Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass

Schlinger, Charles M.; Rosenbaum, Joseph; Veblen, David R.

doi:10.1130/0091-7613(1988)016<0556:fomiwt>2.3.co;2

Cited by 66 publications

(67 citation statements)

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“…T C = 775 K (502 C), corresponding to an unoxidized composition of approximately TM12 [Hunt et al, 1995]. There is significant uncertainty in the best values for these parameters, since the measurements are all made far below the Curie point, but this composition agrees well with those estimated previously [Schlinger et al, 1988[Schlinger et al, , 1991Worm and Jackson, 1999]. The room temperature mass-specific saturation magnetization for this composition is $78.4 A m 2 /kg [Hunt et al, 1995], which for a density of $5150 kg/m 3 yields M S $ 404 kA/m at room temperature.…”

Section: Low-t Hysteresis and Determination Of M S0 And B(t)supporting

confidence: 80%

“…[35] The basal section of the Tiva Canyon Tuff on Yucca Mountain (Nevada) contains fine titanomagnetite grains that crystallized in a silicate glass matrix during cooling after emplacement [Schlinger et al, 1988[Schlinger et al, , 1991. Thermomagnetic analyses indicate that these grains are lowtitanium titanomagnetites with a composition of Fe 3-x Ti x O 4 (x $ 0.10 or TM10).…”

Section: Samples Measurements and Conventional Analysismentioning

confidence: 99%

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Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography

et al. 2006

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[1] In 1965, D. J. Dunlop showed that the joint distribution of particle volumes and microcoercivities f(V, H k0 ) can be determined for magnetically monomineralic, thermally stable single-domain (SSD) ensembles by taking advantage of the joint temperature and field dependence of relaxation time. We have developed a procedure that follows Dunlop's strategy to obtain f(V, H k0 ) for ensembles containing both superparamagnetic and SSD grains, based on backfield remanence curves measured over a range of temperatures. Each point on the derivative curves represents the integrated contribution from grains that lie along a corresponding blocking contour on the Néel plot. A suitable set of such line integral samples can be used to reconstruct the f(V, H k0 ) distribution using the methods of tomographic imaging. Samples of the basal Tiva Canyon Tuff have narrow size distributions of elongate Ti-poor titanomagnetite. Tomographic inversion of the low-temperature backfield spectra yield sharply peaked f(V, H k0 ) distributions, from which we calculate modal grain dimensions in good agreement with those observed by transmission electron microscopy. Analysis of synthetic samples containing bimodal populations clearly distinguishes the two modes. Because our simplified forward calculations incompletely account for the effects of orientation distribution, the width of the coercivity distribution at each temperature is underestimated, and consequently, the inverse calculations yield grain distributions that are overly broad. Frequency-and temperature-dependent susceptibilities calculated for the inverted f(V, H k0 ) distributions accord fairly well with measured susceptibilities for the weakly interacting Tiva Canyon samples, less well for a moderately interacting paleosol specimen, and poorly for a strongly interacting ferrofluid.Citation: Jackson, M., B. Carter-Stiglitz, R. Egli, and P. Solheid (2006), Characterizing the superparamagnetic grain distribution f(V, H k ) by thermal fluctuation tomography,

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Section: Low-t Hysteresis and Determination Of M S0 And B(t)supporting

confidence: 80%

Section: Samples Measurements and Conventional Analysismentioning

confidence: 99%

Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography

et al. 2006

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“…Some workers have interpreted the AMS fabric in ignimbrites as due to a preferred orientation of elongate ferromagnetic grains that moved within the flow (e.g., Hrouda 1982;Jackson and Tauxe 1991;Tarling and Hrouda 1993). Schlinger et al (1988) showed that elongate titanomagnetite microcrystals precipitated at high temperatures in the Paintbrush Tuff. Thomas et al (1992) noted that magnetically susceptible Fe-Ti oxide grains in one analyzed sample were concentrated in the pores of the pumice, and concluded that the AMS fabric may be formed from secondary Fe-Ti oxide particles deposited within vesicle walls prior to their collapse.…”

