ratios ranging between 0.36 to 0.52 and 12.76 to 13.69, respectively suggest their derivation from an enriched mantle source during the opening of the Rheic ocean along the NW edge of Gondwana. The mafic rocks may be interpreted as the mixtures of melts derived from two contrasting mantle sources: (1) a garnet-bearing clinopyroxenitic ultramafic source and (2) an ultramafic source composed of spinel and peridotite. The intermediate and felsic rocks correspond to andesite-dacite and rhyolite with TiO₂ contents and FeO_t/MgO ratios ranging from 0.09 to 1.36 wt% and 1.32 to 4.69, respectively, suggesting their calc-alkaline affinities setting up during a compressive context. The youngest ²⁰⁶Pb/²³⁸U ages for intermediate rocks are 290.29 ± 4.68 and 291.27 ± 4.31 Ma, while the youngest felsic rocks yield a concordia age at 272.83 ± 0.73 Ma (MSWD = 0.25). Petrographic and geochemical data indicate that mafic magmatism in the Amensif-Tnirt region may be the equivalent of the first Cambrian volcanic episode in the High Atlas. Intermediate rocks are chronologically correlated to the Permian volcanic activities recorded in Central Morocco (Tiddas, Khenifra, Chougrane …) whereas felsic activity is correlated to the Permian Azegour granite from the High Atlas.

Original language	English
Article number	104975
Journal	Journal of African Earth Sciences
Volume	205
DOIs	https://doi.org/10.1016/j.jafrearsci.2023.104975
Publication status	Published - Sept 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier Ltd

Funding

This contribution reports part of a Phd project of Ilyasse Loudaoued sponsored by the CMG-MANAGEM through a cooperation program with Cadi Ayyad University (FSTG Marrakech). This contribution reports part of a Phd project of Ilyasse Loudaoued sponsored by the CMG-MANAGEM through a cooperation program with Cadi Ayyad University (FSTG Marrakech). Geochronological dating was provided by the Geochronology and Geochemistry Laboratory of Istanbul University-Cerrahpaşa. We would like to greatly thank Professor André Pouclet for his constructive comments on the first draft of this manuscript, Prof. Dr. Zakaria Hamimi (Associate Editor), and reviewers Dr. EZZ KHALAF, Dr. Abdel-Aal M. Abdel-Karim and the anonymous reviewer for their positive and constructive reviews of the manuscript.

Funders	Funder number
CMG-MANAGEM
Geochronology and Geochemistry Laboratory of Istanbul University-Cerrahpaşa

Keywords

Amensif
Pangea breakup
Rheic ocean
Tnirt
Variscan orogeny
Western high atlas
Zircon U–Pb dating

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.jafrearsci.2023.104975

Cite this

@article{12189bcc7db148e0b975f2c7fa898de6,

title = "Volcanic rocks from Amensif-Tnirt district in the Western High Atlas (Morocco): Geochemistry, magma features and new age dating",

abstract = "The High Atlas Mountains include mafic, intermediate and felsic volcanic-subvolcanic intrusive rocks, representing a result of magmatism related to “Cambrian rift” during the Lower Cambrian. The investigated magmatic rocks in the Amensif-Tnirt area are divided into three main groups as the mafic (SiO2 48.31 to 53.06 wt%), intermediate (SiO2 59.16 to 67.38 wt%), and felsic (SiO2 76.39 to 79.65 wt%) rocks. The mafic rocks correspond to microgabbros with high TiO2 contents (1.98–2.12 wt%) and FeOt/MgO ratios (1.65–1.90), La/Yb (9.09–11.60) and Nb/Zr (0.03–0.04) ratios, providing good evidence of extensive intracontinental tholeiite. The Nb/Yb and Zr/Y ratios ranging between 0.36 to 0.52 and 12.76 to 13.69, respectively suggest their derivation from an enriched mantle source during the opening of the Rheic ocean along the NW edge of Gondwana. The mafic rocks may be interpreted as the mixtures of melts derived from two contrasting mantle sources: (1) a garnet-bearing clinopyroxenitic ultramafic source and (2) an ultramafic source composed of spinel and peridotite. The intermediate and felsic rocks correspond to andesite-dacite and rhyolite with TiO2 contents and FeOt/MgO ratios ranging from 0.09 to 1.36 wt% and 1.32 to 4.69, respectively, suggesting their calc-alkaline affinities setting up during a compressive context. The youngest 206Pb/238U ages for intermediate rocks are 290.29 ± 4.68 and 291.27 ± 4.31 Ma, while the youngest felsic rocks yield a concordia age at 272.83 ± 0.73 Ma (MSWD = 0.25). Petrographic and geochemical data indicate that mafic magmatism in the Amensif-Tnirt region may be the equivalent of the first Cambrian volcanic episode in the High Atlas. Intermediate rocks are chronologically correlated to the Permian volcanic activities recorded in Central Morocco (Tiddas, Khenifra, Chougrane …) whereas felsic activity is correlated to the Permian Azegour granite from the High Atlas.",

keywords = "Amensif, Pangea breakup, Rheic ocean, Tnirt, Variscan orogeny, Western high atlas, Zircon U–Pb dating",

author = "Ilyasse Loudaoued and Ahmed Touil and Namık Aysal and Mohamed Aissa and Mehmet Keskin and İsak Yılmaz and Abdelmalek Ouadjou",

note = "Publisher Copyright: {\textcopyright} 2023 Elsevier Ltd",

year = "2023",

month = sep,

doi = "10.1016/j.jafrearsci.2023.104975",

language = "English",

volume = "205",

journal = "Journal of African Earth Sciences",

issn = "1464-343X",

publisher = "Elsevier Ltd",

}

TY - JOUR

T1 - Volcanic rocks from Amensif-Tnirt district in the Western High Atlas (Morocco)

