GARNET-BIOTITE GEOTHERMOBAROMETRY OF THE CENTRAL METASEDIMENTARY BELT BOUDARY THRUST ZONE OF THE GRENVILLE PROVINCE, ONTARIO, CANADA

摘要

INTRODUCTION The processes related to the plate tectonic assembly of continents is reflected in the metamorphic rocks that were formed during such times. One aspect of the plate tectonic history recorded in these rocks is the pressure-temperature (P-T) conditions that the rocks experienced. Geothermobarometry, a technique used to calculate the equilibrium temperatures and pressures from the measured distribution of elements between coexisting phases, (typically of garnet-bearing ortho and paragneiss) allow metamorphic conditions to be assessed in the Central Metasedimentary Belt boundary thrust zone (CMBbtz) of the southern Gren-ville Province (Figure 1, Peck et al., this volume). Garnet-rich gneisses and schists were acquired from several locations in the CMBbtz, which will allow the comparison with the adjacent Central Gneiss Belt, the Composite Arc Belt, and shed light on tectonic reconstructions of this area. We have identified Garnet-Biotite, Garnet-Aluminosilicate-Silica-Plagioclase (GASP), and Amphibole-rich assemblages in these rocks, and are in the process of analyzing them for their compositions to estimate P-T conditions using Garnet-Biotite thermometry and GASP barometry (e.g. Patino-Douce et al., 1993). The electron micro-probe will be used to conduct geothermobarometry on the available rock samples. The microprobe data will be augmented by phase relationships observed in thin section, which provides rough constraints on the P-T conditions.