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Download Crustal Diapirism - Neutrino Geoscience 2008
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Transcript
Thermal controls of crustal diapirism: implications for the earliest crust and sub-cratonic lithosphere Catherine Robin & Neutrino Geoscience Richard Bailey Sudbury, 2008 1028 1026 1024 1022 1020 1018 1016 Viscosity (Pa s) Cold: H = 5 mW/m3 qm = 20 mW/m2 Intermediate: H = 7 qm = 25 mW/m2 mW/m3 Hot: H = 10 mW/m3 qm = 40 mW/m2 Implications: • Predominantly vertical (diapiric) crustal tectonics in the Early Earth; but also: • Supplies metabasalts to the lower crust to form TTGs (tonalites, trondhjemites and granodiorites) • Leaves a depleted restite which can be harzburgitic to dunitic (for komatiitic volcanism), and which can accumulate from the top-down to form the SCLM (sub-cratonic lithospheric mantle), without calling on large plumes or strong horizontal plates (but doesn’t preclude some of these) The plausibility of vertical tectonics (and the transition to modernday tectonics) depends on the assumed heat source distribution and mode of volcanism of the early earth, and on its evolution with time. Thanks!
