Megacrystic Gore Mountain–type garnets in the Adirondack Highlands: Age, origin, and tectonic implications

McLelland, James M.; Selleck, Bruce

doi:10.1130/ges00683.1

Cited by 22 publications

(42 citation statements)

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“…For instance, the margins of the granulite-facies Adirondack Highlands terrane, which exhibits a domal shape, are the sites of deformed and recrystallized sheets of syn-extensional leucogranite ( Fig. 31; Selleck et al 2005;McLelland et al 2010McLelland et al , 2013McLelland and Selleck 2011;Wong et al 2012). To a first approximation, such an evolution is compatible with numerical models of gravitational collapse of double thickness crust under an orogenic plateau, leading to thinning and sub-horizontal flow of the weak mid crust in the channel as the overlying strong upper crust extends by large-scale boudinage (e.g.…”

Section: P-t Conditions Of Grenvillianmentioning

confidence: 99%

Tectonic Setting and Evolution of the Grenville Orogen: An Assessment of Progress Over the Last 40 Years

Rivers

2015

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SUMMARYThe Grenville Province is known for its high grade of metamorphism, complex ductile gneissic structure, and polyphase reworking, features indicative of residence in the deep crust (orogenic infrastructure) that hamper recognition of protoliths and original relationships and render tectonic interpretations especially challenging. This paper charts the evolving understanding from the 'Grenville Problem' of the 1950s before the plate tectonic paradigm, through a speculative quasiplate tectonic stage in the 1970s that effectively proved to be a dead end, and the first constrained plate tectonic models for pre-Grenvillian Laurentia in the 1980s, to the recent LHO (large hot orogen) and collapsed LHO models for the Grenville Orogen itself. The collapsed LHO model is based on the finding that significant amounts of the superstructure (upper orogenic crust) are preserved, and that the present crustal architecture can be explained by tectonic juxtaposition of infrastructure and superstructure in a late extensional event associated with crustal-scale collapse of a high-strain channel under an orogenic plateau. Conceptual breakthroughs and critical datasets assembled in the period 1980-2000 that were influential in guiding tectonic thinking are discussed and it is argued that present understanding was contingent on the results of 2-D numerical forward modelling of orogenesis, in particular the LHO experiments and the more recent models of orogenic collapse. As a result, for the first time a conceptual plate tectonic model for the convergence and collapse stages of the Grenville Orogen based on empirical field data (the inverse model) is broadly supported by numerical forward-modelling experiments constrained by physically plausible processes in a LHOand both are available for future testing and refinement. Moreover, they may also have application to other enigmatic high-grade Proterozoic orogens that have resisted simple incorporation within the plate tectonic narrative.

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Section: P-t Conditions Of Grenvillianmentioning

confidence: 99%

Tectonic Setting and Evolution of the Grenville Orogen: An Assessment of Progress Over the Last 40 Years

Rivers

2015

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“…7G) during the terminal collapse of the Ottawan Orogen (Wong et al 2011(Wong et al , 2012McLelland et al 2012). The difference between the two areas is that hanging wall rocks are not exposed in the eastern AHT suggesting that a master collapse fault may lie buried beneath the Paleozoic cover to the east (McLelland et al 2011;Wong et al 2012). We suggest that this master fault is an extension of the Tawachiche Shear Zone (Corrigan and van Breemen 1997) whose along-strike projection passes just to the east of the Adirondacks in the Champlain Valley ( Fig.…”

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confidence: 99%

“…Note, however, that Figure 8C, D show white patches of plagioclase (An 40-60 ) together with bronze orthopyroxene (En 50-60 ). The white patches embay into the garnet grains and their rims (McLelland and Selleck 2011). Figure 8D provides a close-up of a fully developed plagioclase and euhedral orthopyroxene rim that embays into the garnet and has consumed essentially the entire hornblende rim.…”

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confidence: 99%

“…4). In either case, the large-scale anatexis of the crust weakened the orogen, which then underwent extensional collapse as AMCG plutons ascended to the mid crust (Selleck et al 2005;McLelland et al 2010a, b;McLelland and Selleck 2011).…”

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confidence: 99%

“…The end of the Ottawan orogenic phase is bracketed by zircon crystallization ages of 1.04 Ga for undeformed pegmatite as well as monazite ages of ca. 1030 Ma (McLelland et al 2010a;Lupulescu et al 2011;McLelland and Selleck 2011;Wong et al 2012).…”

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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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Metamorphism of Mafic Rocks

Bucher

2023

Springer Textbooks in Earth Sciences, Geography and Environment

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Megacrystic Gore Mountain–type garnets in the Adirondack Highlands: Age, origin, and tectonic implications

Cited by 22 publications

References 47 publications

Tectonic Setting and Evolution of the Grenville Orogen: An Assessment of Progress Over the Last 40 Years

Tectonic Setting and Evolution of the Grenville Orogen: An Assessment of Progress Over the Last 40 Years

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

Metamorphism of Mafic Rocks

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