Experiments on divalent cation distribution between Mg–Fe olivine solid solutions and 1 mol/L (Ni2+, Mg2+, Co2+, Zn2+, Fe2+, Mn2+)Cl2 aqueous solutions were carried out at 700 °C and 100 MPa. Regardless of the composition of the Mg–Fe olivine solid solutions, the tendency of divalent cation distribution into the olivine solid solutions against the aqueous chloride solutions was in the order of Ni2+ > Mg2+ > Co2+ > Mn2+ > Fe2+ > Zn2+. Excluding Zn2+, this order corresponds to the order of the sixfold coordinated ionic radius in olivine. This indicates that a smaller ionic radius allows the cation to more easily enter the olivine solid solutions. However, Zn2+ showed a negative distribution anomaly and did not easily enter the sixfold coordinated site of the olivine solid solutions, regardless of the ionic radius. This is because Zn2+ has a strong preference for fourfold coordinated sites. The Mg–Fe olivine solid solutions with more fayalite endmembers have smaller differences in the distribution coefficient of cations. This means that the gradient of the PC–IR curve becomes smaller as the content of fayalite endmembers increases. This trend indicates that fayalite consisting of a large cation (Fe2+) tends to exchange other cations more easily than forsterite consisting of a small cation (Mg2+).

Zircon U–Pb geochronology was carried out on plutonic rocks from Phnom Daek, Phnom Koy Rmeas, Svay Chras, Kon Mom, Koh Nheak, Andong Meas, Oyadav South, Svay Leu, and Phnom Soporkaley. The zircon U–Pb ages from the plutonic rocks determined in this study can be roughly divided into two groups. One is the Late Permian to Triassic ages of 278–202 Ma for the Phnom Daek, Phnom Koy Rmeas, Oyadav South, Svay Leu, and Phnom Soporkaley, and the other is the early Cretaceous ages of 118–98 Ma for the Svay Chras, Kon Mom, Koh Nheak, and Andong Meas samples. The plutonic rocks from Phnom Daek, Phnom Koy Rmeas, Svay Leu, Oyadav South, and Phnom Soporkaley were likely formed by magmatic activity in the Loei Fold Belt. These plutonic rocks were likely formed in an extensional setting and/or a region where the continental crust was thin. The plutonic rocks of Svay Chras, Kon Mom, Koh Nheak, and Andong Meas were likely formed by magmatic activity in the Dalat-Kratie Fold Belt, related to the NW-directed subduction of the Paleo-Pacific Ocean plate. These plutonic rocks are thought to correspond to the Dinhquan suite in southern Vietnam. The Kon Mom and Koh Nheak plutonic rocks fall within the alkaline series, which suggests that the magma genesis was deep and far from the western Paleo-Pacific Ocean plate. Magmatic activity in the Dalat-Kratie Fold Belt migrated oceanward as a whole during the Cretaceous.

The Preah Vihear monument in Cambodia, located close to the border with Thailand, was one of the Khmer temples registered on the UNESCO World Heritage List as a Cultural Property in 2008. It consists of masonry buildings constructed of siliceous sandstone blocks. In this study, the construction sequence of its buildings was inferred from the chemical composition, magnetic susceptibility, and size of the sandstone blocks, along with pediment end style, and the presence or absence of reliefs on the tympana of adjacent buildings. Five construction stages were identified. We revealed that the Western Annex Hall (N2) is the oldest edifice in the Preah Vihear monument. We also reconfirmed that the Preah Vihear monument was constructed over a range of years, spanning the Bakheng style period to the Angkor Wat style period (the end of the 9th century to the end of 12th century). It was clarified that during the construction of Preah Vihear, the style of pediment ends changed from pediments ending in scrolls made from one block, to pediments ending in scrolls made from two blocks, and finally to pediments ending in five-headed nagas. Over the same time span, the size of the sandstone blocks used in construction increased markedly.

<p>The experiments on the simultaneous partitioning of divalent cations (Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, and Mn²⁺) between pyrite or pyrrhotite and 2M aqueous chloride solution were conducted under supercritical hydrothermal conditions of 500, 600, 700, and 800&deg;C, and 1 kb, using standard cold seal type pressure vessels.</p><p>&emsp;The experimental results revealed that the cations are preferentially partitioned into pyrite and pyrrhotite in the following orders, respectively:</p><br/><p>&emsp;Co²⁺=Ni²⁺=Fe²⁺>Zn²⁺>Mg²⁺=Mn²⁺ for pyrite</p><p>and</p><p>&emsp;Co²⁺>Ni²⁺&ge;Fe²⁺>Zn²⁺>Mg²⁺=Mn²⁺ for pyrrhotite.</p><br/><p>&emsp;If we assume that Mg²⁺ shows a partition behavior according to the ionic radius, the partition coefficient vs. ionic radius (PC-IR) curves for both pyrite and pyrrhotite mark a peak at 0.77 &Aring;. Zn²⁺ shows a negative deviation from the PC-IR curves, but Ni²⁺ shows a positive deviation.</p>

