Abstract

Recent work by Brooks (1967) north of Georgian Bay, Ontario, has indicated that the Grenville Front in that area was a zone of sinistral shear in Grenville time during an orogeny which was genetically responsible for the Killarnean granitization through “shear melting” due to energy released by intense plastic distortion. These phenomena are compared with zones of intensive shearing of Precambrian age in southwestern Tanzania ascribed by McConnell (1951) to deep-seated dextral shearing during a “Ubendian” orogeny and considered to have generated metamorphism and granitization through the raising of pressure-temperature conditions by orogenic stress. Reference is also made to the attribution by Lugeon (1930) of post-tectonic granitization in the root zone of the Alps to intensified stress, at a late stage of the orogeny, which caused conversion of mechanical to thermal energy. Experimental studies by Tuttle and Bowen (1958) suggest physico-chemical support for such interpretations of the common association of anatectic granites with intense tectonism.

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