Partition of magnesium and iron between Olivine and spinel,and between pyroxene and spinel

Partition of Fe²⁺ and Mg between coexisting (Mg, Fe)₂SiO₄ spinel and (Mg, Fe)SiO₃ pyroxene was investigated at pressures 80 and 90 kbar and at temperatures 840 and 1050° C, using tetrahedral-anvil type of high pressure apparatus. Olivine-spinel solid solution equilibria in the system Mg₂SiO₄-Fe₂SiO₄ were discussed in the light of the partition reaction. Partition of Fe²⁺ and Mg in both olivine-spinel and pyroxene-spinel systems can not be regarded as that between ideal solid solutions. By applying the simple solution model for the partition of Fe²⁺ and Mg, sign of the heat of mixing was estimated to be positive for all olivine, spinel and pyroxene. Relative concentration of Fe²⁺ in spinel in the pyroxene-spinel system is likely to cause some change in the chemical composition of modified spinel () or spinel () in the transition zone of the mantle. A considerable change is also expected in the transition pressure of to ( + ) and ( + ) to .Presented at the symposium Recent Advances in the Studies of Rocks and Minerals at High Pressures and Temperatures held in Montreal, 1972. Jointly sponsored by the International Mineralogical Association and the Commission on Experimental Petrology.     

Diffusion-controlled growth of wollastonite rims between quartz and calcite: comparison between nature and experiment

Growth rates of wollastonite reaction rims between quartz and calcite were experimentally determined at 0.1 and 1 GPa and temperatures from 850 to 1200 °C. Rim growth follows a parabolic rate law indicating that this reaction is diffusion‐controlled. From the rate constants, the D′δ‐values of the rate‐limiting species were derived, i.e. the product of grain boundary diffusion coefficient D′ and the effective grain boundary width, δ. In dry runs at 0.1 GPa, wollastonite grew exclusively on quartz surfaces. From volume considerations it is inferred that (D′_CaOδ)/(D′_SiO2δ)≥1.33, and that SiO₂ diffusion controls rim growth. D′_SiO2δ increases from about 10^?25 to 10^?23 m³ s^?1 as temperature increases from 850 to 1000 °C, yielding an apparent activation energy of 330±36 kJ mol^?1. In runs at 1 GPa, performed in a piston‐cylinder apparatus, there were always small amounts of water present. Here, wollastonite rims always overgrew calcite. Rims around calcite grains in quartz matrix are porous and their growth rates are controlled by a complex diffusion‐advection mechanism. Rim growth on matrix calcite around quartz grains is controlled by grain boundary diffusion, but it is not clear whether CaO or SiO₂ diffusion is rate‐limiting. D′δ increases from about 10^?21 to 10^?20 m³ s^?1 as temperature increases from 1100 to 1200 °C. D′_SiO2δ or D′_CaOδ in rims on calcite is c. 10 times larger than D′_SiO2δ in dry rims at the same temperature. Growth structures of the experimentally produced rims are very similar to contact‐metamorphic wollastonite rims between metachert bands and limestone in the Bufa del Diente aureole, Mexico, whereby noninfiltrated metacherts correspond to dry and brine‐infiltrated metacherts to water‐bearing experiments. However, the observed diffusivities were 4 to 5 orders of magnitude larger during contact‐metamorphism as compared to our experimental results.     

Coupling between internal and surface waves

In a fluid system in which two immiscible layers are separated by a sharp free interface, there can be strong coupling between large amplitude nonlinear waves on the interface and waves in the overlying free surface. We study the regime where long waves propagate in the interfacial mode, which are coupled to a modulational regime for the free-surface mode. This is a system of Boussinesq equations for the internal mode, coupled to the linear Schrödinger equations for wave propagation on the free surface, and respectively a version of the Korteweg-de Vries equation for the internal mode in case of unidirectional motions. The perturbation methods are based on the Hamiltonian formulation for the original system of irrotational Euler’s equations, as described in (Benjamin and Bridges, J Fluid Mech 333:301–325, 1997, Craig et al., Comm Pure Appl Math 58:1587–1641, 2005a, Zakharov, J Appl Mech Tech Phys 9:190–194, 1968), using the perturbation theory for the modulational regime that is given in (Craig et al. to appear). We focus in particular on the situation in which the internal wave gives rise to localized bound states for the Schrödinger equation, which are interpreted as surface wave patterns that give a characteristic signature of the presence of an internal wave soliton. We also comment on the discrepancies between the free interface-free surface cases and the approximation of the upper boundary condition by a rigid lid.     