Background: In addition to the blackening caused by blue-green algae growth, other black areas on the surface of construction materials (e.g., sandstone, laterite and bricks) are frequently observed in the Khmer temples in Cambodia. A non-destructive on-site investigation was carried out using a portable X-ray fluorescence analyzer (pXRF). In addition, samples were taken from the buildings and were analyzed using an X-ray diffractometer (XRD) and a scanning electron microscope with an energy dispersive X-ray spectrometer, and were observed using a field emission scanning electron microscope.
Results and conclusions: A non-destructive investigation using the pXRF revealed that this blackening was caused by manganese oxide precipitates. The precipitates contained small amounts of Ni, V, Zn, Y, K, Cl, S, Pb, and Cr. The XRD analysis indicated that the manganese oxides were mainly present as an amorphous phase, but some formed birnessite and todorokite. The manganese precipitates were mostly in a hexagonal plate form (100-300 nm), but some were in a rod-shape, which may have been caused by the activity of manganese oxidizing microbes. Preliminary experiments on removal of manganese oxide precipitates were conducted. The manganese oxide precipitates could be easily removed using a reducing agent such as an oxalic acid solution.

The ASEAN-Japan Build-Up Cooperative Education Program for Global Human Resource Development in Earth Resources Engineering (AJ-BCEP) is spearheaded by Kyushu University and supported by universities in Japan and top universities in the Southeast Asian region. The School on the Move Program started in 2013 as part of AJ-BCEP's three step-wise projects, the other two being the International Internship Program and the Double Degree Program. Among the three, the SOM involves the most number of participants, with 35-40 student participants a year from different Japan and ASEAN universities and involvement of at least three universities organizing each leg of the program. The SOM focuses on student mobility and social engagement between Japanese and ASEAN graduate students in the field of earth resources (mining) engineering. Through lectures, field trips and discussions in different countries, the SOM Program has exposed the students to various theories and practices that contributed to their knowledge and expertise as future earth resources engineers or research scientists. The on-going program has contributed extensively to the development of bachelor and master course students in the earth resources field from ASEAN and Japanese universities, by creating bonds both academic and social, for enhanced educative experiences.

Introduction: Koh Ker, one of the provincial cities of the Khmer Empire, was located approximately 85 km northeast of the Angkor monuments. The temples in the Koh Ker monuments were mainly constructed from laterite, sandstone and brick between 921 and 944 AD. The laterites used in the Koh Ker monuments are difficult to classify based on their appearance. However, using a portable X-ray fluorescence analyzer it was possible to distinguish two distinct types of laterite based on Sr content.
Results: Laterite blocks used in construction of the Koh Ker monuments either had a low Sr content of less than 300 ppm or a high Sr content of greater than 400 ppm. Significant quantities of quartz were observed in the low Sr content laterites, whereas the high Sr content laterites had relatively low quartz content. Differences in the magnetic susceptibility also were observed for these laterites. Using both Sr contents and magnetic susceptibilities of the laterite blocks, in combination with the assumption that the construction site proceeded in an outward manner, we identified five distinct laterite types associated with different stages of construction.
Conclusions: Five different stages of construction were identified in the buildings of the Koh Ker monuments; each stage is characterized by a different laterite source rock. We believe that the brick sanctuaries are the oldest buildings, followed by the sandstone sanctuaries, while the laterite sanctuaries were constructed last. The laterite blocks with high Sr content were likely supplied from quarries around the Srayang village, which is located immediately to the south of the Koh Ker monuments; provenance of the low Sr content laterites is yet to be determined.

In this paper, the construction period of the cruciform terraces with columns and the elevated causeways in the Angkor monuments of Cambodia is reconsidered, based on the results of our investigation of magnetic susceptibility and other characteristics of sandstone blocks. From an art-historical point of view, they are generally considered as modifications in the post-Bayon style periodthe period during the reign of Jayavarman VIII (1243-95 ce) or later. However, from a lithological point of view, the average magnetic susceptibilities of the sandstone blocks in the cruciform terraces with columns and the elevated causeways are consistent with the rest of the monument. In addition, the characteristics of the sandstone blocks in the cruciform terraces, such as their shape, the orientation of the bedding plane and the stacking method, suggest that they were constructed in the same period as the rest of the monument.

Sandstone blocks are the main construction materials used in the Angkor monuments in Cambodia. However, a thorough study of the quarries has not yet been carried out. We conducted a field investigation of sandstone quarries from the Angkor period at the southeastern foot of Mt. Kulen, which is approximately 35 km northeast of the Angkor monuments. As a result, we discovered more than 50 sandstone quarries. On the basis of the measurements of magnetic susceptibilities and thicknesses (step heights), we found that they were quarried at different times. These four quarrying areas were identified as the quarries D to G inferred by Uchida et al. (2007). In addition we investigated a canal that was identified on satellite images, connecting quarry sites at the foot of Mt. Kulen to the Angkor monuments. The field investigation suggests a high probability that the canal was used for the transportation of sandstone blocks from Mt. Kulen. © 2012 Elsevier Ltd.

