I have read Corry’s (1985) paper with interest, but disagree with several particular conclusions:... more I have read Corry’s (1985) paper with interest, but disagree with several particular conclusions: (1) that positive potentials do not exist, (2) that current flow is sensibly zero, (3) that potentials are established by connecting the reference electrode outside the mineralization through a conductor to a roving electrode in contact with sulfide mineralization, and (4) that the gradient method is unsuited to mineral surveys.
Vita.I have reexamined the treatise by Gilbert (1877) on laccoliths, using an interplay between c... more Vita.I have reexamined the treatise by Gilbert (1877) on laccoliths, using an interplay between current geophysical methods of investigating geologic structures, and presently available finite element methods of modeling structural problems. My results support every major aspect of Gilbert's work. Thus, my work is remarkable only in that nearly all subsequent workers in the intervening century have differed substantially with Gilbert's interpretation. Gravity surveys of large laccoliths in Texas, Utah, Wyoming, South Dakota, California, and Montana reveal no. detectable density contrast between the laccoliths and the country rock in which they are emplaced. This result strongly supports Gilbert's (1877) hypothesis that control of the level of intrusion is by the density contrast between the rising magma and the weighted mean density of the overburden. The emplacement of laccoliths can be modeled using dislocation theory. The rising magma is treated as dislocation climb using a model given by Weertman (1971a, 1971b). The climb force is developed by the density contrast between the magma and country rock at depth. Weertman's model has been extended, together with field observations of laccolith feeder dikes, to obtain the magma driving pressure. Development of an emplacement model allows determination of the boundary conditions, and the growth of laccoliths is treated as a boundary value problem in continuum mechanics. I have treated the diverse shapes of laccoliths described in the geologic literature as a continuous series of growth modes with two distinct end members. One end member, type A, results from the intrusion of a single dominant sill which loads the roof like a punch, resulting in sheared margins and peripheral faults.
Abstract : This report presents the Pacific abyssal water temperature data accumulated during hea... more Abstract : This report presents the Pacific abyssal water temperature data accumulated during heat flow measurements made by the Scripps Institution of Oceanography from 1966 to 1968. The cruises include TRIPOD (1966), ZETES (1966), SHOW (1966), NOVA (1967), and CIRCE (1968) expeditions. The heat flow measurements are carried out by using Bullard type instrument which is composed mainly of a probe, several sensing thermistors, and a recorder housed in the pressure case. These thermistors are located one meter apart on the probe to measure the relative temperature difference from which the vertical temperature gradient is computed. The thermal conductivity of the sediments is measured either from the gravity core or by an in situ thermal conductivity probe. A product of the thermal conductivity and the temperature gradient yields the heat flux through the ocean bottom at the station. (Author)
SEG Technical Program Expanded Abstracts 1988, 1988
Sulfide systems can be identified in controlled source audio-frequency magnetoteLhuic (CSAMT) sur... more Sulfide systems can be identified in controlled source audio-frequency magnetoteLhuic (CSAMT) surveys by steep to vertically bounded zones of low apparent resistivity (pa) that pmvkle deftitive horizontal resolution of the lateral extent of the suhides. The method proved most effective iflow cost, preliminary self-potential (SP) surveys were used to defme the centers of the sulfide svstems orior to the CSAMT surveys. The technique can L&O be u&d to I&Y the electrical stratigraphy, and dips 260' have been traced. The ability to map subsurface StNCtUrC and stratigraphy also has applications in oil exploration, engineering, and hydrology. introduction Cony, C. E., Emer, D. F., and Zonge, K. L., 1987, Controlled source audiio-frequency magnetotelluric surveys of porphyry sulfide deposits and prospects in the Cordillera of the United States:
SEG Technical Program Expanded Abstracts 1996, 1996
Delineating and monitoring, leakage from aging or ruptured underground storage tanks is both a co... more Delineating and monitoring, leakage from aging or ruptured underground storage tanks is both a common and expensive problem. Typically the site must be extensively drilled and numerous water samples taken and analyzed in order to delineate the contaminant plume. Remediation efforts often require that ground water sampling be continued frequently over several years.
