Retrograde formation of NaCl-scapolite in high pressure metaevaporites from the Cordilleras Béticas (Spain)

A Permo-Triassic pelite-carbonate rock series (with interacalated metabasitic rocks) in the Cordilleras Béticas, Spain, was metamorphosed during the Alpine metamorphism at high pressures (P _min near 18 kbar). The rocks show well preserved sedimentary features of evaporites such as pseudomorphs of talc, of kyanite-phengitetalc-biotite, and of quartz after sulfate minerals, and relicts of baryte, anhydrite, NaCl, and KCl, indicating a salt-clay mixture of illite, chlorite, talc, and halite as the original rock. The evaporitic metapelites have a whole rock composition characterized by high Mg/(Mg+Ca) ratios>0.7, variable alkaline and Sr, Ba, contents, but are mostly K₂O rich (<8.8 wt%). The F (<2600 ppm), Cl (<3600 ppm), and P₂O₅ (<0.24 wt%) contents are also high. The pelitic member of this series is a fine grained biotite rock. Kyanite-phengite-talc-biotite aggregates in pseudomorphs developed in the high pressure stage. Albite-rich plagioclase was formed when the rocks crossed the albite stability curve in the early stages of the uplift. Scapolite, rich in NaCl (Ca/(Ca+Na) mol% 24–40) and poor in SO₄, with Cl/(Cl+CO₃) ratios between 0.6 and 0.8, formed as porphyroblasts, sometimes replacing up to 60% of the rock in a late stage of metamorphism (between 10 and 5 kbar, near 600°C). No reaction with albite is observed, and the scapolite formed from biotite by: $$\begin{gathered} Al - biotite + CaCO_3 + NaCl + SiO_2 \hfill \\ = Al - poor biotite + scapolite + MgCO_3 + KCl \hfill \\ + MgCl_2 + H_2 O \hfill \\ \end{gathered}$$ Calculated fluid composition in equilibrium with scapolite indicates varying salt concentrations in the fluid. Distribution of Cl and F in biotite and apatite also indicates varying fluid compositions.     

Influence of soil flexibility on the seismic behaviour of chimneys

Various methodologies and modelling criteria for analysing seismically reinforced concrete chimneys are now available. All require consideration of the soil-structure interaction (SSI) effects especially in designing tall chimneys. This becomes more critical when the soil deposit, on which the chimney is founded, is softer. Two examples are considered in this paper: a chimney of moderate height (110 meters) founded directly on a sedimentary rock layered half-space and another very tall chimney (230 meters), founded by means of short prefabricated piles on a deep, very soft, sand deposit. The method of analysis used is a conventional response spectrum modal analysis of a chimney lumped mass model, which includes shear deformation of the chimney shaft. To ignore this effect can lead to an underestimation of the shear force at chimney base level. The suggestions of the specification ACI STANDARD 307-88 are also considered. Different hypotheses to account for the SSI effects are assumed in the analyses which provide a set of conclusions of interest to the point of view of the designer.     

Modeling the Uncertainty in the Layout of Geological Units by Implicit Boundary Simulation Accounting for a Preexisting Interpretive Geological Model

Natural Resources Research - An implicit simulation algorithm that uses signed distance functions is proposed to represent subsurface geological configuration while accounting for two sources of...     

An improved algorithm to compute circular functions of Poisson series

The efficiency in the computation of circular functions, such as cos(u) or sin(u), where u is a Poisson series, is important to derive accurate solutions of many problems of Celestial Mechanics, for instance, the orbital or rotational perturbed motion of natural or artificial bodies, since expansions in terms of Legendre functions and multiple Fourier series appear almost everywhere. Therefore, it is worth searching for alternative algorithms with lower computational cost. In this article, we propose a method based on the idea of elimination, which was originally applied to solve numerical problems, mainly in the case of matrix functions. Our comparisons with the traditional Taylor expansion prove that this new method can be more efficient when applied to compute the sine and cosine of a Poisson series.     

Families of Periodic Orbits Emanating From Homoclinic Orbits in the Restricted Problem of Three Bodies

We describe and comment the results of a numerical exploration on the evolution of the families of periodic orbits associated with homoclinic orbits emanating from the equilateral equilibria of the restricted three body problem for values of the mass ratio larger than μ ₁. This exploration is, in some sense, a continuation of the work reported in Henrard [Celes. Mech. Dyn. Astr. 2002, 83, 291]. Indeed it shows how, for values of μ. larger than μ ₁, the Trojan web described there is transformed into families of periodic orbits associated with homoclinic orbits. Also we describe how families of periodic orbits associated with homoclinic orbits can attach (or detach) themselves to (or from) the best known families of symmetric periodic orbits. This revised version was published online in July 2006 with corrections to the Cover Date.