Origin of multilayer corona textures in mafic granulites from the Sandmata Complex, Aravalli Craton (northwestern India): petrological characteristics and tectonic implications

Ghosh, Suranjan; Prabhakar, N.; D’Souza, Joseph

doi:10.1007/s00410-021-01782-9

Cited by 10 publications

(17 citation statements)

References 68 publications

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“…However, due to several limitations in Fe–Mg exchange thermometry, the calculated temperature conditions may not represent the actual peak metamorphic conditions. This assertion is further supported by the P–T estimates of Buick et al (2010) and Ghosh et al (2021) from the Sandmata granulites. Buick et al (2010) calculated Ti‐in‐zircon temperatures (790–870°C) from pelitic granulites, whereas Ghosh et al (2021) retrieved peak metamorphic conditions (7.6–8.2 kbar and 970–1020°C) for a mafic granulite using phase equilibrium modelling.…”

Section: Geological Setting and Sample Descriptionsupporting

confidence: 60%

“…This assertion is further supported by the P–T estimates of Buick et al (2010) and Ghosh et al (2021) from the Sandmata granulites. Buick et al (2010) calculated Ti‐in‐zircon temperatures (790–870°C) from pelitic granulites, whereas Ghosh et al (2021) retrieved peak metamorphic conditions (7.6–8.2 kbar and 970–1020°C) for a mafic granulite using phase equilibrium modelling. Thus, the previous studies are inconclusive about the peak metamorphic conditions in the Sandmata Complex.…”

Section: Geological Setting and Sample Descriptionsupporting

confidence: 60%

“…This complex is geologically well suited for this study because of lithological heterogeneity and variation in the grade of metamorphism. Further, the application of trace element thermometers is useful for understanding the variations in thermal conditions across the Sandmata Complex, where the P–T estimates are limited to the western parts of the complex (e.g., Bhowmik & Dasgupta, 2012; Buick et al, 2010; Dasgupta et al, 1997; Ghosh et al, 2021). Herein, we present the petrography and mineral chemistry of four representative samples, including garnet–biotite gneiss (BSG 11), migmatite gneiss (BSG 22), mafic granulite (SND 2) and Anjana granite (SND 3).…”

Section: Resultsmentioning

confidence: 99%

“…Mafic granulite (SND 2) sample was collected from the west‐central part of the study area, north‐east of Madariya village (Figure 1b). This section provides a brief description of petrography and mineral chemistry for the sample SND 2 (Figure 5c,d); more details on tectonic implications are given in Ghosh et al (2021). The sample SND 2 comprises cumulus orthopyroxene (with exsolved clinopyroxene), plagioclase (with exsolved K‐feldspar), ilmenite and quartz with accessory apatite and zircon.…”

Section: Resultsmentioning

confidence: 99%

“…The mafic granulite (SND 2) occurs as melanocratic lensoidal bodies within megacrystic granite and comprises alternate orthopyroxene‐rich (Opx > Amp > Bt > Ilm) and plagioclase‐rich (Pl > Qz > Kfs) layers. This granulite sample shows multilayer corona textures along the orthopyroxene and plagioclase interface zones (Ghosh et al, 2021). The well‐foliated Anjana granite (SND 3) was collected from the westernmost part of the study area (i.e., west of Madariya village; Figures 1b and 2d).…”

Section: Geological Setting and Sample Descriptionmentioning

confidence: 99%

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Ti‐in‐zircon and Ti‐in‐quartz thermometry using electron probe microanalysis: A promising approach in retrieving thermal conditions of granulite facies metamorphism and felsic magmatism in the Sandmata Complex, Aravalli Craton (NW India)

2023

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The titanium (Ti) concentrations in zircon and quartz and corresponding thermometers have been regarded as powerful monitors that constrain petrogenetically meaningful temperature conditions of crystallization and metamorphism. The precise measurement of trace elements by electron probe microanalyzer (EPMA) is quite challenging as their x‐ray intensities are only slightly higher than the Bremsstrahlung background, leading to significant errors while quantifying the elemental abundances (e.g., Ti‐in‐zircon). We present EPMA‐based protocols for analysing Ti concentrations in zircon and quartz by considering recent analytical and instrumental improvements. High counting times at peak and background positions, simultaneous acquisition of Ti in multiple (three) spectrometers and data processing using the non‐central chi2 test for risk determination in sub‐counting method were employed in Ti‐in‐zircon and Ti‐in‐quartz protocols. Applying these protocols to the Mongolian garnet, San Carlos olivine and NIST 610 glass standards yielded Ti concentrations of 0.60 ± 0.02 wt%, 18 ± 3 ppm and 437 ± 26 ppm (in ±2σ), respectively. The Ti concentrations obtained from these standards are consistent with those published based on high‐precision analytical methods. We use the existing Ti‐in‐zircon and Ti‐in‐quartz thermometers to understand the thermal evolution of various lithologies in the Sandmata Complex, Aravalli Craton (north‐western India). The investigated samples include garnet–biotite gneiss, migmatite gneiss, mafic granulite and Anjana granite. The Ti‐in‐zircon temperatures calculated from the patchy‐zoned zircon cores yield HT–UHT conditions (892–959°C) for garnetiferous granite gneiss, migmatite gneiss and mafic granulite, whereas the zircon overgrowths yield temperatures of 725–871°C. The homogeneous zircon cores from Anjana granite yield temperatures (914–984°C) comparable to zirconium saturation conditions (920–960°C), indicating zircon crystallization from “hot” granitic melt. The oscillatory overgrowths on the zircon core obtain variable temperature conditions for inner overgrowth (811–877°C) and outer overgrowth (714–782°C), suggesting the episodic growth of zircon grains from different magma pulses. Additionally, the application of pressure‐dependent Ti‐in‐quartz thermometry yields quartz recrystallization conditions for garnet–biotite gneiss (430–556°C), migmatite gneiss (423–593°C), mafic granulite (430–679°C) and Anjana Granite (444–533°C). The combination of Ti‐in‐zircon thermometry, Ti‐in‐quartz and conventional thermobarometry demonstrates cooling histories for various high‐grade metamorphic and magmatic rocks in the Sandmata Complex. Based on this study, we emphasize that trace element thermometers can decipher high‐temperature metamorphism, which is otherwise erased in conventional thermometers due to diffusional readjustments during long‐lasting near‐peak and post‐peak metamorphism.

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