Experimental Studies of Phenakite Solubility in Alkaline Granitoid Melts

Doklady Earth Sciences - The solubility of phenakite in aluminosilicate melts of various alkalinity was studied experimentally at T = 1000°C and P = 1 kbar in dry conditions and in the...     

The Early Tertiary chemical remagnetization in the Bakjisan Syncline, Korea: Its geotectonic implications

The Bakjisan Syncline is located in the northwestern part of the Taebaeksan Basin, Korea. New paleomagnetic data for the Upper Carboniferous–Lower Triassic Pyeongan Supergroup from the Pyeongchang area on the west limb of the Bakjisan Syncline have been obtained, and synthesized and compared with previous data from the Jeongseon area on the east limb of the syncline. A total of 350 specimens were collected from 21 sites to clarify the relationship between the spatial distribution of remagnetized areas and the thrust system in the Taebaeksan Basin. The characteristic remanent magnetization (ChRM) isolated from all samples was a remagnetized component acquired after tilting of the strata and carried by various magnetic minerals (magnetite, hematite and pyrrhotite). From rock magnetic studies, electron microscope observations and XRD analyses, the pervasive remagnetization is interpreted to be associated mainly with a fluid-mediated chemical remanent magnetization (CRM). This is consistent with the results of previous work in adjacent areas. The paleomagnetic pole position (88.3°E, 83.9°N, A₉₅ = 4.9°) from the Pyeongan Supergroup in the Bakjisan Syncline indicates that the timing of the remagnetization event is Early Tertiary times (i.e. Paleocene to Eocene) by comparison with reliable paleopoles from the Korean Peninsula. Early Tertiary CRMs are also reported from previous studies of an adjacent region within the northwestern part of the Taebaeksan Basin. In contrast, a primary remanent magnetization was reported in the southeastern part of the Taebaeksan Basin. This implies that the major thrust system (the Gakdong thrust) which separates the two regions has caused them to experience substantially different geologic histories since deposition of the strata. Since many thrusts with NS trend are observed in the northwestern part of the Taebaeksan Basin compared with the southeastern region, it appears that the remagnetizing fluids pervasively penetrated the northwestern part of the basin by utilizing the already well-developed thrust system.     

The system NaAlSi3O8−H2O−H2 (1200° C, 2 kbar): the solubility and interaction mechanism of fluid species with melt

The H₂O and H₂ solubilities in an albite melt at 1200° C and 2 kbar over the entire range of gas phase composition, from pure hydrogen to pure water were studied in gas-media pressure vessels. The water solubility initially increases with increasing hydrogen content until a maximum of 9.19 wt% H₂O atXH ₂ ^v =0.1 is reached, withXH ₂ ^v >0.1 the water solubility decreases. The hydrogen solubility curve has a maximum atXH ₂ ^v =0.42 where the concentration reaches 0.206 wt% H₂O. Over the entire compositional range¹H NMR (nuclear magnetic resonance) spectra show distinct absorption lines due to protons bound to OH groups and to isolated firmly bound water molecules. In NMR and Raman spectra there were no bands attributable to the H–H vibrations of molecular hydrogen. The X-ray photo-electronic spectra of hydrogen-bearing glasses show the Si2p (99 eV) band which corresponds to the zero-valency silicon. The formation of OH groups and molecular water during interaction between hydrogen-bearing fluids and melts under reducing conditions has a qualitative effect, the same as for water dissolution. Another point of interest is that hydrogen-bearing melts undergo more depolymerization than do hydrous melts.     

Phase Distribution of Rare and Rare-Earth Elements in the Silicate–Fluoride Systems at Т = 800–1200°С and Р = 1–2 kbar (Experimental Investigations)

Doklady Earth Sciences - The melt in the alumosilicate (granite) melt–molten fluoride salt system is experimentally studied at Т = 800–1200°С and Р = 1–2...     

Multiphase flow modeling with general boundary conditions and automatic phase-configuration changes using a fractional-flow approach

The multiphase flow simulator moving particle semi-implicit (MPS) method is developed based on the fractional-flow approach, originated in the petroleum engineering literature, considering the fully three-phase flow with general boundary conditions. The fractional flow approach employs water saturation, total liquid saturation, and total pressure as primary variables. Most existing models based upon fractional flow are limited to two-phase flow and specific boundary conditions. Although there appear a number of three-phase flow models, they were mostly developed using pressure-based approaches, which require variable-switch techniques to deal with phase appearance and disappearance. The use of fractional flow-based approaches in MPS makes it unnecessary to use variable-switching to handle the change of phase configurations because the water saturation, total liquid saturation, and total pressure exist throughout the solution domain regardless of whether certain phases are present or not. Furthermore, most existing fractional flow-based models consider only specific boundary conditions, usually Dirichlet-type pressure for water phase and flux-type boundary for nonaqueous phase liquid or particular combinations for individual phase. However, the present model considers general boundary conditions of ten most possible and plausible cases. The first eight cases are the combinations of the phase pressure or the phase flux of each of the three individual phases. The other two cases are the variable boundary conditions: one for water-medium interface and the other for the air-medium interface when the directions of fluxes are not known a priori. Thus, the model’s capabilities of handling general boundary conditions extend the simulators’ usefulness in the field system.     

日本海的末次盛冰期

日本海末次盛冰期的沉积层几乎都是以交替出现的深色纹层、浅色纹层状和均质沉积物为特征。根据日本海中部和南部两个岩心记录的末次盛冰期的沉积特征和表层海水温度变化,讨论了低海平面时期东亚季风对日本海沉积环境的控制作用。24.2~17.8 cal.kaBP,日本海南部纹层沉积的分布均对应了夏季风的相对增强,表明季风降水输入是引起该时期日本海底层水含氧量变化的主要原因。在夏季风的控制下,低盐富营养的东海沿岸水的强弱变化使冲绳海槽北部表层海水温度也在24.2~17.8 cal.kaBP期间出现低值并剧烈变化。30~24.2和17.8~15 cal.kaBP,受增强的冬季风(夏季风减弱)影响,日本海水体的流通性较强,底层水溶解氧含量相对较高。对23~17.5 cal.kaBP日本海的表层海水温度出现异常高值的原因存在很多争论,一般认为是由于季风降雨输入量大于蒸发量、表层水盐度普遍降低、水体出现密度分层、水层间的垂直交换受到限制所致。