Geology topics
J.D. Gleason
Publications and source records attributed to J.D. Gleason.
Deuterium fractionation as water diffuses into silicic volcanic ash
No abstract available
Age and tectonic setting of the Mesozoic McCoy Mountains Formation in western Arizona, USA
The McCoy Mountains Formation consists of Upper Jurassic to Upper Cretaceous siltstone, sandstone, and conglomerate exposed in an east-west–trending belt in southwestern Arizona and southeastern California. At least three different tectonic settings have been proposed for McCoy deposition, and multiple tectonic settings are likely over the ∼80 m.y. age range of deposition. U-Pb isotopic analysis of 396 zircon sand grains from at or near the top of McCoy sections in the southern Little Harquahala, Granite Wash, New Water, and southern Plomosa Mountains, all in western Arizona, identified only Jurassic or older zircons. A basaltic lava flow near the top of the section in the New Water Mountains yielded a U-Pb zircon date of 154.4 ± 2.1 Ma. Geochemically similar lava flows and sills in the Granite Wash and southern Plomosa Mountains are inferred to be approximately the same age. We interpret these new analyses to indicate that Mesozoic clastic strata in these areas are Upper Jurassic and are broadly correlative with the lowermost McCoy Mountains Formation in the Dome Rock, McCoy, and Palen Mountains farther west. Six samples of numerous Upper Jurassic basaltic sills and lava flows in the McCoy Mountains Formation in the Granite Wash, New Water, and southern Plomosa Mountains yielded initial ε Nd values (at t = 150 Ma) of between +4 and +6. The geochemistry and geochronology of this igneous suite, and detrital-zircon geochronology of the sandstones, support the interpretation that the lower McCoy Mountains Formation was deposited during rifting within the western extension of the Sabinas-Chihuahua-Bisbee rift belt. Abundant 190–240 Ma zircon sand grains were derived from nearby, unidentified Triassic magmatic-arc rocks in areas that were unaffected by younger Jurassic magmatism. A sandstone from the upper McCoy Mountains Formation in the Dome Rock Mountains (Arizona) yielded numerous 80–108 Ma zircon grains and almost no 190–240 Ma grains, revealing a major reorganization in sediment-dispersal pathways and/or modification of source rocks that had occurred by ca. 80 Ma.
Deuterium content of water from wells and perennial springs, southeastern California
The areal distribution of the concentrations of the stable isotopes deuterium and oxygen-18 in ground water in southeastern California is depicted and evaluated in this report. The deuterium content of about 300 ground-water samples and the oxygen-18 content of 101 of these samples are presented. Thirty-two of the samples were collected by the U.S. Geological Survey in 1977–78 as part of a study to determine the mineral and brine potential of playa lakes in selected basins in southeastern California. Most of the remaining samples were collected during the winters and springs of 1981 and 1982 as part of the Climate Change Program of the Geological Survey. Selected additional samples were collected through 1986. Stable-isotope data from three previous studies also have been included. These data are for 19 samples from the Coso thermal area east of the southern Sierra Nevada (Fournier and Thompson, 1980, tables 1,2), 5 samples from areas in Nevada just east of Death Valley (Winograd and Friedman, 1972, table 1), and 9 samples from the Imperial Valley (Coplen, 1971, table 1). Also presented for comparison are weighted averages of deuterium content of recent precipitation collected for this report at 32 stations over the 7-year period from April 1982 to April 1989 (Irving Friedman and G.I. Smith, U.S. Geological Survey, written commun., 1989).
