Lithospheric Control of Melt Generation Beneath the Rungwe Volcanic
Province and the Malawi Rift, East Africa
Abstract
The EarthCube BALTO (Brokered Alignment of Long-Tail Observations)
project is aimed at developing new cyberinfrastructures that enables
brokered access to diverse geoscience datasets. Towards achieving this
BALTO objective, we developed a plug-in for the community extensible NSF
open-source code ASPECT (Advanced Solver for Problems in Earth’s
Convection) that permits ASPECT to read data from the BALTO server
(OPeNDAP’s Hyrax open-source data server) over the web. We present a
use-case of the BALTO-ASPECT client, which accesses lithospheric
structures from the BALTO server to constrain a 3-D lithospheric
modulated convection (LMC) modeling and melt generation beneath the
Rungwe Volcanic Province (RVP) and the Malawi Rift. We test the
hypothesis that at least part of the melt feeding the RVP is generated
from LMC. In the model, we assume a rigid lithosphere, while for the
asthenosphere we use non-Newtonian, temperature-, pressure- and
porosity-dependent creep laws of peridotite. We find that a significant
percentage of decompression melt from LMC occurs at a maximum depth of
~200 km beneath the axis of the Malawi Rift, consistent
with the location and maximum depth of imaged low velocity zones. At
shallower depths (~100 km), the melting region is
focused beneath the RVP where there is rapid (~3 cm/yr)
upwelling. Our results suggest that asthenospheric upwelling due to LMC
is the main source of melt beneath the RVP and might also entrain the
plume head materials with reported high 3He/4He values. We, therefore,
propose that part of the melt beneath the northern Malawi Rift feeding
the RVP can be generated by LMC without necessitating plumes impinging
the base of the lithosphere at present. This use-case demonstrates the
capability of the BALTO-ASPECT client to accelerate research by
brokering input data from the BALTO server for modeling LMC and melt
generation.