In the cruciform gallery of Angkor Wat in Cambodia, red, orange, white and black pigments were widely painted on the surfaces of pillars, walls and friezes. The application sequence of the pigments is different from area to area. The following substances were confirmed from the pigments: hematite (laterite), minium, calcium oxalate hydrates (whewellite and weddellite), PbCl compounds (cotunnite, laurionite and blixite), calcium phosphates (whitlockite), gypsum, hydrocerussite, calcite, anglesite, lead dioxide, azurite and carbon black. The orange pigment (minium) underlies the red pigment (hematite). The former may have been applied at the time of the foundation (the Angkor Wat style period), and the latter in the Bayon style period or later, but mainly before the early 17th century of the current era.

We investigated the Jurassic Daebo and Cretaceous Bulguksa granitic rocks in South Korea. The former are distributed mainly in the Gyeonggi and Yeongnam massifs and the latter are present in the Gyeongsan basin and Ogcheon belt. The Daebo granitic rocks generally are of ilmenite series and I to S type. These rocks are associated with AuAg hydrothermal deposits, whereas the Bulguksa granitic rocks are of magnetite series and I type, and are associated with PbZn, Cu and MoW hydrothermal deposits, as well as AuAg hydrothermal deposits. The Daebo granitic rocks show adakitic signatures in their chemical compositions. They are considered to have been derived from partial melting of the thick lower continental crust. Conversely, the Bulguksa granitic rocks in the Gyeongsan basin are non-adakitic and are considered to have been derived from partial melting of a mantle wedge. Magmas of the Daebo granitic rocks formed at relatively shallow levels, but solidified at deep levels compared with those of the Bulguksa granitic rocks. The Bulguksa granitic rocks in the central to western Ogcheon belt are considered to have been formed by fractionation of magmas derived from partial melting of continental crust. The total Al contents of biotite and hornblende in the granitic rocks increased, with the Bulguksa granitic rocks in the Gyeongsan basin &lt; the Bulguksa granitic rocks in the Ogcheon belt and Gyeonggi and Yeongnam massifs and the Daebo granitic rocks in the Ogcheon belt &lt; the Daebo granitic rocks in the Gyeonggi and Yeongnam massifs. This order corresponds to an increase in solidification depth.

In the Angkor monuments of Cambodia, pieces of wood remain (as head frames of doorways, crossbeams, ceiling boards, etc.) in the following 8 monuments: Bakong, Lolei, Baksei Chainkrong, North Khleang, Angkor Wat, Banteay Kdei, Bayou, and Gates of Angkor Thom. Accelerator mass spectrometry (AMS) radiocarbon dating carried Out on 15 wood samples collected from the above 8 monuments revealed that most of the wood samples are original, except for the head frame of a doorway in Baksei Chamkrong, the ceiling boards in the northwest tower. and a crossbeam with pivot hole in the southwest lower of the Inner Gallery of Angkor Wat. The (14)C age for the head frame of a doorway in the inner wall under the central tower of North Khleang supports the hypothesis that the inner walls are additions from a later period.

Chemical analysis of biotite in representative granitic rocks in Japan shows that the total Al (Al-T) content changes with the metal type of the accompanying hydrothermal ore deposits and increases in the following order: Pb-Zn and Mo deposits &lt; Cu-Fe and Sn deposits &lt; W deposits &lt; non-mineralized granitic rocks. The Al-T content of biotite in granitic rocks may be a useful indicator for distinguishing between mineralized and non-mineralized granitic rocks. A good positive correlation is seen between the Al-T content of biotite and the solidification pressure of the granitic rocks estimated by sphalerite and hornblende geobarometers and the mineral assemblages of the surrounding rocks. These facts suggest that the Al-T content of biotite can be used to estimate the solidification pressure (P) of the granitic rocks. The following empirical equation was obtained:
P (kb) = 3.03 x Al-T - 6.53 (+/- 0.33)
where Al-T designates the total Al content in biotite on the basis O = 22. According to the obtained biotite geobarometer, it is estimated that Pb-Zn and Mo deposits were formed at pressures below 1 kb, Cu-Fe and Sn deposits at 1-2 kb, W deposits at 2-3 kb and non-mineralized granitic rocks were solidified at pressures above 3 kb.

