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Petrogenesis of gold-bearing listvenites from the carbonatized mantle section of the Neoproterozoic Ess ophiolite, Western Arabian Shield, Saudi Arabia

Gahlan, Hisham A. and Azer, Mokhles K. and Asimow, Paul D. and Al-Kahtany, Khaled M. (2020) Petrogenesis of gold-bearing listvenites from the carbonatized mantle section of the Neoproterozoic Ess ophiolite, Western Arabian Shield, Saudi Arabia. Lithos, 372-373 . Art. No. 105679. ISSN 0024-4937. https://resolver.caltech.edu/CaltechAUTHORS:20200713-122453085

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Abstract

The variably serpentinized mantle peridotites of the Late Neoproterozoic Ess ophiolite (Western Saudi Arabia) are highly altered along shear zones and thrust planes to form erosion-resistant listvenites. The listvenites are distinguished petrographically and geochemically into three types: carbonate, silica-carbonate and silica (birbirite) listvenites. Geochemical analyses are consistent with expectations from petrography: carbonate listvenite is low in SiO₂ content but high in MgO, Fe₂O₃, and CaO relative to silica-carbonate and birbirite, which is remarkably high in SiO₂ at the expense of all other components. The total REE contents are low in silica-carbonate and carbonate listvenites but highly enriched in birbirite, with a large positive Eu anomaly. The host serpentinites have all the characteristics typically associated with highly depleted mantle harzburgite protoliths in supra-subduction fore-arc settings: bulk compositions are low in Al₂O₃ and CaO with high Mg# [molar Mg/(Mg + Fe)], relict Cr-spinel has high Cr# [molar Cr/(Cr + Al)] and low TiO₂, and relict olivine has high Mg# and NiO content. The Cr-spinel relics are also found in the listvenites; those in serpentinite and carbonate listvenites have significantly higher Mg# than those in silica-carbonate and birbirite, suggesting re-equilibration of Cr-spinel in the later phases of listvenitization. The varieties of listvenite capture successive stages of fluid-mediated replacement reactions. The carbonate listvenite appears to have developed syn-contemporaneously with serpentinization, whereas silica-carbonate listvenite and birbirite formed later. The listvenite formation resulted in leaching and removal of some components accompanied by deposition of others in the solid products, notably CO₃, SiO₂, REE (especially Eu), Au, Zn, As, Sb and K. Our data show that listvenitization concentrated gold at sub-economic to economic grades; measured gold concentrations in the host serpentinite are 0.5–1.7 ng/g, versus 4–2569 ng/g in carbonate listvenite, 43–3117 ng/g in silica-carbonate listvenite and 5–281 ng/g in birbirite. The listvenite deposits in the Jabal Ess area merit further exploration for gold.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.lithos.2020.105679DOIArticle
ORCID:
AuthorORCID
Azer, Mokhles K.0000-0002-3711-8630
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2020 Published by Elsevier B.V. Received 12 June 2020, Revised 2 July 2020, Accepted 3 July 2020, Available online 12 July 2020. Special thanks are paid to King Saud University, Deanship of Scientific Research, Research Group No. RG-1436-036, for their support. PDA acknowledges support from the US NSF, award EAR-1947616. The authors are also indebted to the editor (Prof. Michael Roden) and two anonymous reviewers for their efforts and numerous helpful comments. Declaration of Competing Interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
King Saud UniversityRG-1436-036
NSFEAR-1947616
Subject Keywords:Arabian Shield; Ophiolite; Listvenite; Fuchsite; Sulphides; Gold
Record Number:CaltechAUTHORS:20200713-122453085
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200713-122453085
Official Citation:Hisham A. Gahlan, Mokhles K. Azer, Paul D. Asimow, Khaled M. Al-Kahtany, Petrogenesis of gold-bearing listvenites from the carbonatized mantle section of the Neoproterozoic Ess ophiolite, Western Arabian Shield, Saudi Arabia, Lithos, Volumes 372–373, 2020, 105679, ISSN 0024-4937, https://doi.org/10.1016/j.lithos.2020.105679. (http://www.sciencedirect.com/science/article/pii/S0024493720303169)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104355
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Jul 2020 20:13
Last Modified:24 Jul 2020 22:31

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