Sphene coronites from Hyderabad granites,Andhra Pradesh,India

Sphene coronites around magnetite are recorded in the granodiorite of Hyderabad. The metamorphic origin of the corona is discussed.     

Planets in the early Universe

Several planets have recently been discovered around stars that are old and metal-poor, implying that these planets are also old, formed in the early Universe together with their hosts. The canonical theory suggests that the conditions for their formation could not have existed at such early epochs. In this paper we argue that the required conditions, such as sufficiently high dust-to-gas ratio, could in fact have existed in the early Universe immediately following the first episode of metal production in Pop. III stars, both in metal-enhanced and metal-deficient environments. Metal-rich regions may have existed in multiple isolated pockets of enriched and weakly-mixed gas close to the massive Pop. III stars. Observations of quasars at redshifts z～5, and gamma-ray bursts at z～6, show a very wide spread of metals in absorption from [X/H]??3 to ??0.5. This suggests that physical conditions in the metal-abundant clumps could have been similar to where protoplanets form today. However, planets could have formed even in low-metallicity environments, where formation of stars is expected to proceed due to lower opacity at higher densities. In such cases, the circumstellar accretion disks are expected to rotate faster than their high-metallicity analogues. This in turn can result in the enhancement of dust particles at the disk periphery, where they can coagulate and start forming planetesimals. In conditions with the low initial specific angular momentum of the cloud, radiation from the central protostar can act as a trigger to drive small-scale instabilities with typical masses in the Earth to Jupiter mass range. Discoveries of planets around old metal-poor stars (e.g. HIP 11952, [Fe/H]～?1.95, ～13 Gyr) show that planets did indeed form in the early Universe and this may require modification of our understanding of the physical processes that produce them. This work is an attempt to provide one such heuristic scenario for the physical basis for their existence.     

Apparent resistivity over a three layer earth with anisotropic interstratum

Summary The present work aims at investigating the effects of anisotropy on the apparent resistivity measurements over the surface of a three layer Earth. An appropriate model with the anisotropic layer embedded between two isotropic media is chosen for study. The point current source is assumed to be present at the surface of such a model. After writing the values of the potentials in each layer, expressions for apparent resistivities for Wenner and Schlumberger configurations are derived. Also, the expressions for potential for the limiting cases in which the bottom layer is infinitely resistive or infinitely conducting are derived. It is shown that these expressions can be recast into simpler forms corresponding to isotropic layer (s) on an isotropic half-space.     

Structure of Charnockitic basement in a part of the Krishna-Godavari basin, Andhra Pradesh

A regional magnetic survey was carried out over an area of 8000 km² in Godavari districts of Andhra Pradesh, India, which is covered by the rocks of Eastern Ghat Mobile Belt (EGMB)viz., the Khondalitic series and Charnockites in the northern half and Permian to Mesozoic and Cenozoic sediments in the southern half, and forms a part of the Krishna-Godavari (K-G) basin. The survey brought out a strong NE-SW trending anomaly in the area covered by the rocks of Eastern Ghat Mobile Belt (EGMB), and a mild ENE-WSW trending anomaly in the area covered by the sediments of the Krishna-Godavari (K-G) basin. The NE-SW trending anomaly in the northern half could be attributed to the exposed/near surface Charnockite basement that has come closer to the surface as a result of Eastern Ghat Mobile Belt (EGMB) tectonics. Explanation of the mild ENE-WSW trending anomaly over the sediments of the Krishna-Godavari (K-G) basin required a faulted magnetic basement at depth downthrown towards the south. It is therefore concluded that the Charnockitic basement together with the Khondalite group of rocks which are folded and faulted during the different phases of tectonics of Eastern Ghat Mobile Belt (EGMB) extend into the Krishna-Godavari (K-G) basin and further, were involved in faulting during the phases of formation and sedimentation in the Krishna-Godavari (K-G) basin.