T2 - Geochemistry, magma features and new age dating

AU - Loudaoued, Ilyasse

AU - Touil, Ahmed

AU - Aysal, Namık

AU - Aissa, Mohamed

AU - Keskin, Mehmet

AU - Yılmaz, İsak

AU - Ouadjou, Abdelmalek

PY - 2023/9

Y1 - 2023/9

N2 - The High Atlas Mountains include mafic, intermediate and felsic volcanic-subvolcanic intrusive rocks, representing a result of magmatism related to “Cambrian rift” during the Lower Cambrian. The investigated magmatic rocks in the Amensif-Tnirt area are divided into three main groups as the mafic (SiO2 48.31 to 53.06 wt%), intermediate (SiO2 59.16 to 67.38 wt%), and felsic (SiO2 76.39 to 79.65 wt%) rocks. The mafic rocks correspond to microgabbros with high TiO2 contents (1.98–2.12 wt%) and FeOt/MgO ratios (1.65–1.90), La/Yb (9.09–11.60) and Nb/Zr (0.03–0.04) ratios, providing good evidence of extensive intracontinental tholeiite. The Nb/Yb and Zr/Y ratios ranging between 0.36 to 0.52 and 12.76 to 13.69, respectively suggest their derivation from an enriched mantle source during the opening of the Rheic ocean along the NW edge of Gondwana. The mafic rocks may be interpreted as the mixtures of melts derived from two contrasting mantle sources: (1) a garnet-bearing clinopyroxenitic ultramafic source and (2) an ultramafic source composed of spinel and peridotite. The intermediate and felsic rocks correspond to andesite-dacite and rhyolite with TiO2 contents and FeOt/MgO ratios ranging from 0.09 to 1.36 wt% and 1.32 to 4.69, respectively, suggesting their calc-alkaline affinities setting up during a compressive context. The youngest 206Pb/238U ages for intermediate rocks are 290.29 ± 4.68 and 291.27 ± 4.31 Ma, while the youngest felsic rocks yield a concordia age at 272.83 ± 0.73 Ma (MSWD = 0.25). Petrographic and geochemical data indicate that mafic magmatism in the Amensif-Tnirt region may be the equivalent of the first Cambrian volcanic episode in the High Atlas. Intermediate rocks are chronologically correlated to the Permian volcanic activities recorded in Central Morocco (Tiddas, Khenifra, Chougrane …) whereas felsic activity is correlated to the Permian Azegour granite from the High Atlas.

AB - The High Atlas Mountains include mafic, intermediate and felsic volcanic-subvolcanic intrusive rocks, representing a result of magmatism related to “Cambrian rift” during the Lower Cambrian. The investigated magmatic rocks in the Amensif-Tnirt area are divided into three main groups as the mafic (SiO2 48.31 to 53.06 wt%), intermediate (SiO2 59.16 to 67.38 wt%), and felsic (SiO2 76.39 to 79.65 wt%) rocks. The mafic rocks correspond to microgabbros with high TiO2 contents (1.98–2.12 wt%) and FeOt/MgO ratios (1.65–1.90), La/Yb (9.09–11.60) and Nb/Zr (0.03–0.04) ratios, providing good evidence of extensive intracontinental tholeiite. The Nb/Yb and Zr/Y ratios ranging between 0.36 to 0.52 and 12.76 to 13.69, respectively suggest their derivation from an enriched mantle source during the opening of the Rheic ocean along the NW edge of Gondwana. The mafic rocks may be interpreted as the mixtures of melts derived from two contrasting mantle sources: (1) a garnet-bearing clinopyroxenitic ultramafic source and (2) an ultramafic source composed of spinel and peridotite. The intermediate and felsic rocks correspond to andesite-dacite and rhyolite with TiO2 contents and FeOt/MgO ratios ranging from 0.09 to 1.36 wt% and 1.32 to 4.69, respectively, suggesting their calc-alkaline affinities setting up during a compressive context. The youngest 206Pb/238U ages for intermediate rocks are 290.29 ± 4.68 and 291.27 ± 4.31 Ma, while the youngest felsic rocks yield a concordia age at 272.83 ± 0.73 Ma (MSWD = 0.25). Petrographic and geochemical data indicate that mafic magmatism in the Amensif-Tnirt region may be the equivalent of the first Cambrian volcanic episode in the High Atlas. Intermediate rocks are chronologically correlated to the Permian volcanic activities recorded in Central Morocco (Tiddas, Khenifra, Chougrane …) whereas felsic activity is correlated to the Permian Azegour granite from the High Atlas.

KW - Amensif

KW - Pangea breakup

KW - Rheic ocean

KW - Tnirt

KW - Variscan orogeny

KW - Western high atlas

KW - Zircon U–Pb dating

UR - http://www.scopus.com/inward/record.url?scp=85162128724&partnerID=8YFLogxK

U2 - 10.1016/j.jafrearsci.2023.104975

DO - 10.1016/j.jafrearsci.2023.104975

M3 - Article

AN - SCOPUS:85162128724

SN - 1464-343X

VL - 205

JO - Journal of African Earth Sciences

JF - Journal of African Earth Sciences

M1 - 104975

ER -

Volcanic rocks from Amensif-Tnirt district in the Western High Atlas (Morocco): Geochemistry, magma features and new age dating

Abstract

Bibliographical note

Funding

Keywords

UN SDGs

Access to Document

Other files and links

Fingerprint

Cite this