Core samples from 14 boreholes were investigated to determine the smectite % and composition of exchangeable cations of mica/smectite in alteration area around the Yokota Kuroko deposit, which consists of upper and lower orebodies. The upper orebodies occur in the horizon between the Oshio and Takisawagawa Formations, and the lower orebodies in the strata 150 to 200m lower than the former.
Near the upper orebodies, the smectite % of mica/smectite decreases with depth from about 70% to 20% within 10m below the boundary between the Takisawagawa and Oshio Formations. On the otherhand, at a distance away from orebodies, smectite is converted to mica/smectite containing 40% to 30% smectite at 30 meters or more lower than Oshio-Takisawagawa boundary and mica/smectite zone increases in thickness. Stratiform ore bodies and veinlets are restricted within the zone of 10% smectite in the isopleth map at the bottom of the rhyolite of the Takisawagawa Formation.
Major exchangable interlayer cation in clay fractions in the Takisawagawa to the lowermost part of the Oshio Formations are generally Na+, while those in the lower to middle parts of the Oshio Formation are Ca²⁺.
The changes in smectite % and composition of exchangeable interlayer cation near the boundary between the Takisawagawa and Oshio Formations indicate that a decrease in hydrothermal activity and change in chemical composition occurred at the final stage of Kuroko mineralization.

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Petrography and bulk rock chemistry of volcanic rocks and plutonic xenoliths from HigashiIzu monogenetic volcano group (HIMVG), the Izu Peninsula, central Japan, revealed a bimodal volcanic activity-high alumina basalts to calc-alkaline andesites (SiO₂=48-59 wt%) vs. calcalkaline dacites (SiO₂=68-73 wt%)-. The samples include 7 rock types based on bulk compositions and phenocrysts assemblages; ol + pl ± aug basalts, ol + pl ± aug andesites, ol + pl ± aug + hyp andesites and pl + ho + hyp ± (ol + aug) dacites.
Two types of basalts and andesites with different modal compositions of xenocrystic minerals (corroded quartz and sodic resorbed plagioclase) are found in HIMVG, i.e. X-poor type (less than 1 vol% xenocrysts) and X-rich type (more than 1 vol% xenocrysts). The X-poor type includes mostly of basalts and shows iron enrichment on the SiO₂ vs. FeO^*/MgO diagram. On the other hands, the X-rich type with more than 1 vol% xenocrysts includes mostly andesites and does not show iron enrichment. In the X-poor type, modal composition of phenocrysts of olivine and chromian spinel, and bulk MgO, Ni, and Cr contents decrease abruptly with an increasing SiO₂, whereas in the X-rich type, contents of these elements are variable and decrease moderately.
Partialy fused granitic xenoliths from Omuroyama scoria cone contain quartz, partialy resorbed plagioclase, and glass. Bulk rock composition of these xenoliths are similar to that of dacites.
In the HIMVG area, a concentric zonal pattern of rock types and phenocryst assemblages are observed. The basalts erupted at outer zone, while andesites and dacites, at inner zone. The volcanic products had been basaltic and andesitic untill the eruption of Kawagodaira, after which they became andesitic and dacitic.

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A new method of evaluating the pareodose, the auther presented in 1988, extended the limits of the TL dating method to about 10⁶ years.
In the former article, consideration about the electron-trapping process produced the combination of a competition model and an ordinary saturation model. The competition model accounts for the supralinearity in the low dose range, and the ordinary saturation model explains the sublinearity in the high dose range. In the new method, the experimental data decide the coefficients of the equation directly, without the regressive error. Therefore, in many types of samples, the new method brought good results for evaluation of the pareodose.
In some cases, however, a few errors have appeared in the low dose range. In the former article, the electron-trapping probability of the competition model was doubly approximated, in order to make a solution easy. The double approximation caused a few errors in the calculation of TL responce, in the low dose range, Consequently, the former equation led a smaller value as a pareodose.
For the purpose of a solution, the approximate term of (1-e7^-CR) was exchanged for the correct term of (1+e^-CR+D)-1. The improved equation has offered better-fitting results with experiments, especially in the low dose range.
By this improvement, the new method has enhanced the reliability and has come to be of wide application.

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早川鉱床と釈迦坑鉱床の銅鉛亜鉛鉱化作用の特徴が,単位鉱脈の構造・鉱物組合せ・鉱化ステージそして鉱脈中の石英および母岩の酸素同位体組成に基づきまとめられている。
早川および釈迦坑鉱床には,黄銅鉱-黄鉄鉱-四面安銅鉱-方船鉱-閃亜鉛鉱を随伴する石英脈(銅鉛亜鉛石英脈)と方鉛鉱-閃亜鉛鉱を随伴する石英脈(鉛亜鉛石英脈)が存在する。銅鉛亜鉛石英脈は,鉛亜鉛石英脈より早期に形成された。銅鉛亜鉛石英脈の鉱物組合せは,黄銅鉱,黄鉄鉱,四面安銅鉱-四面砒銅鉱,方鉛鉱,閃亜鉛鉱,硫砒銅鉱,車骨鉱,セムセイ鉱,ヘッス鉱,黄錫亜鉛鉱,砒サルパン鉱,Cu-Fe-Zn-Sn-S系鉱物,硫テルル蒼鉛鉱,アイキン鉱,石英および燐灰石である。鉛亜鉛石英脈の鉱物組合せは,方船鉱,閃亜鉛鉱,黄鉄鉱,黄銅鉱,四面安銅鉱,エレクトラムおよび石英である。閃亜鉛鉱中のFeS含有量は,早期から晩期の鉱化作用にかけて減少する。四面安銅鉱-四面砒銅鉱の単-粒子内では,SbとAsの間に化学組成の顕著な不均質性が認められる。
早川鉱床の銅鉛亜鉛石英脈中の石英のδ¹⁸O値は,1.4～3.1パーミルの範囲を有する。一方,釈迦坑鉱床の銅鉛亜鉛石英脈中の石英のδ¹⁸O値は,1.9パーミルである。早川鉱床の生成に関与した熱水のδ¹⁸O値 (-10.1～-3.3パーミル)は,海水やマグマ水のδ¹⁸O値と比較すると相対的に低い。従って,早川および釈迦坑鉱床の銅鉛亜鉛石英脈は, subvolcanic環境下でしかも天水起源の熱水から形成されたと推定される。

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