Detailed magnetic susceptibility measurement was conducted on the sandstones used for the Angkor monuments constructed in the period spanning the Preah Ko and Angkor Wat styles, and the construction process of the buildings and quarries of the sandstones was considered. Combined with the previous study on the sandstones of the Bayon style [Uchida, E., Cunin, O., Shimoda, I., Suda, C., Nakagawa, T., 2003. The construction process of the Angkor monuments elucidated by the magnetic susceptibility of sandstone, Archaeometry 45, 221-232], the magnetic susceptibility measurement revealed that there were 7 sandstone quarries corresponding to Stages I, II, III, IVa, V, VII and VIIIb during the Angkor period. The sandstones used for the monuments belonging to Stage I show average magnetic susceptibility values ranging from 1.1 to 2.3 × 10-3 SI units. In the Bakheng style period (Stage II), the average magnetic susceptibility of the supplied sandstones decreased gradually from around 10 to 1 × 10-3 SI units over time. The magnetic susceptibility range of the sandstones used for the monuments of Stage III was from 2.3 to 3.0 × 10-3 SI units. In the early Angkor Wat style period (IVb), the average magnetic susceptibility of the supplied sandstones increased over time, reflecting the supply of the sandstones from two different quarries, that is, the quarry corresponding to the Khleang and Baphuon style monuments (Stage IVa), with low average magnetic susceptibilities of 1.1 to 2.4 × 10-3 SI units, and the quarry corresponding to the main Angkor Wat style monuments (Stage V), with high average magnetic susceptibilities ranging from 2.8 to more than 4.3 × 10-3 SI units. The sandstones of Stage VII show low average magnetic susceptibility around 1 × 10-3 SI unit. The sandstones of Stage VId is a mixture of sandstones of Stages V and those of Stage VII. The sandstones with high magnetic susceptibilities are found in the monuments belonging to Stage VIIIb, reflecting the supply from the new sandstone quarry. © 2006 Elsevier Ltd. All rights reserved.

The Angkor monuments in northwestern Cambodia, which are primarily made of sandstone, are suffering from deterioration due to salt weathering. In order to elucidate the sources of the salts and salt weathering process, this paper analyzed bulk chemical compositions and S (sulfur) and Sr (strontium) isotopic ratios for the salts and surrounding environmental materials. At places where bats inhabit the structures, various kinds of sulfate and phosphate salts are formed on the surface of the sandstone. The results of the analysis demonstrate that the S and P (phosphorus) components in the salts are primarily derived from bat guano. Moreover, Ca (calcium), which is the major element in the salts, is suggested to be derived from both bat guano and the sandstone. The isotopic data strongly suggests that bat guano is related to salt weathering. Removal of these animal excrements is essential for future conservation of these monuments. On the other hand, exfoliation of sandstone commonly occurs due to crystallization of calcite (CaCO3) on platform surfaces of pyramid-type monuments. A large amount of Ca in calcite is suggested to be derived from calcite cement of the building sandstone. (c) 2006 Elsevier Ltd. All rights reserved.

Prasat Suor Prat in the Angkor monuments, Cambodia, is situated at the east end of the Royal Plaza and consists of 12 towers numbered N1-N6 and S1-S6 that are mainly made of laterite. Sandstone is also used for pediments, door and window frames, and balusters, etc. Until now, it was thought that Prasat Suor Prat was constructed in the Bayon period. However, the characteristics of the stone materials used for the Angkor monuments suggest that Prasat Suor Prat was constructed in the Angkor Wat period. This is supported by the radioactive carbon age obtained for charcoal fragments collected from the soil between the laterite blocks in the N1 tower and also from the stucco on the inner wall of the N2 tower. © 2005 Elsevier Ltd. All rights reserved.

Experiments on the simultaneous partitioning of divalent metal ions were performed in the systems (1) ZnS (sphalerite)−(Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Cd²⁺)Cl₂−H₂O and (2) Mn₃Al₂Si₃O₁₂ (spessartine)−(Ni²⁺, Mg²⁺, Co²⁺, Zn²⁺, Fe²⁺, Ca²⁺)Cl₂−H₂O in the temperature range of 500 to 800°C at 1 kb. In the former system for ion partitioning in the 4-fold coordination, parabola-shaped PC-IR curves with a peak near Zn²⁺ were obtained and no anomaly was observed for Zn²⁺ and Ni²⁺ but Cd²⁺. In the latter system for ion partitioning in the 8-fold coordination, parabola-shaped PC-IR curves with a peak near Mn²⁺ were obtained, but Zn²⁺ deviates from such a trend and tends to concentrate into aqueous chloride solutions. The PC-IR curves for spessartine are gentle compared with those for sphalerite. The PC-IR curves both for spessartine and sphalerite become gentle with increasing temperature.

