Metamorphic history of high‐pressure granulites in Payer Land, Greenland Caledonides

Abstract

A high‐P granulite facies gneiss complex occurs in north‐west Payer Land (74°28′−74°47′N) in the central part of the East Greenland Caledonian (Ordovician–Devonian) orogen. High‐P metamorphism of the Payer Land gneiss complex resulted in formation of the assemblages Grt + Cpx + Amp + Qtz + Ru ± Pl in mafic rocks, and Grt + Ol + Cpx + Opx + Spl in rare ultramafic pods. Associated metapelites experienced anatexis in the kyanite stability field. Peak metamorphic assemblages formed around 800–850 °C at pressures of c. 1.4–1.7 GPa, corresponding to crustal depths of c. 50 km. Mafic granulites contain abundant reaction textures, including the replacement of garnet by symplectites of Opx + Spl + Pl, indicating that the high‐P event was followed by decompression while the granulites remained at elevated temperatures. Charnockitic gneisses from Payer Land show evidence of late Archean (c. 2.8–2.4 Ga) crustal growth and subsequent Palaeoproterozoic (c. 1.85 Ga) metamorphism. The gneiss complex experienced intense reworking during the Caledonian continental collision. On the basis of Caledonian monazite ages recorded from the high‐P anatectic metapelites, the clockwise P–T evolution and formation of the high‐P granulite facies assemblages is related to Caledonian crustal thickening, which resulted in formation of eclogites approximately 300 km north of Payer Land. The Payer Land granulites comprise a metamorphic core complex, which is separated from the overlying low‐grade supracrustal rocks (the Neoproterozoic Eleonore Bay Supergroup) by a late Caledonian extensional fault zone, the Payer Land Detachment. The steep, nearly isothermal, unloading P–T path recorded by the granulites can be explained by erosional and tectonic unroofing along the Payer Land Detachment.

An Early Palaeozoic HP/HT granulite–garnet peridotite association in the south Altyn Tagh, NW China:P–Thistory and U‐Pb geochronology

“…Garnet peridotite, generally regarded as a HP mantle rock, has been commonly identified in HP granulite units (Becker, 1997; Elvevold et al. , 2003), and its origin and relationship with host HP granulites are significant to the evolution of orogenic belts.…”

“…High‐ P high‐ T granulites are commonly exposed in continental collision belts, and some are associated with eclogites and garnet peridotites, as for instance in the European Variscan belt (Carswell & O'Brien, 1993; Rötzler & Romer, 2001; O'Brien & Rötzler, 2003) and the Greenland Caledonides (e.g. Gilotti & Elvevold, 2002; Elvevold et al. , 2003).…”

Quantitative P–T–X constraints on orthopyroxene‐bearing high‐pressure granulites in felsic–metapelitic rocks: evidence from the Huangtuling granulite, Dabieshan Orogen

“…High-pressure granulites in collisional orogenic belts are generally characterized by the mineral assemblages garnet + clinopyroxene + plagioclase ± quartz in basic rocks (e.g. Baldwin et al, 2003;Elvevold et al, 2003;Shervais et al, 2003;Puelles et al, 2005) and garnet + kyanite + Kfeldspar in felsic-metapelitic rocks (Liu & Zhong, 1997;Ro¨tzler & Romer, 2001;O'Brien & Ro¨tzler, 2003;Tajcmanova´et al, 2006). However, rare orthopyroxene-kyanite-bearing high-pressure granulites have been reported in a few orogens, e.g.…”

Geochronology of high‐pressure mafic granulite dykes in SW Sweden: tracking the P–T–t path of metamorphism using Hf isotopes in zircon and baddeleyite

“…Mørk, 1985; Indares & Dunning, 1997, 2004; Cox et al. , 1998; Cox & Indares, 1999; Elvevold et al. , 2003; O′Brien & Rötzler, 2003).…”