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Dear Tim, can you please cite a reference for this? Since I am working in the Dabie (UHP Marbles and associated rocks) I am very interested in these statements, which I have never hered before. Thanks in advance Robert >Sol & Eric >Dry extension did not occur in the Dabie Region of the Qinling. >Highpressure minerals are trapped as inclusion trails in garnet >porphyroblasts that formed during an early period of orogenesis and the >inclusion trails define about 3 sets of steep & shallow foliations. There >were two subsequent periods of garnet growth, each over a succession of >foliations with differently oriented intersection axes (FIAs), but a >consistent succession in time. Since for both the younger sets of axes >there is a succession of steep and shallow foliations preserved, orogenesis >was similar to any other compressional orogenic belt I have ever worked in. >Presumably the close by rocks with high pressure mineralogy still in the >matrix went through a similar history but were not retrogressed by it. >Perhaps all younger deformation simply partitioned around them? >Porphyroblasts reveal this happens routinely on a large outcrop and greater >scale. Why not for a whole package of rock, especially if it was surrounded >by weaker schists. >Cheers >Tim > >>Sol and all, >> Dry extension. >>Eric >> >> >> >>Talking of metamorphic rocks, does anybody know how ultrahigh metamorphic >>>rocks, as seen in the Dabie Shan China, are transported from mantle depths >>>back to the surface without undergoing extensive retrograde metamorphism or >>>even melting as a result of the rapid decrease in pressure? The ultrahigh >>>metamorphism must be related to continental collision but what is the >>>mechanism of relaxation that allows these rocks to move so rapidly towards >>>the surface? >>>Sol >>> >>> >>>*********************************** >>> >>>Solomon Buckman >>> >>>Department of Earth Science http://147.8.150.90/Sols%20Homepage.htm >>> >>>University of Hong Kong http://www.hku.hk/earthsci/rock.html >>> >>>Ph. 852-28571759, Fax 852-25176912 > > >Prof Tim Bell >School of Earth Sciences >James Cook University >Townsville >QLD 4811 >Australia >ph: +61 7 47814766 >fax: +61 7 47251501 >email: [log in to unmask] ------------------------------------------------------------------ Robert Schmid Institut für Geowissenschaften der Universität Potsdam Postfach 601553 D-14415 Potsdam GERMANY Tel. +49/331/977-2910 Fax +49/331/977-2087 [log in to unmask] http://www.uni-potsdam.de/u/Geowissenschaft/index.htm _______________________________________________ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%