Sayh al Uhaymir 290 (SaU 290) was initially
discovered in the Al Wusta region in Oman on February 13th, 2004
with subsequent pieces found later that year on November 6th.
The meteorite was fragmented over an area of about 10m and 64
dark brown fragments were recovered with a Total Known Weight of
1.796kg. SaU 290 was intially thought to be an anomalous type-3
Enstatite Chondrite but oxygen isotopes ruled this out and it
has since been classified as an exceedingly rare
Carbonaceous Chondrite (CH3).
While this meteorite is relatively visually
unremarkable, it is actually a very important specimen. It is
primarily composed of small
chondrules (<20μm) of various textural types with about
15% fine grained
metal. A few small "matrix lumps" and rare refractory inclusions
are also present. A number of studies have been completed in
regards to the very high solar gas concentrations in SaU 290
which have actually been determined to be the highest of any
member of the CH3 class.
The refractory inclusions or CAI's, have
revealed a lot about the CH chondrite parent-body and early solar system.
Zhang and Hsu (2009) have stated that that the highly refractory
nature of CAIs in CH chondrites reflects a distinct population
of refractory inclusions. They go on further to say:
"The different population of refractory inclusions
was probably due to various formation regions or
formation episodes with different physical-chemical
conditions. If refractory inclusions were formed in
different nebular regions, the formation regions could
have different dust/gas ratios, cooling rates, and peck
heating temperatures. For instance, the more refractory
inclusions are probably related to higher peak heating
temperatures, which require that their formation region
is closer to the center of the protoplanetary disk. The
refractory nature of refractory inclusions in SaU 290,
compared to those in other groups of chondrites,
requires higher peak heating temperatures. If refractory
inclusions were formed in different nebular regions, the
formation region of refractory inclusions in SaU 290 is
probably closer to the center of the protoplanetary disk
than those of other groups of chondrites. If CAIs were
formed in a common region of the solar nebula, those in
SaU 290 were probably formed earlier than those of other
groups of chondrites."
The study also makes mention that while the
iron grains have been weathered, refractory inclusions (CAI's &
Olivine Aggregates)) show no evidence of
terrestrial weathering. This is important because it suggests
that refractory inclusions retain their chemical and
mineralogical features in nebular and/or parent body settings.
They also mention:
"Both regular and irregular refractory inclusions in
SaU 290 have sharp interfaces with surrounding objects. This
indicates that thermal metamorphism on its parent body did not
severely affect refractory inclusions. In addition, no
low-temperature alteration minerals were observed in refractory
inclusions, indicating low-temperature secondary alteration
processes have minimal effects on the refractory inclusions.
Therefore, refractory inclusions in SaU 290 are pristine and
mainly record high-temperature processes in the early solar
The 2.38g Partslice below is part of the Meteorites Australia Collection
Refractory inclusions and aluminum-rich chondrules in Sayh al
290 CH chondrite: Petrography and mineralogy.