Apatites of representative magnetite‐series and ilmenite‐series granitoids were studied in the Japanese Islands. Concentrations of the volatile components F, Cl and SO3 are differently distributed in apatites of these granitoid series. Apatites are always fluoroapatite. They have weakly higher F content in the ilmenite series than in the magnetite series. In contrast, Cl and SO3, are significantly concentrated in apatites of the magnetite series compared to the ilmenite series. These characteristics reflect the original concentrations of these components in the host granitic magmas. A high fO2 seems most important for the S‐concentration as sulfate in apatite of the magnetite series. REE and Y are only erratically high in the studied apatites.

Geochemical and geochronological studies were conducted on basalts and laterites from the Bolaven Plateau in southern Laos in order to evaluate the mobility and mineralization of REE, Y and Sc during laterization. The basalts are classified into three categories: (i) small volumetric alkali basalt (eruption age: 15.7 Ma), large volumetric olivine tholeiite (1.2 Ma) and quartz tholeiite with olivine tholeiite (younger than 0.5 Ϯ 0.2 Ma). Formation of REE minerals during laterization result in mobilization and fractionation of REE and Y in laterite profiles. Occurrence of florencite-(Ce) in a laterite profile derived from alkali basalt immobilizes REE (particularly LREE) and this leads the laterites to be enriched in LREE relative to the parent basalt. Few positive Ce anomalies in this profile suggest that florencite-(Ce) [(Ce)Al 3(PO4)2(OH)2] formation was followed by CeO2 precipitation due to the change of redox condition. In tholeiite-derived laterite profiles, florencite is not recognized and REE and Y tend to be depleted relative to the parent basalts with positive Ce anomalies. This is interpreted as scavenging REE 3+ except for Ce 4+ from the laterite profile in oxidizing conditions. Sc behaves similarly to Fe during laterization and it is more abundant in the tholeiitic laterite than that in the alkali basaltic laterite. Results of sequential extraction indicate that REE of the alkali basaltic laterite are contained in residual phase, which is dominantly florencite-(Ce), but they are rarely present in ion-adsorption phase. It is concluded that basaltic laterites have a low potential of REE resource in terms of low REE contents and a difficulty in REE extraction.

This article reports geochemical behavior and enrichment of Al, Ga and Sc by laterization of basalts and sandstone in the Bolaven Plateau, southern Laos. The Bolaven Plateau consists of NeogeneQuaternary basalts and underlying Cretaceous sedimentary rocks. Laterites derived from the basalts and sedimentary rocks are developed on these parent rocks. With increasing the degree of laterization, loss of mobile elements such as Si, alkali elements and alkaline earth elements lead to the enrichment of immobile elements of Al, Ga and Sc relative to the parent rocks. Accordingly, Al 2 O 3 contents range from 10 to 15 % in the basalts, from 16 to 30 % in the saprolites, from 17 to 48 % in the basaltic laterites and from 15 to 47 % in the sedimentary laterite. Ga contents range from 6 to 20 ppm in the basalts, from 9 to 46 ppm in the saprolites, from 24 to 83 ppm in the basaltic laterites and from 22 to 68 ppm in the sedimentary laterites. Sc contents range from 14 to 23 ppm in the basalts, from 14 to 45 ppm in the saprolites, from 14 to 69 ppm in the basaltic laterites and from 13 to 84 ppm in the sedimentary laterites. No significant difference is recognized in the enrichment of these elements between the basaltic laterites and sedimentary laterites. A similar geochemical behavior and positive linear correlation are recognized between Ga and Al and between Sc and Fe, suggesting that Ga and Sc exist by replacing Al and Fe in the laterites, respectively. Ga/Al ratios range widely but Ga is almost no depleted or slightly enriched relative to Al with increasing the degree of laterization. Sc/Fe ratios indicate that Sc may be slightly depleted relative to Fe by strong laterization.

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