Gilbert (1877) proposed that the level of emplacement of laccoliths is controlled by the density ... more Gilbert (1877) proposed that the level of emplacement of laccoliths is controlled by the density contrast between rising magma and the weighted mean density of the overburden. For felsic laccoliths, his hypothesis is strongly supported by gravity surveys of a number of laccolith groups. Epizonal felsic laccoliths are consistently found to have zero density contrast with the host rocks. Constraining the emplacement level provides a basis for analysis of the growth of laccoliths. Mechanical analysis suggests that the diverse shapes of laccolithic intrusions observed in the field can be represented by a continuous series of intrusion modes between two distinct end members. The simplest end member is an epizonal intrusion formed by a single sill that acts mechanically as a vertical punch. Punched laccoliths are characterized by flat tops, peripheral faults, and steep or vertical sides. The other end member results from the intrusion of multiple sills stacked vertically in a fashion suggestive of a Christmas tree. The multiple-level loading results in plastic deformation of the country rock. Christmas-tree laccoliths lack peripheral faults and have a characteristic rounded dome appearance on the surface. The floor of these laccoliths may, or may not, sag. Gilbert's (1877) laccolith falls between these two end members. The end members of the laccolith growth series are treated as boundary value problems in continuum mechanics. Geometrically and materially nonlinear finite element analysis is used to the solve the boundary value problems. Field observation, a physical model and the theoretical models provide convergent answers to the mechanical analysis of the growth of laccoliths. As a check on the theoretical models, a gazetteer of the dimensions and locations of approximately 900 laccoliths is included. Of these, approximately 600 are located in the United States. If North America represents a statistically valid sample, then there must be between 5,000 and 10,000 laccoliths in the world.
Fifty-three measurements of the outward flow of heat through the ocean floor have been made aroun... more Fifty-three measurements of the outward flow of heat through the ocean floor have been made around the Hawaiian Islands. The heat flow values ranged from a low of 0.71 to a high of 1.9 /zcal/cm•'/sec. The mean value for all the measurements (this includes ten previous measurements) north and east of the islands of Oahu, Maul, and Hawaii is 1.38/zcal/cm2/sec. A statistical analy•s on these values indicates that the mean outward flow of heat through the area southeast of Hawaii, 1.60 /zcal/cm¾sec, is significantly greater than the mdan flow, 1.30/zcal/cm¾sec, through the Hawaiian arch. The similarity of all the values to the oceanic average indicates, however, that neither area is thermally active and suggests that the source of the present activity on I-Iawaii does not extend beyond the island. Introduction. In June and July 1966, the research vessels Argo, and Horizon of the Scripps Institution of Oceanography took part in Expedition Show, a detailed geophysical investigation of the crustal thickness north of Oahu and Maui. During this expedition, fifty-six successful heat flow stations were occupied. The first fourteen measurements made from Horizon were part of a detailed seismic reflection and heat flow survey investigating the correlation between irregularities in surface and subsurface topography and localized differences in heat flow. These stations covered a very small area. The values and their interpretation form the basis of a separate paper [Sclater, 1967], and only the mean position, the mean temperature gradient, and conductivity are presented here. Also shown in this paper are the four heat flow measurements made east of 180øW
Laboratory studies by different investigators using various techniques have expanded the number o... more Laboratory studies by different investigators using various techniques have expanded the number of known ferroelectric ore minerals to about twenty at present from the first discovery of makedonite (PbTiO3) in 1950. These include such common ore minerals as bismuthinite ( B i2S 3), cassiterite (SnO2), chalcocite (Cu2S), pyrrhotite (Fe i -xS), and stibnite ( Sb2S 3 ). Two field investigations of sulfide ore bodies that contain known ferroelectric minerals were undertaken to investigate possible in-situ effects in these deposits. These deposits, at Mount Emmons (38°53'N, 107°03'W), Colorado, and Three R Canyon (31°28'N, 110°46'W) in the Patagonia Mountains, Arizona, demonstrate ferroelectric effects that include directional polarization and apparent resistivity, electrically-excited resonance, and lack of reciprocity. Other phenomena include history-dependent electrical behavior and inductive effects. Ferroelectrics polarize as a function of applied potential. It is much easier to generate a large potential than the high currents commonly used in IP surveys. Thus, in electrical surveys of deposits known, or suspected, to contain ferroelectric minerals it may be advantageous to maximize the applied potential. It may also be relatively easy to induce electrical resonance in these deposits that could provide an inexpensive reconnaissance technique. In IP and CR surveys, ferroelectric effects can mask the deposit since Pa may approach zero in the polar direction, or chargeability may be undetectable. Phase relations will most likely be uninterpretable in CR surveys over such deposits. In CSAMT surveys, directional resonance effects may preclude depth interpretation. Frequency-dependent inductive and capacitive effects may be observed in CR and CSAMT surveys over deposits containing significant quantities of ferroelectric minerals. Ferroelectricity may also be useful in exploitation efforts for electrical beneficiation during ore processing.