The oxygen isotope composition of selected quartzites of White Pine County, Nevada, and nearby areas
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Modification of δ D values in eastern Nevada granitoid rocks spatially related to thrust faults
Stable isotope data have been determined for 13 Mesozoic and Tertiary plutons in eastern Nevada and nearby Utah. In the southern Snake Range of eastern Nevada, where relations are best exposed and have been most intensively studied, δ D, δ 18 O, and apparent K-Ar ages depend on proximity to the Snake Range decollement. Where stresses resulting from late movement on the decollement have caused cataclasis of Oligocene (37 Ma) granitoid rock, δ 18 O, δ D, and K-Ar age values as low as −2.5‰, −155‰, and 18 Ma, respectively, have been determined. Where there has been no cataclasis, δ 18 O values of Jurassic, Cretaceous, and Oligocene granitoid rocks are apparently unaffected, but both δ D values and K-Ar ages have been modified for distances of tens of meters below the decollement. Results similar to those in the southern Snake Range have been observed in other eastern Nevada granitoid rocks spatially related to regional thrust faults, as in the Kern Mountains, the Toana Range, and the northern Egan Range. In each of these areas cataclasis or deformation of granitoid rocks has resulted in lowered δ 18 O, δ D, and K-Ar age values. Where there has been no cataclasis or deformation, δ 18 O values are unaffected, but both δ D and K-Ar age values have been lowered by stresses resulting from postcrystallization movement along overlying thrust faults. Many of the plutons discussed have not been deeply eroded, and spatially related thrust faults crop out. Where thrust faults are not in evidence and the granitoid rocks give δ D values lower than about −130‰ along with spuriously low K-Ar age results, modification of the δ D and K-Ar age values may have been caused by stresses related to late movement along an overlying (now eroded) thrust fault.
Stable isotope compositions of gases and vegetation near naturally burning coal
Our measurements of stable isotope compositions of CO2 issuing from vents produced by naturally burning coal indicate that the coal is oxidized through a kinetic process in which groundwater is the oxidizing agent. The CO2 produced by the oxidation of the coal is extremely depleted in 13C relative to normal atmospheric CO2. The change in the ??13C value of atmospheric CO2 near the vents resulting from the burning coal was not recorded in tree rings from red cedars, but the ??13C values of some C3 and C4 type plants collected from within the area were greatly affected. Our results indicate that the ??13C values of some species of plants may be sensitive indicators of changes in the carbon isotopic composition of atmospheric CO2. ?? 1984 Nature Publishing Group.
The oxygen isotope composition of granitoid and sedimentary rocks of the southern Snake Range, Nevada
Six diverse intrusive igneous types are exposed as discrete outcrops within an area of 900 km2 in the southern Snake Range, White Pine County, Nevada. The previously recognized variety among these igneous types is reflected in the wide range of ??18O values (-1.1 to 13.4 permil) found in these rocks. This range of ??18O values probably results from differences in source material and post-crystallization history of the different intrusive types. The Jurassic intrusive of the Snake Creek-Williams Canyon area represents the chemical equivalent of a large part of a differentiation sequence, with the entire range of composition (63-76 percent SiO2) exposed over a horizontal distance of about five km. The rather regular increase of ??18O values from the most mafic to the most felsic parts of this pluton, together with ??18O values determined for constituent minerals recovered from five of the samples, supports a fractional crystallization model. The high ??18O values found (10.2-12.2 permil) indicate that the magma likely was derived from or assimilated sedimentary materials. Nine samples of the Cretaceous two-mica granite of the Pole Canyon-Can Young Canyon area have ??18O values in the range 10.6-12.1 permil. These high ??18O values, an initial87Sr/86Sr ratio of 0.7165, and the presence of muscovite along with an accessory mineral suite limited to monazite, apatite, zircon, and an allanite-like mineral, characterize this intrusive mass as an S-type granite. It probably formed through anatexis of late Precambrian pelitic rocks. The granitoid rock exposed in the Young Canyon-Kious Basin area is Tertiary (32 m.y.). Most of this intrusive has been cataclastically deformed as a result of late (18 m.y.) movement on the overlying Snake Range decollement. The undeformed portion of this intrusive has ??18O values of 8.7-10.0 permil. However, the deformed portion of this intrusive has ??18O values as low as -1.1 permil, apparently resulting from isotopic exchange between this rock and ground water at the time of cataclasis. Although the igneous types exposed in the southern Snake Range differ petrologically and range in age from Jurassic to Tertiary, most have relatively high ??18O values compared with other granitoid rocks of the Basin-Range Province. ?? 1982 Springer-Verlag.
Map showing the oxygen isotope composition of granitoid rocks of the Basin-Range province
This map presents oxygen suite of granitoid rocks from Province of Nevada, Utah, isotope data for a the Basin and Range California, and Arizona. Two random samples were collected each of two randomly selected plutons within 1° x 1° area. For this study, only the m.nnbered sample was analyzed except in instance when sample GR-128 was substituted its odd-numbered counterpart (CR-127), which lost.
