Tetraammonium Tetrametaphosphimate Tetrahydrate

The tetrametaphosphimate ring in the title compound, (NH4)4+(PO2NH)4-.4H2O exhibits a chair conformation. The tetrametaphosphimate rings are linked by N-HO bonds forming columns along [100]. These columns are interconnected by O-HO and N-HO hydrogen bonds through water molecules and ammonium ions. All H atoms are involved in hydrogen bonding

Petrographic and crystallographic study of silicate minerals in lunar rocks

Optical U-stage measurements, chemical microprobe data, and X-ray procession photographs of a bytownite twin group from rock 12032,44 are compared. Sharp but weak b and no c-reflections were observed for this An89 bytownite indicating a partly disordered structure. Euler angles, used to characterize the orientation of the optical indicatrix, compare better with values for plutonic than for volcanic plagioclase. This indicates that structural and optical properties cannot be directly correlated

Fe-Mg M1 site distribution in some clinopyroxenes from Santa Olalla (Huelva, Spain)

The crystal structures of two clinopyroxenes related to the skarns from Santa Olalla (Huelva. Spain) have been refined. From these refinements it is shown that pyroxene SO-1 of metamorphic origin is almost pure diopside. whereas for pyroxene SO-2 of metasomatic origin the following formula CaMg 0.64 Fe 0,34 Si2 O6. was found. These clinopyroxenes show cation ordering

Zn sorption modifies dynamically the layer and interlayer structure of vernadite

International audienceIn surficial environments, the fate of many trace metals is influenced by their interactions with the phyllomanganate vernadite, a nano-sized and turbostratic variety of birnessite. To advance our understanding of the surface reactivity of vernadite, synthetic vernadite (δ-MnO2) was equilibrated at pH 5 or 7, reacted with dissolved Zn to produce Zn-sorbed δ-MnO2 with Zn/Mn atomic ratios from 0.003 to 0.156, and characterized structurally. The octahedral layers in the Zn-free vernadite contain on average ∼0.15 vacancies, ∼0.13-0.06 Mn3+ and ∼0.72-0.79 Mn4+. The layer charge deficit is compensated in the interlayer by Mn3+ bonded over Mn vacancy sites and Na+ located in the interlayer mid-plane. The average lateral dimension of coherent scattering domains (CSDs) deduced from X-ray diffraction (XRD) modeling is ∼5 nm, consistent with that observed by transmission electron microscopy for individual crystals, indicating that the amounts of edge sites can be estimated by XRD. The average vertical dimension of CSDs is ∼1 nm, equivalent to 1.5 layers and less than the observed 3-4 layers in the particles. Zinc sorption at pH 5 and 7 on pre-equilibrated vernadite induced crystal dissolution reducing the lateral CSD size ∼15-20%. Zinc K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and XRD show that Zn occurs in the interlayer above vacancies as a triple-corner-sharing surface complex, which is fully tetrahedral at low Zn/Mn ratios and increasingly octahedral at higher ratios. As Zn/Mn increases, the site density of layer Mn3+ decreases from 0.13 ± 0.01 to 0.03 ± 0.01 at pH 5 and from 0.06 ± 0.01 to 0.01 ± 0.01 at pH 7, and that of layer vacancies correspondingly increases from ∼0.15 to 0.24 and 0.21 at pH 5 and 7, respectively. These changes likely occur because of the preference of Zn2+ for regular coordination structures owing to its completely filled third electron shell (3d10 configuration). Thus, sorption of Zn into the interlayer causes the departure of layer Mn3+, subsequent formation of new reactive layer vacancies, and an increase in surface area through a reduction in particle size, all of which dynamically enhance the sorbent reactivity. These results shed new light on the true complexity of the reactive vernadite surface, and pose greater challenges for surface-complexation modeling of its sorption isotherms

The Hornblende-Aegirine Augite Reaction Relationships of the Trunk Lake Granite, Maine

Textural relationships indicate that the structure of aegirine augite controlled the secondary formation of hornblende in the Tunk Lake granite. In the marginal rocks of the granite body some grains of aegirine augite may be partially or completely enclosed by hornblende. Hornblende also replaces aegirine augite along fractures. Extensive replacement results in grains which have small cores of aegirine augite surrounded by hornblende. Cleavage patterns and optical orientations of the two minerals indicate that their c axes are parallel. Pyroxene can be transformed to hornblende by a minor shift in orientation of its basic tetrahedral structure. Chemical changes necessary in the transformation are the addition of water, a slight decrease in sodium and the substitution of some aluminum for silicon. The transformation of aegirine augite to hornblende was caused by an increase in magma water vapor pressure and a decrease in temperature

Utilización de diagramas de parámetro matemáticos - composición - deformación - ordenamiento - estructura - (nOr+0.2 - S.I. /10 - tlO - Δ (Δ131)) de feldespatos alcalinos para caraceterización de zonografías pegmatiticas. Cuerpo pegmatítico de los Rancajales (Colmenar Viejo, Madrid, España)

Se han estudiado los feldespatos alcalinos de un cuerpo pegmatítico diferenciado zonado y con procesos de substitucíon del area de los Rancajales (Colmenar Viejo, Madrid, España), Los principales parámetros matemáticos se obtuvieron a partir de los datos estructurales previos de ORX y se proyectaronen diagramas ternarios utilizando un programa original en 6WBASIC, Se propone la utilización del diagrama ternario nOr (composición química) - S.I. (deformación) - tlO (orden / desorden de Si/Al) - ya que es el que mejor muestra la zonalidad del cuerpo pegmatítico. [ABSTRACT] Alkali feldspars from a zoned and differenciated pegmatitc outcrop, showing sustitution processes, in the Rancajales area (Colmenar ViEjo, Madrid, Spain) have been studied, The main mathematic parameters, obtained from X-ray structural data, were plotted in ternary diagrams, using the, GWBASIC Original program. The zonal distribution of the pegmatitic outcrop can be observed by the nOr (chemical cómposition) - S.I. (strain) - tlO (order/disorder of Si/Al> new diagram, wich we proposed

Lunar highland rock types: Their implications for impact induced fractionation

The first step in a petrologic study must be a classification based on observed textures and mineralogy. Lunar rocks, may be classified into three major groups: (1) coarse-grained igneous rocks, (2) fine-grained igneous rocks and (3) breccias. Group 1 is interpreted as primitive lunar crustal rocks that display various degrees of crushing and/or annealing. Group 2 is interpreted as volcanic rocks. Group 3 is interpreted as resulting from impacts on the lunar surface and is subdivided on the basis of matrix textures into fragmental breccias, crystalline breccias that have been annealed, and crystalline breccias with igneous matrices. A synthesis of the relevant data concerning lunar highlands polymict breccias from the fields of petrography, chemistry, photogeology, and impact studies compels the prediction that the breccias should have homogeneous matrices from rock to rock within regions of the highlands of limited size where impact mixing has been efficient and extensive