Non-plume flood basalt volcanism before the emplacement of the Afar
mantle plume head
Abstract
The Ethiopia-Yemen flood basalts are spatially zoned with progressively
lower TiO2 lavas from near the Afar depression toward the margins. The
timing and rate of emplacement of low TiO2 (LT) lavas are poorly known
compared with the ultra-high TiO2 (HT2) lavas. We measured two
high-precision 40Ar/39Ar ages of 29.63 ± 0.14 and 30.02 ± 0.22 Ma (2σ)
from basalts of the 2-km-thick LT lava sequence at the Afar plume head
margin. Using our eruption age model constructed from our and previous
40Ar/39Ar ages with the paleomagnetic directions, we estimate that the
LT lava eruption continued over Chrons C12r-C12n-C11r. The eruption of
the plume head margin started earlier than the plume head axis
emplacement in C12n. Also, the eruption rate was low at the margin, high
at the axis. We estimate that the LT lavas are induced by the
edge-driven convection, the result of a plume-lithosphere interaction,
not a plume head.