High-temperature, low-pressure metamorphism in the Kisseynew domain, Trans-Hudson orogen: crustal anatexis due to tectonic thickening?

White, Donald J

doi:10.1139/e04-087

Cited by 17 publications

(8 citation statements)

References 32 publications

(47 reference statements)

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“…Archean zircon xenocrysts are known in some Trans-Hudson orogen igneous rocks, and Nd and Pb isotopes suggest old-crust contamination in various sectors (e.g., Bickford et al, 2005). Compressional thickening of a great Paleoproterozoic sedimentary pile in the center of the Trans-Hudson orogen can quantitatively account for its dimensions, metamorphism, and anatectic plutonism (White, 2005).…”

Section: Paleoproterozoic Trans-hudson Orogenmentioning

confidence: 99%

Earth's first two billion years—The era of internally mobile crust

Hamilton¹

2007

Geological Society of America Memoirs

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The magmatic and tectonic processes of the pre-2.5 Ga hot, young Earth differed profoundly from those of the modern planet. The ancient rocks differ strikingly in individual and collective composition, occurrence, association, and structure from modern rocks. Widespread forcing of Archean geology into plate-tectonic frameworks refl ects unwarranted faith in uniformitarianism and in inappropriate chemical discriminants, and disregard for the lack of features that characterize plate interactions. Archean crust records extreme and prolonged internal mobility and was far too weak and mobile to behave as rigid plates, required, by defi nition, for plate tectonics. None of the geologic indicators of subduction, arc magmatism, and continental sundering, separation, and convergence have been documented. No Archean oceanic crust or mantle has been recognized, and the only known basement to supracrustal rocks, including the thick basalts, high-Mg basalts, and ultramafi c lavas that typify greenstone successions, consists of tonalite-trondhjemite-granodiorite (TTG) migmatites and gneisses. A thick global melabasaltic protocrust likely formed by ca. 4.45 Ga, and from it TTG suites were extracted by partial melting over the next 2 b.y. Delamination of the increasingly dense restitic protocrust enabled rise of lighter and hotter depleted mantle and hence more melting. The oldest known crustal materials are zircons, which scatter in age back to 4.4 Ga and are recycled in migmatites whose fi nal crystallization was after 3.8 Ga, and in ancient sediments. Earth may have had a dense greenhouse atmosphere, not a hydrosphere, before 3.6 Ga, for the oldest proved supracrustal rocks are of that age, and older felsic crust may have been too hot to permit rise of dense melts. Rigid plates of lithosphere did not stabilize until a billion years after that and then were mostly small and local. Dense lavas erupted atop mobile felsic crust after 3.6 Ga produced a density inversion that was partly righted by sinking of the volcanic rocks and rising of the subjacent TTG. In some places, the early dense rocks retained cohesion and sank as synclinal keels between rising domiform diapiric batholiths. In others, the early dense rocks sank deep into mobile TTG crust, and only later in Archean time was the felsic substrate strong enough to enable dome-and-keel style. The TTG substrate rose slowly, with variable amounts of partial melting to generate more-fractionated melts

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Section: Paleoproterozoic Trans-hudson Orogenmentioning

confidence: 99%

Earth's first two billion years—The era of internally mobile crust

Hamilton¹

2007

Geological Society of America Memoirs

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“…These conditions represent LP-HT metamorphism (De Yoreo et al, 1991;Lux et al, 1986;Scrimgeour et al, 2001). In collisional events such as the Trans-Hudson orogeny, LP -HT D r a f t metamorphic conditions cannot be solely a result of crustal thickening (White, 2005;Sandiford and Powell, 1991). This is based on models which show that the Moho T would exceed the liquidus at the base of the crust if the amount of heat in LP -HT metamorphism is attributed to crustal thickening alone (Sandiford and Powell, 1991).…”

Section: Regional Context For Low Pressure -High Temperature (Lp-ht) mentioning

confidence: 99%

Conditions and timing of low-pressure – high-temperature metamorphism in the Montresor Belt, Rae Province, Nunavut

2019

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Pressure–temperature–time (P–T–t) estimates for the Montresor Belt, obtained using phase equilibria and geospeedometry modelling integrated with in situ U–Th–Pb monazite geochronology, shed new light on the tectonometamorphic effects of the Snowbird phase of the Trans-Hudson orogeny. Typical metapelitic assemblages of the lower Montresor group consist of white mica, biotite, plagioclase, quartz, and andalusite, which in some rocks is partly or completely pseudomorphed by white mica. The observed assemblages reflect peak P–T conditions centring at approximately 575 °C and 3 kbar. Rocks with high bulk Fe/Mg contents contain compositionally zoned garnet, permitting the addition of further constraints on the conditions of metamorphism in the Montresor Belt: Core compositions of earliest-grown garnets indicate initial garnet crystallization at approximately 535 °C and 2.3 kbar, suggesting a nearly isobaric P–T path of prograde metamorphism with a gradient of approximately 50 °C·kbar–1. Chemical age-dating of monazite inclusions in garnet yields ages of ca. 1870 ± 9 to 1837 ± 9 Ma. Retrograde, pseudomorphic andalusite replacement by white mica at approximately 540 °C is inferred to have been controlled by variations in bulk rock chemistry. Morphologically corroded and chemically heterogeneous monazite adjacent to white mica pseudomorphs suggests that andalusite replacement took place at ca. 1792 ± 10 Ma, possibly associated with extension and movement along the detachment fault separating the upper and lower Montresor groups. Simulations of diffusion across chlorite- and biotite-filled cracks in garnet assumed to be coeval with andalusite replacement suggest that the rocks have experienced the retrograde event for at least 20 My.

