Daizo Ishiyama

Mobilization and enrichment of high-field strength elements during late- and post-magmatic processes in the Shuiquangou syenitic complex, Northern China

Abstract The Shuiquangou syenitic complex consists of melasyenite and leucosyenite. In the northeastern part, there is a small area where the leucosyenite was affected by alteration. The altered leucosyenite contains much higher concentrations of high-field strength elements (HFSE), especially Nb, Zr, REE and Y compared to fresh leucosyenite. REE patterns of the altered leucosyenite show moderate negative Eu anomaly, in contrast to the slightly positive to non-anomalous Eu signature of the fresh syenitic rocks. Allanite from the hydrothermal mineral assemblage in the altered leucosyenite also contains much higher concentrations of REE and Ti than the euhedral magmatic allanites in unaltered leucosyenite. The enrichment of HFSE in altered leucosyenite was interpreted to be caused by the hydrothermal fluids based on mineral chemistry and whole-rock data. Within the fresh leucosyenite, allanite occurs in two habits, euhedral ones indicating a primary magmatic origin and anhedral ones suggesting a late-magmatic origin. The latter has higher concentrations of REE and Ti than the former. The anhedral allanite was presumed to be formed coeval with the alteration of the euhedral allanite as a result of residual magmatic fluid derived directly from the syenitic magma. The alteration of magmatic euhedral allanite and the enrichment of REE and Ti in the anhedral late-magmatic allanite suggest that these elements were mobilized by the residual magmatic fluid. Both residual late-magmatic and hydrothermal fluids have an inferred composition characterized by high alkalic and F contents, suggesting that F may be the most ligand that complexed the high-valence cations.

Geochemical characteristics of Miocene Fe-Cu–Pb–Zn granitoids associated mineralization in the Chichibu skarn deposit (central Japan): evidence for magmatic fluids generation coexisting with granitic melt

Abstract In this work we study mechanisms and timing of magmatic fluid generation during magma emplacement. Our focus is the Miocene calc-alkaline granitic rocks from the Chichibu mining area, in Japan. The granitoids consist of northern and southern Bodies and of the Daikoku Altered stocks. Cathodoluminescence observation of quartz phenocrysts from the northern body point towards magmatic resorption, which is thought to be caused by mixing between a more differentiated and a more primitive magma. The coexistence of vapour-rich two-phase and halite-bearing polyphase fluid inclusions in a single quartz crystal from the northern Body supports the possibility of pressure decrease during magma emplacement. The magmatic fluids that originated the Chichibu deposit are thought to have been generated by pressure release, related to magmatic differentiation when the SiO2-content reaches about 65 wt%. As a result, heavy metals, such as copper, gold and arsenic, coexisting with the silicate melt, were transported into the sedimentary strata through degassing of magmatic fluids. A later major fault system caused the intercalation between heavy-metal-free limestone and orebodies, as a secondary skarn-building process took place in the dominant limestone area.

Copper Recovery from the Mine Tailings by Combination of Flotation with High-Pressure Oxidative Leaching and Solvent Extraction

The aim of this research was to develop a copper recovery process from mine tailings (0.34%Cu) using flotation followed by high-pressure oxidative leaching (HPOL) and solvent extraction. The results of HPOL using the concentrate of mine tailings obtained by flotation under the optimal conditions of the previous study shown that an efficient copper dissolution of 94.4% was achieved in an H2O media, while the copper concentration of PLS reached to be 2.9 g/L. The solvent extraction of PLS obtained from the optimal HPOL showed that 91.3% copper was recovered in stripped solution under the determined optimum conditions, in which the copper concentration achieved to be 44.8 g/L. Finally, a proposed copper recovery process from the concentrate of mine tailings was developed by combination of HPOL and solvent extraction, while a total copper recovery of 86% was achieved.

