The Occurrence of Garnet in the Granulite-Facies Terrane of the Adirondack Highlands

Waard, Dirk de

doi:10.1093/petrology/6.1.165

Cited by 68 publications

(24 citation statements)

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“…and occur with orthopyroxene (and/or clinoequilibrium (as has, for instance, been suggested pyroxene)-plagioclase (and/or K-feldspar)~-for similar occurrences in other granulites; de quartz-ilmenite. In these samples garnet is Waard, 1965). However, the garnet and pyroxene rarely in textural equilibrium with both clinocompositions d o not vary significantly on the pyroxene and orthopyroxene (Fig.…”

Section: M Assemblages In Meta-igneous Gneissesmentioning

confidence: 85%

The metamorphic evolution of granulites at Fyfe Hills; implications for Archaean crustal thickness in Enderby Land, Antarctica

Sandiford

1985

Journal Metamorphic Geology

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Granulites at Fyfe Hills in Enderby Land, Antarctica, crystallized at temperatures in excess of 85OoC, and possibly as high as IOOOT, and at pressures of 8-10 kbar during the mid to late Archaean. A number of features, including repeated retrograde metamorphism at 5.1-8 kbar, retrograde reaction textures, and rimward zoning in pressure sensitive systems, suggest that following peak metamorphism the granulites stabilized at a depth of 18-26 km. After stabilization, the granulites cooled near-isobarically to temperatures of 60&7OO0C. Assuming a total crustal thickness of 35-40 km during this late Archaean interval of isobaric cooling, the peak metamorphic crustal thickness is estimated a t 35-56 km. This estimate is significantly less than the 60-70 km obtained by summing the depths of the present levels of exposure ( 2 6 3 4 km) and the thickness of the crust presently beneath Fyfe Hills (approximately 35 km) and is, therefore, consistent with independent evidence for extensive post-Archaean thickening of the Enderby Land crust. Abbreciations used in text andjigurescpx = clinopyroxene grt =garnet hbe =hornblende kfs = K-feldspar ilm = ilmenite mag = magnetite mp = mesoperthite 01 =olivine opx = orthopyroxene phl = phlogopite pig = pigeonite pl = plagioclase qtz =quartz ru = rutile sil = sillimanite spl =spinel spr = sapphirine An = anorhite component Ab = albite component Or = orthoclase component Gr = grossular component Di = diopside component En = enstatite component Py = pyrope component

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Section: M Assemblages In Meta-igneous Gneissesmentioning

confidence: 85%

The metamorphic evolution of granulites at Fyfe Hills; implications for Archaean crustal thickness in Enderby Land, Antarctica

Sandiford

1985

Journal Metamorphic Geology

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“…Clearly the garnet and hornblende have reacted to yield coexisting plagioclase and pyroxene as well as a fluid phase. This is a well-known reaction and has been extensively studied (de Waard 1965;Spear 1993, and references therein). It reflects passage from the upper almandine amphibolite facies (~750°C, 6-7 MPa) into the granulite facies at temperatures at, or slightly above, 800°C and pressures of 6-9 MPa as reported for Adirondack granulite-facies assemblages (Storm and Spear 2005).…”

mentioning

confidence: 99%

Tectonic Evolution of the Adirondack Mountains and Grenville Orogen Inliers within the USA

