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Reference Number: 2721 GeoREF Number: 2006-021428 Publication Year: 2006 Abstract: "The importance of the Cascade Range magmatic arc in understanding the geologic evolution of western North America is widely recognized, and these arc rocks have been extensively studied. The geochemical database presented here represents the first phase of an effort to synthesize and interpret the geochemistry of Western Cascades volcanic arc rocks. Using the large and synoptic body of information in the present database, it is possible to characterize the primary geochemical attributes of the Western Cascades rocks and begin interpretation of their petrologic, tectonic, and metallogenic significance." Descriptors: applications-; bedrock-; California-; Cascade-Range; chemical-composition; data-bases; data-processing; geochemistry-; igneous-rocks; Oregon-; United-States; USGS-; volcanic-rocks; Washington-; western-Cascade-Range Source: U. S. Geological Survey Data Series. 2006. map_coordinates: LAT: N420000; N480000; LONG: W1210000; W1240000.
Data Types:
  • Tabular Data
Reference Number: 2041 GeoREF Number: 2006-900112 Publication Year: 2006
Data Types:
  • Tabular Data
Reference Number: 7391 GeoREF Number: 2007-028091 Publication Year: 2006 Abstract: "The Ironside Mountain batholith consists of the 170-Ma IronsideMountain pluton, the quartz diorite of Happy Camp Mountain, the 167-MaDenny intrusive complex, and the West China Peak intrusive complex.The contact aureole of the Ironside Mountain pluton is present in boththe western and eastern Hayfork terranes, which indicates thatemplacement followed regional thrusting along the Wilson Point thrust.The batholith marks the beginning of a 15-m.y.-long episode of arcmagmatism. Al-in-hornblende barometry suggests emplacement atapproximately 4 kb. The Denny and West China Peak complexes arepredominantly gabbro to olivine pyroxenite characterized by calcicplagioclase. Along with the quartz diorite of Happy Camp Mountain,these plutons have calcic bulk compositions, abundant amphibole, andlow FeO/(FeO+MgO). Their chemical and petrographic features suggestoxidized, H (sub 2) O-rich parental magmas. In contrast, the IronsideMountain pluton has higher FeO/(FeO+MgO), shows K (sub 2) O enrichmentwith increasing SiO (sub 2) to ultrahigh-K compositions, and istypified by 2- and 3-pyroxene assemblages in which hydrous maficsilicates are sparse or absent, except in the most evolved rocks. Theelements Rb, Zr, and Ba all behave incompatibly. Initial Nd and Srisotope ratios (170 Ma) are uniform at epsilon (sub Nd) ofapproximately 5.2 and (super 87) Sr/ (super 86) Sr of approximately0.7037. These data suggest that the pluton lacks significant crustalinput, unlike younger Middle Jurassic plutons, and that it evolvedprimarily by fractional crystallization of a reduced, H (sub 2) O-poorarc tholeiite. Enrichment of K (sub 2) O is interpreted to result fromdifferentiation at relatively high pressure (> or =8 kb), underconditions in which augite fractionation predominated over olivinefractionation. High-P fractionation without appreciable crustal inputis probably related to the thermal structure of the crust. Emplacementimmediately after regional thrusting placed parental magmas into cool,nonreactive host rocks. Succeeding Middle Jurassic magmatismencountered progressively hotter crust, with consequent crustalmelting and assimilation." Descriptors: alkaline earth metals; assimilation; aureoles; basalts; batholiths;chemical composition; chemical fractionation; Denny Complex;differentiation; diorites; emplacement; faults; gabbros; geochemistry;Happy Camp Mountain; host rocks; igneous rocks; intrusions; IronsideMountain Batholith; isotope ratios; isotopes; Jurassic; KlamathMountains; magmas; magmatism; major elements; melting; Mesozoic;metals; Middle Jurassic; mineral assemblages; plutonic rocks; potassiccomposition; pressure; pyroxenite; quartz diorites; Sr-87/Sr-86;stable isotopes; strontium; tholeiite; thrust faults; trace elements;ultramafics; United States; variations; volcanic rocks; water; WestChina Peak Complex Classification: 05A Igneous and metamorphic petrology; 02D Isotope geochemistry Source: "Special Paper - Geological Society of America, vol.410, pp.199-221,2006" map_coordinates: "Latitude:N410000,N430000 Longitude:W1230000,W1243000"
