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High-precision geochronology of ore-forming processes: partial funding for a Triton TIMS

English title High-precision geochronology of ore-forming processes: partial funding for a Triton TIMS
Applicant Heinrich Christoph
Number 128685
Funding scheme R'EQUIP
Research institution Institut für Geochemie und Petrologie ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geochronology
Start/End 01.12.2009 - 30.11.2010
Approved amount 400'000.00
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All Disciplines (2)

Discipline
Geochronology
Geochemistry

Keywords (4)

Geochronology; Geochemistry; mineral ore deposits; magmatic systems

Lay Summary (English)

Lead
Lay summary

A TRITON thermal ionisation mass spectrometer has been purchased and installed at the ETH Zurich, jointly funded by an ETH infrastructure grant and a contribution form the R’Equip program of the Swiss National Science Foundation. The instrument is dedicated to high-precision isotope ratio measurements of heavy elements. Such measurements allow geological age dating based on radioactive decay of long-lived isotopes, in particular U and Th evolving to Pb, and Re decaying to Os. The unique setup of this instrument, combining a very stable ion beam with several ultrasensitive detectors, permits unprecedented precision of geological age determinations. Such precision is essential for understanding geologically rapid processes that occurred in the Earth’s interior, i.e., prior to erosion and exposure of the rocks at the surface. To determine the duration of such processes, we need to resolve small differences in absolute age. For example, we can now date two successive events of magma solidification some 7 million years ago, which were separated in time by 90’000 ± 30’000 years. The two magma ages yield the presently most precise time bracket for the duration of a hydrothermal event that produced one of the world’s largest copper-gold ore deposit. Besides applications related to the origin of mineral resources, the instrument will also contribute to dating the formation of mountain belts including the Alps, or to calibrate the timescale of biological evolution including catastrophic events of species extinctions.

 

 

  The TRITON-PLUS is a commercial prototype instrument equipped with (a) an Ion Counting System for small Pb samples (1e-12 g) of very young minerals, (b) a combination of Faraday detectors (equipped with 1e12 ohms resistors) and ion counters to determine small but old (>500 Ma years) zircon samples and (c) a static multi-ion counting system (Compact Discrete Dynodes) for high-precision Re-Os mineral analyses. Further details about this research can be found at www.geopetro.ethz.ch/research/orefluids

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Associated projects

Number Title Start Funding scheme
128089 Metal transport and ore deposition: The geology, geochemistry and geodynamic setting of mineral resources in Serbia, Macedonia and Bulgaria 01.11.2009 SCOPES
124906 Quantitative Modeling of Ore-Forming Hydrothermal Systems 01.04.2009 Project funding (Div. I-III)

Abstract

We seek to purchase a new solid-source, thermal ionization, multicollector Mass Spectrometer (TIMS) for ETH Zurich’s geochronology lab at the Department of Earth Sciences. The in-strument is dedicated to high-precision isotope ratio measurements of heavy elements, and it is designed for geological age dating based on radioactive decay of long-lived isotopes, in particular U and Th evolving to Pb, and Re decaying to Os. For its core research, the Fluids and Mineral Deposits Group will use the new-generation TIMS to address geological questions at three different scales of time and space, which together control the formation of essential mineral resources. Understanding ore-forming processes requires precise geochronology, to test and complement results from thermal and hydrodynamic modeling and from field-based studies including fluid-inclusion microanalysis. At the plate-tectonic scale, mountain belts give rise to magmatic provinces, which in specific shorter periods generate belts of copper and other metal deposits. Within an ore-forming magmatic-hydrothermal system, fluid flow is short-lived and limited by heat dissipation in the upper crust, and may occur at timescales between 105 and 102 years. The new generation of high-precision TIMS will help resolving the current debate about the duration of ore forming processes.Extensive collaborations within ETH Zurich, in Switzerland and internationally also depend on this new instrument. At ETH Zurich, we concentrate on reconstructing the relationships between accretionary wedge sedimentation (‘flysch’) and nappe tectonics in the Alps. A major collaboration aims at deciphering the geodynamics of Europe’s main Andean-type calcalkaline belt, the Cretaceous Apuseni-Banat-Timok-Srednegorie belt of Romania, Serbia and Bulgaria. This long-term program is funded by SNF, SCOPES and international agencies, and critically depends on precise age dating. In the field of near-surface geochemistry, we are contributing to international efforts to calibrate the geological time scale, affecting biotic recovery events for example. Within the international EARTHTIME research initiative of MIT and US-SNF, we are one of the reference laboratories, and are providing and co-developing a new U-Pb spike.The proposed ‘TRITON-IC’ is equipped with (a) an Ion Counting System for small Pb samples (10-12 g) of very young minerals, (b) a combination of Faraday detectors (equipped with 1012 Ohm resistors) and ion counters to determine small but old (>500 Ma years) zircon samples and (c) a multi-ion counting system (MIC) for high-precision Re-Os mineral analyses. Our new instrument will complement a similar ‘TRITON-F’ in the Isotope Geochemistry Group of Prof. Bourdon group, which is specified and dedicated to long-term measurements of stable and radiogenic isotope ratios. Thanks to our existing prototype LA-ICP-MS instrument, we will be in a unique position to combine spatially resolved zircon ages of lower precision with highest-precision single crystal dates by TIMS. Mineral separation and dedicated clean labs already exist. This request is for partial R'Equip funding from SNF of CHF 500k; the final price will hopefully be a little lower than the quoted 1.33M, thanks to other expected ETH purchases from the same company this year. We are already initiating the WTO Procedure in the next weeks, in the hope of avoiding any delay after the decision by SNF's R'Equip committee.
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