McLelland

Selleck

Bickford³

2013

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Recent investigations in geochronology and tectonics provide important new insights into the evolution of the Grenville Orogen in North America. Here, we summarize results of this research in the USA and focus upon ca. 1.4–0.98 Ga occurrences extending from the Adirondack Mountains to the southern Appalachians and Texas. Recent geochronology (mainly by U/Pb SHRIMP) establishes that these widely separated regions experienced similar tectonomagmatic events, i.e., the Elzevirian (ca. 1.25–1.22 Ga), Shawinigan (ca. 1.2–1.14 Ga), and Grenvillian (ca. 1.09–0.98 Ga) orogenies and associated plate interactions. Notwithstanding these commonalities, Nd model ages and Pb isotopic mapping has revealed important differences that are best explained by the existence of contrasting compositions of deep crustal reservoirs beneath the Adirondacks and the southern Appalachians. The isotopic compositions for the Adirondacks lie on the same Pb–Pb array as those for the Grenville Province, the Granite-Rhyolite Province and the Grenvillian inliers of Texas suggesting that they all developed on Laurentian crust. On the other hand, data from the southern Appalachians are similar to those of the Sunsas Terrane in Brazil and suggest that Amazonian crust with these Pb–Pb characteristics was thrust onto eastern Laurentia during its Grenvillian collision with Amazonia and subsequently transferred to the latter during the late Neoproterozoic breakup of the supercontinent, Rodinia, and the formation of the Iapetus Ocean. The ca. 1.3–1.0 Ga Grenville Orogen is also exposed in the Llano Uplift of Texas and in small inliers in west Texas and northeast Mexico. The Llano Uplift contains evidence for a major collision with a southern continent at ca. 1.15–1.12 Ga (Kalahari Craton?), magmatic arcs, and back-arc and foreland basins, all of which are reviewed. The Grenvillian Orogeny is considered to be the culminating tectonic event that terminated approximately 500 m.y. of continental margin growth along southeastern Laurentia by accretion, continental margin arc magmatism, and metamorphism. Accordingly, we briefly review the tectonic and magmatic histories of these Paleoproterozoic and Mesoproterozoic pre-Grenvillian orogens, i.e., Penokean, Yavapai, and Mazatzal as well as the Granite-Rhyolite Province and discuss their ~5000 km transcontinental span.SOMMAIREDes recherches récentes en géochronologie et en tectonique révèlent d’importants faits nouveaux sur l’évolution de l’orogénie de Grenville en Amérique du Nord. Nous présentons ici un sommaire des résultats de cet effort de recherche aux USA en mettant l’accent sur les indices datés entre env. 1,4 et 0,98 Ga, à partir des monts Adirondack jusqu’au sud des Appalaches et au Texas. Des données géochronologiques récentes (par microsonde SHRIMP principalement) indiquent que les roches de ces régions très éloignées les unes des autres ont subies l’effet d’épisodes tectonomagmatiques similaires, par exemple, aux orogenèses de l’Elzévirien (env. 1.25–1.22 Ga), de Shawinigan (env. 1.2–1.14 Ga), et du Grenvillien (env. 1.09–0.98 Ga), ainsi que des interactions des plaques associées. Malgré ces points communs, la chronologie Nd et la cartographie isotopique Pb a révélé des différences importantes qui s’expliquent plus aisément par des compositions contrastées des réservoirs profonds de croûte sous les Adirondacks et le sud des Appalaches. Les compositions isotopiques des Adirondacks sont de la même gamme Pb-Pb que ceux de la Province de Grenville, de la Province Granite-rhyolite et des boutonnières grenvilliennes du Texas, suggérant qu'ils se sont tous développées sur la croûte des Laurentides. Par ailleurs, les données des Appalaches du sud sont semblables à celles du terrane de Sunsas au Brésil, ce qui incite à penser que la croûte amazonienne, avec de telles caractéristiques Pb-Pb, a été poussée sur la portion est de Laurentia lors de sa collision grenvillienne avec l’Amazonie puis laissée à cette dernière au cours de la rupture du supercontinent Rodinia vers la fin du Néoprotérozoïque, avec la formation de l'océan Iapetus. L’orogène de Grenville (1,3 à 1,0 Ga env.) est également exposé dans le soulèvement de Llano au Texas et dans de petites boutonnières dans l'ouest du Texas et le nord du Mexique. Le soulèvement de Llano montre des indices d'une collision majeure avec un continent au sud, entre env. 1,15 et 1,12 Ga (craton de Kalahari?), des zones d’arcs magmatiques, d'arrière-arc et de bassin d'avant-pays, chacun étant présenté ci-dessous. L'orogenèse de Grenville est considéré comme l'événement tectonique culminant qui marqué la fin d’une période d’environ 500 ma d’accroissement de la marge continentale le long de la bordure sud-est de la Laurentie, par accrétion, magmatisme d’arc de marge continentale, et métamorphisme. C’est pourquoi, nous passons brièvement en revue l'histoire tectonique et magmatique de ces orogènes pré-grenvilliennes paléoprotérozoïques et mésoprotérozoïques, pénokéenne, de Yavapai, et de Mazatzal ainsi que la Province de Granite-rhyolite, et discutons de son étendue sur env. 5 000 km.

