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Clumped isotopes of methane and dolomite to assess the thermal history of orogens and the origin of thermogenic methane (CLUMPME)

English title Clumped isotopes of methane and dolomite to assess the thermal history of orogens and the origin of thermogenic methane (CLUMPME)
Applicant Bernasconi Stefano
Number 200977
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochemistry
Start/End 01.05.2021 - 30.04.2025
Approved amount 1'046'387.00
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All Disciplines (2)

Discipline
Geochemistry
Geology

Keywords (5)

Clumped isotopes; Low grade metamorphism; Methane; Quantum cascade laser spectroscopy; Tectonics

Lay Summary (German)

Lead
Die Geochemie der „clumped isotopes“ befasst sich mit der Bestimmung der Häufigkeit der Moleküle, die mehr als einer der seltene Isotopen ihrer Elemente bestehen. Die Messung der Häufigkeit doppelsubstituierten Moleküle von Methan (13CDH3 und 12CD2H2) und von Karbonat in Dolomit (13C18O16O2) eröffnen neuartige Möglichkeiten ihr Ursprung und Bildungstemperatur zu bestimmen. Wir werden einer neuartige Messmethode für "Clumped" isotope in Methan entwickeln und danach Methan aus Gesteinen extrahieren und damit die maximale Temperatur, dass diese Gesteine in ihre Entstehungsgeschichte erfahren haben Bestimmen.
Lay summary

Im vorliegenden Projekt wird zuerst eine Quantenkaskadenlaser basierte Messmethode für die selektive und präzise Bestimmung der häufigsten doppeltsubstituierten CH4 Isotopenverbindungen 13CDH3 und 12CD2Hentwickelt. Die Analysenmethode umfasst einen Laserspektrometer und eine Aufkonzentriereinheit. Der Vorteil gegenüber existierenden hochauflösenden massenspektrometrischen Messmethoden liegt in der sehr viel einfacheren Anwendbarkeit und der kürzeren Analysendauer. 

Das Potential der neuartigen Messmethode wird anhand einiger Modellanwendungen in der Geologische Forschung getestet. Wir werden Methan aus Sedimentgesteine die unterschiedlich hohe Temperaturen während der Gebirgsbildung ausgesetzt waren, entlang Profile in den Alpen, Appennin und Pyreneen, extrahieren. Durch diese Messungen gekoppelt mit der Messung von Clumped isotope in dolomitische Gesteine, wird es möglich die Thermische Evolution der Gebirgsketten besser zu Charakterisieren, und damit ihre Entstehung besser zu verstehen.  Die Methode wird auch an einen Gas Feld in  Italien Getestet mit dem Ziel die Methan Emissionen die durch die Erdöl Produktion verstärkt wurden werden besser zu quantifizieren. 

Direct link to Lay Summary Last update: 30.03.2021

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Associated projects

Number Title Start Funding scheme
183294 QCL4CLUMPS: Simultaneous QC laser spectroscopic analysis of clumped 13C-D and D-D (2 x 2) isotopes in CH4 01.03.2020 R'EQUIP
169849 Improving the reconstruction of deep-time paleoclimate and diagenetic history of sedimentary basins with carbonate clumped isotopes. 01.01.2017 Project funding

Abstract

This project is a collaboration between the Climate Geology Group (ETH) and the Laboratory for Air Pollution / Environmental Technology (Empa) to advance the use of clumped (doubly substituted) isotopes in methane (CH4) by developing a new quantum cascade laser (QCL)-based spectrometer and its application to geological questions. The clumped isotopic composition of methane is defined as the excess abundance of the rare 13CH3D and 12CH2D2 isotopologues compared to a calculated random distribution. Because heavy isotopes 13C and D have a temperature dependent tendency to bond to other, the clumped isotope composition of a molecule is a proxy for the temperature at which it was formed, provided that this formation was controlled by equilibrium processes. This method has recently been shown to be a powerful tool to understand the origin and fate of thermogenic and biogenic CH4 in the environment. However, this application is still in its infancy, mainly due to the difficult and time-consuming analysis, in particular of 12CH2D2.The first goal of CLUMPME is to develop an analytical method based on a QCL spectrometer and an automated preconcentration device (TREX) for simultaneous, selective and highly precise measurements of ?13CH3D and ?12CH2D2. The spectrometer features a low-volume 413 m multi-pass optical cell, with a dispersive mirror coating specifically designed and manufactured for excellent reflectivity in several spectral windows. These windows (mainly around 4.5 and 9.1 ?m) were identified based on a pre-study using high-resolution FT-IR spectroscopy. In a first step, the yet unexploited spectral range around 4.5 will be tested for optimal sensitivity and selectivity. Based on previous measurements, we target an accuracy of 0.1 ‰ (?13CH3D) and 0.5 ‰ (?12CH2D2), sufficient to resolve 10 °C differences in formation temperature of thermogenic CH4. This is a 2-3 fold improvement in precision, with much shorter analysis time, smaller sample size, and most importantly higher selectivity, compared to emerging high resolution mass spectrometry (HR-IRMS) and mid-IR laser spectroscopy. As illustrative and relevant applications, we will extract thermogenic CH4 entrapped in the occluded porosity of the source rocks along a transect in three regions in the Alps, Apennines and Pyrenees, where the rocks have experienced a progressive heating ranging from ~50 to 300°C, to test, whether CH4 has been formed in thermodynamic equilibrium. We will combine CH4 clumped isotopes with dolomite clumped isotope thermometry and U/Pb dating of carbonates to develop a robust thermometer for the determination of the thermal stress experienced by rocks, from diagenesis to low grade metamorphism. This will provide important constraints for the assessment of the thermal evolution of sedimentary basins during their formation and involvement in orogenic processes, and it is fundamental to reconstruct the history of mountain belts. We anticipate that clumped CH4 analysis will provide a unique, broadly applicable thermometer covering a temperature range from about 100 to 300 °C. This will allow the study of many questions such as formation mechanisms of thermogenic CH4 and burial histories of sedimentary basins, but also open new research areas, such as the CH4 biogeochemical cycle, climate research and atmospheric sciences.
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