Preserved and modified mid-Archean crustal blocks in Dharwar craton: Seismological evidence
作者： Kajaljyoti Borah , SS Rai , Sandeep Gupta , KS Prakasam , Sudesh Kumar
DOI: 10.1016/J.PRECAMRES.2014.02.003
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摘要: Abstract We report significant lateral variability in shear wave velocity and Moho depth the Archean crust, beneath Dharwar craton, using earthquake waveform data recorded over 50 broadband seismographs. The craton is a continuously exposed continental fragment divided into west (WDC) of age 2.7–3.36 Ga, east (EDC) age, dominantly, 2.5 Ga. progressively transitions Southern Granulite Terrain (SGT) with metamorphism around 2.6 Ga. inversion modeling receiver function reveal variation depth, viz., 38–54 km WDC, 40–46 km SGT 32–38 km EDC. average (Vs) crust WDC ∼3.85 km/s as compared to ∼3.6 km/s infer highly variable thickness (16–30 km) mafic cumulate (Vs ≥ 4.0 km/s Vp ≥ 7.0 km/s) contrast thin one ( 50 km) felsic intermediate composition for EDC almost flat (down ∼38 km). These results suggest preserved crustal root middle terrain that has remained inert since then. On other hand, nearly late could be consequence regional delamination lower crust. distinct topography across terrains suggests it compositional boundary. Considering surface exposure 15–20 km based on P–T condition, granulite segment we speculate Himalaya-like (50–70 km) pointing toward plate tectonic-like scenario at ∼3.0 Ga.
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