Al-Sm-Eu-Sr systematics of eucrites and Moon rocks: Implications for planetary bulk compositions |
| |
| Authors: | Paul H Warren |
| |
| Institution: | Institute of Meteoritics, Department of Geology, University of New Mexico, Albuquerque, NM 87131 USA |
| |
| Abstract: | Analysis of the Eu and Sr “anomalies” of eucrites and lunar rocks allows constraints to be placed on the bulk compositions of the eucrite parent body (EPB) and the Moon. The elements Al, REE, and Sr, all are essentially incompatible with the major minerals of these small, low-?(O2) bodies, except for plagioclase, into which Al, Sr, and Eu tend to concentrate. Therefore, the hypothesis that Al, REE, and Sr in the EPB and the Moon are all in proportions close to those in the bulk solar system (i.e., chondrites) leads to certain predictions about the concentrations of these elements in samples affected by plagioclase fractionation. The predictions are almost ideally fulfilled by eucrites and lunar samples. For the EPB, the ratios , , and are constrained to be probably within 10%, almost certainly within 20%, of the chondritic ratios. For the more complicated Moon, the constraints are less precise: is very probably within 25% of chondritic; and are probably within 35% of chondritic. These findings are proof that there is a strong similarity between the bulk compositions of the planets and the compositions of chondritic meteorites.The eucrites' Sm-Eu-Sr systematics are also valuable sources of constraints on the distribution coefficients for Eu and Sr into plagioclase, at low ?(O2). From the slope of data for noncumulate eucrites on a Eu-Sm plot, D(Eu,pl/liq) can be inferred to be 1.1?0.10.2. From the slope on a Sr-Sm plot, D(Sr,pl/liq)) can be inferred to be 1.5 ± 0.3. In the case of D(Eu), this is in excellent agreement with experimental data. In the case of D(Sr), the empirical result is probably more appropriate for eucritic systems than most experimental data, which, due to compositional effects, scatter widely. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
