Scandium chondrites

In Figure 3, aluminum is representative of refractory elements in general and the Al/Si ratios indicate the size of the refractory component relative to the major fraction of the meteorite. It is clear from this figure that the Al/Si ratio of Cl meteorites agrees best with the solar ratio, although the ratios in CM (Type 2 carbonaceous chondrites) and even OC (ordinary chondrites) are almost within the error bar of the solar ratio. The errors of the meteorite ratios are below 10%, in many cases below 5%. A very similar pattern as for aluminum would be obtained for other refractory elements (calcium, titanium, scandium, REEs, etc.), as ratios among refractory elements in meteorites are constant in all classes of chondritic meteorites, at least within —5-10%. The average Sun/CI meteorite ratio of 19 refractory lithophile elements (Al, Ca, Ti, V, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Lu, see Table 2) is... 

The abundances of 39 nongaseous elements in the Sun have assigned errors below 30%. Only the four elements sulfur, manganese, scandium, and strontium differ by more than 20% from Cl abundances. The difference is below 10% for 27 of these elements. The agreement between meteoritic and solar abundances must therefore be considered excellent and there is not much room left for further improvements. Obvious candidates for redetermination of solar abundances are manganese and sulfur. The hmiting factor in the accuracy of meteorite abundances is the inherent variability of Cl chondrites, primarily the Orgueil meteorite. 

The refractory component comprises the elements with the highest condensation temperatures. There are two groups of refractory elements the refractory lithophile elements (RLEs)—aluminum, calcium, titanium, beryllium, scandium, vanadium, strontium, yttrium, zirconium, niobium, barium, REE, hafnium, tantalum, thorium, uranium, plutonium—and the refractory siderophile elements (RSEs)—molybdenum, ruthenium, rhodium, tungsten, rhenium, iridium, platinum, osmium. The refractory component accounts for —5% of the total condensible matter. Variations in refractory element abundances of bulk meteorites reflect the incorporation of variable fractions of a refractory aluminum, calcium-rich component. Ratios among refractory lithophile elements are constant in all types of chondritic meteorites, at least to within —5%. 

Figure 7 shows the abundances of the four refractory lithophile elements—aluminum, calcium, scandium, and vanadium—in several groups of undilferentiated meteorites, the Earth s upper mantle and the Sun. The RLE abundances are divided by magnesium and this ratio is then normalized to the same ratio in Cl-chondrites. These (RLE/Mg)N ratios are plotted in Figure 7 (see also Figure 1). The level of refractory element abundances in bulk chondritic meteorites varies by less than a factor of 2. Carbonaceous chondrites have either Cl-chondritic or higher Al/Mg ratios (and other RLE/Mg ratios), while rumurutiites (highly oxidized chondritic meteorites), ordinary chondrites, acapulcoites, and enstatite chondrites are depleted in refractory elements. The (RLE/Mg)N ratio in the mantle of the Earth is within the range of carbonaceous chondrites.

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