The partitioning of Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺ and Zn²⁺ between spinel group minerals (spinel and magnetite) and 2M aqueous chloride solutions was experimentally investigated in the temperature range of 500 to 800°C, 1 kb. The experimental results were analyzed thermodynamically taking into consideration the aqueous speciation.<BR>The partition coefficient - ionic radius (PC-IR) diagrams are drawn based on the experimental results. PC-IR curve for magnetite is parabola-shaped with a maximum between Co²⁺ and Fe²⁺, whereas Ni²⁺ and Zn²⁺ deviate from such a trend. The anomaly of Zn²⁺ and Ni²⁺ may be attributable to their tetrahedral and octahedral site preferency, respectively. The PC-IR curve becomes gentle with increasing temperature. This means that the element partitioning becomes weak with increasing temperature. On the other hand, PC-IR curve for spinel shows a maximum between Ni²⁺ and Mg²⁺, but Zn²⁺ shows no anomaly unlike the case of magnetite. This is because the element partitioning occurs in the tetrahedral site in the case of spinel.

In order to obtain the stepwise formation constants of tri-chloro complexes of Pb2+ and Sn2+, experiments on the effect of NaCl concentration on the ion exchange equilibria in the systems PbS - ZnS - PbCl2 - ZnCl2 - H2O and CaWO4 - SnWO4 - CaCl2 - SnCl2 - H2O were carried out. The experiments were conducted at 500degrees, 600degrees, 700degrees and 800degreesC (800degreesC is only for Sn2+), 1 kbar and also at 600degreesC, 0.5 kbar using 2 m aqueous chloride solutions. In all the experiments, the Sigmam(Pb)/(Sigmam(Pb)+Sigmam(Zn)) ratio of the aqueous chloride solutions in equilibrium with both PbS and ZnS and the Sigmam(Ca)/(Sigmam(Ca)+Sigmam(Sn)) ratio of the aqueous chloride solutions in equilibrium with both CaWO4 and SnWO4 decrease with the increase of NaCl concentration.
The experimental results were analyzed thermodynamically using the previously published dissociation constants for NaClaq, CaCl2aq and ZnCl3aq-. As a result, the stepwise formation constants (log K) for PbCl3aq- (PbCl2aq + Cl-aq(-) = PbCl3aq-) were obtained to be -0.1 at 500degreesC and 1 kbar, 0.9 at 600degreesC and 1 kbar, 1.4 at 700degreesC and 1 kbar, and 1.3 at 600degreesC and 0.5 kbar. The stepwise formation constants (log K) for SnCl3aq- (SnCl2aq + Cl-aq(-) = SnCl3aq-) were obtained to be 0.5 at 500degreesC and 1 kbar, 1.4 at 600degreesC and 1 kbar, 2.0 at 700degreesC and 1 kbar, 2.6 at 800degreesC and 1 kbar, and 1.9 at 600degreesC and 0.5 kbar.
The stepwise formation constants (log K) of tri-chloro complexes of Pb2+. Sn2+, Fe2+, Mn2+, Co2+, Ni2+, Zn2+ and Cd2+ vary with sixfold coordinated ionic radius showing a parabola-shaped curve with a maximum between Mn2+ and Cd2+. This may suggest that the best ionic radius for tri-chloro complex exists between Mn2+ and Cd2+.

We developed a software package entitled "SuperCritical for Windows^®" that is used for the thermochemical calculation of reactions between minerals and hydrothermal solutions in the temperature and pressure ranges of 0 to 1000°C and 1 to 5000bars, respectively. This package uses the databases of SUPCRT92 developed by Johnson et al. (1992)., however, the source code is newly encoded with Microsoft^® Visual Basic^® to be more suitable for the present PC environment and more user-friendly compared with SUPCRT92. This software package is composed mainly of two parts: one is for the calculation of the Gibbs energy of formation for minerals, fluids and aqueous species, and the other is for the calculation of the Gibbs energy of reactions among them. The output files are avilable as a text file in the CSV form or a worksheet (xis file) of Microsoft® Excel in order to facilitate the data processing and presentation of the calculation results.

Deterioration of the rock-cliff Buddha sculptures (Magaibutsus) in Oita Prefecture, Japan, was evaluated by using portable magnetic susceptibility meter and moisture meter. Investigation was carried out for the Magaibutsus of Sugao, Ogata Miyasako, Inukai, Usuki, Monzen and Oita Motomachi. These Magaibutsus were carved in the rock-cliff of the Aso-4 pyroclastic flow sediments.<br>There is a tendency that magnetic susceptibility is high (more than 7×10⁻³SI unit) for the non-deteriorated Magaibutsus preserving pigments on the surface, and moisture content for those Magaibutsus is low (less than 3%). On the other hand, deteriorated Magaibutsus have low magnetic susceptibility and high moisture content. The results suggest that the deterioration proceeds in the following order: Ogata Miyasako, Sugao<Inukai, Usuki, Monzen<Oita Motomachi. The relationship between magnetic susceptibility and moisture content reveals that magnetic susceptibility is more sensitive than moisture content to deterioration of the Magaibutsus.<br> Deterioration of the Magaibutsus seems to be mainly attributable to salt crystallization and freeze-thaw cycle.

