Provenance and weathering history of Archaean Naharmagra quartzite of Aravalli craton, NW Indian shield: Petrographic and geochemical evidence

抄録

The petrography as well as major, trace and rare earth element (REE) compositions of Mesoarchaean Naharmagra quartzite of Aravalli Craton have been investigated to determine influence of sorting and recycling, source area weathering and provenance composition. The quartzites are mineralogically mature, medium to coarse grained quartz arenite with minor medium grained arkose. Petrographic analysis revealed that the quartzites were primarily derived from granite and metamorphic basement rocks of typical cratonic interior. All samples have SiO₂/Al₂O₃ > 10 (average ∼31), which indicates high maturity consistent with petrographical results. Quartzites are depleted in many major and trace elements due to quartz dilution. Many of the samples have undergone postdepositional K metasomatism. The calculated premetasomatic CIA values (46-92) indicate highly variable degree of source weathering compatible with non-steady state weathering. CIA and PIA values in combination with petrographic evidence favour intense chemical weathering probably under warm and humid climate. Provenance modeling indicates that the quartzites can be best modeled with a mixture having 50% tonalite-trondhjemite-granodiorite, 40% granite and 10% basalt. Probably, the sedimentation of these rocks took place in a stable and young cratonic basin evolved through accretion and tectonic amalgamation of pre-existing continental arcs comprising TTG and granitic bodies.