Near‐isothermal decompression within a clockwise P–T evolution recorded in migmatitic mafic granulites from Clavering Ø, NE Greenland: implications for the evolution of the Caledonides

Abstract

The high grade rocks (metapelites and metabasites) of Clavering é represent the easternmost exposures of granulites in the Palaeozoic Caledonian Orogen of East Greenland. Ma®c granulites which occur as sheet-like bodies and lenses within metapelitic migmatites and orthogneiss complexes have experienced migmatisation and mineral equilibria which de®ne a clockwise P±T path incorporating a near-isothermal decompression segment. Textures demonstrate the existence of early garnet-clinopyroxene-melt assemblages which equilibrated at >8±11 kbar and 850±915 uC. Subsequently, decompression melting led to formation of orthopyroxene-plagioclase-melt assemblages at conditions below >8±11 kbar. Continued syn-deformational decompression is indicated by a combination of both static and syn-deformational recrystallization textures which generated ®ner grained orthopyroxene-plagioclase assemblages. P±T constraints indicate these assemblages equilibrated at c. 5.0±6.5 kbar at 850±915 uC. These data are consistent with the rocks undergoing a stage of rapid tectonic-induced exhumation involving some 3.0±4.5 kbar (c.10±12 km) uplift as part of a clockwise P±T path in a collisional setting.

Syn‐deformational migmatites and magmatic‐arc metamorphism in the Xolapa Complex, southern Mexico

“…In places, the IMC diatexite contains a higher percentage of K‐feldspar associated with its location in S3 high‐strain zones; K‐feldspar is associated microstructurally with quartz, Ti‐rich biotite and titanite. Similar textures have been recorded by Wolf & Wyllie (1994) and Jones & Escher (2002) and are interpreted as simultaneous crystallization of a residual melt.…”

Migmatite gneiss of the Jættedal complex, Liverpool Land, East Greenland: protracted high‐T metamorphism in the overriding plate of the Caledonian orogen

“…430 Ma upper‐amphibolite–granulite facies metamorphism (Leslie & Nutman, ; White & Hodges, ; Gilotti et al ., ) and crustal melting within Hagar Bjerg thrust sheet extending along the thrust front of the southern GC from Renland to Andrée Land (Watt et al ., ; Kalsbeek et al ., , ; Andresen et al ., ). Similar Silurian anatectic gneiss terranes are also found north of Liverpool Land in Clavering Ø and Ardencaple Fjord in the orogenic core of the southern GC (Jones & Strachan, ; Jones & Escher, ; Higgins et al ., ; Gilotti et al ., ). Together, these units define a broad region characterized by high geothermal gradients ≥20 °C km −1 and melt‐weakened rheology during the Silurian that stretched ~600 km along strike in the lower to middle crust of the southern GC (Fig.…”

Evolution of granulite enclaves and associated gneisses from Purulia, Chhotanagpur Granite Gneiss Complex, India: Evidence for 990–940Ma tectonothermal event(s) at the eastern India cratonic fringe zone

“…Such intergrowth is most commonly formed by the breakdown of garnet in mafic granulite (cf. Jones and Escher, 2002). Actually, garnet in this reaction decomposes in presence of quartz in the following manner,…”