Geochemical constraints on the petrogenesis of Patharkhola gneiss, Kumaun Lesser Himalaya, India

A new set of geochemical and mineralogical data of gneisses from the Patharkhola region of the Dudhatoli syncline, Kumaun Lesser Himalaya is discussed to elucidate their petrogenesis and tectonic environment of India. These Patharkhola gneisses exhibit foliated texture and are primarily composed of K-feldspar (KAlSi3O8) and plagioclase (NaAlSi3 O8) with perthite (K,NaAlSi3O8), biotite (K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂), muscovite (KAl2(AlSi3O10)(OH)2), and tourmaline (Na(Mg,Fe,Mn,Li,Al)3 Al6 [Si6O18](BO3)3(O,OH,F)4) as accessory minerals. They exhibit SiO2 > 70 % with average K2O/Na2O = 1.31 % while Nb, V, Zr, La, and Eu show strong negative anomalies normalized to Post Archean Australian Shale (PAAS). The chondrite-normalized rare earth element (REE) concentrations of light rare earth elements (LREE) to heavy rare earth elements (HREE) exhibit varying ratios, ranging from 4.8 to 10.6 for (La/Yb)N. Additionally, there is a significant europium (Eu) anomaly, with Eu/Eu* ratios between 0.3 and 0.6. The authors have done Post Archean Australian Shale (PAAS) normalization as well as chondrite normalization separately and dealt with the variation in both normalization. The ratios of Al2O3/TiO2 (82–112), Th/Sc (1.3–9.4), and Eu/Eu* (0.3–0.6) suggest that the precursor materials of these gneisses were felsic in nature. Based on the petrological and geochemical characteristics of the studied gneisses, it is proposed that the Patharkhola gneisses formed in an active continental margin, where the sediments originated from felsic sources.