玻璃纤维与红土的界面作用特性研究

红土中加入玻璃纤维，其界面作用特性将发生变化。试验结果表明，压实度、含水率、剪切速率、玻璃纤维的特性、干湿状态等因素都会影响玻璃纤维与红土的界面作用能力，总体表现为界面抗剪强度低于红土本身的抗剪强度，其界面作用特性可用界面剪应力因数、界面粘聚力因数和界面摩擦因数来衡量，其界面作用机理可用粘结嵌固作用和隔离作用来解释。     

Petrogenetic relationships between melilitite and lamproite

A detailed petrological study of the S. Venanzo olivine melilitite and Cupaello kalsilitite, located at the NE margin of the Roman Comagmatic Region of Italy has provided new data to evaluate their genetic relationships and related tectonic/magmatic conditions. Early crystallized olivine (Fo₉₂) from S. Venanzo is compatible with crystallization from near primary mantle melts, while late-crystallized olivine from both rocks (Fo_88–79) reflects primarily the high Ca of the host liquids, attained under the volcanic crystallization regime. Magnesiochromite inclusions in the early-crystallized olivine are consistent with near-primary melts close to lamproite in composition. Nepheline and kalsilite from both lavas contain high alkalis (+Ca), relative to Al, and thus correspond more closely with nepheline compositions from carbonatite-related assemblages, than with those from a wide compositional range of Alban Hills lavas. Coexisting melilite has high (Na+K)/Al, reflecting the Peralkalinity Index of the bulk rocks. Diopside and phlogopite from both lavas are characteristic of lamproites and groundmass kimberlites in their high Mg/(Mg+Fe²⁺) ratio (0.86–0.95; 0.80–0.90, respectively) and T-site (Si+Al) deficiencies. Götzenite, Ca₂Na[Zr, Ti]Si₂O₇(O, OH, F)₂, identified in both lavas, is typical of nephelinite-ijolite assemblages. On the other hand, khibinskite, K₄Zr₂Si₄O₁₄, found in the Cupaello lava, may be regarded as a Si-poor variety of wadeite, a mineral characteristic of lamproites. Clinopyroxene and monticellite, coexisting as late-crystallized phases in both lavas, suggest a common P-T liquid path of thermal descent in the system CaMgSi₂O₇–CO₂ in the presence of excess CO₂, but with different intersections with the åkermanite stability field. Substantial differences in SiO₂ saturation combined with high Mg number and liquidus temperatures experimentally determined at atmospheric pressure in both lavas (1276° C and 1260° C, respectively) indicate that a parent-daughter relationship is unlikely under the volcanic P-T regime. In La Roche's Rm-Ri-Rs diagram, the S. Venanzo composition fall close to the Oldoinyo Lengai alkalic pyroxenite trend of Donaldson and Dawson, while the Cupaello compositions follow a lamproitic trend, consistent with that indicated by the quartz-normative glass of the Gaussberg lava. Mantle compositions corresponding to wehrlite-clinopyroxenite and enriched in H₂O, CO₂, F, and LILE, are favoured as potential sources for the lavas. Their origin is probably related to subcrustal fluid transfer promoted by the Tyrrhenian mantle doming.     

Relationships between axial-plane foliations and strain

The relationship between various types of axial-plane foliation, strain history and finite strain are considered from a theoretical point of view. It is concluded that foliations (including slaty cleavage and schistosity) will not be precisely parallel to a principal plane of finite strain in the general case. There are however, a number of special cases that are geologically feasible and these are discussed.     

