ion microprobe - This is an instrument for trace-element and isotopic analysis that focusses ions on a sample to dislodge material which is then analyzed with a mass spectrometer.
fractional condensation - This refers to the removal of solids from a system that is undergoing condensation. It is analogous to the igneous process of fractional crystallization, in which crystals are separated from magma. Fractional condensation is strongly implicated for the formation of a particular kind (Group II) of CAI. If fractional condensation occurs, complete equilibrium cannot be maintained because solids are no longer in chemical communication with the gas.
fractional vaporization - This refers to the removal of melts from a system that is undergoing vaporization. It is opposite to fractional condensation in the sense that temperatures are increasing. If fractional vaporization occurs, complete equilibrium cannot be maintained because liquids are no longer in chemical communication with the gas.
coarse grained CAI - Coarse grained inclusions are those types of inclusions (Type A, B, C) that are sufficiently coarse-grained that they can be conveniently studied with a standard petrographic microscope, as opposed to needing an electron microscope (e.g., SEM).
fine-grained CAI - This type of inclusion includes spinel-clinopyroxene and other types of inclusions which are sufficiently fine-grained that they cannot be conveniently studied with a standard petrographic microscope, and which are best analyzed instead with an electron microscope.
Eu and Yb anomalies - These are either excesses (positive anomalies) or deficits (negative anomalies) in the CI-normalized abundances of these elements when compared with other rare-earth-elements (see Table 1).
Group I, II, III, V, VI and ultrarefractory inclusions - These are CAIs which have been classified according to their rare-earth-element (REE) patterns into various groups (Fig. 10.3.4). (Group IV patterns are associated with olivine-rich aggregates that are not considered to be CAIs.) Table 1 summarizes the characteristics of these groups. These groups can occur in both coarse and fine-grained inclusions of various types, although Group II patterns seem most common with fine-grained inclusions.
Table 1.
| Group designation | REE characteristics |
| I | ~20 x CI abundances except for positive Eu anomaly. |
| II | ~20 x CI abundances for light rare earth elements (La-Sm), with fractionated and mainly depleted abundances of heavy rare earth elements. |
| III | ~20 x CI abundances except for negative Eu and Yb anomalies. |
| V | ~20 x CI abundances. |
| VI | ~20 x CI abundances except for positive Eu and Yb anomalies. |
| ultrarefractory | fractionated pattern with enrichments in some heavy rare earth elements (Gd-Tm, Lu), and depletions in some elements (especially Eu & Yb). Considered to be a signature of the highest-temperature condensate. |
Type A, B, C, and forsterite-bearing inclusions
- These are CAIs that have been classified according to their primary mineral
proportions (Fig. 10.3.6). Most CAIs contain spinel.
Type A inclusions are rich in melilite, and come in two textural varieties
("compact" and "fluffy"). Type B inclusions contain a Ti-Al-rich
diopsidic clinopyroxene (known as fassaite) and anorthite in addition to
melilite, and also come in two textural varieties (compact "B1" and "B2").
Type C inclusions are rich in anorthite. Forsterite-bearing inclusions
contain Mg-olivine and are also known as "poikilitic olivine inclusions"
(POIs).
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Condensation sequence - The condensation
diagram from the last (chondrule) glossary
is reproduced below.
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