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Emplacement temperatures of unsorted and unstratified deposits of volcanic rock debris as determined by paleomagnetic techniques Emplacement temperatures of unsorted and unstratified deposits of volcanic rock debris as determined by paleomagnetic techniques

Unsorted and unstratified deposits of volcanic rock debris typically flank recently active stratovolcanoes. It is often difficult, using standard geologic procedures, to establish whether a particular deposit was emplaced by a pyroclastic flow, lahar, rock avalanche, or glacier. Determination of the emplacement temperatures of clasts contained in the deposit aids in discriminating among...
Authors
Richard P. Hoblitt, Karl S. Kellogg

Origin of reverse-graded bedding in air-fall pumice, Coso Range, California Origin of reverse-graded bedding in air-fall pumice, Coso Range, California

The origin of reverse grading in air-fall pyroclastic deposits has been ascribed to: (1) changing conditions at an erupting vent; (2) deposition in water; or (3) rolling of large clasts over smaller clasts on the surface of a steep slope. Structural features in a deposit of air-fall pumice lapilli in the Coso Range, California, indicate that reverse grading there formed by a fourth...
Authors
W. A. Duffield, C. R. Bacon, G.R. Roquemore

Vesicularity and CO2 in mid-ocean ridge basalt Vesicularity and CO2 in mid-ocean ridge basalt

Vesicles and included CO2 are enriched in deep-sea basalts that are also enriched in light rare earth and incompatible elements. This enrichment probably results from a unique deep mantle origin of such melts but may have been modified by CO2 bubbles rising in shallow magma chambers.
Authors
James G. Moore

A computer-assisted graphical method for identification and correlation of igneous rock chemistries A computer-assisted graphical method for identification and correlation of igneous rock chemistries

We have devised a computer-assisted graphical method for correlating chemical analyses in suites of related igneous rocks. The method provides a direct and empirical means of sample identification using all of the reported chemistry. In a study of basalt of the Columbia River plateau, the method has been used for (1) checking field identifications of rocks, (2) spotting analytical errors...
Authors
Thomas L. Wright, M.S. Hamilton

Mapped offset on the right-lateral Kern Canyon fault, southern Sierra Nevada, California Mapped offset on the right-lateral Kern Canyon fault, southern Sierra Nevada, California

The north-trending Kern Canyon fault, the longest fault within the southern Sierra Nevada, has been mapped from lat 36°00′N to its northern end near lat 36°40′N. The fault cuts and offsets granitic plutons as young as 80 m.y., but despite the fact that many recent earthquake foci plot close to the fault, it does not appear to offset an overlying 3.5-m.y.-old basalt flow. Seven granitic...
Authors
James G. Moore, Edward A. du Bray

High temperature heat content and heat capacity of silicate glasses: experimental determination and a model for calculation High temperature heat content and heat capacity of silicate glasses: experimental determination and a model for calculation

Knowledge of the thermodynamic properties of silicate melts is fundamental to quantitative characterization of igneous systems. This paper presents new data on one of these properties, heat content, for silicate glasses and supercooled silicate liquids and derives partial molar heat contents for the glasses. The high temperature heat contents of two FeO-rich synthetic silicate glasses...
Authors
Charles R. Bacon

Composition and phase chemistry of sulfide globules in basalt from the Mid-Atlantic Ridge rift valley near 37°N lat Composition and phase chemistry of sulfide globules in basalt from the Mid-Atlantic Ridge rift valley near 37°N lat

The electron microprobe was used to determine the bulk composition of immiscible sulfide globules trapped in the glass phase of 25 fresh submarine basalt samples from the Mid-Atlantic Ridge. Twenty-three samples represent a spectrum of primitive through differentiated tholeiites from the FAMOUS dive area; two are differentiated basalts from the Reykjanes Ridge. The analyzed globules...
Authors
G. Czamanske, James G. Moore

Compositional variations of young basalts in the Mid-Atlantic Ridge rift valley near lat 36°49′N Compositional variations of young basalts in the Mid-Atlantic Ridge rift valley near lat 36°49′N

Fifty acoustically positioned samples of fresh basalt were collected by the submersible Alvin from the median valley of the Mid-Atlantic Ridge during the French American Mid-Ocean Undersea Study (FAMOUS) in the summer of 1974. The samples show regular compositional variations from the center of the rift valley (central lava flows) out to the rift valley walls (flank lava flows). The...
Authors
W.B. Bryan, James G. Moore
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