Comparative geobarometry of pelitic hornfelses associated with the Newer Gabbros: a preliminary study

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Abstract
Physical conditions of contact metamorphism have been estimated for pelitic hornfelses collected from the inner aureoles of the Morven–Cabrach, Knock, Huntly and Belhelvie ‘Newer Gabbro’ intrusions using a few well-calibrated mineral equilibria. Inner aureole temperature estimates range from 700°C to 850°C. Calculated pressures all fall between 4 kbar and 5 kbar, implying the existence of between 15 km and 18.5 km of overburden at each locality at the time of intrusion of the Newer Gabbros. The results indicate that the four Newer Gabbros mentioned above were all emplaced at a similar crustal level, and that there has been no net regional tilting of the NE Dalradian since then. The results are not incompatible with some large-scale, late-stage (D 3 ) gentle folding as implied by the regional isograd pattern.