{'fraction_non_alphanumeric': 0.046235138705416116, 'fraction_numerical': 0.03830911492734478, 'mean_word_length': 4.652985074626866, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Composition of the Archaean Mantle and Continental Crust in the Western Dharwar Craton, India

The composition of the primordial mantle has a primary influence on the amount and composition of Earth’s early continental crust. Studying the processes associated with ancient crust formation is complicated due to the limited exposure of Hadean-Archaean (>3.2 Ga) rocks. The western Dharwar Craton, India, (dominantly ~3.4 Ga) is one of the few well-accessible Paleoarchaean cratons that host both high temperature and pressure (deep) melts like komatiites and high to medium pressure (shallow) melts like TTGs. Detrital zircons yield a maximum 207 Pb/ 206 Pb age of ~3.6 Ga which defines the oldest crustal components of the craton (Guitreau et al., 2017). Based on trace element abundances ( 147 Sm/ 144 Nd ~0.16; 176 Lu/ 177 Hf ~0.02) and Sr isotopes (Ravindran et al., 2020), this crust was dominantly mafic. Hafnium and Nd isotopes of TTGs and greenstone mafic rocks of the western Dharwar Craton are well-correlated and support a mildly depleted mantle as their main source. In contrast, ultramafic rocks (komatiites, komatiitic basalts, cumulates) show a very strong depletion and ‘ decoupled ’ Hf-Nd isotope systematics. The initial ɛ Hf of these ultramafic rocks range from +3 to +20. Such extreme initial isotope ratios have also been observed in ultramafic rocks of other Paleoarchaean cratons (e.g. Hoffmann & Wilson, 2017). The whole rock Lu-Hf age of 3182±170 Ma agrees with the U-Pb zircon age (3228±22