A corundum-bearing mafic rock in the Horoman Peridotite Complex, Japan, was derived from upper mantle conditions to lower crustal conditions with surrounding peridotites. The amphiboles found in the rock are classified into 3 types: (1) as interstitial and/or poikilitic grains (Green amphibole), (2) as a constituent mineral of symplectitic mineral aggregates with aluminous spinel at grain boundary between olivine and plagioclase (Symplectite amphibole) and (3) as film-shaped thin grains, usually less than 10 μm in width, at grain boundary between olivine and clinopyroxene (Film-shaped amphibole). The Film-shaped amphibole is rarely associated with orthopyroxene extremely low in Al2O3, Cr2O3 and CaO (Low-Al OPX). These minerals were formed by infiltration of SiO2- and volatile-rich fluids along grain boundaries after the rock was recrystallized at olivine-plagioclase stability conditions, i.e. the late stage of the exhumation of the Horoman Complex.
Chondrite-normalized rare earth element patterns and primitive mantle-normalized trace-element patterns of the Green amphibole and clinopyroxene are characterized by LREE-depleted patterns with Eu positive and negative anomalies of Zr and Hf. These geochemical characteristics of the constituent minerals were inherited from original whole-rock compositions through a reaction involving both pre-existing clinopyroxene and plagioclase. We propose that the fluids were originally rich in a SiO2 component but depleted in trace-elements. Dehydration of the surrounding metamorphic rocks in the Hidaka metamorphic belt, probably related to intrusion of hot peridotite body into the Hidaka crust, is a plausible origin for the fluids. 相似文献
Abstract Permian basalt showing typical spinifex texture with >10 cm-long olivine pseudomorphs was discovered from the Jurassic Tamba accretionary complex in southwest Japan. The spinifex basalt occurs as a river boulder accompanied by many ferropicritic boulders in a Permian chert-greenstone unit. Groundmass of this rock is holocrystalline, suggesting a thick lava or sill for its provenance. Minor kaersutite in the groundmass indicates a hydrous magma. The spinifex basalt, in common with the associated ferropicritic rocks, is characterized by high high field strength element (HFSE) contents (e.g. Nb = 62 ppm and Zr = 254 ppm) and high-HFSE ratios (Al2O3/TiO2 = 3.9, Nb/Zr = 0.24 and Zr/Y = 6.4) unlike typical komatiites. The spinifex basalt and ferropicrite might represent the upper fractionated melt and the lower olivine-rich cumulate, respectively, of a single ultramafic sill (or lava) as reported from the early Proterozoic Pechenga Series in Kola Peninsula. Their parental magma might have been produced by hydrous melting of a mantle plume that was dosed with Fe- and HFSE-rich garnet pyroxenite. The spinifex basalt is an evidence for the Pechenga-type ferropicritic volcanism taken place in a Permian oceanic plateau, which accreted to the Asian continental margin as greenstone slices in Jurassic time. 相似文献
The hypothesized reaction mechanisms for U reduction by the dehydrogenation of hydroxyl groups and aliphatic hydrocarbonaceous moieties of lignite were verified by kinetic U reduction experiments using simple alcohols (1-octadecanol and 2-propanol) and aliphatic hydrocarbons (n-octacosane). The rate constants and activation energies for U reduction by these alcohols are similar to those obtained for U reduction by lignite. The rate-determining step for U reduction by both simple and natural organic matter is hypothesized to be controlled by oxygen diffusion through U oxides. The equilibria of the system lignite-aqueous uranyl have been used to calculate standard free energy changes ΔG° for lignite dehydrogenation. Their comparison with those for the dehydrogenation of simple organic molecules supports the proposed reactions thermodynamically. 相似文献
The orthorhombic MgSiO3 perovskite has been synthesized with the aid of a double-stage split-sphere-type high-pressure apparatus at about 280 kbar and 1000°C. The unit cell dimensions are: a = 4.7754(3)Å, b = 4.9292(4)Å and c = 6.8969(5)Å with the probable space group Pbnm. Calculated density is 4.108 g cm?3. Crystal structure determination has been carried out by means of both the geometrical simulation (DLS) technique and the ordinary powder X-ray analysis. The results indicate that the MgSiO3 perovskite is closer to the ideal perovskite than ScAlO3 perovskite. 相似文献
Interactions between lignite and soluble uranyl species have been investigated experimentally at different temperatures from 20° to 400°C. Fixation of uranyl species by lignite (45° to 250°C) and their reduction to uraninite (120° to 400°C) were observed. The fixation of uranyl species by lignite results in the formation of stable organo-uranyl compounds. The reduction of uranyl species by lignite results in a stoichiometric liberation of H+ in the solution medium and in a dehydrogenation of lignite. This dehydrogenation can be attributed to two different processes. The first is an oxidation of alcohol functional groups into aldehyde or ketone functions accompanied by a simultaneous reduction of uranyl species. The second is a dehydrogenation of hydrocarbonaceous aliphatic moieties induced by the uranium species. The molecular hydrogen produced during this process is subsequently used for an additional reduction of uranyl species. 相似文献
The regional and local variations in the composition of the wolframite series associated with the ilmeniteseries and magnetite-series granitoids in the Inner Zone of SW Japan were investigated using X-ray diffraction and microprobe analyses. It is concluded that the variation in Mn/Fe ratios in the source materials (granitic magmas in most cases) is the dominant factor controlling the regional variation in the wolframite compositions, while, as exemplified by the Kaneuchi mine, Kyoto Prefecture, the wallrock chemistry and pH of ore fluids are responsible for the local variation within a single vein system. Within a fresh euhedral crystal from the mine, only slight compositional variation of less than 3 mole% MnWO4 is found in the form of oscillatory zoning. This study, combined with the fluid inclusion research, indicates that the wolframite compositions (Mn/Fe ratios) cannot be used as a geothermometer. 相似文献
