ニューカレドニァ産の10Å型ガーニーライトを示差熱分析,熱重量分析,連続加熱高温X線分析により調べた。また試料を1000°Cまでの種々の温度に加熱した後に, X線分析と赤外線分析を行なった。未処理の10Å型ガーニーライトの底面反射は巾広く, 2θの角度の小い方に翼を広げた非対称形をしている。この底面反射は水やエチレン・グリコール処理では変化しない。10Å型ガーニーライトのOH領域の赤外線吸収スペクトルは3685cm^-1, 3643cm^-1と3625cm^-1が認められるが, 250°C～500°C加熱処理を行なうと, 3690cm^-1, 3670cm^-1, 3645cm^-1と3625cm^-1の吸収が明瞭になり始め, 750°Cと800°Cの加熱により, 3690cm^-1の吸収が認められなくなり, 3675cm^-1, 3660cm^-1, 3645cm^-1,と3625cm^-1の鋭い吸収が認められる。これらの吸収は3675cm^-1の吸収の強度が強いことを除くと,人工および天然産のニッケルに富むタルクの吸収とよく一致する。この鉱物のOH領域の赤外線吸収スペクルトの変化および吸収の強度比の計算から,この鉱物はニッケルに富む加水タルクとマグネシウムに富む加水タルクの混合物であるか,または八面体層中でニッケルとマグネシウみの不規則な分布をもつニッケルに富む加水タルクであると考えられる。またこの試料には極く微少量のクリソタイルが不純物として含まれている。

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Recently almandine-rich garnet from rhyolite and dacite has been remarked as a high-pressure mineral directly crystallized from an acid hydrous magma at depth. The mineralogy and genesis of almandine-garnets from Yamanogawa, Fukushima Prefecture and Kamitazawa, Yamagata Prefecture were described and discussed from this viewpoint. The former garnet occurs within a hornblende-dacite and the latter is found from an acid tuff. They are different from metamorphic garnets in the following points. (1) The inclusion is characterized by magmatic accessory minerals such as apatite, zircon, rutile, sphene, pyrite, and either magnetite or ilmenite. (2) The zoning patterns of both garnets show neither normal or reverse type but distinct oscillatory type (Figs. 9-14) which is similar to the zoning pattern of associated plagioclase phenocryst (Fig. 16). One of the most probable explanations of such oscillatory zoning may be a model of magma chamber rising step-by-step from depth which causes the decrease of load pressure and accordingly the repeated change of Mg, Ca and Ti. (3) Though slightly corroded, the garnets exhibit conspicuous euhedral form up to 3mm or more in diameter. (4) The almandine-rich composition is what is characteristic of magmatic or synthetic garnets (Fig. 15). The slightly Ca-rich composition of the Yamanogawa garnet may be corresponding to the bulk composition of host dacite.
Judging from these features with reference to recent literatures, the both Yamanogawa and Kamitazawa garnets are considered to be of a deep origin under a high pressure. The garnet-bearing calc-alkaline acid magmas may have been generated within the upper mantle or the lowest crust and then risen up to the surface through and along some cites of tectonic disturbance. Such environment may be suggested in the case of the Yamanogawa garnet-bearing dacite which occurs along the Yanagawa-Shirasawa tectonic zone developing between the Green Tuff region and the non-Green Tuff region and composing a part of the Morioka-Shirakawa tectonic line (Fig. 18). As for the Kamitazawa garnet-bearing acid tuff, it seems geologically significant that the rock occurs in an area of widespread acid volcano-plutonic formation including welded tuffs (Fig. 19).

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A rapid method for the quantitative microprobe analysis of carbonate minerals is proposed and the determinative diagrams are given under the following conditions; take-off angle 40° and accelerating voltage 15 kV. Other methods with EPMA for carbonate analysis are also discussed.

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