An anthropo-ecological approach to landscape use optimization

A method of landscape evaluation based on the anthropo-ecological approach is worked out. The procedure consists of three stages, viz., general, special and optimization. Within the general stage, the structural arrangement of the landscape is evaluated by means of the concept of geo-ecological sites (GES), which are distributed into four zones (A, B, C, D) according to the degrees of their anthropic disturbance. The zoning performed makes it possible to select those geo-ecological sites where eco-critical relationships can be expected to appear; in order to eliminate such situations, transition zones are calculated for the geo-ecological sites concerned. The outcome of this approach is a proposal of a new structural arrangement of the geo-ecological sites, solving eco-critical situations and serving as a basis for the special and optimization stages of the anthropo-ecological method.     

High temperature calorimetry of sulfide systems

The standard enthalpies of formation of FeS (troilite), FeS₂ (pyrite), Co_0.9342S, Co₃S₄ (linnaeite), Co₉S₈ (cobalt pentlandite), CoS₂ (cattierite), CuS (covellite), and Cu₂S (chalcocite) have been determined by high temperature direct reaction calorimetry at temperatures between 700 K and 1021 K. The following results are reported: $$\Delta {\rm H}_{f,FeS}^{tr} = - 102.59 \pm 0.20kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,FeS}^{py} = - 171.64 \pm 0.93kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_{0.934} S} = - 99.42 \pm 1.52kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_9 S_8 }^{ptl} = - 885.66 \pm 16.83kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_3 S_4 }^{In} = - 347.47 \pm 7.27kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,CoS_2 }^{ct} = - 150.94 \pm 4.85kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Cu_2 S}^{cc} = - 80.21 \pm 1.51kJ mol^{ - 1} ,$$ and $$\Delta {\rm H}_{f,CuS}^{cv} = - 53.14 \pm 2.28kJ mol^{ - 1} ,$$ The enthalpy of formation of CuFeS₂ (chalcopyrite) from (CuS+FeS) and from (Cu+FeS₂) was determined by solution calorimetry in a liquid Ni_0.60S_0.40 melt at 1100 K. The results of these measurements were combined with the standard enthalpies of formation of CuS, FeS, and FeS₂, to calculate the standard enthalpy of formation of CuFeS₂. We found \(\Delta {\rm H}_{f,CuFeS_2 }^{ccp} = - 194.93 \pm 4.84kJ mol^{ - 1}\) . Our results are compared with earlier data given in the literature; generally the agreement is good and our values agree with previous estimates within the uncertainties present in both.     

Precursory swarm and its application for long range earthquake forecasting in Taiwan region

At trenches a few earthquake swarms of low magnitude have been observed before the medium size earthquake swarms. The first swarm was designated as precursory swarm and the second as mainshocks. Seismicity fluctuations before six such mainshocks events of medium size earthquakes of magnitudes ranging from 5.3 to 6.1 occurring in the east belt of Taiwan region have been discussed. A precursory gap between the precursory swarm and mainshock events has been observed. The duration of the gaps increases with magnitudes of the mainshocks suggesting a causal relationship between the two. Regression equations between the largest magnitude in the precursory swarms, the largest mainshock magnitude and the precusory gaps have been given.     

Description and interpretation of the composition of fluid and alteration mineralogy in the geothermal system,at Svartsengi,Iceland

The bulk composition and mineralogy of hydrothermally altered tholeiite, along with the composition and speciation of fluid, have been determined for a well-defined alteration zone at 240°C and 110 bars at Svartsengi, Iceland. Mass balances between the geothermal fluid and altered tholeiite, relative to a seawater/fresh water mixture and unaltered tholeiite, indicate the overall reaction per 1000 cm³ is: 1325 gm plagioclase + 1228 gm pyroxene + 215 gm oxide-minerals break down to form 685 gm chlorite + 636 gm albite + 441 gm quartz + 249 gm epidote + 266 gm calcite + 201 gm oxide-minerals + 15 gm pyrite, requiring an influx of 123 gm CO₂, 10 gm H₂S and 4 gm Na₂O and a release of 57 gm SiO₂, 35 gm FeO, 21 gm CaO, 8 gm MgO and 4 gm K₂O.Principal reactions, deduced from textural evidence, include Na-Ca exchange in plagioclase, precipitation of quartz, calcite and anhydrite, and formation of chlorite and epidote by reactions between groundmass minerals and fluid.Thermodynamic analyses of authigenic minerals and downhole fluid indicate that the fluid maintains a state close to equilibrium with the secondary mineral phases chlorite, epidote, albite, quartz, calcite, prehnite, anhydrite, pyrite and magnetite, whereas remnant primary labradorite and augite are out of equilibrium with the fluid.Water/rock ratios for the system are determined under a variety of assumptions. However, the open nature of the system makes comparisons with experimental and theoretical closed system studies ambiguous.     