The basalt JB-1a was reacted with 2M NaCl solutions, and the leaching behavior of the cations Na, K, Ca, Mg, Fe, Mn, Zn and Co was monitored. The experiments were carried out using standard cold-seal pressure vessels in the temperature range from 300 to 800 degrees C under the constant pressure of 1000 bars and also in the pressure range from 500 to 1000 bars at 600 degrees C.
The concentrations of Fe, Mn, Zn and Co in the hydrothermal solutions increased significantly with increasing temperature and with decreasing pressure. The thermodynamic analysis of the experimental results suggests that this is due to the formation of trichloro-complexes and also partly due to the temperature dependence of ion exchange between augite and aqueous chloride solution. The Na concentration in the aqueous solution decreases with increasing temperature and with decreasing pressure. On the other hand, the behavior of K, Ca and Mg is complex and their concentrations seem to be controlled by the coexisting minerals.
Judging from the experimental results, it is concluded that the transition elements are effectively leached from the basalt under higher temperatures and lower pressures. This means that higher temperature and lower pressure conditions are preferable for the production of ore-forming hydrothermal solutions.

Experiments on the partitioning of Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺ and Zn²⁺ between olivine (forsterite and fayalite) and 2 N aqueous chloride solutions were performed in the temperature range of 500 to 800°C, 1 kb.<br> The partition coefficient, which is defined as K_PN(Fo)=(X_Me2SiO4/X_Mg2SiO4)/(m_MeCl2^°aq/m_MgCl2^°aq) or K_PN(Fa)=(X_Me2SiO4/X_Fe2SiO4)/(m_MeCl2^°aq/m_FeCl2°_aq), vs. ionic radius (PC-IR) diagrams are drawn based on the experimental results. In the case of forsterite, the PC-IR curve has a local maximum near Ni²⁺ and shows a concave curve in the region of larger ionic size. However Zn²⁺ deviates from such a trend. In the case of fayalite, the PC-IR curve shows a convex curve with a peak near Ni²⁺ except for 500°C. Also in this case, Zn²⁺ deviates from such a trend. The anomaly of Zn²⁺ may be attributable to its tetrahedral site preferency. The K_PN value for Ni²⁺ decreases with increasing temperature, whereas those for the other elements except for Ca²⁺ increase. The optimum ionic radius for forsterite and fayalite seem to increase slightly with increasing temperature.

We developed a software package entitled "SuperCritical for Windows^®" that is used for the thermochemical calculation of reactions between minerals and hydrothermal solutions in the temperature and pressure ranges of 0 to 1000°C and 1 to 5000bars, respectively. This package uses the databases of SUPCRT92 developed by Johnson et al. (1992)., however, the source code is newly encoded with Microsoft^® Visual Basic^® to be more suitable for the present PC environment and more user-friendly compared with SUPCRT92. This software package is composed mainly of two parts: one is for the calculation of the Gibbs energy of formation for minerals, fluids and aqueous species, and the other is for the calculation of the Gibbs energy of reactions among them. The output files are avilable as a text file in the CSV form or a worksheet (xis file) of Microsoft® Excel in order to facilitate the data processing and presentation of the calculation results.

"PEQ" is a QuickBASIC program package for the construction of mineral phase equilibrium diagrams such as P-T, T-X_CO2, P-X_CO2, lnf_O2-T and μ_x-μ_y diagrams using a personal computer. The thermodynamic datasets for minerals of Helgeson et al. (1978) and Holland and Powell (1990) are incorporated into the program. The non ideal mixing of H₂O and CO₂ can also be taken into account. Some examples of the construction of phase diagrams using "PEQ" are given.

Aqueous speciation of zinc in 2N chloride solution was determined experimentally at 500 to 700 degrees C and 0.5 to 1.0 kb by monitoring the effect of NaCl on ion exchange equilibria in the system CaTiO3-ZnTiO3-CaCl2-ZnCl2-H2O. The Ca/(Ca + Zn) value of the 2N aqueous chloride solution in equilibrium with both CaTiO3 and ZnTiO3 decreased with the increase of NaCl under all experimental conditions. This is due to the formation of tri-chloro zinc complex. The formation constant of tri-chloro zinc complex was estimated to be 1.1, 2.1 and 2.7 at 500, 600 and 700 degrees C, 1 kb, respectively, and 2.6 at 600 degrees C, 0.5 kb in logarithm. The formation constant of tri-chloro zinc complex increases with increasing temperature and decreasing pressure. This suggests that zinc can be effectively leached from rocks and magmas under higher temperature and lower pressure conditions.

Aqueous speciation of cadmium in 2 M chloride solutions was determined at 500 and 600 degrees C, 1 kbar and 600 degrees C, 0.5 kbar in the system CaTiO3-CdTiO3-CaCl2-CdCl2-NaCl-H2O using the same experimental method as Uchida et al. (1998). Thermodynamic analysis of the experimental results gives 1.3, 2.3 and 2.9 for the logarithm of the stepwise formation constant of tri-chloro cadmium complex at 500 and 600 degrees C, 1 kbar and 600 degrees C, 0.5 kbar, respectively. The formation constant increases with increasing temperature and decreasing pressure.

