講演情報
[R8-08]Archean tectonic models vs. Field relations: Insights from the Dharwar Craton
*Sreehari LAKSHMANAN1 (1. Shimane University)
キーワード：
Early earth、Plate tectonics、Deformation、Failed rift、Archean tectonics
How the early Earth formed and deformed remains one of the central questions in geology. The Archean Eon represents the earliest period from which significant rock records are preserved, and our understanding of continental crust formation and evolution is largely derived from these Archean archives. Cratons — the ancient, stable cores of continents — retain critical evidence of early geodynamic processes. One such region is the Dharwar Craton in southern India, which preserves exceptionally well-exposed Archean terranes, making it an ideal natural laboratory for investigating early tectonic history.In this talk, I present how field and structural relations across the Dharwar Craton compare with and inform prevailing models of Archean tectonics. Detailed mapping and geochemical investigations in multiple schist belts reveal stratigraphic contrasts between the shallow marine successions of the Western Dharwar Craton and ocean plate stratigraphy in the east. Multiple deformation phases (D0–D5) are identified, with D2 recording fold-and-thrust structures interpreted as rift inversion in a back-arc or intra-cratonic setting. D3 sinistral shear zones reflect regional transpression.Geochemical signatures and zircon U–Pb ages constrain multiple rifting events (ca. 3300–2500 Ma), none of which led to oceanic crust formation, suggesting failed or immature rift systems.
Previous non–plate tectonic geodynamic models proposed for the evolution of Archean terranes appear inconsistent with the field relationships observed in the Dharwar Craton. In contrast, the structural and stratigraphic evidence from the region supports the feasibility of plate tectonic processes operating at least from the Meso- to Neoarchean. It is also possible that plate tectonics represents one endmember within a spectrum of Archean geodynamic regimes. However, the field data from the Dharwar Craton suggest that plate tectonics was not only viable but likely the dominant mechanism shaping crustal evolution during this time.
Previous non–plate tectonic geodynamic models proposed for the evolution of Archean terranes appear inconsistent with the field relationships observed in the Dharwar Craton. In contrast, the structural and stratigraphic evidence from the region supports the feasibility of plate tectonic processes operating at least from the Meso- to Neoarchean. It is also possible that plate tectonics represents one endmember within a spectrum of Archean geodynamic regimes. However, the field data from the Dharwar Craton suggest that plate tectonics was not only viable but likely the dominant mechanism shaping crustal evolution during this time.
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