I have read Corry’s (1985) paper with interest, but disagree with several particular conclusions:... more I have read Corry’s (1985) paper with interest, but disagree with several particular conclusions: (1) that positive potentials do not exist, (2) that current flow is sensibly zero, (3) that potentials are established by connecting the reference electrode outside the mineralization through a conductor to a roving electrode in contact with sulfide mineralization, and (4) that the gradient method is unsuited to mineral surveys.
Vita.I have reexamined the treatise by Gilbert (1877) on laccoliths, using an interplay between c... more Vita.I have reexamined the treatise by Gilbert (1877) on laccoliths, using an interplay between current geophysical methods of investigating geologic structures, and presently available finite element methods of modeling structural problems. My results support every major aspect of Gilbert's work. Thus, my work is remarkable only in that nearly all subsequent workers in the intervening century have differed substantially with Gilbert's interpretation. Gravity surveys of large laccoliths in Texas, Utah, Wyoming, South Dakota, California, and Montana reveal no. detectable density contrast between the laccoliths and the country rock in which they are emplaced. This result strongly supports Gilbert's (1877) hypothesis that control of the level of intrusion is by the density contrast between the rising magma and the weighted mean density of the overburden. The emplacement of laccoliths can be modeled using dislocation theory. The rising magma is treated as dislocation climb using a model given by Weertman (1971a, 1971b). The climb force is developed by the density contrast between the magma and country rock at depth. Weertman's model has been extended, together with field observations of laccolith feeder dikes, to obtain the magma driving pressure. Development of an emplacement model allows determination of the boundary conditions, and the growth of laccoliths is treated as a boundary value problem in continuum mechanics. I have treated the diverse shapes of laccoliths described in the geologic literature as a continuous series of growth modes with two distinct end members. One end member, type A, results from the intrusion of a single dominant sill which loads the roof like a punch, resulting in sheared margins and peripheral faults.
Abstract : This report presents the Pacific abyssal water temperature data accumulated during hea... more Abstract : This report presents the Pacific abyssal water temperature data accumulated during heat flow measurements made by the Scripps Institution of Oceanography from 1966 to 1968. The cruises include TRIPOD (1966), ZETES (1966), SHOW (1966), NOVA (1967), and CIRCE (1968) expeditions. The heat flow measurements are carried out by using Bullard type instrument which is composed mainly of a probe, several sensing thermistors, and a recorder housed in the pressure case. These thermistors are located one meter apart on the probe to measure the relative temperature difference from which the vertical temperature gradient is computed. The thermal conductivity of the sediments is measured either from the gravity core or by an in situ thermal conductivity probe. A product of the thermal conductivity and the temperature gradient yields the heat flux through the ocean bottom at the station. (Author)
SEG Technical Program Expanded Abstracts 1988, 1988
Sulfide systems can be identified in controlled source audio-frequency magnetoteLhuic (CSAMT) sur... more Sulfide systems can be identified in controlled source audio-frequency magnetoteLhuic (CSAMT) surveys by steep to vertically bounded zones of low apparent resistivity (pa) that pmvkle deftitive horizontal resolution of the lateral extent of the suhides. The method proved most effective iflow cost, preliminary self-potential (SP) surveys were used to defme the centers of the sulfide svstems orior to the CSAMT surveys. The technique can L&O be u&d to I&Y the electrical stratigraphy, and dips 260' have been traced. The ability to map subsurface StNCtUrC and stratigraphy also has applications in oil exploration, engineering, and hydrology. introduction Cony, C. E., Emer, D. F., and Zonge, K. L., 1987, Controlled source audiio-frequency magnetotelluric surveys of porphyry sulfide deposits and prospects in the Cordillera of the United States:
SEG Technical Program Expanded Abstracts 1996, 1996
Delineating and monitoring, leakage from aging or ruptured underground storage tanks is both a co... more Delineating and monitoring, leakage from aging or ruptured underground storage tanks is both a common and expensive problem. Typically the site must be extensively drilled and numerous water samples taken and analyzed in order to delineate the contaminant plume. Remediation efforts often require that ground water sampling be continued frequently over several years.
