Geochemistry, petrogenesis, and geodynamic implications of NE–SW to ENE–WSW trending Palaeoproterozoic mafic dyke swarms from southern region of the western Dharwar Craton

Abstract

A number of NE–SW to ENE–WSW trending Palaeoproterozoic mafic dykes, intruded within the Archean basement rocks and more conspicuous in the southern parts of the western Dharwar Craton (WDC), was studied for their whole‐rock geochemistry to understand their petrogenetic and geodynamic aspects. Observed mineralogical and textural characteristics classify them either as meta‐dolerites or dolerites/olivine‐dolerites. They show basaltic to basaltic–andesitic compositions and bear sub‐alkaline tholeiitic nature. Three geochemically distinct groups of mafic dykes have been identified. Group 1 samples show flat REE patterns (LaN/LuN = ~1), whereas the other two groups have LaN/LuN = ~2–3 (Group 2; enriched LREE and flat HREE patterns) and LaN/LuN = ~4 (Group 3; inclined REE patterns). Chemistry is not straightforward to support any significant role of crustal contamination and probably reflect their source characteristics. However, their derivation from melts originated from a previously modified metasomatized lithospheric mantle due to some ancient subduction event cannot be ignored. Most likely different mantle melts were responsible for derivation of these distinct sets of mafic dykes. The Group 2 dykes are derived from a melt generated within spinel stability field by ~10% batch melting of a lithospheric mantle source, whereas the Group 3 dykes have their derivation from a melt originated within the spinel–garnet transition zone and were fed from slightly higher (~12–15%) batch melting of a similar source. The Group 1 samples were also crystallized from a melt generated at the transition zone of spinel–garnet stability field by higher degrees (~20%) of melting of a primitive mantle source. Geochemistry of the studied samples is typical of Palaeoproterozoic mafic dykes emplaced within the intracratonic setting, reported elsewhere globally as well as neighbouring cratons. Geochemistry of the studied mafic dyke samples is also compared with the mafic dykes of the eastern Dharwar Craton (EDC). Except the Group 3 samples, which have good correlation with the 1.88–1.89 Ga Hampi swarm, no other group shows similarity with the EDC mafic dykes. There is an ample possibility to have some different mafic magmatic events in the WDC, which could be different from the EDC. However, it can only be confirmed after precise age determinations.

Spatial and Temporal Distribution of Large Igneous Provinces in the Indian Shield – Highlights of Recent Investigations

“…However trace element modeling result indicates their derivation from a pyroxenite mantle source near the spinel-garnet transition zone (Liao et al, 2019). Rai et al (2019) studied the geochemistry of undated NE-SW to ENE-WSW trending Palaeoproterozoic mafic dyke swarms from the western Dharwar craton (WDC) and identified three distinct groups, which may represent three different swarms. They compared geochemistry of these WDC mafic dykes with the dated swarms of the eastern Dharwar craton (EDC).…”

“…However, several other workers have also supported genesis of these distinct Paleoproterzoic mafic dykes of the EDC emplacement in an intracratonic setting, but instead of crustal contamination favoured a role of metasomatized lithospheric mantle that had been modified during an earlier ancient subduction event (cf. Ernst 2014; Rai et al, 2019). Shellnutt et al (2018Shellnutt et al ( , 2019 presented geochemical and Nd-and Sr-isotope data on the Bastar tholeiitic dykes emplaced ca.…”

Annals of Precambrian Lithospheric Evolution and Metallogeny in the Dharwar Craton, India: Recent Paradigms and Perspectives

“…Petrogenetic and geodynamic aspects of NE-SW to ENE-WSW trending Paleoproterozoic mafic dyke swarms from southern part of WDC have been evaluated by Rai et al (2019). Their petrological and geochemical characteristics suggest a basaltic to basaltic-andesitic composition and a sub-alkaline, tholeiitic nature of precursor melts.…”

Trace and rare earth element geochemistry of clinopyroxene in mafic dykes from Western Dharwar craton, southern India

“…1). The dykes in the WDC are classified into two main categories based on their lithological and geochemical characteristics as younger dolerite dykes and older meta-dolerite dykes (Silpa and Satish-Kumar, 2018;Rai et al, 2019). The current report deals with the unmetamorphosed dolerite dykes in WDC that preserves ophitic and poikilitic textures and pristine mineralogical characteristics.…”