[meteorite-list] petrological type

From: Jim Wooddell <jim.wooddell_at_meteoritecentral.com>
Date: Sat, 12 Apr 2014 12:08:26 -0700
Message-ID: <53498F2A.5030100_at_suddenlink.net>

Hi Alan and all,


Is not the description/s part of the classification so that the
researcher can better describe what is found
without having to baffle over a number or preset definition that
might...kind of...come close to what is found??

Jim

On 4/12/2014 10:01 AM, Alan Rubin wrote:
> Since Van Schmus and Wood (1967), the group/petrologic type designation has
> been entrenched (i.e., LL3.0, H4, L6), that it would be impossible to purge.
> So, calling Semarkona LL T3 just won't work -- no one would adopt it as a
> new convention. If we wanted to call Semarkona LL3.00 A2.8, that might be
>
> okay, but you would have to convince people first that a two-tier system is
> needed. It is probably best to exclude weathering and shock stage since we
>
> cannot designate every property in a classification (e.g., average olivine
>
> Fa content, cosmic-ray exposure age, oxygen-isotopic composition, chondrule
> size, etc.). A problem of course is that it may be difficult to disentangle
> thermal metamorphism from aqueous alteration, leaving a researcher baffled
>
> as to what to designate a particular rock. It would be better to leave out
> a classificatory parameter and to just guess and have the rock
> misclassified.
>
> Alan Rubin
> Institute of Geophysics and Planetary Physics
> University of California
> 3845 Slichter Hall
> 603 Charles Young Dr. E
> Los Angeles, CA 90095-1567
>
> office phone: 310-825-3202
> fax: 310-206-3051
> e-mail: aerubin at ucla.edu
> website: http://cosmochemists.igpp.ucla.edu/Rubin.html
>

-- 
Jim Wooddell
jim.wooddell at suddenlink.net
http://pages.suddenlink.net/chondrule/

Received on Sat 12 Apr 2014 03:08:26 PM PDT