Sophisticated computer modeling of the formation of lunar multi-ringed basins by impact indicate that substantial volumes of impact melt are produced, leading to melt bodies hundreds of kilometers in diameter and tens of kilometers deep. The impressively large bodies of magma created by the impact of a projectile 50 to 300 kilometers across might have differentiated, producing a zoned body with...

•80 data have been obtained on 7 of the 17 intrusive centers of diorite and granodiorite (Miocene?) that lie along a N-S belt about 50 km west of the High Cascades. Whole-rock $ values (per mil relative to SMOW) in the intrusive stocks are: -[-2.3 to -t-4.9 (South Umpqua River), -0.7 to -t-3.8 (Bohemia mining district), -t-4.3 to -t-4.6 (Vida stock), -0.2 to -t-5.5 (Nimrod stock), --1.7 to -}-0...

Background: The concentrations of radionuclides like 226Ra, 232Th and 40K and the dose rate are measured in igneous and metamorphic rock formations in and around Chickmagalur. A total of 236 samples from 13 different locations around study area were analyzed. Materials and Methods: The activity concentrations of the three radioactive elements were determined for mean period of 25000 s using HPG...

A recurring challenge to ion microprobe U^Pb zircon geochronology has been to discriminate between preservation of original igneous zircon populations and inherited grains. This has proved particularly problematic in studying the polyphase metamorphic rocks that dominate Early Archean gneissic terranes. For example, differing interpretations exist for the origin of complex zircon populations in...

[1] Theoretical geochemical modeling has been used to evaluate the formation conditions of amorphous silica during aqueous alteration of typical Martian igneous rocks at 0 C. The models show that some silica can form during low-temperature alteration of mafic to ultramafic rocks over a large range of pH and water/rock ratios. Silica-dominated deposits, like those found at the Columbia Hills in ...

The primordial earth surface exposed minerals comprised mainly of carbonates, silicates and smaller amounts of phosphates. Weathering eventually led to the dissolution of the surface rock and the leaching of their components into the rivers, lakes and oceans. There, complex chemistry depending upon the temperature, pH, pressure, and atmospheric carbon dioxide content led to the reprecipitation ...

Igneous intrusions are common features within rifted sedimentary basins. With advances in technology, exploration has progressed into more complicated petroleum systems where sediments segmented and altered by networks of dykes sills. Magmatism increases temperatures fluid pressures adjacent host rocks. This can lead to mobilisation mineral-rich hot fluids through pores fractures, which alters ...