Estimating original thickness and extent of the Semail Ophiolite in the eastern Oman Mountains by paleothermal indicators

L. Aldega, E. Carminati, A. Scharf, F. Mattern, M. Al-Wardi

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7 Citations (Scopus)

Abstract

The Oman Mountains preserve Permo-Mesozoic sedimentary rocks of the Arabian passive margin that were overridden during Late Cretaceous time by deep-water sediments of the Hawasina units and by the Semail Ophiolite, a portion of the Neo-Tethyan oceanic crust and upper mantle. Passive margin sequences are exposed in the Jabal Akhdar Culmination (JAC) and in the Jabal Salakh Range at the Oman Mountains thrust front. Samples of these sequences were investigated by X-ray diffraction of the clay size fraction to evaluate the thermal evolution of the subophiolite rocks and estimate the thickness and extent of the obducted ophiolites. The sedimentary succession from the northern flank of the JAC shows a clay mineral assemblage characterized by long-range ordered mixed layer I-S with an illite content between 85% and 92% and the occurrence of pyrophyllite and/or paragonite, suggesting maximum paleotemperatures between 150° and 200 °C in deep diagenetic conditions. On the southern flank of the JAC, temperature dependent clay minerals indicate maximum paleotemperatures, ranging between 120° and 150 °C, indicating a reduced ophiolite thickness towards the south. Ooid strain analyses of the subophiolite rocks from the northern flank of JAC show a component of flattening and stretching in the z-x plane as a result of plastic deformation and pressure solution. On the southern flank, such ductile deformation is absent, suggesting a brittle rheology for the subophiolite carbonates and a reduced overburden. 1D thermal modeling reveals that the sub-ophiolite units of the JAC were overthrust by 4.5 km-thick Semail Ophiolite and Hawasina units during the Coniacian, and exhumed since the Campanian. The subophiolite rocks of the Jabal Salakh Range were buried under 1.35 km of synobduction clastics and overthrust by 2 km-thick Hawasina units, suggesting a decrease of the thickness of allochthonous units from NE to SW, consistent with strain analysis and their direction of emplacement.

Original languageEnglish
Pages (from-to)18-33
Number of pages16
JournalMarine and Petroleum Geology
Volume84
DOIs
Publication statusPublished - Jun 1 2017

Fingerprint

Oman
ophiolite
mountains
clays
estimating
rocks
mountain
margins
paleotemperature
passive margin
minerals
pyrophyllite
clay mineral
illite
sedimentary rocks
deep water
flattening
rock
ooid
rheology

Keywords

  • Jabal Akhdar Culmination
  • Jabal Salakh Range
  • Mixed layer illite-smectite
  • Oman
  • Ooid strain analysis
  • Ophiolite thickness and extent
  • Thermal modeling

ASJC Scopus subject areas

  • Oceanography
  • Geophysics
  • Geology
  • Economic Geology
  • Stratigraphy

Cite this

@article{c6e14e14ded347cd829b077b919e382c,
title = "Estimating original thickness and extent of the Semail Ophiolite in the eastern Oman Mountains by paleothermal indicators",
abstract = "The Oman Mountains preserve Permo-Mesozoic sedimentary rocks of the Arabian passive margin that were overridden during Late Cretaceous time by deep-water sediments of the Hawasina units and by the Semail Ophiolite, a portion of the Neo-Tethyan oceanic crust and upper mantle. Passive margin sequences are exposed in the Jabal Akhdar Culmination (JAC) and in the Jabal Salakh Range at the Oman Mountains thrust front. Samples of these sequences were investigated by X-ray diffraction of the clay size fraction to evaluate the thermal evolution of the subophiolite rocks and estimate the thickness and extent of the obducted ophiolites. The sedimentary succession from the northern flank of the JAC shows a clay mineral assemblage characterized by long-range ordered mixed layer I-S with an illite content between 85{\%} and 92{\%} and the occurrence of pyrophyllite and/or paragonite, suggesting maximum paleotemperatures between 150° and 200 °C in deep diagenetic conditions. On the southern flank of the JAC, temperature dependent clay minerals indicate maximum paleotemperatures, ranging between 120° and 150 °C, indicating a reduced ophiolite thickness towards the south. Ooid strain analyses of the subophiolite rocks from the northern flank of JAC show a component of flattening and stretching in the z-x plane as a result of plastic deformation and pressure solution. On the southern flank, such ductile deformation is absent, suggesting a brittle rheology for the subophiolite carbonates and a reduced overburden. 1D thermal modeling reveals that the sub-ophiolite units of the JAC were overthrust by 4.5 km-thick Semail Ophiolite and Hawasina units during the Coniacian, and exhumed since the Campanian. The subophiolite rocks of the Jabal Salakh Range were buried under 1.35 km of synobduction clastics and overthrust by 2 km-thick Hawasina units, suggesting a decrease of the thickness of allochthonous units from NE to SW, consistent with strain analysis and their direction of emplacement.",
keywords = "Jabal Akhdar Culmination, Jabal Salakh Range, Mixed layer illite-smectite, Oman, Ooid strain analysis, Ophiolite thickness and extent, Thermal modeling",
author = "L. Aldega and E. Carminati and A. Scharf and F. Mattern and M. Al-Wardi",
year = "2017",
month = "6",
day = "1",
doi = "10.1016/j.marpetgeo.2017.03.024",
language = "English",
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pages = "18--33",
journal = "Marine and Petroleum Geology",
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publisher = "Elsevier BV",

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TY - JOUR

T1 - Estimating original thickness and extent of the Semail Ophiolite in the eastern Oman Mountains by paleothermal indicators

AU - Aldega, L.

