Metamorphic P–T–t–d evolution of the Mesoproterozoic Pur‐Banera supracrustal belt, Aravalli Craton, northwestern India: Insights from phase equilibria modelling and zircon–monazite geochronology of metapelites

Abstract

The Pur-Banera belt of metasedimentary rocks, in the Bhilwara region of the Aravalli Craton, northwestern India, constitutes a Mesoproterozoic rift-related supracrustal sequence. The Pur-Banera belt, while containing psammitic, calcareous, and ferruginous metasediments, is dominated by garnet-staurolite-kyanite-bearing metapelites. Here we integrate data on outcrop-and microscopic-scale deformation structures with pseudosection modelling and zircon-monazite geochronology to decipher the P-T-t-d evolution of these metapelites. The metapelites record three distinct deformation events. The first two (D 1 -D 2 ) produced a composite S 1 // S 2 foliation, and a younger event of dextral shearing (D 3 ) produced crenulations superimposed on the foliation. Textural and compositional data indicate two stages of growth of garnet, whose core compositions were significantly altered during peak metamorphism. The textures combined with pseudosection modelling and conventional thermobarometry reveal that the garnet cores continued to grow up to staurolite-grade prograde metamorphism, followed by a second stage of garnet growth (syn-D 2 ; 7.3-7.9 kbar and 665-690°C) during kyanite-grade peak metamorphism. Fibrolite grew in the matrix during post-peak readjustments due to uplift and decompression, whereas fluid-induced retrograde metamorphism (480-540°C) resulted in the formation of euhedral staurolite prisms and narrow rims around garnet porphyroblasts. Detrital zircons of magmatic origin yield a weighted mean 207 Pb/ 206 Pb age of 1,827 ± 7 Ma (95% confidence) indicating a Palaeoproterozoic igneous source rock for the sediments, consistent with a Mesoproterozoic (1.6-1.3 Ga) age of deposition as inferred in previous work on the Pur-Banera quartzofeldspathic gneisses. Monazite U-Th-(total) Pb ages indicate the timing of commencement of prograde metamorphism at c. 1.3 Ga, peak metamorphism at c. 1.2-1.1 Ga, and fluid-induced retrograde metamorphism at c. 0.85-0.75 Ga. Our combined results indicate that the metapelites experienced two deformation events (D 1 and D 2 ) during the closure of the Pur-Banera basin and the consequent burial of the sediments to lower crustal depths. These were followed by post-collisional uplift wileyonlinelibrary.com/journal/jmg

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)

“…Conventional thermobarometry is a widely applied technique to constrain the P–T conditions of an equilibrium mineral assemblage using exchange and net transfer reactions. However, many studies have shown that the conventional thermobarometry results obtained for the prograde and peak metamorphic episodes are usually underestimated due to elemental diffusion during the prolonged high‐grade peak metamorphism (Caddick et al, 2010; La Roche et al, 2015) and retrograde cooling process (D'Souza et al, 2021; Spear & Florence, 1992), respectively. Therefore, textural relationships should be carefully considered while pairing different minerals for estimating equilibrium P–T conditions of different metamorphic episodes.…”

Rift‐related multistage evolution of the Mangalwar Complex, Aravalli Craton (NW India): Evidence from elemental and Sr–Nd isotopic features of Proterozoic amphibolites

“…These authors also reported that the age range between 1,725–1,621 Ma represents granulite metamorphism and exhumation and related them to the Delhi basin opening. D'Souza et al (2019); D'Souza, Prabhakar, Sheth, and Xu (2021) have studied the depositional time of the Pur‐Banera supracrustals (basin within the Mangalwar Complex) using U–Pb zircon and U–Th–Pb monazite technique on paragneisses and structural data and found to vary between 1.6 and 1.3 Ga. Their model of Pur‐Banera rift basin evolution also supports this assertion that the sedimentation processes took place during 1.6–1.3 Ga which is synchronous with the Delhi basin (1.7–1.0 Ga), whilst 1.3 Ga of the Pur‐Banera marks the closure event (compressional event) and deformation. So, the G3 type amphibolites could be associated with the depositional age of the sediments of the Pur‐Banera basin (pull‐apart basin), that is, 1.6–1.3 Ga, and were emplaced largely around 1.6 Ga during the rifting stage.…”

“Geochronology and geochemistry of pelitic granulite from the South Delhi Terrane of the Aravalli Delhi Mobile Belt, NW India: implications for petrogenesis and geodynamic model”

“…Additionally, due to deformations that occurred millions of years ago in the Aravalli-Delhi mountain ranges, the Sandmata rocks that are found along the terrane boundary have been bent (Naha & Halyburton, 1974; Sen, 1980; Srivastava, 2001; Bhowmik et al 2010; Singh et al 2010, 2020; Roy et al 2012, 2016; Tiwari & Biswal, 2019; Biswal et al 2022; Tiwari et al 2022). Therefore, the older ages of the Mangalwar and Sandmata complexes are reset to younger ages, particularly in the northern part of the Banas shear zone (Bhowmik & Dasgupta, 2012; Ahmad & Mondal, 2016; Kumar et al 2019; D’Souza et al 2021). It is generally agreed that the collision between the Bundelkhand craton and the Marwar craton was the primary driving force behind the orogeny that resulted in the development of the ADMB (Bhowmik et al 2010; Singh et al 2010, 2020; Tiwari & Biswal, 2019; Biswal et al 2022; Tiwari et al 2022).…”