VH-nuclei cosmic ray tracks in silicate minerals of howardites: A regolith stage of parent body formation

Natural tracks in pyroxene and plagioclase crystals from Erevan and Kapoeta howardites are due to irradiation by both galactic and solar cosmic rays.     

Shock metamorphism on the surface of the Moon

The material characteristics of lunar materials are discussed as indicators of shock metamorphism. As lunar materials are subjected to both impact shock modification due to energetic particles formed at locations of collisionless plasma shocks in cosmic space, it is necessary to identify specific features of each process. All types of lunar glasses formed by various impacts under high pressure ( 90 GPa) are found as impact glass, ropy glass, agglutinates and brecciated rocks. The agglutinates and iron particles are identified from X-ray diffraction measurements. Fine-grained lunar materials, including the agglutinates and breccias bonded by crystals and glasses due to impact shocks, contain hydrogen and helium from the energetic particles of collisionless shocks. Lunar shocked minerals of plagioclase and silica show anomalous compositions and densities. The shock metamorphism shows evidence for two major impact processes on evolved and primordial lunar surfaces: (1) shocked silica phases with minor Al contents formed from plagioclase-rich primordial crusts of the Moon, and (2) shocked quartz formed by silica-rich target rocks, especially on evolved parts of the Moon. Silica subjected to both impact and energetic particle modification can grow to coarse-grained normal crystals by long existence in vapor plume under high-temperature or after gradual high-temperature evolution, with the result that original effects of the impact process cannot be distinguished.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

EPR and optical absorption characteristics of sodic plagioclase from granite pegmatite in Kadavur,India

The electron paramagnetic resonance (EPR) spectra of sodic plagioclase from dykes of granitic pegmatite occurring in the Kadavur area, Tamil Nadu, India, were examined at room temperature to identify paramagnetic impurities in a “low plagioclase” using EPR and optical techniques. The EPR spectra showed the presence of Fe(III) and Mn(II) impurities. After heating the plagioclase samples for various durations at 600 °C, it has been observed that the concentration of Mn(II) remained as such in one sample but completely disappeared in another sample, while there was no change in Fe(III) ion concentration after the heat treatment in either sample. Optical absorption spectra also showed Fe(II) and Fe(III) in addition to Ti(III) impurities in sodic plagioclase before heating, while after heating the relative concentration of Fe(II) and Fe(III) changed, accompanied by the disappearance of Ti(III).