AU - Carminati, E.

AU - Scharf, A.

AU - Mattern, F.

AU - Al-Wardi, M.

PY - 2017/6/1

Y1 - 2017/6/1

N2 - The Oman Mountains preserve Permo-Mesozoic sedimentary rocks of the Arabian passive margin that were overridden during Late Cretaceous time by deep-water sediments of the Hawasina units and by the Semail Ophiolite, a portion of the Neo-Tethyan oceanic crust and upper mantle. Passive margin sequences are exposed in the Jabal Akhdar Culmination (JAC) and in the Jabal Salakh Range at the Oman Mountains thrust front. Samples of these sequences were investigated by X-ray diffraction of the clay size fraction to evaluate the thermal evolution of the subophiolite rocks and estimate the thickness and extent of the obducted ophiolites. The sedimentary succession from the northern flank of the JAC shows a clay mineral assemblage characterized by long-range ordered mixed layer I-S with an illite content between 85% and 92% and the occurrence of pyrophyllite and/or paragonite, suggesting maximum paleotemperatures between 150° and 200 °C in deep diagenetic conditions. On the southern flank of the JAC, temperature dependent clay minerals indicate maximum paleotemperatures, ranging between 120° and 150 °C, indicating a reduced ophiolite thickness towards the south. Ooid strain analyses of the subophiolite rocks from the northern flank of JAC show a component of flattening and stretching in the z-x plane as a result of plastic deformation and pressure solution. On the southern flank, such ductile deformation is absent, suggesting a brittle rheology for the subophiolite carbonates and a reduced overburden. 1D thermal modeling reveals that the sub-ophiolite units of the JAC were overthrust by 4.5 km-thick Semail Ophiolite and Hawasina units during the Coniacian, and exhumed since the Campanian. The subophiolite rocks of the Jabal Salakh Range were buried under 1.35 km of synobduction clastics and overthrust by 2 km-thick Hawasina units, suggesting a decrease of the thickness of allochthonous units from NE to SW, consistent with strain analysis and their direction of emplacement.

AB - The Oman Mountains preserve Permo-Mesozoic sedimentary rocks of the Arabian passive margin that were overridden during Late Cretaceous time by deep-water sediments of the Hawasina units and by the Semail Ophiolite, a portion of the Neo-Tethyan oceanic crust and upper mantle. Passive margin sequences are exposed in the Jabal Akhdar Culmination (JAC) and in the Jabal Salakh Range at the Oman Mountains thrust front. Samples of these sequences were investigated by X-ray diffraction of the clay size fraction to evaluate the thermal evolution of the subophiolite rocks and estimate the thickness and extent of the obducted ophiolites. The sedimentary succession from the northern flank of the JAC shows a clay mineral assemblage characterized by long-range ordered mixed layer I-S with an illite content between 85% and 92% and the occurrence of pyrophyllite and/or paragonite, suggesting maximum paleotemperatures between 150° and 200 °C in deep diagenetic conditions. On the southern flank of the JAC, temperature dependent clay minerals indicate maximum paleotemperatures, ranging between 120° and 150 °C, indicating a reduced ophiolite thickness towards the south. Ooid strain analyses of the subophiolite rocks from the northern flank of JAC show a component of flattening and stretching in the z-x plane as a result of plastic deformation and pressure solution. On the southern flank, such ductile deformation is absent, suggesting a brittle rheology for the subophiolite carbonates and a reduced overburden. 1D thermal modeling reveals that the sub-ophiolite units of the JAC were overthrust by 4.5 km-thick Semail Ophiolite and Hawasina units during the Coniacian, and exhumed since the Campanian. The subophiolite rocks of the Jabal Salakh Range were buried under 1.35 km of synobduction clastics and overthrust by 2 km-thick Hawasina units, suggesting a decrease of the thickness of allochthonous units from NE to SW, consistent with strain analysis and their direction of emplacement.

KW - Jabal Akhdar Culmination

KW - Jabal Salakh Range

KW - Mixed layer illite-smectite

KW - Oman

KW - Ooid strain analysis

KW - Ophiolite thickness and extent

KW - Thermal modeling

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U2 - 10.1016/j.marpetgeo.2017.03.024

DO - 10.1016/j.marpetgeo.2017.03.024

M3 - Article

VL - 84

SP - 18

EP - 33

JO - Marine and Petroleum Geology

JF - Marine and Petroleum Geology

SN - 0264-8172

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