Zircon U-Pb/Lu-Hf and monazite chemical dating of the Tirodi biotite gneiss: implication for latest Palaeoproterozoic to Early Mesoproterozoic orogenesis in the Central Indian Tectonic Zone

Abstract

In this investigation, we reconstruct the latest Palaeoproterozoic to Early Mesoproterozoic orogenic events along the southern margin of the Central Indian Tectonic Zone (CITZ), using sensitive high resolution ion microprobe (SHRIMP) U-Pb zircon dating and Lu-Hf isotope analyses of zircon and Th-U-Pb chemical dating of monazite from samples of the Tirodi biotite gneiss (TBG) unit in the Sausar Mobile Belt (SMB), the latter constituting the southernmost litho-tectonic component of the CITZ. U-Pb zircon dating of one migmatitic gneiss sample from the type locality of the Tirodi biotite gneiss in the northern domain of the SMB has yielded an age of 16188 Ma, which is considered to be the time of magmatic crystallization of its protolith. Combined U-Pb zircon and monazite chemical dating of two granite gneiss samples from the southern domain of the SMB broadly constrain magmatic crystallization between 160323 Ma and 158417Ma and an overprinting metamorphic recrystallization event at 15727 Ma. Monazites from the granite gneiss samples also record a terminal metamorphic event at 141523 Ma. Lu-Hf isotopic analyses of zircons reveal fundamentally different source rock reservoirs for the protoliths of these magmatic rocks across the SMB. While the type TBG from the northern domain was derived from an Early Palaeoproterozoic source TDM c(Hf) from 2093 to 2523 Ma, with a mean value at 2379 Ma) of essentially juvenile material with minor crustal components (eHf(t) from 3.3 to þ3.7), the granite from the southern domain had a mature crustal source (eHf(t) from 12.5 to21.9) of Palaeoarchaean age TDM c(Hf) from 3051 to 3630 Ma, with a mean value at 3218 Ma). When integrated with metamorphic information previously obtained from the 1.6 Ga ultra-high temperature granulite facies metamorphic event in the SMB, the discrete magmatic and metamorphic events between 1.62/1.60 Ga and 1.42 Ga can be correlated with the formation of an Early Mesoproterozoicaccretionary orogen in the CITZ.