Geochronology and Isotope Geology MPC
MPC-01 General contributions to geochronology and isotope geology Åke Johansson et al.
Isotope geology has developed from the classical field of geochronology to a broad range of applications within the geosciences, including petrogenetic and ore genetic studies, studies of mantle composition and crustal growth, and geochemical investigations of exogenic processes with bearing on environmental problems. This symposium invites contributions from all fields of isotope geology, including classical geochronology, and in particular such ones highlightning new methods and analytical techniques or new and innovative applications.
MPC-02 Geochronology of metamorphic reactions and deformation in high-grade orogenic settings Jenny Andersson, Bernard Bingen, Ulf Söderlund, David Cornell Invited speakers: Daniela Rubatto, Johannes Glodny
The combination of field geology, metamorphic petrology and application of different geochronological-geochemical microbeam analytical techniques is a growing field of interest to pin down the metamorphic conditions and timing of tectonothermal events in high-grade orogenic terranes. This session will focus on the connection between metamorphic reactions and the behaviour of different isotopic systems and geochronometers in high-grade rocks. Contributions will highlight the application of isotope geochronology and geochemistry to construct, characterise, and directly date the P-T-t evolution and tectonic build up of high-grade metamorphic complexes. The session aims to bring together structural geologists, metamorphic petrologists, isotope geochemists and other geoscientists to combine their expertise in understanding geochronology and modelling geotectonic cycles and, thereby, the crustal evolution of our continents. Some case studies on this topic will be presented during the pre-conference field trip entitled “The Sveconorwegian orogen of southern Scandinavia: P-T-t-evolution of polymetamorphic high-grade domains”.
MPC-03 Precambrian isotope chemostratigraphy Alcides Nobrega Sial, Claudio Gaucher, Valderez Pinto Ferreira Invited speaker: Alan Jay Kaufman
In a Precambrian world lacking fossils with definable ranges, chemostratigraphy holds the promise of providing a time line for the profound biogeochemical and climatic events of the Proterozoic Eon. Providing a way to tell Precambrian time, the number of studies relying on isotope stratigraphy in both the Proterozoic and Archean eons has grown exponentially over the past twenty years. While the golden spike at the Precambrian-Cambrian boundary was decided on biostratigraphic grounds, the spike defining the base of the ratified Ediacaran Period was largely based on chemostratigraphy of cap-carbonates atop glacial diamictites. These deposits which accumulated during post-glacial transgression record the most profound carbon, sulfur and strontium isotope variations in Earth history and are the centerpiece of the controversial ‘snowball Earth Hypothesis’. This symposium will highlight the use of chemical and isotope stratigraphy in Precambrian successions and their correlations worldwide as a tool to understanding environmental and global climatic changes. We hope to gather specialists from different continents and that the symposium can bring some additional information on some well-known C- isotope anomalies (e.g Lomagundi) and on some extreme isotope excursions of the Neoproterozic corresponding to abrupt climatic changes. Although Precambrian chemostratigraphy is the main goal of this symposium, scientific contributions dealing with the Precambrian-Cambrian transition and Cambrian SPICE and SNICE anomalies will be also allowed.
MPC-04 Constraining timing and rates of surface processes by low temperature thermochronology Bart W.H. Hendriks, Tim F. Redfield
Low temperature thermochronology is routinely used to quantify denudation rates and to constrain the timing of processes in the uppermost few kilometers of the earth's crust. Rapid progress in the development of thermochronological methods and also the application of these methods to a rapidly extending range of mineral phases has enabled the study of the coupling of tectonic, geodynamic and surface processes. However, the apparent incompatibility of certain results from different thermochronometers, the irreproducibility of other results, and the creation of modeling artefacts stemming from our incomplete understanding of the physics underlying the methods themselves frequently spawn difficulties - and even controversies - in the interpretation of low temperature thermal histories. In this session we invite specialists in the various low temperature thermochronological techniques to discuss the fundamental reasons for these problems as well as the changes in analytical techniques and modeling approaches that might help to solve them. We also invite applied studies that illustrate low temperature thermochronometric problems or - especially encouraged - the solution of such problems. Presentations of applied studies that illustrate the pros and cons of low temperature thermonology are particularly encouraged.
MPC-05 Evolution of the crust and oceans through Re-Os geochemistry: A decade of discovery Holly Stein, Judith Hannah
Pioneering analytical work on Re-Os geochronology made extensive use of samples from Nordic localities. In the 1960s, early workers realized that molybdenite provided a single mineral geologic clock, and the Baltic shield was rich with molybdenite. In the last decade, advances in analytical methods led to high-precision Re-Os isotopic data, and applications of Re-Os geochemistry exploded to include a range of minerals and geologic environments in crustal regimes. This symposium will focus on Re-Os applications that document the chronology of crustal processes and the evolution of Os isotopic compositions in the earth’s crust and oceans through geologic time. Topics include but are not limited to: (i) Re-Os geochronology of igneous, metamorphic, and sedimentary processes; (ii) Re-Os isotopic constraints on tectonic processes; (iii) evolution of the Os geochemical cycle in surface environments through earth history; (iv) applications of Re-Os isotope geochemistry to hydrocarbon generation and migration. The emphasis will be on new methods and new approaches to long-standing problems.
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