The effect of NaCl on ion exchange equilibria in the system CaWO4-MeWO(4)-CaCl2-MeCl(2)-H2O (Me: Mg, Sr, Ni and Co) was experimentally monitored at 600 degrees C and 1 kbar. The Ca/(Ca + Me) ratio of the aqueous chloride solution in equilibrium with both CaWO4 and MeWO(4) was constant for Mg and Sr in spite of the addition of NaCl, whereas the ratio decreased significantly for Ni and Co with the increase of NaCl. The experimental results indicate that both Ni2+ and Co2+ do form higher-order chloro-complexes such as NiCl3 aq and CoCl3aq-, whereas both Mg2+ and Sr2+ may not. The thermodynamic analysis of the experimental results gives 1.5 and 2.1 in logarithm units for the formation constants for NiCl3 aq and CoCl3aq- respectively. By combining the results of Uchida et al. (1995), MeCl(2aq2aq) tends to forms MeCl(3 aq) in the order of SrCl2aq CaCl2aq = MgCl2aq much less than NiCl2aq &lt; FeCl2aq &lt; CoCl2aq &lt; MnCl2aq at 600 degrees C and 1 kbar. Based on ligand field theory, the above order may suggest that the transition metal cations exist as tetrahedral chloro-complexes with low-spin state in the supercritical hydrothermal solutions.

Experiments on ion exchange of Ca²⁺, Fe²⁺ and Mn²⁺ between grossularalmandine-spessartine garnet solid solution and 2N aqueous chloride solution were conducted at 600°C and 1 kb under relatively reducing conditions in order to determine the stability relation and mixing property of the garnet solid solution. The experimental results revealed that calcium ion is slightly preferentially partitioned into aqueous chloride solution compared with ferrous and manganese ions. Grossular, almandine and spessartine form an almost continuous solid solution except for the semicircular region along the grossular-almandine join, where mineral assemblages of fayalite+anorthite and hedenbergite+anorthite+wustite appear instead of the garnet solid solution. Mixing properties of the garnet solid solution were evaluated from the experimental results by considering the formation of FeCl₃⁻_aq and MnCl₃⁻_aq in the aqueous phase. Almandine-spessartine solid solution shows slightly negative deviation from ideality. On the other hand, grossular-spessartine solid solution shows slightly positive deviation. Mixing property of grossular-almandine solid solution was not well determined due to the large unstable region.

Aqueous speciation of iron and manganese chlorides in supercritical hydrothermal solutions was determined by monitoring the effects of NaCl and KCl on the Ca/(Ca + Fe) and Ca/(Ca + Mn) ratios of aqueous chloride solutions in equilibrium with scheelite and ferberite and with scheelite and huebnerite, respectively. The experiments were carried out under supercritical conditions of 400 and 600 degrees C, and 1 kbar. The ratios decrease significantly with increasing NaCl and KCl concentrations at both 400 degrees C and 600 degrees C. This is attributable to the formation of higher-order aqueous chloride complexes of Fe and Mn, presumably FeCl3aq- and MnCl3aq-. Based on the thermodynamic analysis of the experimental results using published dissociation constants for NaClaq, KClaq and CaCl2aq, logarithms of the formation constants for FeCl3aq- were obtained to be 0.2(NaCl) and 1.2(KCl) for 400 degrees C, and 1.9(NaCl) and 1.9(KCl) for 600 degrees C, and those for MnCl3aq- to be 0.4(NaCl) and 1.1(KCl) for 400 degrees C and 2.3(NaCl) and 2.3(KCl) for 600 degrees C. This means that the supposition of m(MeCl(2aq)) = Sigma m(Me) for supercritical hydrothermal solutions is invalid.

