Deformation of feldspars

Because the feldspars are the most abundant minerals of the Earth s crust, their mechanical properties have been investigated in some detail. A review has been provided by Gandais and Willaime (1984). Thus, only a 

At least a dozen slip systems have been identified by TEM in experimentally and naturally deformed feldspars (see Gandais and Willaime 1984). In many cases, the dislocations are dissociated, though the separation of the partial dislocations is usually small ( 50 nm). The dissociation of dislocations of b = [100] gliding in (010) in experimentally deformed sanidine was first observed by Kovacs and Gandais (1980), who suggested the following reactions  

Gandais and Strunk (1983) observed that dislocations of b = [100] and b = [101] gliding in (010) tended to interact according to the reaction 

Olsen and Kohlstedt (1984) analyzed the dislocations in some naturally deformed intermediate plagioclase feldspars. All the known Burgers vectors except b = [100] were identified, and most, perhaps all, dislocations were dissociated by up to 20 nm. The microstructure was dominated by screw dislocations of b = [001], which had dissociated in (010) probably according to the reaction 

More recently, Montardi and Mainprice (1987) made a detailed TEM study of dislocations in naturally deformed calcic plagioclases (An6 -7o)-As in the specimens studied by Olsen and Kohlstedt (1984), the microstructure was dominated by the slip system (010) [001]. The [001] dislocations dissociated according to the reaction just given, the separation being about SO nm. The pair of gliding partial dislocations left behind a fault characterized by fringes of low contrast, as previously discussed. Image 

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