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Norman G. Banks

Publications and source records attributed to Norman G. Banks.

At least 19 recordsLinked to original sources
USGS1996

Direct temperature measurements of deposits, Mount St. Helens, Washington, 1980-1981

A program of temperature studies of the eruptive products of Mount St. Helens was established May 20, 1980, 2 days after the catastrophic eruption of May 18. Temperature-depth profiles were measured by thermocouple to determine the emplacement temperatures of deposits of the debris avalanche and blast of May 18 and of deposits of the pyroclastic flows of May 18, May 25, June 12, July 22, August 7, and October 17, 1980. At some of the localities where deposits had cooled appreciably before measurement, emplacement temperatures were recovered mathematically from data gathered from observations of the cooling histories of the deposits. In addition, methodologies and specialized temperature-measuring equipment were developed to maximize efficiency in data collection and to minimize risk to personnel. In general, the more recent eruptive deposits were emplaced at higher temperatures than the earlier ones. Emplacement temperatures of deposits of the debris avalanche ranged from about 70 to 100°C. Temperatures of deposits of the blast ranged from about 100 to 325°C and varied with the azimuth of the measurement site from the vent; the higher temperatures were measured in the northeast sector. Emplacement temperatures of the later pumiceous pyroclastic-flow deposits ranged from about 300 to 680°C, and temperatures in nearvent facies were about 750 to 850°C. The most important features shown by the data obtained from the deposits produced by the blast are (1) their generally lower temperature relative to deposits emplaced by the subsequent pumiceous pyroclastic flows, attributed to relatively low temperatures of the cryptodome and admixing of significant amounts of accidental material and air; (2) an azimuthal variation of emplacement temperatures, hotter toward the east, attributed to thermal inhomogeneities in the source material and differential cooling associated with differing grain sizes and terrains over which the blast traveled; (3) emplacement temperatures that exhibited little change with distance from the vent to distances as great as 20 km, attributed to little cooling along the path, preferential elutriation of the cooler, finer particles, preferential interaction between air and the blast material at the head of the flow, and production of heat during the flow, possibly by friction; (4) thermal stratigraphy observed in some of the ponded pyroclastic-flow deposits in major valleys, attributed in part to a grain-size effect (finer upward) and in part to longer residence of the younger deposits as veneer deposits on the adjacent ridges before their secondary mobilization into the valleys; and (5) temperatures in the veneer deposits and moving blast cloud that were possibly higher than emplacement temperatures of the ponded pyroclastic-flow deposits. The most important features shown by the data obtained from the postblast, pumiceous pyroclastic-flow deposits are (1) generally hotter deposits in the later eruptions than in the earlier ones, attributed to less admixing of the pyroclastic material with air because of the observed progressive decrease in vigor of the successive eruptions; (2) little heat loss (100-200°C) of near-vent material during eruption, as predicted by simple adiabatic expansion; (3) little downflow cooling in the deposits after the first several hundred meters of travel, attributed to the same factors proposed for the blast deposits; (4) multiple flow units that were emplaced at different temperatures by most of the eruptions, attributed to differential cooling through differing amounts of admixed air in accordance with the vigor of the individual eruptive pulses; and (5) cooler material in the ash-cloud deposits than in the source pyroclastic flows because of more effective cooling of the elutriated finer material by the admixed air. Descriptions of the materials and methods we used, and the tabular data and temperature-depth profiles that support our findings, are included as appendices.

Professional Paper↗
USGS1980

Geology of a zone of metamorphic core complexes in southeastern Arizona

An elongate northwest-trending zone of batholith-size metamorphic core complexes extends some 130 km from the Rincon Mountains to the Picacho Mountains in southeastern Arizona. The complexes are characterized by undeformed to gneissic granitic intrusions, gneissic to phyllonitic xenoliths and wall rocks derived mainly from Precambrian granitic rock, shallow-dipping foliation, and remarkably uniform directions of lineation. Parts of this zone have been recognized and studied extensively for more than 30 yr, but there remains a divergence of opinion about the age, depth of emplacement, and origin of the complexes. Field relations indicate that host rocks as young as or younger than Mesozoic were involved in cataclasis. K-Ar and fission-track ages indicate that the complexes were at temperatures uniformly in excess of 400°C in the middle Tertiary (20 to 30 m.y. ago) and that the bedrock between and very near the complexes was not thermally affected. Tertiary plutons characteristically associated with the high-grade metamorphic rocks are also cataclastically deformed, and stratigraphic depths to the top of metamorphic terranes were no more than 6 km and possibly less than 3 km. These and other data suggest to some that the complexes developed during intrusion of composite batholiths at shallow depth in an anisotropic stress field during the middle Tertiary. On the other hand, Rb-Sr and U-Th-Pb techniques yielded older ages (≥44 m.y.) for some samples. These and additional data suggest to others that major development of cataclasis preceded the middle Tertiary and included regional thrusting.