A new solid state diffusion model applied to inverse zoning and diffusion rims in minerals

Any oxide and silicate mineral which is nominally anhydrous but crystallized in the presence of H₂O incorporates traces of H₂O in solid solution. In the case of MgO it can be shown that OH^? pairs convert into H₂+O ₂ ^2? . If the H₂ molecules are lost, the O ₂ ^2? remain in the lattice as excess oxygen stabilized by excess cation vacancies. When the O ₂ ^2? anions decay either thermally or by decompression unbound O^? states (positive holes) are generated which lead to surface charges and subsurface space charge layers. Calculated space charge profiles are presented. O^? concentrations as small as 10–20 ppm suffice to create electric surface fields of the order of 4·10⁷ V·m^?1. The diffusion mechanism which derives from these premises incorporates novel features: the cation diffusion is coupled to the counterdiffusion of unbound and vacancy-bound O^? states. The cation diffusion is predicted to be very fast because first, it is field-enhanced (electrochemically driven) and second, it is not rate-limited by the intrinsic cation vacancy concentration nor by the counter-diffusion of other cations. The model may apply to cases of inverse zoning and diffusion rim formation in minerals under certain P-T conditions.     

A study on the interpretation of spontaneous potential and resistivity logs in layered aquifer sequence of Pondicherry Region,South India

Geophysical logs provide a strong mechanism for interpretation and determination of the depositional environments, facies and also help in interpretations of hydrogeologic units. Spontaneous potential (SP) and resistivity logs can be used as an indicator of textural parameters. Pondicherry region has a complicated geology and with formation of different ages. The boreholes (BH) of this region are examined for litholog, SP and resistivity from four different BH locations, viz, Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu. These locations were studied and interpreted by using the shapes of the curves to identify the depositional environments, and this was later compared with the vertical litholog profile. Comparing the variation of these logs, the lateral variation of sedimentary facies was also attempted. The average resistivity values of Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu are 42.4, 30.4, 50.4 and 28.3?Ωm, respectively. Majority of the resistivity values corresponds from fine- to medium-grained sand, clayey pebbles, fine to very coarse sand and clayey sand with lignite. Frequency of resistivity values in each BH were identified for determining the dominant representative grain size. The study has pointed out the lithological variation of the system laterally and vertically using geophysical well logs.     

Transition from shoshonitic to adakitic magmatism in the eastern Pontides,NE Turkey: Implications for slab window melting

The formation of the eastern Pontides orogenic belt has been widely assigned to a northward subduction of the Neotethyan oceanic slab during the late Mesozoic–Cenozoic. Here we provide an alternate model based on new geological, geochemical and isotopic data. The magmatic activity in the far south of the belt started in the early Campanian with shoshonitic trachyandesites and associated pyroclastics. This sequence is covered by the late Campanian–early Maastrichtian reefal limestones and another stage of high-K volcanism represented by analcimized leucite-rich ultrapotassic rocks of the Maastrichtian–early Paleocene (?) ages. The shoshonitic and ultrapotassic rocks, with K₂O contents ranging from 0.26 to 6.95 wt.%, display broadly similar rare earth and multi-element distribution patterns. Both rock types are enriched in LILE and LREE and depleted in HFSE (Nb, Ta and Ti), suggesting a subduction-enriched mantle source for the magma generation. Subsequently, during the late Paleocene, a stage of acidic magmatism (SiO₂ of 53.25–73.61 wt.%) that shows adakitic geochemical characteristics including high Sr/Y (46–416) and La/Yb (11–51) and low Y (2.6–12.2 ppm), is documented characterized by melting of a mafic source such as the MORB crust with garnet in the residue. The adakitic magmatism began at ~ 56 Ma and migrated toward the north through time, culminating with porphyritic andesites (~ 47 Ma) that were emplaced in the Gumushane–Bayburt line and its vicinity. North of this line, coeval magmas show typical calc-alkaline nature and continued to develop toward further north until the middle to late Eocene. Based on the spatial and temporal variations in the magmas generated in the eastern Pontides orogenic belt, we propose a new geodynamic model to explain the tectonomagmatic evolution of these rocks and correlate the adakitic magmatism to ridge subduction and slab window process within a south-dipping subduction zone. Our model is in contrast to the previous proposals which envisage partial melting or delamination of thickened lower continental crust due to the collision in the south during the Paleocene–Eocene.     

Physical Libration of the Moon: An Extended Problem

Astronomy Reports - The work is devoted to the study of the physical libration of the Moon. Interest in the traditional topic related to the rotation of the Moon is stirred up by the activity of...