Data Types:
  • Tabular Data
Reference Number: 2542 GeoREF Number: 2006-049735 Publication Year: 2006 Abstract: "The eastern Snake River plain in southern Idaho, Western UnitedStates, is characterized by 1-2 km of Pleistocene to late Pliocenebasalt overlying rhyolite caldera complexes. Cyclic variations in thechemical composition of basalts from 1136 m of scientific drill coreshow that the parent magmas of these lavas evolved by crystalfractionation at shallow to intermediate crustal depths, punctuated byepisodic recharge with more primitive compositions and assimilation ofadjacent wall rock. We have identified 10 upward fractionation cyclesand four reversed cycles; assimilation of sialic crust was limited andmainly affects the oldest basalts, which directly overlie rhyolites.We infer that the crystal fractionation and/or recharge cycles tookplace in a series of sill-like intrusions at intermediate crustaldepths that now form a layered mafic intrusion that underlies theeastern Snake River plain at depth. This layered sill complex isrepresented by the approximately 10-km-thick ""basaltic sill"" that hasbeen imaged seismically at approximately 12-22 km depth. Theassociation of this mid-crustal sill complex with geochemicalfractionation cycles in basalt supports the concept that exposedlayered mafic intrusions may be linked to overlying basalt provincesthat have since been removed by erosion." Descriptors: alkaline earth metals; assimilation; basalts; chemical fractionation;cores; crust; crystal fractionation; cycles; electron probe data;geochemical cycle; geochemistry; granitic layer; Idaho; igneous rocks;INEEL; intrusions; isotope ratios; isotopes; lava; layered intrusions;lead; mafic composition; magmas; major elements; metals; middle crust;Pb-208/Pb-204; radioactive isotopes; rhyolites; sills; Snake Riverplain; southern Idaho; Sr-87/Sr-86; stable isotopes; strontium; traceelements; United States; volcanic rocks; volcanism Classification: 02D Isotope geochemistry; 05A Igneous and metamorphic petrology Source: "Geology (Boulder), vol.34, no.5, pp.365-368, May 2006" map_coordinates: "Latitude:N432200,N440200 Longitude:W1122600,W1131000"
Data Types:
  • Tabular Data
Reference Number: 2053 GeoREF Number: 2007-043967 Publication Year: 2006 Descriptors: basalts; basement; Basin and Range Province; Big Pine volcanic field;California; Cenozoic; chain silicates; chemical composition; chemicalreactions; clinopyroxene; Coso volcanic field; crystallization;eruptions; geochemistry; geologic barometry; geologic thermometry;igneous rocks; inclusions; intrusions; major elements; mantle; mineralcomposition; Neogene; North America; Owens Valley; petrography;phenocrysts; Pliocene; pyroxene group; rhyolites; silicates; Tertiary;textures; United States; volcanic fields; volcanic rocks; volcanism;xenoliths Classification: "05A Igneous and metamorphic petrology; 02C Geochemistry of rocks,soils, and sediments" Source: "Contributions to Mineralogy and Petrology, vol.152, no.1, pp.111-124,Jul 2006"
Data Types:
  • Tabular Data
