Zircons from Collisional Granites, Garhwal Himalaya, NW India: U–Th–Pb Age, Geochemistry and Protolith Constraints

Abstract

In the present work, we studied zircons from the less foliated granites of the Chail Group, which form a thrust sheet of the Lesser Himalayan Sequences, Garhwal region. Compositionally, these granites are S–type, formed in a collisional tectonic setting. Zircons possess an internal structure, mineral inclusions, and geochemical characteristics typical of magmatic origin. The U–Th–Pb geochronology and geochemistry were assessed using the laser ablation multi–collector inductively coupled plasma spectrometry (LA–ICP–MS) technique. U–Th–Pb isotope dating of zircons from two different samples revealed their age, estimated from the upper intersection of the discordia, to be 1845 ± 19 Ma. Zircons from one sample contained inherited cores belonging to three age groups: Paleoarchean (3.52 Ga), Neoarchean (2.78 Ga and 2.62 Ga), and Paleoproterozoic (2.1 Ga). Zircons with ages of 3.52, 2.62, and 2.1 Ga were interpreted as magmatic based on their geochemical characteristics. The 2.78 Ga core was interpreted as metamorphic. The observed inheritance is consistent with the melting of sedimentary rocks. The inherited zircons could have originated from Aravalli and Bundelkhand Craton and Paleoproterozoic Aravalli Fold Belt rocks. This confirms that the studied granites are S–type and could have been formed in a collisional environment at 1.85 Ga on the western flank of the Columbia Supercontinent.

Palaeoproterozoic S‐type granites from Garhwal Himalaya, NW India: Geochemistry, Sm–Nd isotope systematics and tectonic implications

“…In the present study, we contribute geochemistry, and whole‐rock Sm–Nd isotopic data from Chail Group granites in the Garhwal region of Lesser Himalayan Crystalline Sequence (LHCS). We suggest that these Palaeoproterozoic granites are S‐type in origin based on geochemical, and isotopic studies (Mishra et al, 2021). This contribution could potentially shed some light on the current debate around Palaeoproterozoic Pre‐Himalayan granitoids and crustal evolution.…”

“…The Sm–Nd model ages of granites were calculated using a two‐stage T DM2 model (Champion, 2013). The crystallization time of the granites was considered to be 1,845 ± 19 Ma (Mishra et al, 2021). Sm–Nd model ages are estimated at 2,717, 2,469, 2,562 Ma and εNd ( T ) values: −5, −2, −3 for the samples HM1802, HM1804, and HM1805, respectively (Figure 7).…”

“…The granite rocks are well exposed around Toneta village (Figure 3a; Negi, Sinha, & Pandey, 1980; Mishra et al, 2019). The U–Th–Pb age of these granites is 1,845 ± 19 Ma (Mishra et al, 2021). These granitic rocks (HM1801, HM1802) are medium‐ to coarse‐grained with megacrysts of feldspar and quartz along with muscovite and biotite (Figure 3b,c).…”

“…2.1–1.8 Ga) Columbia supercontinent (Pisarevsky, Elming, Pesonen, & Li, 2014 and references therein). The zircon U–Pb ages of Lesser Himalaya (LH) granites range from about 2,200 to 1,750 Ma (Kumar, Gupta, Sensarma, & Bhutani, 2020; Mishra, Slabunov, Svetov, Kervinen, & Nesterova, 2021, and references therein), resembling the age of the Palaeoproterozoic supercontinent Columbia. In the earlier studies on the Himalaya, various geochemical, geochronological, and isotopic data have been used extensively (Kohn, Paul, & Corrie, 2010; Larson, Piercey, & Cottle, 2019; Miller, Klötzli, Frank, Thöni, & Grasemann, 2000; Parrish & Hodges, 1996).…”

Editorial for Special Issue “U-Pb Dating and Chemistry of Zircon in Metamorphic, Magmatic and Sedimentary Rocks”

“…The metasomatic effect of the continental crust on the lithosphere mantle is revealed by monitoring the chemical and isotopic evolution of magmatic rocks [8,9]. Although the partial melting of younger, thinned continental crust against thickened continental crust in the temporal evolution of subduction [10,11] can be defined using classical geochemical data, isotopic markers in zircon allow more precise and accurate interpretations. The timing of the evolution of the subduction zone can be defined using U-Pb zircon data from magmatic rocks in many contexts [12,13].…”