- 著者
- Iwao Kawabe
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.26, no.6, pp.309-335, 1992-12-20 (Released:2008-04-08)
- 参考文献数
- 73
- 被引用文献数
- 51 70
The refined spin-pairing energy theory (RSPET) has been improved in order to understand quantitatively the tetrad or double-double effects recognized in the Ln3+ ionic radii. Since the ionic radii have been determined from the lattice constants and structural parameters of LnO1.5 and LnF3, the lattice energies of the compounds and the enthalpy difference of ΔHfo(LnF3)-ΔHfo(LnO1.5) have been examined by the improved RSPET. The RSPET parameters for the lowest levels of 4fq electronic configurations strongly depend upon the effective nuclear charge (Z*). Such effects due to Z* have been taken into account. This made it possible to separate the variations in the lattice energies and the enthalpy difference across the Ln3+ series into the following two parts: (1) the large variation as a smooth function of q (the lanthanide contraction trend), and (2) the small zig-zag variation referred to the tetrad or double-double effect. The lattice energy of LnO1.5 and ΔHfo(LnF3) − ΔHfo(LnO1.5) exhibit upward concave tetrad curves in their plots against q of Ln3+. The tetrad effect in the lattice energy of LnF3 is less conspicuous. This means that the Racah parameters for Ln3+ decrease very slightly in going from the gaseous free Ln3+ to LnF3, and then decrease greatly to LnO1.5, in accordance with the nephelauxetic series. The differences in Racah parameters between LnF3 and LnO1.5 have been estimated from ΔHfo(LnF3) − ΔHfo(LnO1.5) by means of an inversion technique based on the improved RSPET. The RSPET results for the thermochemical data are consistent with the careful spectroscopic determinations of Racah parameters for NdF3 and NdO1.5. Both the tetrad effect and the smooth lanthanide contraction seen in the Ln3+ ionic radii can be interpreted in terms of the quantum mechanical energetics of 4f electrons.
- 著者
- Iwao Kawabe
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.29, no.4, pp.213-230, 1995-08-20 (Released:2008-04-08)
- 参考文献数
- 42
- 被引用文献数
- 23 42
All fourteen REE and Y have been determined for eight GSJ reference rocks including granitic and rhyolitic samples by ICP-AES with a preconcentration method. The two rhyolites (JR-1 and JR-2) and one granite (JG-2) exhibit convex tetrad effects of the M-type even in their chondrite-normalized REE patterns. Their tetrad effects, however, are modified from ideal ones by some step-like variations in their abundances from Tm to Lu. Similar step-like irregularities are seen commonly in chondrite-normalized patterns of other samples: granodiorites (JG-1, JG-1a, and JG-3), a fresh water lake sediment (JLk-1), and an alkali basalt (JB-1). We normalized the REE analyses for JR-1, JR-2, and JG-2 by those for JB-1, and then found that they clearly indicate quite regular convex tetrad effects of the M-type without apparent irregularities in heavy REE. The other samples, when similarly normalized by JB-1, also display analogous but less marked convex tetrad effects except for JG-3. Our present results are strong evidence for the tetrad effect in magmatic processes relevant to granitic and rhyolitic rocks formations. There are common chemical characteristics among JG-2, JR-1, and JR-2: (1) large negative Eu anomalies, and (2) rather high F contents of about 1, 000 ppm. The chemical characteristics and the theoretical basis of tetrad effects may suggest that the granitic and rhyolitic rocks with the convex tetrad effects of the M-type are residual silicate melts having partitioned REE with fluids in late stages of differentiation processes. The basalt-normalization appears to be so effective for extracting tetrad effects of granitic and rhyolitic rocks. It filters off the REE characteristics common in magmatic products like the step-like irregularities in heavy REE abundances when normalized by chondrite. This makes it easier to identify lanthanide tetrad effects in magmatic rocks.