Arizona↗
USGS1980

A catalogue of drill core recovered from Kilauea Iki lava lake, from 1967 to 1979

The purpose of this report is to serve as a descriptive catalogue for drill core recovered from Kilauea Iki lava lake, from 1967 to 1979. Kilauea Iki lava lake was formed when lavas of the 1959 summit eruption were ponded in Kilauea Iki pit crater, a large pit crater at the extreme upper end of Kilauea's east rift zone (Fig. 1). This eruption is one of the best documented of Kilauean eruptions: Murata and Richter (1966) and Richter and Murata (1966) presented data on the chemistry and petrography of the lavas, respectively, and Richter et al. (1970) described the complex filling of the pit crater in considerable detail. Investigation of the lava lake began a few months after the crust stabilized, with the establishment of two perpendicular lines of levelling stations on the surface of the lake. In 1960-62, four holes were drilled through the upper crust in the center of the lake; the crust was 22-44 feet (6.7-13.4 m) thick at that time. Richter and Moore (1966) presented petrographic, modal, and chemical data on the core recovered from this early drilling. The upper crust of Kilauea Iki was drilled again in 1967 by staff members of the Hawaiian Volcano Observatory, and core was recovered from three holes. In 1975, U.S. Geological Survey workers drilled three more holes, each a few feet away from one of the 1 967 holes. A summary of all work done on Kilauea Iki and other Hawaiian lava lakes through 1975 has been given by Wright et al. (1976). The lake has been redrilled twice since 1975, by workers from Sandia Laboratories, as part of their Magma Energy Research program, in cooperation with the U.S. Geological Survey. In 1976, they drilled two holes near the center of the lake. In 1978-79, they drilled a total of six holes; one, commissioned by the U.S. Geological Survey, went completely through the lava lake near its north edge, into the pre-1959 lavas below.

Hawaii↗
USGS1977

Some observations that bear on the origin of porphyry copper deposits

Observations at Ray, Ariz., suggest that upper crustal calc-alkaline plutons associated in time and space with the deposit might not have been capable of producing much water by differentiation and that any water released likely had restricted access to the best copper-sulfur sources in the magmas. Observation of concentrations of sulfides around isolated pockets of partially melted rocks below the Stillwater Complex. Mont., suggest to us a variant model of porphyry copper generation that does not require calc-alkaline plutons to be the vessels that transport copper and sulfur to upper crustal sites.

Open-File Report↗
USGS1977

Igneous rocks and copper mineralization in the Ray porphyry copper district, Arizona

The Ray porphyry copper district is approximately 110 km north of Tucson and 120 km east-southeast of Phoenix in southeastern Arizona. The major disseminated copper deposit at Ray has reserves estimated at 650 million tonsl of both primary and secondary ore, and occurs mostly in Precambrian Pinal Schist and diabase, but partly in the Granite Mountain Porphyry of Laramide age. The Granite Mountain Porphyry is part of a suite of Laramide igneous plutons and dikes in the Ray area that range in age from 70 to 60 m.y. and in composition from diorite to quartz monzonite. Hydrothermal biotite from the copper deposit at Ray has been dated at 65 m.y. (K-Ar age), and apatite in mineralized diabase has been reset at 60 m.y. (fission-track age). These ages indicate a close temporal and possibly genetic relationship with these Laramide igneous rocks.

Arizona↗
USGS1977

Magmatic behavior of Cu, S, Cl, F, and H 2 O in igneous rocks associated with the Ray porphyry copper deposit, Arizona

Porphyry copper deposits are the subject of a large volume of literature indicating that controversy still reigns as to which model or combination of models explains their origin, and yet, over 70 years ago we reached agreement that the well-documented space-time relationship between the deposits and calc-alkaline plutons indicates a genetic tie between them. This genetic tie is generally assumed to indicate a causitive role for an exposed or nearby hidden pluton. There are many variants, but the two end-member models that incorporate this causitive assumption are the meteoric water model and the orthomagmatic model. It is my opinion that the controversy originates from use of indirect data and variant models to explain new observational data and experimental studies that threaten the survival of the basic end-member models. One of many examples of this is the end-stage magmatic evolution of chlorine-rich water required of the orthomagmatic model. This evolution is required because the low copper content of calc-alkaline plutons demands a large source magma, that, because it generally is not visible, has to be buried. Additionally, much of the ore minerals in porphyry deposits is along fractures. Both conditions require transportation of the ore components from the magma, and to transport enough ore components, given the limited amount of water soluble in a melt and the low solubility of base-metal sulfides in water without benefit of chloride complexing, we required of the original Lindgren magmatic model that the source pluton produced chloride-rich water. However, we did not investigate the rocks associated with deposits to substantiate the hypothesis. We went to the laboratory and found that sufficient water and chlorine could be dissolved in silicate melt in a gold capsule in a high-pressure high-temperature bomb to allow postulation of sufficient water and chlorine in the stocks associated with porphyry deposits; in other words, we invested in indirect rather than direct studies.

