L. Barbero, GRANULITE-FACIES METAMORPHISM IN THE ANATECTIC COMPLEX OF TOLEDO, SPAIN - LATE-HERCYNIAN TECTONIC EVOLUTION BY CRUSTAL EXTENSION, Journal of the Geological Society, 152, 1995, pp. 365-382
The Anatectic Complex of Toledo consists of a heterogeneous suite of h
igh-grade metamorphic rocks, mainly granulitic migmatites of pelitic c
omposition and orthogneisses, and different types of syn-orogenic gran
itoids with minor associated basic rocks. None of the metamorphic rock
types records evidence of the early prograde history, and only the pe
ak and retrograde P-T conditions can be estimated. The intrusion of th
e syn-orogenic granitoids is either slightly before or synchronous wit
h the metamorphic climax. These rock types thus can be used to make P-
T estimates of the peak and retrograde conditions. Microtextural analy
sis of reaction textures in conjunction with a petrogenetic grid, has
enabled construction of an incomplete ''clockwise'' P-T path that is c
haracterized by an isothermal decompression after or during the metamo
rphic peak temperatures. The peak estimates from different geothermoba
rometers are 800 degrees +/- 50 degrees C and 4-6 Kbar, the highest te
mperatures recorded in this part of the Iberian Hercynian Belt. It is
proposed that this high-T/low-P metamorphism is at least partially rel
ated to an extensional process, possibly due to gravitational collapse
of previously thickened crust.