Growth and retrograde zoning in garnets from high-grade, metapelites: Implications for pressure-temperature paths

Tuccillo, Mary Ellen; Essene, Eric J.; Pluijm, Ben A. van der

doi:10.1130/0091-7613(1990)018<0839:garzig>2.3.co;2

Cited by 83 publications

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“…1190-980 Ma) metamorphism. Some authors have presented P-T-t paths that have been interpreted in terms of Grenvillian thermal and tectonic processes (e.g., Anovitz & Chase 1990, Tuccillo et al 1990, Jamieson et al 1995. However, the well-documented superposition of multiple pre-Grenvillian and Grenvillian high-grade metamorphic and tectonic events in many parts of the Grenville orogen (e.g., Jamieson et al 1992, Tuccillo et al 1992, Ketchum et al 1994, Culshaw et al 1997) means that constructing and interpreting P-T-t paths from these rocks requires careful assessment of timing and overprinting relationships, and the degree to which maximum P-T estimates really reflect peak P-T conditions (e.g., Frost & Chacko 1989, Frost et al 1998, Pattison 1998.…”

Section: Sommairementioning

confidence: 99%

Grenvillian Metamorphism of Monocyclic Rocks, Georgian Bay, Ontario, Canada: Implications for Convergence History

Wodicka¹,

Ketchum²,

Jamieson³

2000

The Canadian Mineralogist

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The Parry Sound and Shawanaga domains of the Central Gneiss Belt along Georgian Bay, Ontario, contain monocyclic rocks that originated at or near the southeastern margin of Laurentia between ca. 1450 and 1120 Ma. Their deformation and metamorphism are entirely attributable to Grenvillian orogenesis. Metamorphic assemblages, fabrics, and P-T-t paths from these rocks therefore provide important constraints on Grenvillian thermal and tectonic history. Rocks in the interior and basal Parry Sound assemblages of the northern Parry Sound domain were metamorphosed to granulite-facies conditions during an early phase of Grenvillian tectonism, i.e., at ca. 1161 and 1163 Ma, respectively. The most likely setting for high-P -high-T granulite-facies metamorphism in the interior Parry Sound assemblage was at or near the base of crust that was underplated by voluminous mafic magma. In contrast, heat advected from anorthosite could account for intermediate-P granulite-facies metamorphism in the basal Parry Sound assemblage. In the upper part of the basal Parry Sound assemblage, retrogression from the granulite to upperamphibolite facies likely occurred in response to thrust emplacement of the interior Parry Sound assemblage onto this part of the basal Parry Sound assemblage at ca. 1159 Ma. In the lower part of the basal Parry Sound assemblage, thrust deformation and reequilibration at lower-amphibolite-facies conditions took place at ca. 1120 Ma. In the southern Parry Sound domain, a highly attenuated sequence of quartzites and mafic rocks, deposited some time after 1140-1120 Ma, was affected by upper-amphibolitefacies metamorphism before or at 1080 Ma. Northwest of and structurally below the Parry Sound domain, rocks in the Shawanaga domain were affected by eclogite-facies metamorphism at ca. 1090-1085 Ma, suggesting deep burial or partial subduction of the Laurentian margin beneath the Central Metasedimentary Belt at this time. Widespread upper-amphibolite-facies metamorphism after ca. 1080 Ma was associated with a major phase of northwest-directed thrusting and crustal thickening. Sillimanite-grade conditions in the Shawanaga domain were maintained until at least ca. 1020 Ma, the time of major extensional deformation. Data on metamorphic grade and age are consistent with progressive northwest-directed juxtaposition of lithotectonic assemblages metamorphosed at progressively later times, and may thus record progressive or multistage convergence at the southeastern margin of Laurentia. Evidence for multiple phases of Grenvillian high-grade metamorphism in the Parry Sound and Shawanaga domains suggests that construction and interpretation of P-T-t paths from these rocks require careful assessment of timing and overprinting relationships. Derived P-T-t paths suggest that exhumation of interior Parry Sound granulites resulted from thrusting soon after peak metamorphism, whereas those for rocks of the Shawanaga domain suggest that exhumation was likely associated with both thrusting and extension.

