Título
Nature of petrological, geochemical, geochronological settings and evolution of bundelkhand greenstone complexes in the Bundelkhand Craton, India
Autor
PRADIP KUMAR SINGH
Colaborador
SANJEET KUMAR VERMA (Director)
Nivel de Acceso
Acceso Abierto
Materias
Resumen o descripción
This doctoral thesis describes the geology, petrography, geochemistry, mineralogy, Sm–Nd isotope geochemistry and geochronology of mafic–ultramafic rocks, TTG (tonalite-trondhjemite-granodiorite) gneisses and high-K granitoids to decipher the nature and origin of the geodynamic changes that took place between ~3.59 and 2.50 Ga in the Central Bundelkhand Greenstone Complex (CBGC), Bundelkhand Craton (BC), India. The CBGC consists of mainly two greenstone belts: (1) the Babina greenstone belt (2) the Mauranipur greenstone belt. The petrography and mineral assemblages of these mafic–ultramafic volcanic rocks indicate that they experienced greenschist to amphibolite facies metamorphism. The mafic volcanic rocks from the Babina belt are characterized by SiO2 = 43.9–51.2 wt%, MgO = 5.4–11.0 wt% and Mg# = 44–77 [Mg# = 100 × (Mg2+/(Mg2+ + Fe2+))], whereas those from the Mauranipur belt are characterized by higher silica (51.8–55.6 wt%), MgO = 6.9–9.5 wt% and Mg# = 59–70. The ultramafic rocks of the Babina and Mauranipur belts contain SiO2 = 46.9–50.3 wt%, MgO = 20.2–21.1 wt% and Mg# = 77–82. The Babina mafic rocks show a nearly flat REE and HFSE profile [(La/Yb)CN = 0.87–1.40] with negative Nb (Nb/Nb* = 0.13–0.77) and positive Pb anomalies that could be attributed to subduction-related metasomatic agents. On the other hand, the Mauranipur mafic rocks have total REE (26.0–40.7 ppm) and display flat chondrite normalized LREE [(La/Yb)CN = 1.1–1.7; (La/Sm)CN = 1.1–2.0] with no Eu anomalies (Eu/Eu* = 0.89–1.0) and negative Nb anomalies (Nb/Nb* = 0.13–0.77), which are most probably the effects of crustal contamination. Additionally, the whole-rock isotopic (Sm–Nd) data of the mafic–ultramafic volcanic rocks from the Babina belt yield an isochron age of ~3.44 Ga, which represents the first estimation of the age of these rocks. Isotopic and geochemical characteristics of mafic–ultramafic volcanic rocks of the CBGC reveal that they were generated from a mantle source with long-term depletion. The outcrops mafic–ultramafic volcanic rocks in the Babina and Mauranipur belts are remnants of oceanic crust possibly emplaced in a subduction-related setting. LA-SF-ICP-MS zircon dating reveals that TTG magmatism mainly developed around ~3.51–3.20 Ga at regular intervals of 100 Myr although it has also found evidence of younger Neoarchean TTG magmatism at 2.71–2.67 Ga."
Fecha de publicación
julio de 2019
Tipo de publicación
Tesis de doctorado
Recurso de información
Formato
application/pdf
Repositorio Orígen
Repositorio IPICYT
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