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Thermal evolution of the Ryoke metamorphic belt, southwestern Japan: Tectonic and numerical modeling: Reply
Author(s) -
Okudaira Takamoto
Publication year - 2002
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1046/j.1440-1738.2002.00358.x
Subject(s) - geology , metamorphic rock , andalusite , muscovite , migmatite , sillimanite , metamorphism , geochemistry , cordierite , isograd , staurolite , petrology , gneiss , metamorphic facies , biotite , geomorphology , kyanite , quartz , facies , paleontology , biochemistry , chemistry , structural basin , catalysis
The Ryoke metamorphic belt of southwestern Japan is composed of Cretaceous Ryoke granitoids and associated metamorphic rocks of low-pressure facies series. The Ryoke granitoids are divided into sheet-like bodies (e.g. Gamano granodiorite) and stock-like bodies. The Gamano granodiorite intruded concordantly into the high-grade metamorphic rocks without development of a contact metamorphic aureole, and the intrusion ages of the granodiorite are similar to the ages of thermal peak of the low pressure (low-P) metamorphism. It is suggested that the low-P Ryoke metamorphism resulted from the intrusion of the Gamano granodiorite. In this study, a simple 1-D numerical model of conductive heat transfer was used to evaluate the thermal effects of emplacement of the Gamano granodiorite. Calculated temperature-time (T-t) paths are characterized by a rapid increase of metamorphic temperature and a relatively short-lived period of high temperature. For example, the 5"-t path at the 15-km depth is characterized by a rapid average increase in temperature of 1.4 x 10-3"C/year and high temperatures for < ca 0.5 Ma. The calculated peak temperature for each depth is nearly equal to the petrologically estimated value for each correlated metamorphic zone. The results suggest that the magma-intrusion model is one possible thermal model for low-pressure facies series metamorphism.