Discussion of 'Metamorphic P - T and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland'

K. Aoki, B. F. Windley, S. Maruyama & S. Omori reply: First, we thank Viete, Oliver & Wilde for their interesting and thought-provoking comments on the timing of the high-pressure granulite facies (HGR) metamorphism recorded in metamorphic rocks at Cairn Leuchan, Scotland, published by Aoki et al. (2013). Based on new metamorphic data of garnetites and garnet-amphibolites at Cairn Leuchan and new zircon U-Pb ages of amphibolitized eclogite at Tomatin, we suggested in our publication that the HGR metamorphism was retrograde after eclogite facies before the c. 470 Ma 'Barrovian metamorphism'. Viete, Oliver & Wilde however speculate that the HGR metamorphism at Cairn Leuchan may have occurred at c. 1000 Ma, as a result of their new U-Pb zircon age of the Cowhythe Gneiss at Portsoy and from previous studies of the geological structure and geochronology. We are grateful for this opportunity to describe, albeit in a preliminary manner, our new understanding and tectonic model of the Caledonian orogen in Scotland and western Ireland of which the Barrovian metamorphism is a key component. A reply to a comment is not the correct place to propose an entirely new paradigm for such a classic orogen, but we will present our model more fully in a future publication.. Copyright © Cambridge University Press 2014

Metamorphic records of multiple seismic cycles during subduction

Large earthquakes occur in rocks undergoing high-pressure/low-temperature metamorphism during subduction. Rhythmic major-element zoning in garnet is a common product of such metamorphism, and one that must record a fundamental subduction process. We argue that rhythmic major-element zoning in subduction zone garnets from the Franciscan Complex, California, developed in response to growth-dissolution cycles driven by pressure pulses. Using electron probe microanalysis and novel techniques in Raman and synchrotron Fourier transform infrared microspectroscopy, we demonstrate that at least four such pressure pulses, of magnitude 100–350 MPa, occurred over less than 300,000 years. These pressure magnitude and time scale constraints are most consistent with the garnet zoning having resulted from periodic overpressure development-dissipation cycles, related to pore-fluid pressure fluctuations linked to earthquake cycles. This study demonstrates that some metamorphic reactions can track individual earthquake cycles and thereby opens new avenues to the study of seismicity

Thermo-mechanical properties of Bundelkhand granite near Jhansi, India

Creation of optimal fracture networks through enhanced geothermal system within the reservoir for the extraction of the geothermal energy will require proper understanding of the thermo-mechanical behavior of the reservoir rocks i.e. granites. Current research work has focused the thermo-mechanical properties of granite under various temperature and strain rate conditions. Bundelkhand granite of India has been investigated for the proposed research work. Four different strain rates viz. 0.05, 0.5, 5.0 and 50.0 mm/min at three different temperatures viz. room temperature (25 °C), 200 and 400 °C were considered for experimental analysis. It was observed that at room temperature, with increasing strain rate the uniaxial compressive strength of the rock increases and the same trend is also observed at higher temperature conditions. However, at low strain rate (0.05 mm/min) the compressive strength decreases with increase in temperature and the trend is irregular at higher strain rates. It was also observed that Young’s modulus of Bundelkhand granite increases with increase in strain rate however it reduces with increase in temperature. Thermal conductivity value of Bundelkhand granite ranges from 3.1 to 3.6 W/m K

TESTING HYPOTHESES OF NEURAL EVOLUTION IN GYMNOTIFORM ELECTRIC FISHES USING PHYLOGENETIC CHARACTER DATA

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137285/1/evo02255.pd