This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The margins of continents have been subducted to profound depths (more than 100 km) deep within Earths interior many times throughout the last 500 million years; this process has likely had a major influence on the composition and evolution of the continents and underlying mantle. Understanding how such rocks form and are returned to Earths surface continues to be one of the outstanding questions about plate tectonics. This research uses an enormous region of high-pressure rocks in Norway to understand whether such regions form from one large piece or from many smaller pieces. The impact of this research should be considerable within the earth sciences community because the Norwegian terrane is an archetypal example of continental subduction.
The research approach is two-pronged: U-Pb zircon dating of eclogite to assess whether crustal blocks with different ages exist, and structural petrology to characterize shear zones between the blocks. Following careful petrology, eclogite-facies zircon genesis will be assessed by optical and back-scattered electron petrography, cathodoluminescence, trace-element abundances, and Raman spectroscopy. After reconnaissance secondary-ion mass spectrometry and laser-ablation multi-collector inductively coupled-plasma mass spectrometry dating, single zircon grains and grain fragments will be analyzed by high-precision U-Pb thermal-ionization mass spectrometry (TIMS) and chemical-abrasion thermal-ionization mass spectrometry. The strength of this approach lies in its use of state-of-the-art zircon geochronology and petrology, collaboration with researchers at cutting-edge facilities, and our familiarity with other ultrahigh-pressure orogens.
