Premium
High‐temperature cordierite migmatites in the north‐eastern Grenville Province
Author(s) -
PERREAULT S.,
MARTIGNOLE J.
Publication year - 1988
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1988.tb00448.x
Subject(s) - migmatite , geology , geochemistry , biotite , metamorphism , hornblende , partial melting , cordierite , anorthosite , geothermobarometry , pegmatite , metamorphic rock , plagioclase , crust , gneiss , paleontology , chemistry , biochemistry , quartz , catalysis
In the northeastern part of the Grenville Province, along the gulf of St Lawrence, cordierite is widespread in the migmatites of Baie Jacques Cartier (BJC) and Baie des Ha! Ha! (BHH). In the BJC area, rafts of mesosome occur in a pervasive network of leucosome consisting of cordierite‐bearing pegmatite. In BHH, however, the mesosome and leucosome are well segregated and locally separated by thin biotite –hornblende melanosomes. Leucosomes in the BJC area record the highest temperatures (oxide thermometry = 900°C), whereas leucosomes of BHH and mesosomes of both areas indicate peak temperatures around 800°C (oxide thermometry; biotite–garnet thermometry with fluorine‐rich biotite). Peak pressures were constrained at 720 MPa using the Ilm‐Sil–Qtz–Grt–Rt (GRAIL) equilibrium. The area is thought to have undergone extensive melting under relatively modest pressures. The highest temperatures recorded in the BJC area are probably related to a pervasive impregnation of this terrane by aluminous granitic melts. Most post‐peak P–T estimates for the mesosomes fall on a nearly isobaric, clockwise, P–T path (0.6 MPa/°C) with the exception of the high‐temperature leucosomes of BJC, which fall about 100°C away from this path; this is additional evidence for the external origin of these leucosomes. The ultimate source of heat that generated the migmatites is thus though to be an underlying plutonic complex (anorthosite?).