Spatio-temporal tectonic progression in the Dharwar Craton: Insights from volcanic records of Archean greenstone belts

Abstract

Volcanic episodes serve as precursors for the formation and evolution of continental crust and directly impact the mantle compositions. Here, we present elemental, zircon U-Pb and Sm-Nd isotopic datasets of published and newly generated data on the Archean volcanic sequences from the Dharwar Craton and constrain the thermal and chemical evolution of the Archean mantle, continental growth, geodynamic evolution and craton formation. The data reveal three phases of ultramafic volcanism at 3.4–3.25 Ga, 3.2–3.05 Ga and 2.7–2.6 Ga; two major phases of mafic volcanic activity at 3.35–3.15 Ga and 2.75–2.5 Ga, and three felsic volcanic episodes at 3.4–3.2 Ga, 2.9–2.7 Ga and 2.65–2.5 Ga, which are associated with granitoid formation at ca. 3.4–3.25 Ga, 3.1–3.0 Ga, 2.7–2.6 Ga and 2.56–2.54 Ga. The εNd(t) values of +2 to +6 and εHf(t) values of −5 to ∼10 of these suites depict heterogeneous mantle reservoirs. These temporal isotopic variations are further constrained spatially through elemental ratios, which suggest the origin of ultramafic melts from deeper, primitive to highly depleted mantle reservoirs, with traces of crustal contamination.

The origin of the Paleo- to Neoarchean (3.4–2.54 Ga) volcanism in the Dharwar Craton is explained through the evolving tectonics in the early Earth, where mantle plume activity initiated ultramafic volcanism. A decrease in temperature and pressure, an increase in the degree of partial melting, and a compositional change in the komatiites are consequences of the thermal evolution of the mantle within the Paleoarchean to Neoarchean timeframe. Among the arc basalts, the first two phases that are the melt products of enriched mantle, reflect the subduction of oceanic plateau-type proto-crust. The third phase, representing enriched to depleted mantle sources, supports the existence of an array of oceanic to continental arcs. The three phases can be correlated with tectonic stages involving predominant plume-subordinate arc (Stage I), subordinate plume-predominant arc (Stage II) and prevalent arc (Stage III) volcanism, followed by the accretion of arcs and craton formation spanning the Paleo- and Neoarchean timeframe. These studies reveal that the Dharwar Craton has formed through successive stages of greenstone volcanism and plutonism in a transient tectonic environment.