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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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North America
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Rocky Mountains
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Southern Rocky Mountains (1)
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San Juan Basin (1)
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United States
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Arizona
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Navajo County Arizona
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Hopi Buttes Field (1)
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Kansas
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Maine (2)
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Montana
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New Mexico
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Eddy County New Mexico
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Grants mineral belt (3)
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Luna County New Mexico
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Florida Mountains (1)
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McKinley County New Mexico
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Ambrosia Lake mining district (1)
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San Juan County New Mexico (1)
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Sandia Mountains (3)
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commodities
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elements, isotopes
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metals
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gold (1)
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oxygen
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fossils
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Primary terms
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absolute age (13)
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carbon
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Cenozoic
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clay mineralogy (1)
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economic geology (5)
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geochronology (9)
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igneous rocks
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carbonatites (1)
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kimberlite (2)
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plutonic rocks
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granites
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aplite (1)
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lamprophyres (1)
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pegmatite (2)
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syenites
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inclusions (2)
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intrusions (2)
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Invertebrata
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Ostracoda (1)
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Trilobita (1)
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isotopes
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stable isotopes
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C-13/C-12 (1)
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Sr-87/Sr-86 (3)
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magmas (2)
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Mesozoic
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Cretaceous
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Dakota Formation (1)
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Middle Cretaceous (1)
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Upper Cretaceous
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Kirtland Shale (1)
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Jurassic
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Upper Jurassic
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Morrison Formation (1)
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Triassic (1)
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metal ores
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gold ores (1)
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rare earth deposits (1)
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uranium ores (4)
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metals
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actinides
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uranium (1)
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alkaline earth metals
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strontium
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Sr-87/Sr-86 (3)
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gold (1)
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rare earths (1)
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metasomatism (1)
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mineral deposits, genesis (4)
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mineral exploration (1)
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minerals (2)
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North America
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Rocky Mountains
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Southern Rocky Mountains (1)
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oxygen
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O-18/O-16 (1)
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Paleozoic
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Devonian (1)
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Permian
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Eskridge Shale (1)
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Lower Permian (1)
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Stearns Shale (2)
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Silurian (1)
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petrology (3)
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Precambrian
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Sandia Granite (3)
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upper Precambrian
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Proterozoic (2)
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sedimentary rocks
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clastic rocks
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shale (2)
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sedimentation (1)
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stratigraphy (1)
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sulfur (1)
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United States
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Arizona
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Navajo County Arizona
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Hopi Buttes Field (1)
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Colorado Plateau (1)
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Kansas
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Riley County Kansas (1)
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Maine (2)
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Montana
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Mineral County Montana (1)
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Park County Montana (1)
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New Mexico
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Bernalillo County New Mexico (2)
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Eddy County New Mexico
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Waste Isolation Pilot Plant (1)
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Grants mineral belt (3)
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Luna County New Mexico
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Florida Mountains (1)
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McKinley County New Mexico
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Ambrosia Lake mining district (1)
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San Juan County New Mexico (1)
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Sandia Mountains (3)
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Valencia County New Mexico
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Grants New Mexico (2)
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Western U.S. (1)
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Wyoming (1)
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waste disposal (1)
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sedimentary rocks
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sedimentary rocks
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clastic rocks
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shale (2)
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volcaniclastics (1)
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sediments
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volcaniclastics (1)
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Precambrian rocks of the Sandia Mountains have been dated previously by the U, Th-Pb methods at about 1.46 Ga. Rb-Sr geochronology yields a similar age, 1.44 Ga, although local open-system conditions in the granite are indicated by data that fall off the whole-rock isochron. It is not known if this scatter reflects multi-domains in the granite or whole-rock-scale incipient alteration. Potassium-argon dates for micas yield 1.3 to 1.4 Ga, and Rb-Sr biotite dates yield 1.35 Ga; this age is commonly noted in north-central New Mexico. We interpret this date as either a thermal event affecting the granite, or possibly extended cooling at temperatures high enough to reset mineral Rb-Sr systematics. The Rb-Sr whole-rock age of the Juan Tabo metamorphic rocks at the north end of the Sandia Mountains is 1.61 Ga. Pegmatites and aplites of the same area yield a date of 1.41 Ga, but with a high initial 87 Sr/ 86 Sr ratio of 0.712 to 0.714. Granulitic xenoliths from the granite yield a date of 1.48 Ga, and may be older crust sampled by the granite. Our geochronologic data, and the geochemical data of Majumdar (1985), do not support the hypothesis of Condie and Budding (1979) that there are two major plutons in the Sandia granite. We propose instead one major pluton with some slight and systematic chemical variation within it.
