[meteorite-list] NWA 4801 - New 'Time Marker' Standard

[Greg Hupe]

Good Afternoon All,

In the recent past there has been discussion of whether meteorites from the 
hot deserts of Northwest Africa are superior or inferior to those from 
Antarctica or anywhere else, including witnessed falls.  NWA 4801 is a very 
fresh angrite from Northwest Africa that has been adopted by many of the 
world's scientists as the new 'Benchmark Standard' for age dating (Time 
Marker) of certain 'older' meteorites.

In the words of one of the top meteorite researchers, "This new "benchmark" 
is relevant only for very old specimens like angrites, brachinites and CAI 
that formed when Mn-53 was still alive to decay to Cr-53.  Basically, NWA 
4801 has replaced LEW 86010 as the point of calibration (or anchor) for 
Mn-Cr ages by correlation with precise ages determined on the same specimens 
with lead isotopes."

This once again illustrates that meteorites from the hot deserts of 
Northwest Africa are an important part of modern meteoritics! Here is a link 
to an abstract with NWA 4801 used as the new 'standard':

http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1381.pdf

Best regards,
Greg

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