rosborne979 wrote:farmerman wrote:Quote:I wonder if other impact sites of similar size also have recoil events on the other side of the globe
The PErmian flood basalts are being traced back to a polar opposite based upon the brekup of Pangea and the vagaries of spherical geometry, they have a number of plausible solutions that depend upon specific paths that the continents may have taken while drifting around
When did India begin its geological 'slide' into the asian subcontinent? Was that before or after the Deccan Traps?
Introduction: Flood Basalt Genesis in the
Mantle Plume Model
The mantle plume initiation model for the origin of
continental flood basalts (CFBs) (Richards et al., 1989;
Campbell and Griffiths, 1990), has been widely accepted.
The model postulates that intraplate, "hotspot" volcanism
is caused by mantle plumes - abnormally hot upwellings
that originate at the core-mantle boundary. The model is
largely based on fluid dynamical experiments, which show
that plumes should develop large "heads" by entrainment
of surrounding mantle as they rise through the mantle,
and the heads remain connected to the source region by
narrow, pipe-like "tails". A plume head produces
voluminous flood basalts, whereas a plume tail produces
hot picritic melts. The model has been widely applied to
the Deccan Traps of India, one of the largest and best
examples of CFBs in the world (see Sheth, 2005 and
references therein). The mainstream view is that (i) the
currently active RĂ©union hotspot on the African plate
represents the tail phase of a deep mantle plume, and
(ii)
the Deccan Traps originated from the head of the same
plume during late Cretaceous time when the Indian
subcontinent was drifting over it. This widely accepted
model has been questioned on various grounds, however
(Burke, 1996; Sheth, 1999a, b, 2000, 2005).
The original plume model (Richards et al., 1989;
Campbell and Griffiths, 1990), which assumed a
peridotititic mantle plume, was subsequently revised.
Cordery et al. (1997) found it impossible to produce the
observed amounts of magma in CFBs by melting
peridotitic mantle alone, and argued that mantle plumes
must contain significant amounts of eclogite to be able to
melt sufficiently. Eclogite (and pyroxenite) melt at much
lower temperatures than peridotite (e.g., Yasuda et al.,
1994, 1997; Hirschmann and Stolper, 1996). Eclogite is
essentially a bimineralic rock made up of garnet and
clinopyroxene (omphacite), and accessory minerals like
rutile, quartz, kyanite etc
http://www.mantleplumes.org/WebDocuments/ShethGR2005.pdf
http://pubs.usgs.gov/gip/dynamic/himalaya.html