Geology topics
Publications and source records attributed to C. S. Ross.
The Valles Mountain region lies in northern New Mexico about 30 miles west of Santa Fe, 50 miles north of Albuquerque, and just west of the Rio Grande. The elevation varies from 6,500 feet at the Rio Grande to 1,200 feet on the higher peaks. ©1931. American Geophysical Union. All Rights Reserved.
The feldspathic rock with which the titanium deposits of Virginia are associated appears to be an anorthosite, although the plagioclase is somewhat more sodic than in normal anorthosites. That is, this rock shows evidence of having been introduced as a mush‐like mass of crystals and intersititial magma, and of undergoing very thorough crushing during introduction. This rook was later very thoroughly altered by hydrothermal solutions which migrated through the fractures in the feldspar rook and new minerals including the titanium minerals—rutile and ilmenite—were introduced. The elements introduced into the feldspathic rock ware TiO 2 FeO, MgO, P 2 O 5 , and F. The other elements that went into the formation of new minerals were derived from the feldspar originally present. There was a distinct order in the abstraction of the introduced elements from the carrying solutions, as shown by the zonal relatione of the secondary minerals. Ferrous iron was abstracted first in the formation of the ferromagnesian silicates and ilmenite. Magnesium and titanium, in the absence of iron, traveled farther from the source of the solutions and deposited rutile and magnesian silicates. At greater distances most of the introduced elements had been abstracted from the solutions but notwithstanding this the feldspar was extensively altered, but without any marked changes between the chemical composition of the original feldspar rook and the resulting altered rook. ©1934. American Geophysical Union. All Rights Reserved.
The igneous rocks and the minerals of Magnet Cove, Arkansas, have long interested geologists and mineralogists, but in much of the area rock‐exposures are so sparse that many of the geologic, relations have remained obscure. However, recent prospecting and the mining of titanium ores have uncovered rocks that throw new light on the geology of the region. The regional rocks of the area are sandstones, slates, and novaculite of Paleozoic age. They were folded and underwent metamorphism in late Paleozoic time. In Cretaceous time they were intruded by a series of igneous rocks. ©1938. American Geophysical Union. All Rights Reserved.
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Recent studies of rhyolitic and pyroclastic materials, and in particular of welded tuffs and bentonites, show that they occur over wide areas and in volumes which greatly exceed earlier evaluations. Volcanic ash and bentonite occur in the eastern United States where such materials were long unrecognized. In most of the western States, only preliminary studies have been made, but they indicate the presence of these materials in volumes measured in thousands of cubic miles. Less is known about pyroclastic materials in most other parts of the world, but local studies in New Zealand, Australia, and the Dutch East Indies show immense volumes of pyroclastic materials. © 1955, The Geological Society of America, Inc.
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