Formation of the
Kerguelen Large Igneous Province,
Gondwana Breakup, Lost Continents
and Growth of the Indian Ocean
Professor Fred Frey
MIT
Large igneous provinces (LIPs) form when copious amounts of
mantle-derived magma are injected into localized regions of Earth's
crust. They have an intense regional
effect because they cover large
areas (up to 1 million km2) with magma. In addition, LIPs
may have widely distributed effects because of climate changes
resulting from injection of volatiles and dust into the stratosphere.
Although the Kerguelen Plateau, a
classic LIP, is now submarine, it was
above sea level in the eastern Indian Ocean during Cretaceous time. The
Ocean Drilling Program sampled the igneous basement of this LIP at 11
sites. Rock cores show that the uppermost basement is dominantly
tholeiitic basalt similar to that forming islands but unlike mid-ocean
ridge basalt; hence the plateau appears to be related to the Kerguelen
plume which created the Cenozoic Kerguelen Islands. However, the LIP
formed after breakup of eastern Gondwana, and over tens of million of
years. This prolonged formation time is inconsistent with a melting
pulse associated with a large plume head. At several locations the
tholeiitic basalt was contaminated by continental crust; at one site,
ancient continental fragments occur in a conglomerate intercalated with
basalt flows. Evidently pieces of eastern Gondwana were isolated in the
nascent Indian Ocean during continental breakup. At several sites
volcanism ended with explosive eruptions of trachyte and rhyolite; such
eruptions can inject materials directly into the stratosphere. Dr. Frey
sailed as Co-Chief Scientist on ODP Leg 183, and as a shipboard
scientist on Legs 121 and 197.