Section: Campanian Ignimbritementioning

confidence: 98%

Anisotropy of magnetic susceptibility studies of depositional processes in the Campanian Ignimbrite, Italy

et al. 2002

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The late Pleistocene trachytic Campanian Ignimbrite underlies much of the Campanian Plain near Naples, Italy, and occurs in valleys in the mountainous area surrounding the plain out to about 80 km from its source, the Campi Flegrei caldera. At sites within 15 km of the Campi Flegrei, anisotropy of magnetic susceptibility (AMS) principal directions indicate that, in the absence of significant topography, deposition came from a flow moving in a roughly radial direction. AMS studies of the more distal ignimbrite reveal downhill and/or downvalley flow directions prior to deposition, even where these directions are at high angles to a generally radial transport direction from the vent. On the flanks of Roccamonfina Volcano, flow was directly downhill, as if the source of the ignimbrite was the summit of the volcano. In most localities, the ignimbrite consists of a single massive deposit. In a few localities in the Apennine Mountains, however, the confluence of multiple drainage systems off mountains resulted in multiple local flow units that cannot be correlated between valleys. A detailed study of the ignimbrite in the flat Titerno River valley near Massa shows that the AMS fabrics are not due to late-stage creeping during deposition or compaction. Well-defined, but non-parallel AMS fabrics from vertical and lateral sections in the Massa area are best explained by the merging of gravity currents flowing down the valley and steep valley sides to form a single aggradational deposit. Clast compositions and AMS axes at Mondragone indicate that the pyroclastic flow encountered the Monte Massico massif and was partially blocked, so that flow during deposition was toward the Campi Flegrei. Similar AMS data from sites along the edge of the Campanian Plain indicate back-flow off the first ridge of the Apennine Mountains reached at least 5 km from their base. The Campanian Ignimbrite was deposited from a density-stratified pyroclastic flow. The depositional system consisted of the lower, denser portion of the current, and was controlled by topography. The grouping of the AMS axes is interpreted to indicate that deposition occurred under laminar flow conditions.

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“…Instead, post depositional re-mobilization of pyroclastic material produces rheomorphic flow structures in densely welded ignimbrites. Paleomagnetic studies of ash-flow tuffs (ignimbrites) have shown that ignimbrites, whether densely welded or loosely consolidated, bear fine-grained iron oxides that can faithfully reflect an accurate record of the geomagnetic field during rapid post-emplacement cooling (e.g., Hatherton, 1954;Beck et al, 1977;Reynolds, 1977;Geissman, 1980;Geissman et al, 1983;Schlinger et al, 1986Schlinger et al, , 1988aSchlinger et al, ,b, 1991Rosenbaum, 1993;Palmer et al, 1996;Worm and Jackson, 1999;Gee et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

Hong

Doh

et al. 2016

Front. Earth Sci.

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The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k 3 (minimum axis of magnetic susceptibility) and shallow dispersal of k 1 (maximum axis of magnetic susceptibility) and k 2 (intermediate axis of magnetic susceptibility). Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT) as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination.

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Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass

Cited by 66 publications

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Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography

Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography

Anisotropy of magnetic susceptibility studies of depositional processes in the Campanian Ignimbrite, Italy

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

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Fe-oxide microcrystals in welded tuff from southern Nevada: Origin of remanence carriers by precipitation in volcanic glass

Cited by 66 publications

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Characterizing the superparamagnetic grain distribution f(V, Hk) by thermal fluctuation tomography

Characterizing the superparamagnetic grain distribution f(V, Hk) by thermal fluctuation tomography

Anisotropy of magnetic susceptibility studies of depositional processes in the Campanian Ignimbrite, Italy

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

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Product

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Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography

Characterizing the superparamagnetic grain distribution f(V, H_k) by thermal fluctuation tomography