Gilbert (1877) proposed that the level of emplacement of laccoliths is controlled by the density ... more Gilbert (1877) proposed that the level of emplacement of laccoliths is controlled by the density contrast between rising magma and the weighted mean density of the overburden. For felsic laccoliths, his hypothesis is strongly supported by gravity surveys of a number of laccolith groups. Epizonal felsic laccoliths are consistently found to have zero density contrast with the host rocks. Constraining the emplacement level provides a basis for analysis of the growth of laccoliths. Mechanical analysis suggests that the diverse shapes of laccolithic intrusions observed in the field can be represented by a continuous series of intrusion modes between two distinct end members. The simplest end member is an epizonal intrusion formed by a single sill that acts mechanically as a vertical punch. Punched laccoliths are characterized by flat tops, peripheral faults, and steep or vertical sides. The other end member results from the intrusion of multiple sills stacked vertically in a fashion suggestive of a Christmas tree. The multiple-level loading results in plastic deformation of the country rock. Christmas-tree laccoliths lack peripheral faults and have a characteristic rounded dome appearance on the surface. The floor of these laccoliths may, or may not, sag. Gilbert's (1877) laccolith falls between these two end members. The end members of the laccolith growth series are treated as boundary value problems in continuum mechanics. Geometrically and materially nonlinear finite element analysis is used to the solve the boundary value problems. Field observation, a physical model and the theoretical models provide convergent answers to the mechanical analysis of the growth of laccoliths. As a check on the theoretical models, a gazetteer of the dimensions and locations of approximately 900 laccoliths is included. Of these, approximately 600 are located in the United States. If North America represents a statistically valid sample, then there must be between 5,000 and 10,000 laccoliths in the world.
Fifty-three measurements of the outward flow of heat through the ocean floor have been made aroun... more Fifty-three measurements of the outward flow of heat through the ocean floor have been made around the Hawaiian Islands. The heat flow values ranged from a low of 0.71 to a high of 1.9 /zcal/cm•'/sec. The mean value for all the measurements (this includes ten previous measurements) north and east of the islands of Oahu, Maul, and Hawaii is 1.38/zcal/cm2/sec. A statistical analy•s on these values indicates that the mean outward flow of heat through the area southeast of Hawaii, 1.60 /zcal/cm¾sec, is significantly greater than the mdan flow, 1.30/zcal/cm¾sec, through the Hawaiian arch. The similarity of all the values to the oceanic average indicates, however, that neither area is thermally active and suggests that the source of the present activity on I-Iawaii does not extend beyond the island. Introduction. In June and July 1966, the research vessels Argo, and Horizon of the Scripps Institution of Oceanography took part in Expedition Show, a detailed geophysical investigation of the crustal thickness north of Oahu and Maui. During this expedition, fifty-six successful heat flow stations were occupied. The first fourteen measurements made from Horizon were part of a detailed seismic reflection and heat flow survey investigating the correlation between irregularities in surface and subsurface topography and localized differences in heat flow. These stations covered a very small area. The values and their interpretation form the basis of a separate paper [Sclater, 1967], and only the mean position, the mean temperature gradient, and conductivity are presented here. Also shown in this paper are the four heat flow measurements made east of 180øW
Laboratory studies by different investigators using various techniques have expanded the number o... more Laboratory studies by different investigators using various techniques have expanded the number of known ferroelectric ore minerals to about twenty at present from the first discovery of makedonite (PbTiO3) in 1950. These include such common ore minerals as bismuthinite ( B i2S 3), cassiterite (SnO2), chalcocite (Cu2S), pyrrhotite (Fe i -xS), and stibnite ( Sb2S 3 ). Two field investigations of sulfide ore bodies that contain known ferroelectric minerals were undertaken to investigate possible in-situ effects in these deposits. These deposits, at Mount Emmons (38°53'N, 107°03'W), Colorado, and Three R Canyon (31°28'N, 110°46'W) in the Patagonia Mountains, Arizona, demonstrate ferroelectric effects that include directional polarization and apparent resistivity, electrically-excited resonance, and lack of reciprocity. Other phenomena include history-dependent electrical behavior and inductive effects. Ferroelectrics polarize as a function of applied potential. It is much easier to generate a large potential than the high currents commonly used in IP surveys. Thus, in electrical surveys of deposits known, or suspected, to contain ferroelectric minerals it may be advantageous to maximize the applied potential. It may also be relatively easy to induce electrical resonance in these deposits that could provide an inexpensive reconnaissance technique. In IP and CR surveys, ferroelectric effects can mask the deposit since Pa may approach zero in the polar direction, or chargeability may be undetectable. Phase relations will most likely be uninterpretable in CR surveys over such deposits. In CSAMT surveys, directional resonance effects may preclude depth interpretation. Frequency-dependent inductive and capacitive effects may be observed in CR and CSAMT surveys over deposits containing significant quantities of ferroelectric minerals. Ferroelectricity may also be useful in exploitation efforts for electrical beneficiation during ore processing.
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Papers by Charles Corry