Geochemistry and petrogenesis of Neoarchaean high-Mg low-Ti mafic igneous rocks in an intracratonic setting, Central India craton: Evidence for boninite magmatism

Abstract

The southern Central India craton (also known as Bastar craton) has experienced several episodes of mafic magmatism during the early Precambrian time. These mafic igneous rocks are emplaced as dyke and volcanic rocks. A set of mafic dyke swarm and few exposures of mafic volcanics, both emplaced in the Neoarchaean time, contain high-SiO 2 (>52 wt%), high-MgO (>8 wt%), and low-TiO 2 (mostly <0.5 wt%) and classified as boninites on IUGS classification scheme. Al 2 O 3 / CaO ratio classifies these high-Mg mafic igneous rocks into high-Ca and low-Ca (Type 3) boninites. High-Ca boninites show typical boninitic geochemical characteristics, whereas low-Ca variety shows geochemical characteristics similar to the high-Mg norites. Siliceous high-magnesium basalts (SHMB) show similar geochemical properties as observed for the high-Mg norites. Early Precambrian high-Mg norites are reported from the rift setting environment but, on the other hand, boninitic magmatism represents an enigmatic style of magmatism and commonly formed at convergent margin settings. Most boninites are Phanerozoic in age and rarely reported from the Archaean terrains. The established geological and tectonic setting of the Archaean Bastar craton clearly suggests existence of a stable continental rift environment in the region since the Archaean time. Thus, report of Neoarchaean boninite-like rocks in an intracratonic setting is an important feature noticed in the Archaean terrain of Indian peninsula. A highly refractory mantle source region is required to form boninitic magma. Refractory lithosphere may be result of extensive extraction of mafic magma during Mesoarchaean. The preservation of refractory reservoir beneath the Bastar craton for long period of time corroborates a high degree of crustal stability during the Meso-Neoarchaean time. Trace element modelling suggests that high-Mg mafic igneous rocks under study are product of different pulses of boninitic magma produced by ~20-25% melting of a refractory mantle source.

Sr–Nd isotope geochemistry of the early Precambrian sub-alkaline mafic igneous rocks from the southern Bastar craton, Central India

“…None of the other mafic dykes have been radiometrically dated. However, on the basis of field relationships, the ages of granitoid rocks, and stratigraphic relationship between different rock units (Ramakrishnan, 1990;Sarkar et al, 1993;Srivastava et al, 1996;Singh, 2003b, 2004;Srivastava, 2006a), their approximate emplacement ages may be inferred. It is proposed that the BD1 swarm was emplaced in the Mesoarchaean and BD2 swarm in the Paleoproterozoic (1.88 Ga).…”

Neoarchean siliceous high-Mg basalt (SHMB) from the Taishan granite–greenstone terrane, Eastern North China Craton: Petrogenesis and tectonic implications

“…They were considered to be a volcanic equivalent of Late Archean high-Mg norites that mostly occur as a part of major layered igneous complexes or as dyke swarms Hall and Hughes, 1990). SHMB is rare, even in Archean greenstone belts (Smithies et al, 2004a;Srivastava, 2006Srivastava, , 2008Srivastava et al, 2010), and is characterized by high MgO (>8%) and SiO 2 (51-55%), and low TiO 2 (<0.5%) and HFSE contents (Redman and Keays, 1985;Hall and Hughes, 1987;Cadman et al, 1997;Srivastava and Singh, 1999;Smithies, 2002;Smithies et al, 2004a,b;Gao and Zhou, 2013). Such signatures are comparable to common Phanerozoic boninites (Sun and Nesbitt, 1978;Cameron et al, 1979;Crawford et al, 1989;Falloon and Crawford, 1999).…”

“…Some workers believe that most Archean SHMBs were derived from komatiites through assimilation-fractional crystallization (AFC) processes (Barley, 1986;Arndt and Jenner, 1986;Seitz and Keays, 1997;Sensarma et al, 2002;Zhou et al, 2002), since SHMBs are commonly associated with komatiites. However, other workers propose a similar petrogenesis to Phanerozoic boninites based on the fact they are not always closely associated with komatiites, they show no geochemical evidence of significant crustal contamination, and their major element compositions are similar to boninites (Cameron et al, 1979;Redman and Keays, 1985;Hamlyn and Keays, 1986;Hatton and Sharpe, 1989;Srivastava, 2006Srivastava, , 2008. Hence, identification of SHMBs and probing their origin by using geochemical data, particularly radiogenic isotopes, has important implications for understanding their origin.…”

Métallogénie des minéralisations aurifères de la propriété Opinaca, Baie-James, Québec /

“…Les nombres en gras représentent les valeurs qui sont similaires aux dykes de type 2 et 3. ' Kerrich et al-, 1998, Shchipansky et al, 1999, Manikyamba e^ al., 2005, Smithies el ai, 2005, Srivastava, 2006. ' ' Arndt et Jenner, 1986, Sun étal., 1989r Hollings et Kerrick, 1999a, Hollings et Kerrich, 1999b.…”

“…Le contexte géodynamique des boninites archéennes est toutefois moins bien compris. Smithies et al (2004) (Srivastava, 2006). Néanmoins, les teneurs en TiO 2 et les ratios AI 2 O 3 /TiO 2 de ces boninites demeurent inférieurs à ceux de l'EMBJ (figure 7.12).…”