Browsing by Author "Farley K.A."

Browsing by Author "Farley K.A."

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  • 4HE/3HE THERMOCHRONOMETRY 
    Shuster D.L.; Farley K.A. (2004)
    Using classical diffusion theory, we present a mathematical technique for the determination of 4He concentration profiles in minerals. This approach should prove useful for constraining the low-temperature cooling histories ...
  • ABSENCE OF EXTRATERRESTRIAL 3HE IN PERMIAN-TRIASSIC AGE SEDIMENTARY ROCKS 
    Farley K.A.; Ward P.; Garrison G.; Mukhopadhyay S. (2005)
    Helium concentration and isotopic composition were measured in a suite of samples across the Permian–Triassic boundary at Opal Creek, Canada, to determine whether high extraterrestrial helium concentrations are associated ...
  • AN ALTERNATIVE AGE MODEL FOR THE PALEOCENE-EOCENE THERMAL MAXIMUM USING EXTRATERRESTRIAL 3HE 
    Farley K.A.; Eltgroth S.F. (2003)
    A continuous age model for the brief climate excursion at the Paleocene-Eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3He (3HeET) to the seafloor. 3HeET measurements from ODP Site 690 ...
  • ATMOSPHERIC ENTRY HEATING AND HELIUM RETENTIVITY OF INTERPLANETARY DUST PARTICLES 
    Farley K.A.; Love S.G.; Patterson D.B. (1997)
    We have modeled atmospheric entry heating of interplanetary dust to characterize the population of particles carrying extraterrestrial He to the seafloor. We find that ~0.5% of the mass and ~4% of the surface area of the ...
  • DIFFUSION KINETICS OF PROTON-INDUCED 21NE, 3HE, AND 4HE IN QUARTZ 
    Shuster D.L.; Farley K.A. (2005)
    A natural quartz sample free of mineral and fluid inclusions was irradiated with a 200 MeV proton beam to produce spallogenic 21Ne, 3He and 4He. Temperature-dependent diffusivities of these three nuclides were then determined ...
  • HELIUM CHRONOMETRY OF APATITE AND TITANITE USING ND-YAG LASER HEATING 
    House M.A.; Farley K.A.; Stockli D. (2000)
    We developed a technique for extracting 4He from apatite and titanite using laser heating that permits measurement of U and Th and, hence, (U-Th)/He ages, on a single sample aliquot. Unlike direct laser heating, quantitative ...
  • HELIUM DIFFUSION AND (U-TH)/HE THERMOCHRONOMETRY OF TITANITE - A POTENTIAL THERMOCHRONOMETER 
    Reiners P.W.; Farley K.A. (1999)
    We have explored the diffusivity characteristics of radiogenic He in titanite (sphene) and have developed analytical techniques for (U-Th)/He dating of this mineral. Results of incremental He outgassing experiments performed ...
  • HELIUM DIFFUSION AND LOW-TEMPERATURE THERMOCHRONOMETRY OF APATITE 
    Wolf R.A.; Farley K.A.; Silver L.T. (1996)
    To investigate the potential of the (U-Th)/He system for low-temperature thermochronometry, we have studied helium diffusion and have measured helium ages on Durango fluorapatite and on apatites from a gabbro and two ...
  • MANTLE NEON AND ATMOSPHERIC CONTAMINATION 
    Farley K.A.; Poreda R.J. (1993)
    The apparent distinction between atmospheric and mantle²⁰Ne²²Ne ratios may provide a technique to quantify air contamination in mantle-derived materials. In the absence of mantle nuclear reactions, which produce either²⁰Ne ...
  • MODELING OF THE TEMPERATURE SENSITIVITY OF THE APATITE (U-TH)/HE THERMOCHRONOMETER 
    Wolf R.A.; Farley K.A.; Kass D.M. (1998)
    Apatite (U-Th)/He apparent ages will generally reflect residence for extended periods at temperatures where helium is neither quantitatively retained nor lost by diffusion. To characterize the response of apatite He ages ...
  • NOBLE GASES IN THE EARTH'S MANTLE 
    Farley K.A.; Neroda E. (1998)
    Noble gas isotopic ratios in mantle-derived samples require variability in the time-integrated ratio of volatile to lithophile elements in the Earth. Documentation of mantle 3He/4He variability is becoming increasingly ...
  • OXYGEN ISOTOPE VARIATIONS IN OCEAN ISLAND BASALT PHENOCRYSTS 
    Eiler J.M.; Farley K.A.; Stolper E.M.; Valley J.W.; Hauri E.; Craig H.; Hart S.R. (1997)
    Oxygen isotope ratios are reported for olivine phenocrysts from sixty-seven samples of ocean island basalts (OlBs), mid-ocean ridge basalts (MORBs), and related peridotites, including representatives of the various isotopic ...
  • QUANTIFYING THE DIFFUSION KINETICS AND SPATIAL DISTRIBUTIONS OF RADIOGENIC 4HE IN MINERALS CONTAINING PROTON-INDUCED 3HE 
    Shuster D.L.; Farley K.A.; Sisterson J.M.; Burnett D.S. (2004)
    Apatite, titanite and olivine samples were bombarded with a ~150 MeV proton beam to produce ~108 atoms/mg of spallation 3He. High-precision stepped-heating experiments were then performed in which the artificial 3He and, ...
  • SINGLE GRAIN (U-TH)/HE AGES FROM PHOSPHATES IN ACAPULCO METEORITE AND IMPLICATIONS FOR THERMAL HISTORY 
    Min K.; Farley K.A.; Renne P.R.; Marti K. (2003)
    The cooling history of the Acapulco meteorite for >400°C is well established using various chronometers suggesting extremely fast cooling (>1000°C/Ma). In contrast, the thermal history for low temperatures (<400°C) is ...
  • TERRESTRIAL COSMOGENIC ARGON 
    Renne P.R.; Farley K.A.; Becker T.A.; Sharp W.D. (2001)
    Cosmogenically enriched 38Ar/36Ar ratios are detectable in Ca-bearing terrestrial samples, and are resolvable from a uniform background value of 0.18826+/-0.00018 for materials lacking nucleogenic or kinetic mass fractionation ...
  • THE EFFECTS OF LONG ALPHA-STOPPING DISTANCES ON (U-TH)/HE AGES 
    Farley K.A.; Wolf R.A.; Silver L.T. (1996)
    A mathematical framework for quantitative evaluation of alpha-stopping effects on (U-Th)/He ages has been developed. Alpha stopping ranges in the 238U, 235U, and 232Th chains vary between ~ 10 and ~ 30 μm, depending on ...
  • (U-TH)/HE GEOCHRONOLOGY OF SINGLE ZIRCON GRAINS OF KNOWN TERTIARY ERUPTION AGE 
    Tagami T.; Farley K.A.; Stockli D.F. (2003)
    We performed a systematic study of (U-Th)/He ages of volcanic zircons of known eruption age to establish a reliable protocol for zircon He dating and to validate the resulting ages. Using laser He extraction and dissolution ...