Chondrites major elements

The acapulcoites (Fig. 6.7a) have recrystallized textures, but a few relict chondrules have been reported (McCoy et al., 1997a). The relative proportions of the minerals (olivine, orthopyroxene, diopside, plagioclase, metal) in acapulcoites are similar to those in ordinary chondrites, and the abundances of the major elements are nearly chondritic. However,... 

Larimer, J. W. and Anders, E. (1970) Chemical fractionations in meteorites-III. Major element fractionations in chondrites. Geochimica et Cosmochimica Acta, 34, 367-387. 

Major-element compositions (weight ratios of Mg/Si and Al/Si) for mantle rocks (peridotites) and estimates of the primitive mantle composition of the Earth compared with various groups of chondrites and the Sun. No mixture of chondrite types provides an exact match to the primitive mantle composition, although some carbonaceous chondrites provide the closest match. Modified from Righter et al. (2006). 

New phosphoms and titanium XRF data for Cl chondrites were reported by Wolf and Palme (2001). The change in phosphorus is significant. The new Cl abundance is 926 ppm, which is much lower than the values in the older compilations, 1,105 ppm in Palme and Beer (1993) and 1,200 ppm in Anders and Grevesse (1989), respectively. The new phosphorus contents are considered to be more reliable. The changes in titanium are small. Wolf and Palme (2001) also reported major element concentrations of Cl meteorites and other carbonaceous chondrites. Their magnesium and silicon contents were almost identical to those given by Palme and Beer (1993) 10.69% versus 10.68% (for silicon) in Palme and Beer (1993) and 9.60% versus 9.61 % (for magnesium) in Palme and Beer (1993). The aluminum, calcium, and iron concentrations... 

F. M., and Parsad P. M. (2000) Major element chemical and isotopic compositions of refractory inclusions in C3 chondrites the separate roles of condensation and evaporation. Geochim. Cosmochim. Acta 64, 2879-2894. 

Two analytical approaches have been adopted in attempts to obtain stable-isotopic information on insoluble organic matter in carbonaceous chondrites stepped-combustion analysis (e.g., Kerridge, 1983 Swart et al, 1983) and CSIA of pyrolysis products (e.g., Sephton et al, 1998). Stepped-combustion analysis has proved to be more successful in providing information on the major-elemental constituents of chondritic organic matter, i.e., carbon, hydrogen, nitrogen, and oxygen, whereas CSIA has started to yield detailed carbon isotopic and structural information. 

A clast from Mount Padbury has a mg of 36, a molar FeO/MnO of 36, and a flat REE pattern at 9-10 X Cl chondrite abundances (Mittlefehldt, 1979)—all within the ranges for basaltic eucrites. However, many basaltic clasts are distinct in major element composition, with higher mg s and lower molar FeO/MnO ratios than those of basaltic eucrites, and have LREE-depleted patterns and (Eu/Sm)ci > 1— patterns unknown among unaltered basaltic eucrites. Some gabbro clasts are similar to cumulate eucrites in major-and trace-element contents, but many are distinct in having extreme depletions in the most incompatible elements (Mittlefehldt, 1979 Rubin and Mittlefehldt, 1992). In extreme cases, samarium abundances are only 0.02-0.03 X Cl chondrites (Rubin and Jerde, 1987 Rubin and Mittlefehldt, 1992), much less than the 1-2 X Cl typical of cumulate eucrites. These clasts have (Eu/Sm)ci of 220-260, the most extreme ratios known among solar system igneous rocks (Mittlefehldt et al., 1992). 

Hutchison R. (2002) Major element fractionation in chondrites by distillation in the accretion disk of a T Tauri Sun Meteoritics 37, 113-124. 

The major-element compositions of 200 chondritic IDPs were measured by EDS (Table 1 and Figure 12). All of the particles were identified as extraterrestrial because they have approximately chondritic compositions or consist predominantly of a single mineral grain like forsterite or pyrrhotite (commonly found within chondritic IDPs) 37% of the particles are CSIDPs, 45% are CP IDPs, and 18% IDPs composed predominantly of a single mineral. Table 1 summarizes the compositions of the IDPs. Within a factor of 2 the abundances of oxygen, magnesium, aluminum, sulfur, calcium, chromium, manganese, iron, and nickel are approximately chondritic. CP IDPs are a closer match to Cl carbonaceous chondrites than CS IDPs, and they are closer to Cl bulk than to Cl... 

Figure 3 A ternary plot (upper) and binary ratio plot (lower) of the differing proportions (in wt.%) of Si, Fe, and Mg (three out of the four major elements) in chondrites and the Earth. These elements, together with oxygen, constitute >90% by mass of chondrites, the Earth, and other terrestrial planets. Data for the chondrites are from Wasson and Kellemeyn (1988) and for the Earth are from Table 2. The regression line is derived using only chondrites and does not include the EH data.

If melt or fluid re-enrichment or some other form of disturbance affects a peridotite subsequent to melting then this should be reflected in PGE patterns and PGE-major element syste-matics. Modelling of melt re-enrichment involving the addition of new sulphides to variably depleted melt residues during magma-solid interaction produces elevation of the Pd/Ir ratio to supra-chondritic levels, and elevated P-PGE contents (Rehkamper et al. 1999 Fig. 4). Combined major element, PGE and Re-Os isotope systematics therefore provide a potential means to evaluate the validity of Re-Os isotope model ages (Trd V. Tma)-... 

After the accretionary event in which the Earth acquired its volatiles, other processes took place which caused it to lose them. There are two lines of evidence which tell us about the early Earth s loss of volatiles. The first comes from a comparison between the volatile concentrations in the outer Earth and those of carbonaceous chondrite meteorites (the most primitive and most volatile-rich of all the meteorite groups). It is clear from Fig. 5.6 that the Outer Earth Reservoir has two to three orders of magnitude less volatiles than carbonaceous chondrites. In addition it is evident that the lighter major elements are more depleted than the heavy ones. 

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