Oxygen isotopes of some trondhjemites, siliceous gneisses, and associated mafic rocks
Analyses of oxygen isotopes in whole-rock samples of 58 Precambrian and Phanerozoic trondhjemites and siliceous gneisses and of 28 cogenetic mafic to intermediate rocks from North America, Fennoscandia, and southern Africa give the following results: 1. (1) 47 trondhjemites, tonalites, and mostly Archean acidic gneisses that apparently are not isotopically disturbed show an overage δ 15 O +7.3‰ "> +7.3‰ and a range of 5.2–8.9‰; 11 other samples are slightly to moderately disturbed and show higher values; and 2. (2) the mafic rocks show a wide range of δ-values, from about 0–9‰ but the undisturbed ones give an average δ 18 O of 5.2‰ "> 5.2‰ . The δ 18 O values of the trondhjemitic intrusives and siliceous gneisses of similar composition are lower than those of most granitic rocks and support models for derivation of these rocks from basaltic parents. This approach, however, cannot be used to determine if individual bodies formed by differentiation or by partial melting.
Meteoric water in magmas
Oxygen isotope analyses of sanidine phenocrysts from rhyolitic sequences in Nevada, Colorado, and the Yellowstone Plateau volcanic field show that δ 18 O decreased in these magmas as a function of time. This decrease in δ 18 O may have been caused by isotopic exchange between the magma and groundwater low in 18 O. For the Yellowstone Plateau rhyolites, 7000 cubic kilometers of magma could decrease in δ 18 O by 2 per mil in 600,000 years by reacting with water equivalent to 3 millimeters of precipitation per year, which is only 0.3 percent of the present annual precipitation in this region. The possibility of reaction between large magmatic bodies and meteoric water at liquidus temperatures has major implications in the possible differentiation history of the magma and in the generation of ore deposits.
Water and carbon in rusty lunar rock 66095
Lunar rock 66095 contains a hydrated iron oxide and has an unusual amount of water for a lunar rock (140 to 750 parts per million), 90 percent of which is released below 690°C. The δof water released at these low temperatures varies from -75 to -140 per mil relative to standard mean ocean water (SMOW). The small amount of water released between 690° and 1300°C has a δ of about -175 ±25 per mil SMOW. These δ values are not unusual for terrestrial water. The δ 18 O of water extracted from 110° to 400°C has a value of +5± I per mil SMOW, similar to the value for lunar silicates from rock 66095 and different from the value of -4 to -22 per mil found for samples of terrestrial rust including samples of rusted meteoritic iron. The amount of carbon varies from 11 to 59 parts per million with a δ 13 C from -20 to -30 per mil relative to Pee Dee belemnite. Only very small amounts of reduced species (such as hydrogen, carbon monoxide, and methane) were found, in contrast to the analyses of other lunar rocks. Although it is possible that most of the water in the iron oxide (goethite) may be terrestrial in origin or may have exchanged with terrestrial water during sample return and handling, evidence presented herein suggests that this did not happen and that some lunar water may have a δD that is indistinguishable from that of terrestrial water.
A new silicate intercomparison standard for 18O analysis
No abstract available.
Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material
The water content of the breccia is 150 to 455 ppm, with a δD from—580 to —870 per mil. Hydrogen gas content is 40 to 53 ppm with a δD of —830 to —970 per mil. The CO 2 is 290 to 418 ppm with δ 13 C = + 2.3 to + 5.1 per mil and δ 18 O = 14.2 to 19.1 per mil. Non-CO 2 carbon is 22 to 100 ppm, δ 13 C = —6.4 to —23.2 per mil. Lunar dust is 810 ppm H 2 O (D = 80 ppm) and 188 ppm total carbon(δ 13 C = —17.6 per mil). The 18 O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100° to 1300°C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.
Deuterium: Natural variations used as a biological tracer
The suggestion is made that isotope tracing be carried out by monitoring the natural variations in deuterium concentrations. As an example, the natural variations in deuterium concentrations between food and water collected in Illinois and food and water collected in Colorado were used to determine the residence time of water in the blood and urine of rats. We observed not only a 51/2-day turnover time of water in the blood and urine, but also evidence for the influx of water vapor from the atmosphere through the lungs into the blood.