The excess Gibbs energy of mixing for a regular solution can be derived systematically by defining the interaction energy for particle groups composed of closest neighbors at equivalent site. The internal energy of a system is regarded as the sum of the interaction energy for particle groups and the excess function is derived from the sum of the interaction energy change caused by the formations of particle groups.
In the present paper, we have derived the excess Gibbs energy of mixing for ternary and quaternary regular solutions with a closest packing. For a ternary regular solution, the molar excess Gibbs energy of mixing is given as follows, (G) over bar(ex) = X(A)X(B)(X(A)W(AAB)+X(B)W(ABB))+X(B)X(C)(X(B)W(BBC)+X(C)W(BCC))+X(C)X(A)(X(C)W(CCA)+X(A)W(CAA)+2X(A)X(B)X(C)W(ABC), where X(i) is a mole fraction of the component i and W-ijk is an interaction parameter of [ijk] triplet. The following expressions for n-component systems are derived by the similar method by supposing interaction energy among r particles. Some previously proposed models can be derived from our model.
n=2, r=2: (G) over bar(ex)=X(A)X(B)W(AB) (symmetric binary regular solution model) n=2, r=3:(G) over bar(ex)=X(A)X(B)(X(A)W(AAB)+X(B)W(ABB) (asymmetric binary regular solution model) n=3, r=2:(G) over bar(ex)=X(A)X(B)W(AB)+X(B)X(C)W(BC)+X(C)X(A)W(CA) (symmetric ternary regular solution model) n=3, r=3: (G) over bar(ex) = X(A)X(B)(X(A)W(AAB)+X(B)W(ABB))+X(B)X(C)(X(B)W(BBC)+X(C)W(BCC)) +X(C)X(A)(X(C)W(CCA)+X(A)W(CAA))+2X(A)X(B)X(C)W(ABC) (new ternary model: stated above) n=4, r=4: (G) over bar(ex)=X(A)(3)X(B)W(AAB)+X(B)(3)X(A)W(BBBA)+X(A)(3)X(C)W(AAAC)+X(C)(3)X(A)W(CCCA) +X(A)(3)X(D)W(AAAD)+X(D)(3)X(A)W(DDDA)+X(B)(3)X(C)W(BBBC)+X(C)(3)X(B)W(CCCB) +X(B)(3)X(D)W(BBBD)+X(D)(3)X(B)W(DDDB)+X(C)(3)X(D)W(CCCD)+X(D)(3)X(C)W(DDDC) +3/2X(A)(2)X(B)(2)W(AABB)+3/2X(A)(2)X(C)(2)W(AACC)+3/2X(A)(2)X(D)(2)W(AADD) +3/2X(B)(2)X(C)(2)W(BBCC)+3/2X(B)(2)X(D)(2)W(BBDD)+3/2X(C)(2)X(D)(2)W(CCDD) +3X(A)(2)X(B)X(C)W(AABC)+3X(A)(2)X(B)X(D)W(AABD)+3X(A)(2)X(C)X(D)W-AACD +3X(B)(2)X(A)X(C)W(BBAC)+3X(B)(2)X(A)X(D)W(BBAD)+3X(B)(2)X(C)X(D)W(BBCD) +3X(C)(2)X(A)X(B)W(CCAB)+3X(C)(2)X(A)X(D)W(CCAD)+3X(C)(2)X(B)X(D)W(CCBD) +3X(D)(2)X(A)X(B)W(DDAB)+3X(D)(2)X(A)X(C)W(DDAC)+3X(D)(2)X(B)X(C)W-DDBC +6X(A)X(B)X(C)X(D)W(ABCD).

The Taebaek Pb-Zn(-Ag) deposit of the Yeonhwa I mine, Republic of Korea, occurs in a broadly folded and reverse-faulted terrain of Paleozoic sedimentary rocks: the Taebaeksan basin. The orebodies consist of several thin tabular orebodies of hydrothermal replacement type where they are hosted by carbonate rocks. The Pb-Zn(-Ag) mineralization can be divided into four distinct stages based upon the mode of occurrence of ore minerals, ore textural relationships and their composition. Based on temperatures inferred from arsenopyrite compositions by means of electron microprobe and fluid inclusions, the estimated temperatures for the stages I, II, III and IV reach 330 to 350-degrees-C, 270 to 340-degrees-C, 230 to 250-degrees-C, and &lt; 220-degrees-C, respectively. The sulphur activity (atm) of ore formation at the Taebaek deposit was estimated for each stage as 10(-11) to 10(-11.5), 10(-9.5) to 10(-13), 10(-13.5) to 10(-15), and &lt; 10(-15), respectively. Even though application of sphalerite geobarometry is problematic because of the absence of good mineral assemblages, sphalerite coexisting with pyrite but not with pyrrhotite was used to estimate the minimum mineralization pressure (about 1 kbar).

Stability relations among minerals in the system CaSiO₃-FeSiO₃-MnSiO₃-H₂O have been determined experimentally by means of ion exchange at 600°C and 1kbar. Aqueous chloride solution was used as a transport and exchange medium for cations. Stable minerals under the experimental conditions are wollastonite, bustamite-ferrobustamite solid solution, hedenbergite, pyroxmangite, rhodonite and fayalite+quartz instead of ferrosilite. Bustamite occupies a wide stability field along the CaSiO₃-MnSiO₃ join, and forms a continuous solid solution with ferrobustamite. Both pyroxmangite and rhodonite have elongated stability fields parallel to the FeSiO₃-MnSiO₃ join. The mineral assemblages hedenbergite+bustamite+fayalite+quartz and bustamite+pyroxmangite+fayalite+quartz were confirmed to be stable under the experimental conditions. Ferrous and manganese ions are preferentially incorporated into the solid phases in contrast to calcium ion.