[meteorite-list] Classification for Novato (name pending approval)

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Mon, 29 Oct 2012 21:17:22 -0700 (PDT)
Message-ID: <1351570642.26599.YahooMailClassic_at_web39306.mail.mud.yahoo.com>

Greetings All,

It is my distinct pleasure to have the honor of passing along the following characterization of the "Novato" meteorite. Here is the message that I received from Dr. Alan Rubin:

I just finished analyzing the Novato "N01" stone:

It is an L6 breccia. W0 S4
olivine Fa 24.1?0.4 (n=21)
Low-Ca pyx Fs20.7?0.5 Wo1.5?0.2 (n=22)
Ca-pyx Fs8.0?0.7 Wo44.7?0.8 (n=5)
The chromite grains are somewhat richer in Al2O3 (6.4 wt.%) and MgO (3.4 wt.%) than unshocked OC chromite, but are more characteristic of shocked and shock-melted chromite grains.
Most of the metallic Fe-Ni is taenite with 77.7?5.0 wt.% Fe, 21.4?5.4 wt.% Ni and 0.51?0.18 wt.% Co (n=18). Only one kamacite grain was identified (7.2 wt.% Ni and 1.1 wt.% Co).
The Co content of this single grain is intermediate between the ranges for L (0.70-0.95 wt.% Co) and LL (1.42-37.0 wt.% Co) chondrites, but is closer to L.

Plagioclase: Ab86.0?0.6 Or7.0?0.4 (n=14) is richer in alkalis than typical OC plagioclase, and probably reflects shock melting.

Troilite is essentially pure FeS; it contains no detectable Cr, Co or Ni.

And as I said before:

Silicates have weak mosaic extinction. Plagioclase grains range from 50-200 ?m. There are lots of troilite veins going through large portions of the rock (silicate darkening). Chromite grains are fractured; many have troilite veins transecting them. There are a few chromite-plagioclase assemblages.
I found one 12x20-?m-size grain of metallic Cu.
Some of the troilite grains are polycrystalline.
There are some patches where plagioclase has been melted and mobilized. There is localized melting around some of the metal and sulfide grains. There are a few silicate shock melt veins replete with small metal and sulfide blebs. There are some chondritic clasts with far fewer veins that have moderately large, highly recrystallized barred olivine and porphyritic olivine-pyroxene chondrules that are well integrated into the matrix. These chondritic clasts are much lighter-colored in transmitted light than the matrix of the rock.

Please pass this info along to all interested parties.

End of message from Dr. Rubin.

With best regards,
Bob V.
Received on Tue 30 Oct 2012 12:17:22 AM PDT