Ca. 2.85 Ga Magmatism in the Central Dharwar Block, India: Petrogenesis and Geological Implications
Yuhua HU , Yan ZHAO , Chengli ZHANG , Mingguo ZHAI , P.M. GEORGE , Wenhao AO , Longlong GOU , Junsheng LU
Acta Geologica Sinica (English Edition) ›› 2025, Vol. 99 ›› Issue (6) : 1657 -1672.
The Dharwar Craton (DC) in India consists of three distinct Archean blocks. Previous research suggests that the Central Dharwar Block (CDB) experienced a geological history (3.3–2.5 Ga) comparable to the Western Dharwar Craton (WDC). However, 3.0–2.7 Ga geological records are missed in the CDB. This study identified the 2.85 Ga gabbroic xenoliths within the Closepet batholith in the CDB. The ∼2.85 Ga inherited zircons and zircon Hf model ages in CDB further provide evidence for this significant magmatic event. The gabbroic xenoliths are characterized by E-MORB REE patterns and Nb, Ta, and Ti depletions, together with high radiogenic isotopic signatures, including zircon Hf (εHf(t)min = –3.2), whole-rock Nd (εNd(t) = –0.8–0.7), and Pb isotopes (κ = 4.9–7.9), indicating derivation from a slightly enriched mantle source. Additionally, they have high Nb (4.41 to 4.73 ppm), low Ti/V (23.4 to 22.5), and elevated Th/Yb (0.38 to 0.61). All these suggest a subduction-related back-arc basin setting. Coupled with widespread early Neoarchean subduction-related igneous rocks in the DC, the 2.85 Ga gabbroic magmatism signifies that the DC had transitioned into a tectonic stage dominated by lateral movement of continental blocks around 2.85 Ga, corresponding to global ∼2.85 Ga magmatic events.
gabbroic xenoliths / E-MORB / late Mesoarchean / back-arc basin / Dharwar Craton
2025 Geological Society of China
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