Reference Number: 2045 GeoREF Number: 2007-028084 Publication Year: 2006 Abstract: "The western Jurassic belt of the Klamath Mountains represents one ofthe Earth's best-preserved exposures of ancient marginal ocean basinlithosphere and chiefly consists of the coeval Rogue-Chetcovolcanic-plutonic oceanic arc and Josephine ophiolite. This LateJurassic ocean basin is hypothesized to have formed in response torifting that initiated at ca. 165 Ma along the western margin of NorthAmerica, disrupting a Middle Jurassic arc that had been constructed onolder Klamath terranes and forming a marginal ocean basin with anactive arc, inter-arc basin, and remnant arc. Previous workerscharacterized a ""rift-edge"" facies in the remnant-arc region. Thischapter describes field, age, and geochemical data that suggest that asimilar rift-edge facies exists in the vicinity of the active arc, onthe opposite side of the marginal basin. The rift-edge facies in theactive arc setting consists of two main lithotectonic units, hereinnamed informally as the Onion Camp complex and Fiddler Mountainolistostrome. The Onion Camp complex is partly composed of acharacteristic metabasalt and red chert association. Red chert yieldedscarce radiolarians of Triassic(?) and Early Jurassic age. A distinctchert-pebble conglomerate occurs at scarce localities withinmetasedimentary rocks. Concordant, composite bodies of amphibolite andserpentinized peridotite represent another distinctive feature of theOnion Camp complex. The metamorphic and lithologic features of theOnion Camp complex are similar to the lower melange unit of theRattlesnake Creek terrane, and the units are interpreted to becorrelative. The Fiddler Mountain olistostrome is composed of LateJurassic (Kimmeridgian?) pelagic and hemipelagic rocks interlayeredwith ophioliteclast breccia and megabreccia, similar in character toolistostromal deposits associated with the rift-edge facies of theremnant arc. The occurrence of the Rattlesnake Creek terrane and anassociated olistostromal deposit within the western Jurassic belt ofsouthwestern Oregon may therefore represent the rift-edge facies inthe active arc setting, at the transition between the Rogue-Chetco arcand Josephine ophiolite, further corroborating previous models for theLate Jurassic tectonic evolution of the Klamath Mountains." Descriptors: California; depositional environment; fabric; Fiddler Mountain;Invertebrata; Josephine Ophiolite; Jurassic; Klamath Mountains;lithofacies; lithosphere; major elements; Mesozoic; metals;microfossils; olistostromes; Onion Camp; Oregon; plate tectonics;Protista; provenance; Radiolaria; rare earths; Rattlesnake CreekTerrane; rifting; Rogue-Chetco Arc; sedimentary structures; softsediment deformation; trace elements; United States; Upper Jurassic Classification: "18, Solid-earth geophysics" Source: "Special Paper - Geological Society of America, vol.410, pp.53-76,2006" map_coordinates: "Latitude:N410000,N430000 Longitude:W1230000,W1243000"
Data Types:
  • Tabular Data
Reference Number: 2845 GeoREF Number: 2006-071430 Publication Year: 2006 Abstract: "The Carlin trend contains the largest concentration of Carlin-type gold deposits in the world. Two major controversies about these giant gold deposits have been their age, which is now firmly established as Eocene, and the source of heat, fluids, and metals, which remains debated. We present data that demonstrate an intense period of Eocene magmatism coincided in time and space with deposit formation and was arguably the primary heat source. Geologic studies over the last 40 years have emphasized the stratigraphy and structure of Paleozoic sedimentary rocks, which are the major ore hosts. However, four igneous episodes affected the Carlin trend, in the Jurassic, Cretaceous, Eocene, and Miocene. A Jurassic diorite-granodiorite laccolith and related dikes were emplaced at about 158 Ma in the northern Carlin trend. A Cretaceous granite intruded the north-central part of the trend at 112 Ma. Abundant Eocene dikes intruded along most of the trend and were accompanied by lavas in a large volcanic field along the southwest edge of the trend between approximately 40 and 36 Ma. Miocene rhyolite lavas erupted just west of and across the southern part of the trend at approximately 15 Ma. Exposed Eocene rocks consist predominantly of silicic to intermediate dikes, lavas, and epizonal intrusions, which we interpret to be sourced from a large Eocene plutonic complex underlying the Carlin trend. Eocene dikes are present in most