High-pressure granulites in the Grenvillian Grand Lake thrust system, Labrador: Pressure-temperature conditions and tectonic evolution

Krauss, Jason B.; Rivers, Toby

doi:10.1130/0-8137-1197-5.105

Cited by 6 publications

(2 citation statements)

References 31 publications

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“…Similar rocks have also been identified in the eastern Grenville Province (Fig. 1) where Krauss & Rivers (2004) described HP assemblages in intermediate orthogneisses which yield peak conditions of 14 kbar and 875 °C.…”

Section: Geological Settingsupporting

confidence: 75%

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Borosilicate‐ and phengite‐bearing veins from the Grenville Province of Labrador: evidence for rapid uplift

Korhonen

Stout

2005

Journal Metamorphic Geology

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Quartzo-feldspathic veins emplaced within a migmatite terrane near Wilson Lake in the Grenville Province of central Labrador record a metamorphic event not evident in the host rocks. The discordant veins are undeformed and have undisturbed primary igneous/hydrothermal textures. Most of the veins contain euhedral kyanite, as well as aggregates of kyanite, K-feldspar, phlogopite and minor dumortierite which are likely pseudomorphs after primary phengite. The reconstructed phengite compositions range from 3.1 to 3.2 Si per 11 oxygen formula unit. The pseudomorph assemblage is interpreted as the product of phengite + quartz melting under H 2 O-undersaturated conditions, which brackets P-T conditions of formation to about 9-16 kbar and 775-875°C. A parallel vein that is likely of the same generation contains the borosilicate phases, dumortierite, prismatine and grandidierite, but no kyanite. The borosilicate assemblages constrain the P-T conditions of vein crystallization to ‡10 kbar and c. 750-850°C. Vein emplacement is constrained to T £ 875°C at the same pressures, which is well within the kyanite zone. Because the host rocks and veins must have experienced the same P-T history following vein emplacement, the presence of unreacted sillimanite in the host migmatites implies insufficient time for host rock equilibration. Slow reaction rates because of anhydrous conditions are not a likely explanation given the abundance of biotite and hornblende in the host rocks. The ductility implied by the breakdown of a hydrous phase (phengite) and the production of an H 2 Oundersaturated melt in the veins contrasts with the apparently brittle behaviour of the host rocks. The absence of deformation since the time of vein emplacement, even at temperatures above 750°C, suggests that the deep crust in this part of Labrador had a very short residence time under conditions of the kyanite zone. Rapid decompression from those conditions is consistent with quartz + phengite melting and accounts for the relatively brittle behaviour of the terrane as it was uplifted.

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Section: Geological Settingsupporting

confidence: 75%

“… Tectonic subdivision of the Grenville Province (after Rivers et al. , 2002; Krauss & Rivers, 2004), including the location of the Wilson Lake terrane (WLT; Fig. 2).…”

Section: Geological Settingmentioning

confidence: 99%