Physical Properties of Wave Motion in Inclined Magnetic Fields within Sunspot Penumbrae

At the surface of the Sun, acoustic waves appear to be affected by the presence of strong magnetic fields in active regions. We explore the possibility that the inclined magnetic field in sunspot penumbrae may convert primarily vertically-propagating acoustic waves into elliptical motion. We use helioseismic holography to measure the modulus and phase of the correlation between incoming acoustic waves and the local surface motion within two sunspots. These correlations are modeled by assuming the surface motion to be elliptical, and we explore the properties of the elliptical motion on the magnetic-field inclination. We also demonstrate that the phase shift of the outward-propagating waves is opposite to the phase shift of the inward-propagating waves in stronger, more vertical fields, but similar to the inward phase shifts in weaker, more-inclined fields.     

Alpine tectonics of granites in basement of Ysyk-Köl Basin,northern Tien Shan

The Ysyk-Köl Basin filled with Lower Jurassic–Quaternary sedimentary rocks is the largest intermontane negative structural unit of the northern Tien Shan. The basement of this basin is composed of Precambrian–Paleozoic rocks, largely of Ordovician and Silurian granitoids exposed in mountain ranges of the basin framework and as separate anticlinal domes situated in areas occupied by the Mesozoic–Cenozoic sedimentary cover. The postmagmatic tectonic internalstructure of the Chonkurchak (Chunkurchak), Kyzyl-Choku, Kyzyl-Bulak, and Prishib massifs emplaced in the basement, as well as their relationships to the sedimentary cover, are described in the paper. The study was carried out using the morphostructural method, detailed geological mapping, structural kinematic analysis, and petrographic examination of rocks. The internalstructure of Paleozoic granites in the basement and indications of their 3D tectonic flow are characterized. It is shown that granites underwent 3D deformation after their emplacement in the consolidated crust, and this process had a substantial influence on tectonic processes at the plate and orogenic stages of regional evolution.     

The private sector and local economic development in South Africa

The objective in this paper is to analyse private sector involvement in LED in South Africa. Four key spheres of private sector involvement in LED are identified and discussed: (1) as participator and occasional initiator of local development processes, (2) as major partner in the development activities of public-private sector partnerships, (3) as lead role player in certain direct initiatives for reviving South Africa's inner cities, and (4) as promoter and facilitator of local small business development. It is argued that the concept of local dependence could be usefully applied to interpret private sector involvement in LED in South Africa.     

Experiments in tracing underground waters in limestones

Two experiments were conducted in the Carboniferous Limestone aquifer of the Mendip Hills, Somerset, to compare the relative merits of differing groundwater tracers. The tracers employed were lithium acetate, polyethylene powder, Lycopodium spores and the fluorescent dye Pyranine Conc.; all were introduced into the aquifer at stream sinks. The first two tracers were totally unsuccessful. In the two experiments the rates of travel of the fluorescent dye and Lycopodium spores were very similar. Only relative concentrations can be measured from the recovery of spores as opposed to absoute concentration for dye which were determined using a field continuous flow fluorometer. The quantitative dye concentration data can be used with simultaneous measurements of discharge at the spring to deduce the flow geometry of the system; the input, tributary, distributary and maximum discharges in the system and the volume of the underground conduits. Data are presented which indicate that exchange takes place between the flooded conduit, and the surrounding fissured bedrock in a manner analogous to bank storage in rivers flowing on alluvium.In conclusion fluoresent tracers are valuable for the detailed investigation of a single sink to rising system; Lycopodium spores, which can be used to trace several sinks simultaneously, are a valuable technique in exploratory tracing.     

Petrogenetic Aspects of Acid and Basaltic Lavas from the Paran? Plateau (Brazil): Geological, Mineralogical and Petrochemical Relationships

The acid volcanics (Lower Cretaceous) of the Paran? basin coveran area of about 150000 km² and are represented by dominantrhyodacites and subordinate rhyolites. They may be divided intotwo main types, characterized respectively by relatively lowand relatively high contents of Ti, P, and other incompatibleelements (La, Ce, Zr, etc.), i.e. the Palmas acid volcanics(PAY) and Chapec? acid volcanics (CAV), respectively. PAV arewidespread in the southern Paran? basin and are closely associatedwith basaltic and andesitic rock-types similarly characterizedby low Ti, P, and other incompatible elements. In contrast,CAV are dominant in the northern Paran? basin, where they areclosely associated with basalts containing high Ti, P, and otherincompatible elements. The generation of the Palmas and Chapec? acid melts appearsto be in part consistent with crystal fractionation processes,starting from the associated basic rocks and accompanied bycrustal contamination. However the relative absence of intermediaterock-types (‘silica gap’: 54–56 to 63–65wt. per cent), and the confinement of the acid volcanics towardsthe continental margin suggests that a model involving lowercrustal basic material of significantly different compositionin the northern and southern Paran? basin may be a more plausiblealternative. In this preferred model the basic parent materialmay be represented by mafic granulites of different compositions,or by basalts trapped at the crust-mantle discontinuity andcorresponding in composition to the contrasting low- and high-TiO₂basalts that flooded the Paran? basin in Lower Cretaceous times.The melting of these underplated materials may explain the closegeochemical relationships between fissure acid volcanics andthe closely associated basalt types (e.g., Ethiopia, Paran?).The beginning of the major rifting related to continental break-upshould therefore correspond to the stage when the melting processaffected the lower part of the continental crust. ^*Reprint requests to E. M. Piccirillo