Browsing by Author "Jackson, Mike"
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Item Compositional control of anisotropy of remanent and induced magnetization in synthetic samples(Geophysical Research Letters (American Geophysical Union), 1991) Johns, Mary; Jackson, MikeItem Curie temperatures of titanomagnetite in ignimbrites: Effects of emplacement temperatures, cooling rates, exsolution, and cation ordering(American Geophysical Union, 2014) Jackson, Mike; Bowles, JuliePumices, ashes, and tuffs from Mt. St. Helens and from Novarupta contain two principal forms of titanomagnetite: homogeneous grains with Curie temperatures in the range 350–500 C and oxyexsolved grains with similar bulk composition, containing ilmenite lamellae and having Curie temperatures above 500 C. Thermomagnetic analyses and isothermal annealing experiments in combination with stratigraphic settings and thermal models show that emplacement temperatures and cooling history may have affected the relative proportions of homogeneous and exsolved grains and have clearly had a strong influence on the Curie temperature of the homogeneous phase. The exsolved grains are most common where emplacement temperatures exceeded 600 C, and in laboratory experiments, heating to over 600 C in air causes the homogeneous titanomagnetites to oxyexsolve rapidly. Where emplacement temperatures were lower, Curie temperatures of the homogeneous grains are systematically related to overburden thickness and cooling timescales, and thermomagnetic curves are generally irreversible, with lower Curie temperatures measured during cooling, but little or no change is observed in room temperature susceptibility. We interpret this irreversible behavior as reflecting variations in the degree of cation ordering in the titanomagnetites, although we cannot conclusively rule out an alternative interpretation involving fine-scale subsolvus unmixing. Shortrange ordering within the octahedral sites may play a key role in the observed phenomena. Changes in the Curie temperature have important implications for the acquisition, stabilization, and retention of natural remanence and may in some cases enable quantification of the emplacement temperatures or cooling rates of volcanic units containing homogeneous titanomagnetitesItem Experimental deformation of synthetic magnetite-bearing calcite sandstones: effects on remanence, bulk magnetic properties, and magnetic anisotropy(Journal of Geophysical Research (American Geophysical Union), 1993) Jackson, Mike; Borradaile, Graham; Hudleston, Peter; Banerjee, SubirItem Grain sizes of susceptibility and anhysteretic remanent magnetization carriers in Chinese loess/paleosol sequences(American Geophysical Union, 2004) Liu, Qingsong; Banerjee, Subir; Jackson, Mike; Maher, Barbara; Pan, Yongxin; Zhu, Rixiang; Deng, Chenglong; Chen, FahuItem IRM Quarterly, Volume 06, Number 1 (Spring 1996). Cover article: The Hitchhiker’s Guide to the IRM(University of Minnesota. Institute for Rock Magnetism, 1996) Jackson, MikeItem IRM Quarterly, Volume 06, Number 2 (Summer 1996). Cover article: Paleointensity, Paleoclimate Share Spotlight in Santa Fe(University of Minnesota. Institute for Rock Magnetism, 1996) Jackson, MikeItem IRM Quarterly, Volume 06, Number 3 (Fall 1996). Cover article: Poor Richard’s Theory of the Earth(University of Minnesota. Institute for Rock Magnetism, 1996) Jackson, MikeItem IRM Quarterly, Volume 06, Number 4 (Winter 1996-1997). Cover article: Sample Preparation Specifications(University of Minnesota. Institute for Rock Magnetism, 1997) Jackson, MikeItem IRM Quarterly, Volume 07, Number 4 (Winter 1997-1998). Cover article: In the Shadow of the Comet: The Geophysical Bounty of Edmond Halley(University of Minnesota. Institute for Rock Magnetism, 1998) Jackson, MikeItem IRM Quarterly, Volume 08, Number 2 (Summer 1998). Cover article: Santa Fe IV The Geodynamo and Environmental Change: Interpreting Paleorecords through Rock Magnetism(University of Minnesota. Institute for Rock Magnetism, 1998) Jackson, MikeItem IRM Quarterly, Volume 08, Number 4 (Winter 1998-1999). Cover article: New Low-Temperature Measurement Capabilities(University of Minnesota. Institute for Rock Magnetism, 1999) Jackson, Mike; Marvin, JimItem IRM Quarterly, Volume 09, Number 1 (Spring 1999). Cover article: Measure for Measure: The Beauty of Magnetic Units(University of Minnesota. Institute for Rock Magnetism, 1999) Jackson, MikeItem IRM Quarterly, Volume 09, Number 3 (Fall 1999). Cover article: Astronomical Magnetic Fields(University of Minnesota. Institute for Rock Magnetism, 1999) Jackson, MikeItem IRM Quarterly, Volume 09, Number 4 (Winter 1999-2000). Cover article: Gilbert On the Magnet, MDC(University of Minnesota. Institute for Rock Magnetism, 2000) Jackson, MikeItem IRM Quarterly, Volume 10, Number 2 (Summer 2000). Cover article: Santa Fe V(University of Minnesota. Institute for Rock Magnetism, 2000) Jackson, MikeItem IRM Quarterly, Volume 10, Number 3 (Fall 2000). Cover article: Wherefore Gadolinium? Magnetism of the Rare Earths(University of Minnesota. Institute for Rock Magnetism, 2000) Jackson, MikeItem IRM Quarterly, Volume 11, Number 2 (Summer 2001). Cover article: von Humboldt’s Equinoxial Journey(University of Minnesota. Institute for Rock Magnetism, 2001) Jackson, MikeItem IRM Quarterly, Volume 11, Number 3 (Fall 2001). Cover article: The Rock-Magnetic Bestiary(University of Minnesota. Institute for Rock Magnetism, 2001) Solheid, Peat; Jackson, MikeItem IRM Quarterly, Volume 11, Number 4 (Winter 2001-2002). Cover article: On Sample Size and Shape Effects or Exactly How Magnetic Is Your Sample?(Institute for Rock Magnetism, 2002) Jackson, Mike; Solheid, Peat; Marvin, JimItem IRM Quarterly, Volume 12, Number 1 (Spring 2002). Cover article: Seahenge, Susceptibility, and more ways to be wrong(University of Minnesota. Institute for Rock Magnetism, 2002) Linford, Neil; Jackson, Mike; Marvin, Jim
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