Transcript Crustal Diapirism - Neutrino Geoscience 2008

Thermal controls of crustal diapirism:
implications for the earliest crust and
sub-cratonic lithosphere
Catherine Robin
&
Neutrino
Geoscience
Richard Bailey
Sudbury, 2008
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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!