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Genesis of massive sulphide deposits in Oman

English title Genesis of massive sulphide deposits in Oman
Applicant Diamond Larryn W.
Number 188567
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geochemistry
Start/End 01.10.2019 - 31.03.2023
Approved amount 635'600.00
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Keywords (4)

hydrothermal; alteration; ophiolite; ore-deposit

Lay Summary (German)

Lead
Seit längerem ist bekannt, dass sich während eines Grossteils der Erdgeschichte wertvolle Kupfer-, Zink- und Gold-Lagerstätten am Meeresboden gebildet haben. Solche Prozesse laufen auch heute noch am Meeresboden in der Nähe aktiver Vulkane ab. Jene chemischen und physikalischen Prozesse der Bildung solcher Lagerstätten, welche direkt beobachtet werden können (z.B. der Austritt heisser, metallhaltiger Wässer am Meeresboden), sind heute gut verstanden. Prozesse die unterhalb des Meeresbodens ablaufen und daher nur sehr schwer zugänglich sind, wurden bisher hingegen nur ungenügend geklärt. Dieses Projekt erforscht deshalb tief unterhalb des Meeresbodens ablaufende Prozesse anhand von fossilen Gegenstücken zu aktiven Hydrothermalsystemen, welche wesentlich einfacher zugänglich sind.
Lay summary

Das Feldgebiet, ein fossiles Stück ozeanische Kruste, welches durch tektonische Prozesse auf den Kontinent aufgeschoben wurde, befindet sich im Sultanat Oman. Dort kartieren wir vulkanische Gesteine, die durch Reaktionen mit heissem Meerwasser mineralogisch stark verändert wurden. Gesteinsproben werden entnommen und später im Labor chemisch untersucht, um zu verstehen durch welche Prozesse die Metalle Kupfer, Zink und Gold freigesetzt werden. Die gewonnen Daten werden anschliessend als Grundlage für Computersimulationen benutzt, welche die Entstehung von Erzlagerstätten nachbilden.

Wir erwarten, dass die Ergebnisse dieser Studie den Kenntnisstand über die fundamentalen Prozesse der Meerwasser - Gesteins Interaktion in der tiefen ozeanischen Kruste erweitern werden. Unsere Erkenntnisse könnten zudem Explorationsgeologen bei der weltweiten Suche nach massiv-sulfidischen Lagerstätten unterstützen.
Direct link to Lay Summary Last update: 18.11.2019

Lay Summary (English)

Lead
Valuable accumulations of copper, zinc and gold ore are known to have formed on the ocean floor throughout much of Earth's history. These processes are still happening today on the ocean floors near actively erupting volcanoes. Many details of the chemical and physical processes involved in forming these so-called "massive sulfide deposits" are well understood, because they can be observed today on the seafloor (for example, the discharge of hot, metal-rich solutions in "black smokers"). However, the steps of the formation process that occur deep below the seafloor cannot be observed directly, and so understanding is less clear. This project aims to investigate the deep features below massive sulfide deposits by examining a segment of ancient oceanic crust that is tectonically tilted and exposed on the Earth's surface in the Oman mountains.
Lay summary

Our field work in Oman will involve mapping and sampling the basalts of the oceanic crust that have been chemically and mineralogically transformed by reaction with hot, downwelling ocean water. Various chemical and mineralogical analyses of the rocks in the laboratory will be performed to deduce when and where the copper, zinc and other ore metals were leached from the crust by the heated seawater, before being transported in dissolved form to discharge sites on the seafloor, where the metals precipitated as massive accumulations of sulfide minerals. Theses results will provide input for computer simulations that aim to reconstruct the ore-forming processes.
          The results of this project will hopefully fill the important gaps in our understanding of the fundamental process of seawater-rock interaction deep in the oceanic crust. Our findings will also provide guidelines to industry geologists who are exploring various sites around the globe for this type of ore deposit. 

Direct link to Lay Summary Last update: 18.11.2019

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
169653 Genesis of massive sulphide deposits in Oman 01.10.2016 Project funding (Div. I-III)

Abstract

This project addresses water-rock interaction and mass redistribution in sub-seafloor hydrothermal systems within basaltic oceanic crust. Such systems include huge volumes of altered rock and associated volcanogenic massive sulphide (VMS) deposits, which are important metal resources for industry and which are targets of exploration worldwide. Current models of hydrothermal circulation in oceanic crust are ambiguous with respect to how and where VMS metals are liberated from their source rocks, and whether the large metasomatic bodies of epidote + quartz ("epidosites") play an essential role in VMS genesis. Our aim is to clarify these issues by investigating the VMS-bearing upper oceanic crust exposed in the Semail Ophiolite, Oman. Our previous work in Oman has documented the distribution and timing of VMS deposits and deep footwall alteration, its tectonic and structural setting, the chemical compositions of deep hydrothermal fluids, the porosity and permeability of the altered rocks and the mechanisms of epidosite formation. The present project is a follow-on of SNF project 200020_169653. Emphasis will be on tracking the liberation of metals from the altered crust as a function of depth within the ophiolite and as a function of time. A doctoral candidate will characterize the widely variable contents of VMS metals in the Semail upper crust by field sampling and laboratory analysis, particularly along the fluid downflow path, and deduce the mineralogical and other controls on metal leaching en-route to the VMS deposits. A postdoctoral researcher will first perform numerical reactive-transport simulations of the downflow path (using the code PFlotran) to reproduce the new observations, followed by simulations of the full circulation cycle to the VMS deposits, integrating our knowledge of fluid compositions, alteration patterns and characteristics of the upflow path. The two researchers will collaborate closely in predicting the characteristics of the source area of the epidotizing fluid and in finding and characterizing it in the field. The results of this project will be presented at international conferences and published in international, peer-reviewed, open-access scientific journals. By advancing our understanding of the hydrothermal circulation in the oceanic crust, the new results will impact on studies of the exchange of heat and mass between seawater and the crust. Further, by linking metal source-rocks and alteration styles to the VMS system our results will be of practical significance to the VMS exploration industry. Finally, the project will provide scientific training for four young scientists and several MSc students.
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