Constraints on the depth of generation and emplacement of a magmatic epidote‐bearing quartz diorite pluton in the Coast Plutonic Complex, British Columbia

Abstract

Petrology and P–T estimates indicate that a magmatic epidote‐bearing quartz diorite pluton from Mt. Gamsby, Coast Plutonic Complex, British Columbia, was sourced at pressures below ∼1.4 GPa and cooled nearly isobarically at ∼0.9 GPa. The P–T path indicates that the magma was within the stability field of magmatic epidote early and remained there upon final crystallization. The pluton formed and crystallized at depths greater than ∼30 km. REE data indicate that garnet was absent in the melting region and did not fractionate during crystallization. This suggests that the crust was less than or equal to ∼55 km thick at 188 Ma during the early phases of magmatism in the Coast Plutonic Complex. Late Cretaceous contractional deformation and early Tertiary extension exhumed the rocks to upper crustal levels. Textures of magmatic epidote and other magmatic phases, combined with REE data, can be important for constraining the P–T path followed by magmas.

Magmatic garnet in the Cordilleran-type Galiléia granitoids of the Araçuaí belt (Brazil): Evidence for crystallization in the lower crust

“…6d and e). The latter features have been previously reported by Chang and Andronicos (2009) and Hammarstrom (1984a, 1984b) whose proposed contrasting interpretation. The epidote crystals are only rarely in between biotite and quartz in the Bt-free garnet granodiorite.…”

“…In fact, epidote inclusions are ragged, cracked, and commonly zoned showing corroded and/or resorbed rims. Following Chang and Andronicos (2009) and Dawes and Evans (1991), we interpret these inclusions as early magmatic crystals followed by resorption before plagioclase overgrowth during successive magmatic stages. Epidote crystals within the MMEs share similar textural and compositional (Ps = 11.8-17.3 mol%) features with those in the granites, thus they are also interpreted as being magmatic.…”

Tectonic setting and geochronology of the Cadomian (Ediacaran-Cambrian) magmatism in Central Iran, Kuh-e-Sarhangi region (NW Lut Block)

“…The presence of magmatic epidote (Ps 20-26 ) in the Kuh e Sarhangi granites, with a composition comparable to those observed in North America Cordillera granitoids (Zen and Hammastrom, 1984;Zen, 1985;Dawes and Evans, 1991), suggests a melt origin and crystallisation/emplacement at moderately to high pressure (P6 8 kbar; e.g. Zen and Hammastrom, 1984;Schmidt and Thompson, 1996;Schmidt and Poli, 2004;Chang and Andronicos, 2009). This is in agreement with (i) occurrence of Grs rich and Sps poor garnet in the magmatic assemblage, since the Grs end member increases in garnet with increasing pressure (>6 kbar), whereas a higher Sps content (MnO > 4 wt%) stabilises garnet at shallow depths (cfr.…”