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Response to Phil Bigelow's Wed, 14 Jan 2004 02:30:52 post.
Phil wrote: "as I understand it, iridium does
not aerosolize out of basalt flows. In fact,
iridium doesn't aerosolize at all. The
chlorides, fluorides, and oxides of iridium
(which have to be produced under laboratory
are all dense solids."
In 1983, Bill Zoller, Josef Parrington, and Janet
Phelan Kotra published a milestone paper titled
"Iridium enrichment in airborne particles from
Kilauea volcano: January 1983" (Science, 1983) in
which it was shown for the first time that
volcanos can release iridium into the atmosphere.
The authors stated, "The iridium enrichment
appears to be linked with the high fluorine
content of the volcanic gases, which suggest that
the iridium is released as a volatile IrF6."
Fluorine gases are found only in volcanoes fed by
a deep magma source, possibly the mantle. And,
"The calculated mass of Ir in the K/T boundary
layer is approximately 200 kilotons and would
require an eruption much larger...than
Kilauea...the Deccan flood basalts...were of
sufficient magnitude to have introduced the Ir
found in the K-T layer."
In 1989, Toutain and Meyer published a paper
titled "Iridium-bearing sublimates at a hot-spot
volcano (Piton de la Fournaise, Indian Ocean)"
(Geophysical Research Letters, 1989). They
pointed out that iridium seems to be
preferentially released by hot-spot type
volcanoes. They also noted that Piton de la
Fournaise is related to the hot-spot track which
generated the Deccan Traps, and that volcanic
gaseous iridium can be related to the KTB. And,
that if investigations of the Deccan volcanics do
not evidence significant iridium contents, it has
been calculated that Ir amounts about three times
less than iridium in lavas of Piton de la
Fournaise (0.25±0.03 ppb) are sufficient to
produce the KTB iridium anomaly (Rocchia et al.
In 1986, Olmez, Finnegan, and Zoller published a
paper titled "Iridium emissions from Kilauea
volcano" (Journal of Geophysical Research, 1986).
Following is a direct quotation from the paper:
"...Kilauea is a small volcano with insignificant
eruptions....To estimate the importance for the
mass extinction hypothesis, one must consider
eruptions of a much larger scale, such as
those...65 m.y. ago. One such eruption has been
discussed by McLean , who believes that the
Deccan Traps basalts were a likely
candidate....The Deccan probably did not occur on
a short time scale, but let us estimate the
quantity of Ir that could be emitted if the
emissions were Kilauea-like in nature. Since
approximately 10 x 10^6 km^3 of magma were
emitted by the Deccan, the Ir emissions would be
expected to be of the order of 30,000 tons, a
little less than the mass believed to be
contained in the KT boundary layer."