Arizona↗
USGS1977

Middle Tertiary plutonism in the Santa Catalina and Tortolita mountains, Arizona

Recent reconnaissance geologic mapping in the Santa Catalina and Tortolita Mountains of southeastern Arizona, supplemented by new and published potassium-argon and fission-track ages, suggests that a large composite batholith of middle Tertiary (about 25 million years) age crops out extensively in both mountains. More than two-thirds of the batholith and contiguous wallrocks is gneissic, the gneissosity comprising strong cataclasis and mylonitization, penetrative planar and linear structures, and crystallization of muscovite and biotite in the foliation planes. New radiometric ages indicate that the deformation followed the crystallization of the batholith so closely that the K-Ar dating method cannot distinguish a difference, whereas previously published ages from the gneisses indicate a short time between the two events.

Arizona↗
USGS1976

Middle Tertiary plutonism in the Santa Catalina and Tortolita Mountains, Arizona

Recent reconnaissance geologic mapping in the Santa Catalina and Tortolita Mountains of southeastern Arizona, supplemented by new and published potassium-argon and fission-track ages, suggests that a large middle Tertiary (about 25 m.y.) composite batholith crops out extensively in both mountains. More than two-thirds of the batholith and the contiguous wallrocks are gneissic, the gneissosity comprising strong cataclasis and mylonitization, penetrative planar and linear structures, and crystallization of muscovite and biotite in the foliation planes. New radiometric ages indicate the deformation followed the crystallization of the batholith so closely that the K-Ar dating method cannot distinguish a difference, whereas previously published ages from the gneisses indicate a short time interval between the two events.

Arizona↗
USGS1976

Halogen contents of igneous minerals as indicators of magmatic evolution of rocks associated with the Ray porphyry copper deposit, Arizona

The contents of Cl, F, and H 2 O+ (calculated) in some hydrous igneous minerals in intrusive rocks of Laramide age (70-60 m.y.) near Ray, Ariz., appear to be related to the age and the chemistry of the whole-rock samples. Apatite and biotite in younger, more silicic rocks contain more F but less Cl and H 2 O+ than apatite and biotite in older, more mafic rock; the same relations hold for F and H 2 O+ in sphene. Correlations of the abundance of Cl, F, and H 2 O+ in hornblende with rock chemistry and age are not as strong as for apatite, biotite, and sphene; igneous (?) epidote does not contain Cl and F in amounts detectable by electron microprobe analysis. The contents of Cl, F, and H 2 O+ in whole-rock samples decrease with increasing differentiation index and decreasing age. Data for a single pluton of variable composition mirror the results for a suite of different plutons and dikes. The data are satisfactorily although not exclusively explained by postulating that the melts each contained progressively less Cl, F, and H 2 O and that the hydrons minerals consumed most of the Cl, F, and H 2 O in the magmas. The data may also be explained by postulating that (1) the stocks evolved Cl-bearing water during their ascent and crystallization, or that (2) Cl and H 2 O were concentrated during differentiation of the stocks but the minerals failed to record their buildup. Both alternative explanations find problems with and require special conditions to satisfy field, chemical, and experimental data. If many of the special conditions are not met, a nearby batholithic parent to the stocks is not a favorable source of the mineralized fluids at Ray. Propylitic alteration of biotite results in Cl-poor chlorites and may have provided some Cl to hydrothermal fluids; biotite may have also supplied some F to propylitizing fluids through alteration.

Arizona↗
USGS1974

Distribution of copper in biotite and biotite alteration products in intrusive rocks near two Arizona porphyry copper deposits

Biotite and its alteration products (primarily chlorite) from igneous rocks around the Ray and Esperanza (Esperanza-Sierrita) porphyry copper deposits, Arizona, were analyzed for copper by electron microprobe. The copper occurs in amounts >90 p/m (limit of detection) in most of the chlorites analyzed, is concentrated at the optical and chemical boundary of chlorite and biotite, and is not associated with sulfur. Most unaltered igneous and hydrothermal biotites analyzed contain <90 p/m Cu, and except for one sample, all copper that was detected can be explained as contamination by copper from chlorite grains. The paucity of detectable copper in igneous and hydrothermal biotite and its presence in daughter chlorite suggest that the positive association noted by some workers between the proximity of an ore deposit and the copper content of biotite might be partly the result: of increased amounts of chloritization of biotite near a deposit coupled with difficulty in physically cleaning the biotite separates. Additionally, previous speculations that (1) part of the copper in a deposit may come from altered biotite, and (2) copper in biotite indicates how copper behaves in a differentiating magma, are of doubtful value if based on data derived from analyses of bulk mineral separates.

Arizona↗