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Section: Sommairementioning

confidence: 99%

Grenvillian Metamorphism of Monocyclic Rocks, Georgian Bay, Ontario, Canada: Implications for Convergence History

Wodicka¹,

Ketchum²,

Jamieson³

2000

The Canadian Mineralogist

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“…Those who both calibrated thermometers and barometers and tested them in the Grenville Province included Eric Essene and his many co-workers (e.g. Essene 1977, 1980;Essene 1982;Perkins et al 1982;Bohlen et al 1985;Anovitz and Essene 1990;Tuccillo et al 1990), and Indares andMartignole (1984, 1985). Geothermometry on upper amphibolite-and granulite-facies gneisses in the Grenville hinterland revealed temperatures in the range 700 ± 50°C or higher, a not unexpected result although subsequently shown to commonly underestimate peak T due to post-peak resetting (the granulite uncertainty principle; Frost and Chacko 1989).…”

Section: Geothermobarometrymentioning

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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“…Due to the complications mentioned above, the lower pressure limit remains uncertain: the 2 kbar values obtained from garnet cores using the calibrations of Newton and Haselton (1981) and Ghent and Stout (1981) would appear unreasonably low, unless it could be shown that these garnet cores developed during the thermal event. The pressure of 6.2 kbar derived using the dataset of Holland and Powell (1990) is probably the most reliable, and is geologically realistic as it would indicate a P increase of 3.0 kbar during garnet growth, compared with a decrease of up to 2.7 kbar during garnet growth reported by St-Onge (1987), and a decrease of 5kbar by Tuccillo et al (1990). We conclude that the rocks were regionally metamorphosed within a small range in T = 577+428C, under increasing pressure, realistically up to a maximum of 10 kbar (Table 2, Fig.…”

Section: Resultsmentioning

confidence: 96%

“…As Tracy (1982) has concluded that intra-crystalline diffusion in garnets is not important at T < 6508C, and other workers have shown that Ca-zoning is preserved in garnets that have been heated subsequently to around 7008C (Petrakakis, 1986;Tuccillo et al 1990), we infer that the temperatures at Ben Vuirich were not high enough to cause chemical homogenization of the garnet, and conclude that it is unjusti ed to appeal to later, post-crystallization, Ca diffusion to explain their high-Ca rims.…”

Section: Interpretation Of the Resultsmentioning

confidence: 96%

P-Tconditions during emplacement, and D2 regional metamorphism, of the Ben Vuirich Granite, Perthshire, Scotland

Ahmed-Said¹,

Tanner

2000

Mineral. mag.

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The 590+2 Ma Ben Vuirich Granite was intruded into late Proterozoic Dalradian rocks prior to the Grampian orogeny, during which it was affected by upper amphibolite facies regional metamorphism. Spotted cordierite and andalusite (chiastolite) hornfelses at the granite margin were altered to kyaniteand garnet-bearing assemblages during regional metamorphism. From the inferred mineralogy of the hornfels, together with the normative Qz Ab Or values of the granite and the application of a simple cooling model, we conclude that the country rocks immediately adjacent to the granite were hornfelsed at T =~6008C and P 4 2 kbar.The hornfelsed rocks were subsequently metamorphosed during the regional D2 event to form an equilibrium mineral assemblage of muscovite + biotite + garnet + plagioclase + quartz + kyanite (after chiastolite). Garnet which grew during this event shows unusual reversed chemical zoning, with Ca increasing systematically from core to rim as Fe, Mg and Mn decrease. A study of element partitioning between coexisting phases in equilibrium (including zoned garnets), and use of an internally consistent thermodynamic dataset, suggest that isothermal (T = 577+428C) compression (from P = 6.2+1.6 kbar to 9.0+1.9 kbar) occurred during crustal thickening. K-feldspar-plagioclase-quartz veinlets found in the hornfels close the granite contact are demonstrated to be of igneous origin.

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Growth and retrograde zoning in garnets from high-grade, metapelites: Implications for pressure-temperature paths

Cited by 83 publications

References 0 publications

Grenvillian Metamorphism of Monocyclic Rocks, Georgian Bay, Ontario, Canada: Implications for Convergence History

Grenvillian Metamorphism of Monocyclic Rocks, Georgian Bay, Ontario, Canada: Implications for Convergence History

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

P-Tconditions during emplacement, and D2 regional metamorphism, of the Ben Vuirich Granite, Perthshire, Scotland

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