Mineral Chemical and Geochemical Characteristics of Archean Tonalite–Trondhjemite–Granodiorite ( <scp>TTG</scp> ) of the Bundelkhand Craton, Central Indian Shield: Rare Earth Element Constraints on Petrogenesis

ABSTRACT Tonalite–trondhjemite–granodiorite (TTG) plays an important role in the evolution of the Archean continental crust. The present study deals with textural and mineral chemical variations of TTG from the Bundelkhand Craton (BuC). TTG consists of plagioclase, K‐feldspar, quartz, biotite, epidote, Fe–Ti oxides (magnetite, Mn‐ilmenite) and accessory phases include titanite, chlorite, zircon and apatite. Their major and accessory minerals depict their igneous nature but also show transformation of some phases from primary magmatic to post magmatic low grade metamorphism. REE modelling indicates heterogeneous mafic sources/protoliths with varying amounts of garnet up to 5% at deeper sources for highly fractionated REE patterns, and shallower garnet free source regions/protoliths for highly enriched samples with less fractionated and lower LREE/HREE ratios. Thus, the studied TTG were generated over a range of depths and partial melting of enriched sources followed by feldspar fractionation at shallower depths. Ti‐in‐biotite geothermometer of TTG indicate temperatures between 490°C and 700°C for re‐equilibrated primary biotites and the estimated equilibration temperature and log f O 2 of ilmenite‐magnetite assemblage of tonalite range between 394°C and 480°C, and −25.86 to −28.79, respectively with NNO and HM buffers which may be regarded as re‐equilibration temperatures. Such variation in estimated temperatures and log f O 2 is attributed to hydrothermal alteration and low grade metamorphism. This further infers the short‐range equilibration during low‐grade metamorphism of TTG from the BuC.