POWRE: Isotopic and Geochemical Comparison of Metavolcanic Sequences in the South-Central Scandinavian Caledonides

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

0075034 McClellan The Scandinavian Caledonides are a classic area for study of thrust and nappe tectonics, and particularly with the advent of plate tectonic theory, for the study of ancient ocean crust that was thrust onto the continent during Paleozoic orogenic events. In the central Norwegian Caledonides, a majority of these exotic and suspect terranes occur in a thrust complex termed the Trondheim Nappe Complex (TNC). Ophiolitic sequences in the western TNC have received much attention and study, in part because they are commonly intact, of low metamorphic grade, and may be associated with fossiliferous sedimentary rocks that constrain their age. In the eastern TNC, however, such sequences are generally more highly deformed and metamorphosed and fossil preservation is uncommon, therefore obscuring the tectonic setting(s) represented by the igneous successions and relationships between rock units. This proposal addresses the age and tectonic setting of three metavolcanic complexes in the eastern TNC, and offers a test of two recently proposed hypotheses that concern revisions to the traditional nappe terminology and stratigraphy: (1) that the volcanic rocks in question actually do not represent oceanic crust, but extruded into a sedimentary basin on continental crust after a period of ophiolite obduction and erosion; or (2) that the volcanic complexes are related components of an oceanic arc or back-arc complex that was thrust onto continental crust, and underlie a major unconformity. Results of such a study could be applied t more far-reaching problems concerning the nature of a vast ophiolitic belt throughout the Caledonides, and the presence of a "belt-length, terrane-linking unconformity" developed above it. The metavolcanic sequences in question are all well represented in the study area, and the project would build upon previous mapping by the PI, completed for dissertation work. A one-month field session is planned, for detailed mapping along critical contacts and to collect samples for geochemical and isotopic analyses. The PI has recently relocated to the University of Kansas (KU), because of the prospect of professional opportunities for both her and her spouse. At KU, the instrumentation (ICP-MS, ICP-AES, mass spectrometer) and support structure is available for the proposed work, and colleagues with expertise in this area are willing to assist in the "learning process." The proposed activity is in accord with intent of the POWRE Program, as the study would furnish the PI with an opportunity to become proficient with modern instruments and current analytical methods, to collaborate with colleagues abroad and at KU, and to contribute to the KU Tectonics initiative. Finally, this study would support a student as a field and lab assistant, and facilitate building a research program that would provide international prospects for future students.