High-pressure phase relations in ZnSiO3 and Zn2SiO4 were investigated at about 1000°C and in the pressure range of 100–500 kbar, using a double-staged split-sphere type of high-pressure apparatus.Clinopyroxene-type ZnSiO3 transforms directly into a polymorph with the ilmenite structure at 120 kbar. The hexagonal unit cell dimensions of the ZnSiO3 ilmenite are determined to be under ambient conditions.The following reactions are also recognized at about 1000°C: and: The stabilities of silicate ilmenites, especially the absence of ilmenite of transition metal silicate composition, is discussed. It is pointed out that data on phase relations in zinc silicates may be informative for the consideration on those in magnesium silicates under very high pressures. It is suggested that the silicate ilmenite may be a major constituent in the lower mantle. 相似文献
We have searched for excesses of 36S derived from the decay of extinct 36Cl in sodalite, a secondary Cl-rich mineral, in Ca-Al-rich inclusions (CAIs) from the Vigarano and Allende CV3 chondrites and in a chondrule from the Ningqiang carbonaceous chondrite. The presence of sodalite in two CAIs from Vigarano and its absence from surrounding CAI fragments suggests sodalite formation after CAI fragmentation. As for sodalite in the Allende Pink Angel CAI, oxygen isotopic compositions have been interpreted as indicative of high temperature interactions, thus suggesting formation prior to accretion to the parent body, probably in a nebular setting. Sodalite in the Ningqiang chondrule is considered to have formed via alkali-Ca exchange, which is believed to have occurred before accretion to the parent body.Sodalites in the Vigarano CAIs and in the Ningqiang chondrule show no clear evidence for the presence of radiogenic 36S. The inferred 2σ upper limits for 36Cl/35Cl at the time of sodalite formation are 1.6 × 10−6 (Vigarano CAIs) and 3.3 × 10−6 (Ningqiang chondrule), respectively. In the Pink Angel CAI sodalite exhibits small 36S excesses which weakly correlate with 35Cl/34S ratios. The inferred 36Cl/35Cl ratio of (1.8 ± 2.2) × 10−6 (2σ error) is lower than that found by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg, G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct 36Cl and 26Al in meteorites. Astrophys. J. 640, 525-529], thus indicative of heterogeneous distribution of 36Cl in this CAI. Spallation reactions induced by energetic particles from the young Sun are suggested for the origin of 36Cl, similar to the case of 10Be. While 10Be appears to be present in roughly equal abundance in all studied CAIs, our study indicates the level of 36Cl abundances to be variable so that there seems to be no simple relationship between 10Be and 36Cl. This would be expected if trapped cosmic rays rather than Early Solar System spallation were the dominant source of 10Be in the Early Solar System, since their contribution to 36Cl would have been tiny.If the variability of 36Cl abundances is caused by temporal differences in the alteration that formed sodalite, sodalite in the Vigarano CAIs and in the Ningqiang chondrule may have formed ?0.5 and ?0.2 Ma after formation of the sodalite in the Ningqiang CAI analyzed by Lin et al. [Lin, Y., Guan, Y., Leshin, L. A., Ouyang, Z. and Wang, D. (2005) Short-lived chlorine-36 in a Ca- and Al-rich inclusion from the Ningqiang carbonaceous chondrite. Proc. Natl. Acad. Sci. USA 102, 1306-1311]. The Pink Angel sodalite that we analyzed may have formed ∼0.3 Ma after formation of the sodalite in the Pink Angel analyzed by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct 36Cl and 26Al in meteorites. Astrophys. J. 640, 525-529]. The estimated temporal differences suggest that alteration extended over at least 0.5 Ma. If previous works showing very low initial 36Cl/35Cl in the Allende CAIs and a H3 chondrite CAI are also considered, then alteration processes may have been more than 1.7 Ma. 相似文献
Groundwater which occurs in fractured rock or porous aquifers or other geological weak zones such as faults and fractures is usually extracted via boreholes, hand wells or other sources such as springs.Water scarcity has become a severe problem due to many factors, such as an alarming increase in population and per capita water consumption, over exploitation of groundwater resources and abrupt global climatic change along with its related eco-environmental geological problems. In such situation, application of artificial recharge systems(e.g. surface recharge basin and deep injection well systems) can help to effectively manage and augment the unitization of groundwater resources. However, the clogging problem,which may be caused by a complex interdependent mechanisms of physical, chemical and biological has been a challenge for the efficacy and the implementation of recharge facilities. Clogging can reduce the permeability, recharge rate and longevity of recharge facilities and increase the operational and maintenance costs. Major influencing factors associated with the occurrence of clogging include the chemical composition of groundwater(both the recharge water and native groundwater), aquifer medium and microbial diversity, together with other environmental factors such as temperature, pressure, total dissolved solids, total soluble salts, pH, Eh, nutrients, gases, carbonates and others; these factors ultimately increase the piezometric head but reduce the permeability and infiltration rates of porous/seepage media.Pretreatment of recharge water can minimize the potential clogging. In the case of clogged wells,rehabilitation methods need to be deployed. In the meantime, there is an urgent needs to understand the basic causes and developmental processes/mechanisms of clogging in order to mitigate this problem. This paper reviews the major clogging mechanisms and their possible preventive measures and redevelopments in artificial recharge systems. 相似文献