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“…Garnet forms coronitic microstructures and, in some cases, displays honeycomb-type texture surrounding plagioclase, amphibole or pyroxene grains formed by the reaction Pl + Cpx 1 (Opx) = Grt + Cpx 2 + Qtz, typical of high-pressure metamorphism (Bard 1980, Best 1982, De Waard 1965, Harley 1985. In some other cases, the progression of this reaction forms larger poikiloblastic crystals with abundant inclusions of orthopyroxene, plagioclase and opaque minerals.…”

Section: Petrography and Metamorphism Of The Granulitic Rocksmentioning

confidence: 99%

Granulite-facies metamorphism at ca. 570-580 Ma in the Porangatu Granulite Complex, central Brazil: implications for the evolution of the Transbrasiliano Lineament

et al. 2017

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ABSTRACT:The Porangatu Granulite Complex is exposed in the central part of the Neoproterozoic Tocantins province in central Brazil, along the boundary between the Brasília Belt to the east and the Araguaia Belt to the west. This is part of the transcontinental Transbrasiliano-Kandi shear system. The complex includes garnet-rich enderbite and charnockite, high-grade gneisses as well as lenses of garnet-bearing mafic granulite or amphibolites, and in situ anatectic charnockite, elongated in the NNE-SSW direction along the Talismã Shear Zone (TSZ). These rocks represent suites of ortho-derived rocks of calc-alkaline affinity and small contributions of tholeiitic basalts and aluminous paragneisses. The structural framework records thrust components probably related to the early stages of an oblique collision during the evolution of Neoproterozoic Brasiliano orogens, and can be understood as involving a collisional system of two crustal blocks, initially with thrust components which in its final stage evolved to a transcurrent system with dextral movement. This led to intense imbrication, generation of mylonitic foliation, stretching lineation, tectonic banding and rotation of structures and minerals. The heterogeneous and progressive ductile deformation was accompanied by metamorphic re-equilibrium in late Neoproterozoic time. Granulite facies conditions reached a metamorphic maximum at temperature and pressure above 850°C and 10 kbar, in an almost anhydrous environment, with or without anatexis. Zircon U-Pb SHRIMP analyses for two selected rock samples indicated the combined age of 580 ± 7 Ma for a charnockite and 548 ± 48 Ma for a mafic granulite from which the charnockite is throught to have been derived. The mafic granulite contains zircon grains of ca. 2.1 Ga, indicating Paleoproterozoic igneous protoliths involved in Neoproterozoic high-grade metamorphism. In addition, older inherited zircon grains of ca.

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The Occurrence of Garnet in the Granulite-Facies Terrane of the Adirondack Highlands

Cited by 68 publications

References 0 publications

The metamorphic evolution of granulites at Fyfe Hills; implications for Archaean crustal thickness in Enderby Land, Antarctica

The metamorphic evolution of granulites at Fyfe Hills; implications for Archaean crustal thickness in Enderby Land, Antarctica

Tectonic Evolution of the Adirondack Mountains and Grenville Orogen Inliers within the USA

Granulite-facies metamorphism at ca. 570-580 Ma in the Porangatu Granulite Complex, central Brazil: implications for the evolution of the Transbrasiliano Lineament

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