Ca-Al rich phases in the allende meteorite

“…Marvin et_ al^. [25] and Clarke ej^ aT. [24] have noted the similarity between the composition and mineralogy of the aggregates and the early condensates in a cooling nebula.…”

Section: Properties Of the Early Condensatementioning

confidence: 96%

“…chondrites, for example Kaba [28], Sharps [29], Bali £4], Vigarano [30], Lance [31], Felix [32], Murchison [33], Leoville [34], , Grosneja, Orans, and Warrentun [25 ].…”

Section: Properties Of the Early Condensatementioning

confidence: 99%

The composition and origin of the moon

Anderson

1973

“…1, bulk compositions of type C inclusions are projected from SPINEL (MgAI204; SP) and PEROVSKITE (CaTiO3; PV) onto the plane GEHLENITE (GE)-ANORTHITE (CaA12Si2Os; AN)-FOR-STERITE (Mg2SiO4; FO). Also plotted is the glass composition from a glass-spinel inclusion described by Marvin et al [26]. This inclusion is discussed later.…”

Section: Determination Of Original Condensate Mineralogymentioning

confidence: 99%

“…Marvin et al [26] gave glass analyses for several glass-spinel inclusions from Allende. The composition of one of these, glass G, is shown in Fig.…”

Section: Relationships Of Type C's To Other Caismentioning

confidence: 99%

The origin of type C inclusions from carbonaceous chondrites

Beckett

Grossman

1988

Type C inclusions are plagioclase-rich, Ca-, Al-rich inclusions found in carbonaceous chondrites. They formed as solid condensates which were later melted in an event that destroyed the original condensate grains. Neither the melting event nor secondary alteration had a significant effect on bulk composition. Two stages in the condensation history can be discerned on the basis of major element bulk compositions. As in type A inclusions, the condensate phase assemblage originally consisted of melilite + spinel + perovskite + hibonite. Type C's were, however, significantly enriched in spinel relative to unaltered portions of most type A's. In contrast to type A's, condensate grains of spinel and melilite in type C's reacted partially with a coexisting gas to produce anorthite + diopside. One-half to two-thirds of the silica now in type C inclusions was introduced by this process. The reactions involving melilite and spinel that are predicted by equilibrium condensation calculations for a cooling gas of solar composition did not occur, probably due to kinetic constraints. Type C's may be related to Al-rich chondrules in ordinary chondrites by the addition of olivine and albite. Bulk compositions of Al-rich chondrules in enstatite chondrites are consistent with the addition of orthopyroxene and albite to type C inclusions. Thus, types A and C inclusions and Al-rich chondrules could represent sequences of condensates removed from interaction with the primitive solar nebula at progressively lower temperatures. If Al-rich chondrules represent the high-temperature component in chondritic material, then type C inclusions rather than the more common subgroups of CAIs could be the true parents of chondrites.

“…The coarse-grained, Ca-Al-rich inclusions in the Allende meteorite are thought to be the earliest, highest-temperature condensates from the cooling vapor of the solar nebula [4,5], representing ~5 wt.% of the total condensable matter [6]. These inclusions are several millimeters to 2 cm in size, subspherical to angular in shape and white in color, sometimes with gray patches.…”

Section: Origin Of Allende Inclusionsmentioning

confidence: 99%

The case for an unfractionated244Pu/238U ratio in high-temperature condensates

Ganapathy

Grossman

1976

The coarse-g~ained, Ca-rich inclusions in the AUende meteorite are the highest-temperature condensates from the cooling solar nebula and, as such, the oldest solid objects in the solar system. All refractory elements with condensalion points above the accretion temperature of the inclusions whose eoneentrarions in them have been measured are seen to be present in the inclusions in unfractionated proportion to one another relative to C1 ehondrites when data ate averaged for a large number of inclusions. Observational data for U and theoretical data for both U and Pu'suggest that these elements exhibited refractory behavior in the solar nebula. An experiment is proposed in which fissiogenic Xe and U contents are measured in a suite of these inclusions to obtain the 244pu/238U ratio of the solar system at the time of initial condensation with an uncertainty of + 15%.