Several volcanic ash units that have recently been discovered in the Kirtland Shale (Cretaceous) in the northwestern part of the San Juan Basin, New Mexico, occur some 20 m (sample 62) to 39 m (sample 54) above the uppermost rocks of the Fruitland Formation. The ashes are of extremely great value in attempting to work out the stratigraphy of the rocks in this area, especially as there is some question concerning the interpretation of faunal assemblages and paleomagnetic signatures; contradicting “dates” of earliest Tertiary to latest Cretaceous have been suggested for the part of the Kirtland Shale sampled. A systematic study of the Potassium-Argon geochronology of some of the ashes has been undertaken with the following results: (1) highest ash (sample 54): sanidine concentrates—72.4 ± 3.1 to 74.4 ± 2.6 Ma; biotite concentrates—73.2 ± 2.7 to 76.1 ± 2.8 Ma; (2) lowest ash (sample 62): sanidine concentrate—75.0 ± 2.7 Ma; and (3) upper middle ash (sample 93): sanidine concentrate—69.8 ± 2.5 Ma. Petrographic and scanning-electron microscope studies show the biotite and sanidine to be primary phases, containing negligible amounts of detrital material. The rare earth element and other chemical studies of the ashes show them to be slightly different from each other, and this information may allow rare earth element distribution data to be used for purposes of ash correlation. We interpret the Potassium-Argon ages as suggesting a Late Cretaceous age for the part of the Kirtland Shale sampled, a view consistent with recent paleontological and paleomagnetic studies.
Geology and geochemistry of the Snowbird Deposit, Mineral County, Montana
Uranium and other trace element geochemistry of the Hopi Buttes volcanic province, northeastern Arizona
Geochronologic Studies near WIPP Site, Southeastern New Mexico: Summary and Interpretation
Tertiary Mineralization in Part of Grants Mineral Belt, New Mexico
Rubidum-Strontium Minimum Ages of Sedimentation, Uranium Mineralization, and Provenance, Morrison Formation (Upper Jurassic), Grants Mineral Belt, New Mexico: Reply
Mount Taylor Uranium Deposit—Description and Comparison with Wyoming Roll Fronts
Mount Taylor Uranium Deposit, San Mateo, New Mexico: ABSTRACT
SEM Investigation of Paragenesis of Uranium Deposits, Grants Mineral Belt, New Mexico: ABSTRACT
Igneous origin of the Orbicular Rocks of the Sandia Mountains, New Mexico
Igneous origin of the orbicular rocks of the Sandia Mountains, New Mexico: Summary
Rubidium-Strontium Minimum Ages of Sedimentation, Uranium Mineralization, and Provenance, Morrison Formation (Upper Jurassic), Grants Mineral Belt, New Mexico
Geochronologic Contributions to Stratigraphic Interpretation and Correlation in the Penobscot Bay Area, Eastern Maine
The Rb-Sr whole-rock method has been used to test stratigraphic correlations in the Penobscot Bay area, eastern Maine. The Castine Volcanics, Thorofare Andesite-Vinalhaven Rhyolite, and Cranberry Islands Volcanics are consanguineous and were probably formed 390 ± 5 m.y. ago; this Devonian age is supported by new paleontologic evidence. Calcite-bearing rocks from these three formations usually yield spurious results and are considered unsuitable for Rb-Sr work; careful petrographic and x-ray studies are necessary for selection of suitable samples. Rb-Sr ages of Cambrian-Ordovician (or possibly older) rocks were determined for the Ellsworth Schist that unconformably underlies the Devonian Castine Volcanics and Middle Silurian Ames Knob Formation on the east side of Penobscot Bay. The part of the Penobscot Formation on the west side of Penobscot Bay, informally called Benner Hill by C. V. Guidotti, yielded an age of 460 ± 10 m.y., in good agreement with new fossil evidence for a Middle to Late Ordovician age. Silurian or older ages were obtained for the Penobscot, Appleton Ridge, and Battie Formations; however, the overlap in error limits leaves their relative ages in doubt. Retrograded high-grade rocks in a horst in Islesboro Township have been dated as Precambrian; a muscovite pegmatite cutting these rocks yields a late Precambrian mineral date. These are the first Precambrian rocks reported from Maine. The major faults mapped by D. B. Stewart on either side of Islesboro Township occurred before Middle Devonian time, according to dates determined for the stratigraphic units and for the plutons that cut and seal the faults.