Relationship between water-soluble cations and palaeosalinity

Finely ground shale samples from a Carboniferous borehole sequence were shaken in water and the concentration of the water-soluble Na, K, Ca and Mg determined. The marine shales in the sequence were characterized by low concentrations of Na and K, and high concentrations of Ca and Mg. The reverse situation was found for the non-marine and brackish shales. The electrical conductivity of the water extract was higher for the marine shales than for the non-marine/brackish shales. It is suggested that the water-soluble cations were present in the sediment at the time of deposition as exchangeable cations which were released into the pore water during diagenesis as some of the exchange sites were eliminated.     

地球深部与表层的相互作用

板块理论和全球变化是20世纪地球科学中的2大突破性进展.进入21世纪,地球系统科学进入将这两方面结合起来,探索地球深部和表层系统的相互作用,即"固体地球动力学与行星循环(planetary cycle)"的新阶段.根据最近国际综合大洋钻探计划关于2013年后学术新方向的讨论,从俯冲带加工厂、大洋中脊与巨型火成岩省3个方面进行介绍,提出我国打破传统的学科界限、迎接新方向的建议.     

Relationship between exchangeable cations and palaeosalinity

In Carboniferous shales a relationship has been found between exchangeable cations and palaeosalinity. In the marine shales the concentration of exchangeable Mg is higher than in shales deposited in fresh and brackish water, and the concentrations of exchangeable Ca, Na and K are lower. The same relationships have been observed in modern sediments. When the cation concentrations in the whole rock are compared with the exchangeable cation concentrations, incorporation into the sediment of K and possibly Mg in the marine environment is indicated. Furthermore, the loss of Ca and Na from the sediment can be accounted for by the loss from exchange sites. Reactions taking place during halmyrolysis would appear to be more important than those taking place during diagenesis.     

Relationship between plume and plate tectonics

The relationship between plate- and plume-tectonics is considered in view of the growth and breakdown of supercontinents, active rifting, the formation of passive volcanic-type continental margins, and the origin of time-progressive volcanic chains on oceanic and continental plates. The mantle wind phenomenon is described, as well as its effect on plume morphology and anisotropy of the ambient mantle. The interaction of plumes and mid-ocean ridges is discussed. The principles and problems of plume activity analysis in subduction- and collision-related foldbelts are considered and illustrated with examples.     

The boundary between Cambrian and Precambrian

Generally, the Olenellus -bearing beds and associated fauna have been regarded by Russian geologists as occurring in the upper one-third of a continuous sedimentary sequence which was unfossiliferous below and which rested on crystalline basement. Presumably early fossil groups began producing carbonate skeletal material at different times and migrated so as to arrive in various areas earlier or later than elsewhere. Hence, paleontological identification of the Lower Cambrian boundary requires knowledge, now lacking, of vertical distribution of the skeleton-producing organisms, of the conditions of their emergence, and of related sedimentary facies. Previously used physical criteria for the recognition of the Cambrian-Precambrian boundary are unsatisfactory. It is suggested that this boundary be determined by absolute dating. The author reviews recent findings on geologic age, absolute age, and faunal content of many formations in the Siberian Platform and adjacent regions that bear on this problem. — C. G. Tillman.     

气藏盖储层压力配置类型及与储量丰度的关系

通过研究气藏盖层排替压力与储层压力特征,对其盖储层压力配置类型及与储量丰度关系进行了研究,结论为盖高储低压配置类型最有利于天然气富集,其次是盖高储常压配置类型和盖较高储低压配置类型,其它配置类型较差.通过统计得到:我国46个大中型气田盖储层压力配置类型有4种,以盖高储高压配置类型最多,其次是盖高储弱高压配置类型,再次是盖高储常压配置类型,盖高储低压配置类型最少;我国46个大中型气田中低储量丰度的大中型气田个数最多,其次是高、中储量丰度的大中型气田,特低储量丰度的大中型气田个数最少.通过我国46个大中型气田盖储层压力配置类型与天然气储量丰度之间关系研究发现,盖储层压力配置类型为盖高储常压配置类型和盖高储高压配置类型最有利于形成高、中天然气储量丰度的大中型气田.     

