Metamorphic evolution of the UHT granulites from Mandikota, Eastern Ghats Mobile Belt, India: Constraints from phase equilibria modelling, fluid inclusions and monazite U-Th-total Pb geochronology

The Svecofennian orogeny in Fennoscandia is an example of a long-lived orogeny characterised by low pressure, high temperature (LP–HT) metamorphism. In this paper, we present new LA-ICP-MS age data on monazite from fifteen paragneiss samples and two granitoid samples from the southeastern part of the Svecofennian orogen, including the Sulkava granulite complex. The high-grade rocks in the study area were metamorphosed at ca. 750–800 °C and 5–6 kbar, followed by near-isothermal decompression down to 3–4 kbar. The analysed monazites yielded 207Pb/206Pb dates from 1953 to 1737 Ma. The youngest dates are typically yielded by rims and overgrowths of monazites and by younger domains in patchy monazite grains. Psammitic and pelitic layers from the same outcrop display differences in monazite date distributions, with younger dates being more common in pelitic layers. Both detrital and metamorphic origins are possible for the ≥1.91 Ga monazite grains found in some samples. For the younger (<1.91 Ga) monazite grains, we found three main age peaks. The peak at 1.89–1.86 Ga fits well with the high-grade metamorphic event at 1.89–1.88 Ga observed elsewhere in southern and central Finland. The 1.87–1.86 Ga interval dates a near-isothermal decompression stage. The age peak at 1.83–1.82 Ga records the age of younger high-grade metamorphism in the study area. The age peak at 1.80–1.77 Ga is interpreted to represent isotopic resetting due to fluid-induced alteration during a shield-wide exhumation stage, when waning magmatism, leucosome crystallisation and a change towards brittle-ductile deformation led to localised fluid flow before cratonisation. The dates between the age peaks could be explained in part by mixed isotopic ages in patchy grains without clear growth zones.

Orogeny

Pelite

10.1016/j.lithos.2022.106654

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Citations (7)

Refinement of geothermobarometry for cordierite granulites

Journal of Earth System Science (1993)

S. Bhattacharya

Cordierite

Geothermobarometry

10.1007/bf02871952

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Citations (7)

Pressure-Temperature-Time Paths of Granulite Metamorphism and Uplift, Zambesi Belt, N.E. Zimbabwe

Springer eBooks (1990)

Peter J. Treloar John Carney M. J. Crow Jane Evans Corey Barton

Orogeny

10.1007/978-94-009-2055-2_12

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Citations (10)

Evidence of extension in the granulite facies lower crust of Calabria during the Hercynian orogeny.

Vincenzo Festa Annamaria Fornelli A. Paglionico A. Pascazio G. Piccarreta

Orogeny

Source

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Oblique Terrane Assembly in the Late Paleoproterozoic during the Labradorian-Gothian Orogeny in Southern Scandinavia

The Journal of Geology (1996)

I. C. Starmer

The earliest deformation of the curved Kongsberg-Bamble Belt in Norway produced a northwestward-directed tectonic wedge, suggesting oblique NW-SE collision during the Labradorian-Gothian Orogeny in southern Scandinavia. Oblique terrane assembly, with the outboard (western) units colliding last, explains the trapping of the Ostfold-Marstrand island arc (formed at c. 1760 Ma) between younger (1700-1600 Ma) terranes, the apparent lack of Svecofennian crust west of the Trans-Scandinavian Igneous Belt, and the apparent lack of Labradorian-Gothian age crust in the British Isles. The Labradorian of North America may have also resulted from oblique terrane assembly.

Orogeny

10.1086/629829

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Citations (14)

Mineral reactions and geothermobarometry in a suite of granulite facies rocks from Paderu, Eastern Ghats granulite belt: A reappraisal of the P-T trajectory

Journal of Earth System Science (1997)

Supratim Pal Sankar Bose

Geothermobarometry

Pyroxene

10.1007/bf02839282

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Citations (20)