[meteorite-list] Publications of the Carancas event

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Mon, 8 Oct 2007 18:21:34 -0500
Message-ID: <13ac01c80a01$f874ac20$b92ee146_at_ATARIENGINE>

Hi, Katsu, List, and Petrological Fans Everywhere,

Here is a first rough cleaned-up machine translation
of one of the documents on the University of San Andres
website, the most recent petrographic analysis. Please,
any absurdities and holes in the road are likely mine.

A "smart" machine, the translator; it identified several
"usages" as Costa Rican. I wonder if oine of the authors
was from Costa Rica. If so, my respect for translating
machines just went up...

Here it is, from
http://fcpn.umsa.bo/fcpn/app?service=external/PublicationDownload&sp=232

ANALYSIS

by

Ing. Hugo Alarc?n,
Docente titular de Yacimientos Minerales Met?licos
Ing. Elena Gorinova,
Docente Titular de Mineralog?a.


The polished section of a fragment of
the meteorite to been observed by means
of light polarized in the microscope of
reflection, deciding the following minerals
or metals:

MINERAL COMPONENTS AND APPROXIMATE PERCENTAGES
TEANITE (Alloy of Fe with Ni) 25-30 %
Mackiwanita-vallerita ((Fe, Ni, Cr) 9S8* 8-10%
Un-identified phase <1 %
Rock 50 -- 60 %
* This phase can be named also as TROILITE AND/OR
cosmic periodotite, depending on its chemical
elements and nature with relation to their origin.

GENERAL DESCRIPTION OF THE SAMPLE
The sample is constituted basically by a rock
counterfoil, which includes fragments of teanite,
troilite, of millimeter dimensions, primarily and
minor dimensions to 0.5 mm secondarily, existing
also as particles spread in the rock with dimensions
much changed in the range from 50 to 200 microns and
minors to 20 microns. (Photograph 1)


TEANITE
It appears in anhedral particles with a metallic sheen
of soft color, generally it presents inclusions of
silicates and less of troilita. The Teanite seems
to be partially replaced by the rock and this way
the glazing presents irregular forms. (Photograph 2)


TROILITE
The troilite corresponds to another phase of mineral in the
sample, it is of pink color and strongly anisotr?pic, very
similar to periodotite, the library [literally, bibliography] characterizes
this one mineral as Mackiwanita-Vallerita, a isomorphic series
of sulfides of iron with Iron, Nickel, Chromium and Cobalt
but it can be named Troilite when it has a cosmic origin or
also cosmic perriodite. The TroIlite happens as inclusions in
rock and also as inclusions in the Teanite. (Photograph 3).


UN-IDENTIFIED PHASE
A un-identified third phase happens as inclusions in the
Teanite, the phase is of light gray color, is?tropic and
it might possibly be loadstone (?). (Photograph 4)


ROCK
The rock is characterized by presenting glazing of the silicates,
and it grazes very thin, the rock has been characterized as a
Peridotite in the petrographic analysis.


CONCLUSIONS
The studies so far of petrography as mineragraphy in the sample
might indicate the sample corresponds to a METEORITE OF THE TYPE
CONDRITE.

The sample is characterized by the predominance of the lithic
phase over the metallic phase (a pallasitic condrite or siderolite)
with a hetereogenous cummulative texture and the following
mineralogical composition:

Orthopiroxene 70 - 73 %
Olivine 5 - 6 %
Condrules 2 - 3 %
Fitosilicato (mafic mica?) <0.5 %
Metallic Minerals 8-10 %
Oxides and hydroxides of Fe 3 - 4 %
Glass 5 - 7 %

The orthopiroxene is probably represented by the variety bronsite,
is in the anhedral form, sometimes of fibrous aspect. It shows
perfect exfoliation, numerous breaks and texture of "printfingers".
The sizes are heterogeneous, changing between thin particles of 450
micrometers of length. (Photographs 5,6).


The olivine with anhedral forms is subrounded, sporadically stuffed
into the intergranular spaces of the orthopiroxenes and generally it
happens as heaps in the rock. Sizes of olivines are homogeneous between
70 and 100 micrometers of diameter. They are observed some light
features of alteration, probably interacting in the interstices
[literally, probably talking each other of idingstita.] (Photographs 7 and
8)


In the very limited quantity there happens the fitosilicato (mafic mica)
of a scaly aspect, the thinnest, whose exact identification needs study
under the microprobe. The presence of "chondrules" is clear with forms
that are ferrule-like [esferul?ticas ?], refilled by one thinnest substance
of the scaly aspect, fibrously distributed in radial form.
(Photographs 9 and 10).

The metallic phase happens as inclusions and diseminations in the rock.
The glass occurrence is observed, formed by impact in the meteorite.

IDENTIFICATION OF THE SAMPLE:
METEORITE -- CONDRITE OF THE TYPE
(SIDEROLITE) WITH THE LITHIC PHASE
PREDOMINANT, REPRESENTED BY
PERIDOTITE ( THE VARIETY:
ORTHOPIROXENITE OLIVINE).

--------------------------- end -----------------------------------

The pictures in the article are pretty good. One of
them, showing a big shape of the free metal phase
looks almost the same as a photo I've seen of Portales:
http://www.psrd.hawaii.edu/Sept05/PSRD-PortalesValley.pdf

There is also a big jpeg microphoto (800+Kb) at
http://fcpn.umsa.bo/fcpn/app?service=external/PublicationDownload&sp=232
Very detailed; I would call it "high resolution."

Interesting rock. Obviously, it has been shocked all
to hell and not in landing (this time), full of fractures
and fissures on every scale, "numerous breaks," with
what I think is their description of impact melt, and is
7-8% "glasses." I'm not sure what they mean by "glasses,"
but to me it says that this rock has had a rough life history,
a hot time in the old solar system...

Please, Listo-Petrologists, comment!


Sterling K. Webb
--------------------------------------------------------------------
----- Original Message -----
From: "K. Ohtsuka" <ohtsuka at jb3.so-net.ne.jp>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, October 08, 2007 9:37 AM
Subject: [meteorite-list] Publications of the Carancas event


Hello list members,

I have just reached the Carancas' publication list site in Peru:

http://fcpn.umsa.bo/fcpn/app?service=page/Planetarium_PublicationList

where some articles have already been introduced by some list members,
but the rest ones are not introduced yet and seem indeed interesting,
although
I cannot understand Spanish at all.

Does anyone translate and introduce their summary?

Best wishes,

Katsu OHTSUKA
Tokyo, JAPAN

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Received on Mon 08 Oct 2007 07:21:34 PM PDT