Development of copper recovery process from flotation tailings by a combined method of high‒pressure leaching‒solvent extraction

Sulfide copper mineral, typically Chalcopyrite (CuFeS2), is one of the most common minerals for producing metallic copper via the pyrometallurgical process. Generally, flotation tailings are produced as a byproduct of flotation and still consist of un‒recovered copper. In addition, it is expected that more tailings will be produced in the coming years due to the increased exploration of low‒grade copper ores. Therefore, this research aims to develop a copper recovery process from flotation tailings using high‒pressure leaching (HPL) followed by solvent extraction. Over 94.4% copper was dissolved from the sample (CuFeS2 as main copper mineral) by HPL in a H2O media in the presence of pyrite, whereas the iron was co‒dissolved with copper according to an equation given as CCu = 38.40 × CFe. To avoid co‒dissolved iron giving a negative effect on the subsequent process of electrowinning, solvent extraction was conducted on the pregnant leach solution for improving copper concentration. The result showed that 91.3% copper was recovered in a stripped solution and 98.6% iron was removed under the optimal extraction conditions. As a result, 86.2% of copper was recovered from the concentrate of flotation tailings by a proposed HPL‒solvent extraction process.

Factors Controlling the Fractionation and Seasonal Mobility Variations of Ga and In in Systems Impacted by Acidic Thermal Waters: Effects of Thermodynamics and Bacterial Activity

This work assessed both the fractionation and the seasonal mobility variations of Ga and In in systems impacted by acidic thermal waters. This was accomplished by performing thermodynamic calculations using the PHREEQC algorithm and by assessing the activity of acidophilic iron-oxidizing bacteria. The pH of the Kusatsu thermal waters in Gunma Prefecture, central Japan, is rapidly increased following the addition of a lime suspension. After an abrupt pH increase, under which conditions free ions of Ga and In and their complexes with Cl− and SO42− exist only in negligible quantities, the majority of dissolved Ga and In is removed by sorption onto suspended hydrous ferric oxides (HFOs). These HFOs are then transported to an artificial lake without significant sedimentation along the river. Subsequently, the suspended HFOs settle out and are added to sediments without significant fractionation between Ga and In. The Tamagawa thermal waters in Akita Prefecture, northeast Japan, are also treated with lime. However, complete neutralization requires mixing with some tributary streams, leading to a gradual downstream increase in pH. Dissolved Ga is, in general, sorbed by HFOs in upstream areas, leading to wide dispersal of Ga across the entire watershed. In comparison, In is transported to the lake inlet predominantly as a Cl− complex species without significant removal along the river, with the majority being precipitated in an artificial lake, where Cl− concentrations are too low to form stable complex species with In, and thus, dissolved In is sorbed by HFOs. As a result, In is effectively concentrated within downstream lakebed sediments, whereas Ga is dispersed along the river. Seasonal variations in Ga mobility within the Tamagawa field between snowmelt and low-flow seasons are primarily controlled by pH, because hydrolysis reactions of these metals, which are related to sorption reactions, tend to occur in the upstream regions in the snowmelt season. However, under warmer conditions, HFO formation preferably occurs due to the activity of acidophilic iron-oxidizing bacteria. Thus, under similar pH variations, dissolved Ga is more effectively removed by HFOs during warmer seasons. On the contrary, because HFOs are abundantly formed in low-flow season, even under colder conditions, before In hydrolysis reaction starts to occur, In mobility is less affected by water temperature and then bacterial activity.

Mineralization of Indium in Northern Vietnam: A Study on Mineralogy and Geochemistry of the Na Bop and Lung Hoai Deposits in the Cho Don and Cho Dien Mining Area

The Cho Don (including the Na Bop, Na Tum, Pu Sap, Ba Bo and Lung Vang deposits) and Cho Dien (including the Phia Khao, Lung Hoai, La Poanh, Bo Pen, Binh Chai, Deo An, Bo Luong deposits) mining areas are characterized by the large reserve and high grade of Pb-Zn ore and indium in Cho Dien district, Bac Kan Province, northeast Vietnam (Fig. 1). Total ore reserves in these mining areas reach up to 20.1 Mt of ores, in which there are 0.99 Mt of metals (Pb+Zn) (Dovzhikov et al., 1965; Tran et al., 2012, Nguyen et al., 2000). Some earlier studies classified ore deposits in the Cho Don and Cho Dien mining areas into Mississippi Valley type deposits (MVTs). Some of the later studies assign them to Pb-Zn hydrothermal deposits classified into magmatic hydrothermal system based on the mineral assemblage and trace elements characteristics. The aim of this study is to clarify the type of the Na Bop deposit in the Cho Don mining area and the Lung Hoai deposit in the Cho Dien mining area based on the characteristics of mineralogy, geochemistry and formation environment.

