Axelsson Emelie, Pape Jonas, Berndt Jasper, Corfu Fernando, Mezger Klaus, Raith Michael M. (2018), Rutile R632 - A New Natural Reference Material for U-Pb and Zr Determination, in Geostandards and Geoanalytical Research
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Naumenko-Dèzes Maria O., Nägler Thomas F., Mezger Klaus, Villa Igor M. (2018), Constraining the 40K decay constant with 87Rb-87Sr – 40K-40Ca chronometer intercomparison, in Geochimica et Cosmochimica Acta
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O. Extension of proposalThis proposal asks for a one year extension of the project: An evaluation of the K-Ar-Ca and U-Pb-rutile chronometers and the global Mo cycle (SNF Nr. 200021-131916). The part of the proposal concerning the global Mo-cycle was not funded and is not discussed any further. The text segments referring to this part of the proposal are no longer part of this proposal and have been removed. The proposal asks for the continued funding of 2 PhD projects that were initially funded for three years to enable the students to complete the projects.The proposal text includes the original background information and research plan with the new additions in italics (section A3 and B3), all of which refer to the progress of the project and its planned extension until completion. 1. SummaryThis project will use natural isotope variations due radioactive decay and fractionation processes in the litho- and hydrosphere to help constrain the dynamics of geologic processes. The determination of the branching ratio of the decay of 40K to 40Ar and 40Ca will improve the quality of one of the most widely used geochronometers in the Earth Sciences. This branching ratio will be determined on natural rock samples containing K-rich minerals whose geologic history is extremely well known. The rock samples chosen contain minerals that are known to yield concordant U-Pb and Rb-Sr ages. The mineral rutile is widespread in medium to high grade rocks and is potentially a useful chronometer that provides high precision ages using the U-Pb system and metamorphic temperatures using the Zr-in-rutile thermometer. It is planned to study the behavior of the U-Pb system and the equilibration of the Zr-contents in natural rutiles from high grade rocks of the petrologically well studied Eastern Ghats belt, India. The results will provide key constraints on the geological meaning of U-Pb rutile ages and the robustness of the Zr-in-rutile thermometer. The distribution of ages in a rutile obtained by in situ spot analyses will be modeled to derive the thermal history of the minerals grains and their host rocks. The result of this project will be the development of a geochronometer for medium to high grade metamorphic rocks that can be used to reconstruct the dynamic evolution of the lithosphere.