Geochemical and radiogenic isotopic signatures of granitic rocks in Chanthaburi and Chachoengsao provinces, southeastern Thailand : Implications for origin and evolution

The Chanthaburi, Pliew, Klathing, Khao Cha Mao, and Khao Hin Son granitic bodies in Chanthaburi and Chachoengsao provinces in southeastern Thailand, which are located on the southwestern side of the Mae Ping Fault and eastern side of the Klaeng Fault, were investigated. In this study, magnetic susceptibility measurements, whole-rock chemical composition and Nd-Sr isotope analyses, and zircon U-Pb dating were conducted on these granitic bodies. The surveyed granitic rocks are classified as I- to A-type granites, are of the ilmenite series, and show clearly negative Eu anomalies, which suggest they formed under reducing conditions. Nd-Sr isotope ratios indicate continental crust material involvement in the formation of these granite bodies. The magnetic and geochemical signatures are similar to those of granite bodies in southwestern Cambodia. The study area is thus considered an extensional area of southwestern Cambodia, corresponding to the Sukhothai Zone (the Chanthaburi-Kampong Chhnang Zone). Zircon U-Pb dating yields ages of 208–214 Ma (the Late Triassic) for granite bodies except for the Khao Cha Mao granitic body, which dates to 55 Ma. The former age corresponds to the collision time of the Sibumasu and Indochina terranes, and the latter age is likely related to the collision time of the Indian and Eurasian continents

下顎犬歯236歯の根管形態についての検討

To achieve the effect of mechanical preparation of root canals, transparent specimens of extracted 236 mandibular canines were investigated for canal configuration, thickness and curvature of the root canal, condition of any accessory canals, and location of the apical foramen. Fewer than 25% of the specimens showed accessory canals that were impossible to clean mechanically. The majority of the lateral branches were 0.15mm<and≦0.20mm. Although apical foramina located away from the apex were observed in 18% of the mandibular canines. All apical foramina were located within 0.5mm of the apex. Data on the thickness of the root and main canal in the apical portion and curvature of the root canal suggest that for adequate apical preparation, a #60 file must be able to reach the apical constriction

Siliceous Sandstones Used in Local Khmer Temples in Battambang, Ta Keo, and Kampong Cham Provinces, Cambodia

Siliceous sandstones used in Khmer temples such as the Prasat Basset, Wat Ek Phnom, and Phnom Banan temples in Battambang Province, Phnom Chisor and Ta Prohm temples in Ta Keo Province, and Wat Nokor Bachey temple in Kampong Cham Province in Cambodia were investigated in this study to determine the supply source of the siliceous sandstones used in these temples. Chemical composition analyses and magnetic susceptibility measurements were conducted for the sandstone blocks used in these temples. Siliceous sandstone is the primary construction material in the investigated temples, except for the Phnon Chisor (bricks). Two types of siliceous sandstone, pale brown and red, were found. Pale brown siliceous sandstone was used for the construction of all the investigated temples. In contrast, red siliceous sandstone was found only in the Wat Ek Phnom, Prasat Basset, and Phnom Banan temples. It is suggested that the pale brown siliceous sandstone originated from the Phra Wihan Formation within the Khorat Group. Based on the chemical composition analysis, the pale brown siliceous sandstone in the Ta Prohm temple at Tonle Bati and the Wat Nokor Bachey temple may have been sourced from the lower level of the Phra Wihan Formation. In contrast, the pale brown siliceous sandstone used in the Prasat Basset, Wat Ek Phnom, Phnom Banan, and Phnom Chisor temples was likely sourced from the upper level. The origin of the red siliceous sandstone is proposed to be from the Sao Khua Formation, which is situated above the Phra Wihan Formation

Experiments on Distribution of Divalent Metal Cations between Olivine Solid Solutions and Aqueous Chloride Solutions at 700 &deg;C and 100 MPa

Experiments on divalent cation distribution between Mg&ndash;Fe olivine solid solutions and 1 mol/L (Ni2+, Mg2+, Co2+, Zn2+, Fe2+, Mn2+)Cl2 aqueous solutions were carried out at 700 &deg;C and 100 MPa. Regardless of the composition of the Mg&ndash;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+ &gt; Mg2+ &gt; Co2+ &gt; Mn2+ &gt; Fe2+ &gt; 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&ndash;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&ndash;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+)

Simultaneous Partitioning of Divalent Metal Ions between Alabandite and 1 mol/L (Ni, Mg, Co, Zn, Fe)Cl2 Aqueous Solutions under Supercritical Conditions

To clarify the element partitioning behavior between minerals and aqueous chloride solutions, we conducted experiments to investigate simultaneous partitioning of Ni2+, Mg2+, Co2+, Zn2+, Fe2+, and Mn2+ ions between alabandite (MnS) and 1 mol/L (Ni, Mg, Co, Zn, Fe)Cl2 aqueous solutions at 500&ndash;800 &deg;C and 100 MPa. The bulk partition coefficients calculated using the following equation were in the order of Fe2+ &gt; Co2+ &gt; Ni2+ &asymp; Zn2+ &gt; Mn2+ &gt;&gt; Mg2+; KPN = (xMeS/mMeaq)/(xMnS/mMnaq). A partition coefficient-ionic radius (PC-IR) curve was plotted with the logarithmic value of the partition coefficient on the y-axis and the ionic radius at the six-fold coordinated site on the x-axis. The peak of this curve was located near the ionic radius of Fe2+ and not near the ionic radius of Mn2+. Zn2+ showed a slight negative partitioning anomaly, which increased in the order of sulfide minerals &lt; arsenic sulfide minerals &lt; arsenide minerals as the covalent bond became stronger. Ni2+ showed a positive partitioning anomaly, which indicated that it preferred an octahedral structure. The width of the PC-IR curve decreased in the order of sulfide minerals &gt; arsenic sulfide minerals &gt; arsenide minerals as the covalent bond became stronger, that is, the ion selectivity became stronger

Estimated Construction Order of the Major Shrines of Sambor Prei Kuk Based on an Analysis of Bricks

Sambor Prei Kuk is a predominantly brick monument complex identified as Ishanapura, the capital of the Chenla Dynasty, which reached the height of prosperity in the first half of the 7th century. In the east area of this ancient city, the religious area was formed by three temple complexes which are composed of brick shrines and a multiple number of smaller temples with single or a few shrines scattered in the area. One of the challenging issues is to identify the dates and order in which these structures are constructed. Previous studies based on epigraphy and decorative style have estimated a simple dating of the three temple complexes. In this research, 59 major brick structures which are relatively well preserved in this area were analyzed in terms of the size and chemical composition of their component bricks. This analysis revealed that these brick structures can be classified into several groups corresponding to construction stages. The results revealed that the individual shrines in each temple complexes were built in a more complex process than previously stated, and the construction stages of the individual shrines in the vicinity were also identified as an equally complex process