Triassic Epithermal Au and Porphyry Related Cu-Mo Mineralization of the Chatree Deposit, Central Thailand

The Chatree mining area is located in the LoeiPhetchabun-NakhonNayok volcanic belt, about 300 km north of Bangkok in Thailand. The Chatree deposit consists of five defined prospects and five open pits. The A and Q prospects (Au mineralization) are located in the northern part of the Chatree deposit. The C, H, D, Kw and Ke pits (Au mineralization) are distributed in the central part of the deposit. The B (Au mineralization), N and V (Cu-Mo mineralization) prospects occur in the southern part of the deposit. Ore bodies studied are the Q, A, B, N and V prospects. Geology of the Chatree deposit consists of andesite lava, monomictic andesitic breccia, polymictic andesitic breccia, volcanic sedimentary breccia and fiamme breccia. Andesite dikes cut these strata and ore bodies. Au mineralization (250±0.8 Ma, Salam et al., 2008) is developed in polymictic andesitic breccia and volcanic sedimentary breccia strata. Granodiorite occurs at the N and V prospects approximately 2 km far from the Q prospect. The granodiorite (243±5 Ma, Salam et al., 2008) intruded into andesite lava. Cu-Mo mineralization is recognized in the granodiorite (N and V prospects). The age of mineralization of the Chatree deposit is Early Triassic. The aim of study is to elucidate the styles of gold and copper mineralization and to estimate the source of gold in the Chatree deposit.

Characteristic Features of Ra‐Pb‐Sr‐Rare Metal‐bearing Tamagawa Acidic Thermal Water Derived from a Deep‐seated Magmatic System in Akita Prefecture, Japan

Ohbuki hot spring in the Tamagawa hot spring area, which is associated with volcanic activity, is a famous hot spring characterized by strong acidity and presence of radium. Many studies on the thermal water of Ohbuki hot spring have been carried out. Iwasaki et al. (1963) reported that the anions in thermal water of Ohbuki hot spring are transported by volcanic gas derived from active magma, while Yoshiike (1996) proposed that the cations in the thermal water are derived from volcanic rocks in the shallow underground part around Tamagawa. We examined the chemical characteristics of thermal water on the basis of concentrations of major and trace elements and Sr, Nd and Pb isotopic ratios of the thermal water and estimated the source of elements in the thermal water.

Instrumental Neutron Activation Analysis of Tungsten Content in Mineralized and Non-mineralized Granite.

Tungsten content in granitic rocks is precisely determined by an instrumental neutron activation analysis method (INAA) using several standard samples. Natural geostandard rocks are GSJ geostandard of JG-1, JG-1a, JG-2, JR-2 and JR-3, and artificial standard materials of JR-2 with added scheelite powder and tungsten-doped quartz sand were employed for the analysis. Each sample (100mg) was irradiated for short time (1min, 2min and 3min) at thermal neutron flux 2.8×1013n/cm2/s and for long time (60min) at thermal neutron flux 2.3×1013n/cm2/s. Gamma-ray spectrum of 187W at 685.72keV was used for the tungsten analysis in geostandards. The 187W gamma-ray spectrum was not recognized for Na-rich JG-1 (W concentration=1.5ppm), while the gamma spectrum of that was recognized for JR-2 (1.8ppm). S/N ratios of 187W for geostandards that irradiated for 3min and after cooling for 6 day were higher than those of another irradiation conditions. The analytical error of tungsten in geostandards with the confidential limit of 95% was ± 4.7ppm. This INAA with 3min irradiation is the most suitable method for the tungsten-bearing samples was successfully applied to wide range of tungsten (i. e. low W concentration of non-mineralized granites to high W concentration of mineralized granite and scheelite-bearing ore).