deposits, are generally altered, but, with a few exceptions, were poor ore hosts. Distinct Eocene igneous suites, which are restricted to specific areas of the trend, are from north to south" Descriptors: "absolute-age; alteration-; aplite-; Ar-Ar; Basin-and-Range-Province; Carlin-Trend; carlin-type-deposits; Cenozoic-; chemical-composition; dates-; dikes-; Emigrant-Deposit; emplacement-; Eocene-; fission-tracks; giant-deposits; gold-ores; Goldstrike-Laccolith; granites-; Great-Basin; host-rocks; igneous-rocks; intrusions-; lamprophyres-; magma-chambers; magmas-; magmatism-; metal-ores; mineral-composition; mineral-deposits,-genesis; mineralization-; Nevada-; North-America; northeastern-Nevada; ore-forming-fluids; Paleogene-; pegmatite-; plutonic-rocks; plutons-; Railroad-mining-district; Rain-Mine; rhyolites-; Tertiary-; U-Pb; United-States; volcanic-rocks; Welches-Canyon" Source: "Economic Geology and the Bulletin of the Society of Economic Geologists. 101; 2, Pages 347-383. 2006. " map_coordinates: LAT
Data Types:
  • Tabular Data
Reference Number: 2055 GeoREF Number: 2007-064894 Publication Year: 2006 Abstract: "Whole-rock major and trace element and O, Sr, Nd and Pb isotopic dataare reported for 3.0-0.89 Ma lamproites from the Leucite Hills,Wyoming, USA. The two main groups of lamproites, madupitic lamproitesand phlogopite lamproites, are geochemically distinct and cannot berelated to one another by either fractional crystallization or crustalcontamination. It seems likely that the geochemical differencesbetween these two rock types are related to variations in sourcemineralogy and depth of partial melting. The high Mg-number and largeion lithophile element abundances and negative epsilon Nd values ofthe lamproites indicate a mantle source that has experienced stages ofboth depletion and enrichment. The negative Nb, Ta and Ti anomalies inmantle-normalized trace element diagrams and low time-integrated U/Pb,Rb/Sr and Sm/Nd ratios of both lamproite groups and other Cenozoicigneous rocks from the Wyoming Archean Province indicate an ancientmetasomatic enrichment (>1.0 Ga) of the mantle source associatedwith the subduction of carbonate-bearing sediments. Other chemicalcharacteristics of the Leucite Hills lamproites, especially their highK (sub 2) O and volatile contents, are attributed to more recentmetasomatism (<100 Ma) involving influx from upwelling mantleduring back-arc extension or plume activity." Descriptors: alkaline earth metals; geochemistry; igneous rocks; isotope ratios;isotopes; lamproite; lead; Leucite Hills; Leucite Hills Lamproites;lithogeochemistry; metals; metasomatism; Nd-144/Nd-143; neodymium;O-18/O-16; oxygen; Pb-206/Pb-204; plutonic rocks; radioactiveisotopes; rare earths; Rock Springs Wyoming; Sr-87/Sr-86; stableisotopes; strontium; Sweetwater County Wyoming; United States; wholerock; Wyoming Classification: 02D Isotope geochemistry; 05A Igneous and metamorphic petrology Source: "Journal of Petrology, vol.47, no.12, pp.2463-2489, Dec 2006" map_coordinates: "Latitude:N414700,N414700 Longitude:W1090000,W1090000"
Data Types:
  • Tabular Data
Reference Number: 9165 GeoREF Number: 2007-064006 Publication Year: 2006 Classification: 24 Quaternary geology; 02D Isotope geochemistry Source: "Journal of Volcanology and Geothermal Research, vol.153, no.3-4, pp.331-356, 15 May 2006"
Data Types:
  • Tabular Data
Reference Number: 3175 GeoREF Number: 2006-075627 Publication Year: 2006 Descriptors: areal-geology; cross-sections; faults-; folds-; geologic-maps; Grande-Ronde-River-basin; hydrology-; lithostratigraphy-; maps-; mineral-resources; natural-resources; Oregon-; petrology-; stratigraphic-units; surficial-geology; tectonic-elements; Union-County-Oregon; United-States Source: "Open File Report - State of Oregon, Department of Geology and Mineral Industries. 2006." map_coordinates: LAT: N450000; N454500; LONG: W1173000; W1184500.
Data Types:
  • Tabular Data
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