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“…The heat source is a current issue of discussion in regions affected by HT-LP metamorphism (Wickham and Oxburgh, 1987;Escuder Viruete, 1999;White, 2005). From thermal modelling, Gerbi et al (2006) conclude that the following mechanisms, operating alone, are able to induce anatexis in typical pelitic rocks: 1) Magmatic advection by pervasive flow, 2) Crustal-scale detachment faulting, and 3) The presence of a high-heat producing layer.…”

Section: W E P U N C O V Is C a N A Fo Rm A Ti O N S C H Is T M Ig M mentioning

confidence: 99%

The Sierra de Cachi (Salta, NW Argentina): geological evidence about a Famatinian retro-arc at mid crustal levels

Hongn¹,

Tubía²,

Esteban³

et al. 2014

Journal of Iberian Geology

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The Cachi mountain ranges, located in Salta (NW Argentina), form an inlier where Neoproterozoic and Paleozoic materials of the Andes crop out in a plutono-metamorphic dome surrounded by Mesozoic and Cenozoic sedimentary rocks. The pre-Mesozoic rocks record a regional metamorphism of low pressure and high temperature conditions, which reached partial melting conditions and was coeval with the intrusion of sheeted granite and trondhjemite plutons. The metamorphic evolution and the emplacement of the plutons took place in an extensional tectonic setting. New U-Pb zircon dating by TIMS and SHRIMP methods yields similar ages for the migmatization (479.7 ± 3.5 Ma) and the emplacement of granites (472.1 ± 11 Ma), constraining the extensional event to Early Ordovician times. We also report the finding of gabbro boulders, which also yield a similar U-Pb SHRIMP zircon age of 477.5 ± 3.9 Ma. So, we propose that the extensional event recognized in Sierra de Cachi took place in a retro-arc setting linked to the Famatinian subduction along the western border of Gondwana. The shortening produced by younger east-verging folds evidences the superposition of a compressional stress field, probably related with the Ocloyic orogeny (Middle/Late Ordovician-Devonian).Keywords: U-Pb geochronology, Famatinian retro-arc, Cachi ranges, Argentina Resumen En la Sierra de Cachi, situada en Salta (NO de Argentina), afloran rocas neoproterozoicas y paleozoicas de los Andes en un domo plutono-metamórfico flanqueado por rocas sedimentarias mesozoicas y cenozoicas. Estas rocas registran un metamorfismo de alta temperatura y baja presión, que alcanzó condiciones de fusión parcial y fue coetáneo del emplazamiento de plutones de granitos y trondhjemitas. El metamorfismo y el emplazamiento de los plutones se produjo en condiciones extensionales. Nuevos análisis de U-Pb en zircones, por los métodos TIMS y SHRIMP, proporcionan edades similares para la migmatización (479,7 ± 3,5 Ma) y el emplazamiento de los granitos (472,1 ± 11 Ma), acotando el evento extensional al Ordovícico Inferior. También describimos el hallazgo de bloques de gabros que dan una edad U-Pb SHRIMP en circones semejante, de 477,5 ± 3,9 Ma. Por lo tanto, se propone que el evento extensional descrito en la Sierra de Cachi tuvo lugar en una zona de retro-arco asociada a la subducción famatiniana del borde occidental de Gondwana. El acortamiento producido por los pliegues más jóvenes vergentes al E refleja la superposición de un campo de esfuerzos compresivos, probablemente relacionados con la orogenia Oclóyica (Ordovícico Medio/Superior-Devónico).Palabras clave: geocronología U-Pb, retro-arco famatiniano, Sierra de Cachi, Argentina

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High-temperature, low-pressure metamorphism in the Kisseynew domain, Trans-Hudson orogen: crustal anatexis due to tectonic thickening?

Cited by 17 publications

References 32 publications

Earth's first two billion years—The era of internally mobile crust

Earth's first two billion years—The era of internally mobile crust

Conditions and timing of low-pressure – high-temperature metamorphism in the Montresor Belt, Rae Province, Nunavut

The Sierra de Cachi (Salta, NW Argentina): geological evidence about a Famatinian retro-arc at mid crustal levels

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