RE: A biological explaination of Iridium in the KT boundary

["Bonnie Blackwell, x 3332" <bonn@qcvaxa.acc.qc.edu>]

that would make a certain sense, in that Ir and Au share many similarities
geochemically.  we can also make a good case, however, that exceedingly 
acidic conditions produced by high SO2, CO2, or whatever gas you want
to add to the dust cloud, would be enough to erode the Ir out of the 
rocks and deposit in the clays.  like Au it is a species that adsorbs
well on to surface particles.  but the biological argument is intriguing.
both may well apply.
b

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bonnie Blackwell,                               bonn@qcvaxa.acc.qc.edu
Dept of Geology,                                (718) 997-3332
Queens College, City University of New York,    fax:  997-3349
Flushing, NY 11367-1597