Distribution of major and minor constituents between mica and host ultrabasic rocks,and between zoned mica and zoned spinel

Ultrabasic rocks with Niggli values for si between 26 and 100, and k between 0.6 and 1 have been chosen for the study of the distribution of 23 major and minor constituents between phlogopite and the host rock. The rocks include kimberlites, carbonatites and lamprophyres which contain abundant zoned micas and a few zoned spinels. Chemical variations in zoned mica and spinel were determined by electron probe microanalysis, and distribution coefficients for Al, Ti, Fe, Cr, Mg, Mn, and Ni were calculated between mica and spinel for the average composition of the mica and spinel, and for chemically-related and adjacent zones. The spinel changes from chromite in the centre to chromian ulvöspinel in the rim, and the mica from chromian phlogopite, through titaniferous biotite to chromium-poor phlogopite. Distribution coefficients for Cr and Fe between adjacent zones in spinel (0.8 and 0.02 for Cr; 1.1 and 3.1 for Fe) and in mica (0.4 and 0.1 for Cr; 2 and 0.3 for Fe) show more variation than the distribution coefficients between the cogenetic phlogopite and chromite (0.04 for Cr, 0.2 for Fe), and biotite and ulvöspinel (0.08 for Cr; 0.2 for Fe). It is concluded that distribution coefficients for major and minor constituents between related zones are more meaningful than those calculated from the average chemical composition of zoned minerals.The results indicate that phlogopite is the principal carrier of potassium, rubidium, aluminium, fluorine and primary water in kimberlite and carbonatite. Minor elements, such as chlorine, lithium, barium, nickel, chromium, titanium and zinc are present mainly in the mica, whereas sodium, strontium, calcium, carbon and manganese are more abundant in other minerals.     

Reciprocity Effect between Silicate Bacteria and Wollastonite

This paper studied the reciprocity effect between wollastonite and a strain silicate bacterium from purple soil. We analyzed the changes of pH value, glucose (GLU) residual concentration, electrolyte and Mn, Si, Fe etc. in the culture liquid with wollastonite after 48 h. The results show that the GLU wastage of silicate bacteria with wollastonite is 2.5 times of the bacterial contrast. It showed wollastonite could obviously accelerate silicate bacteria growth, but bacterial cell broken and distorted badly have been found by SEM analysis. The solubilization of silicate bacteria to Si element of wollastonite reached above 10 times. At the same time, three apices in FTIR of wollastonite (898 cm-1, 925 cm-1, 962 cm-1) descended obviously after the action of silicate bacteria, which shows that a great deal of Si has dissolved out. So we can get that wollastonite has remarkable effect to the growth of silicate bacteria and silicate bacteria has obvious solubilization to Si of wollastonite.     

Similarities between GSH,hypoplasticity and KCR

Accounting for elasto-plastic motion in granular media, hypoplasticity is a state-of-the-art constitutive model derived from data accumulated over many decades. In contrast, GSH, a hydrodynamic theory, is derived from general principles of physics, with comparatively few inputs from experiments, yet sporting an applicability ranging from static stress distribution via elasto-plastic motion to fast dense flow, including non-uniform ones such as a shear band. Comparing both theories, we find great similarities for uniform, slow, elasto-plastic motion. We also find that proportional paths and the Goldscheider rule used to construct barodesy, another, more recent constitutive model, are natural results of GSH’s equations. This is useful as it gives these constitutive relations a solid foundation in physics and, in reverse, GSH a robust connection to reality. The same symbiotic relation exists between GSH and KCR, or Kamrin’s non-local constitutive relation, a model that was successfully employed to account for a wide shear band in split-bottom cells.