Inside... Visiting Fellow Reports 2 Current Abstracts 4 New & Recent Visiting Fellows 11
Fall 2003, Vol. 13, No. 3
northwestern side of the Golfo di Napoli) and refers to unconsolidated pyroclastic deposits erupted by the Campi Flegrei volcanic field during the Pleistocene and the Holocene. In ancient times (~3rd Century BCE) it was discovered that mixing these pozzolanic deposits with
, by Frank A. Perret, lime produced an exceptional cement. Vitruvius, in his ten-volume De Architectura, devotes a chapter (Book II, ch. VI) to this “powder which, by nature, produces wonderful results. It is found in the region of Baia and in the lands of the municipalities round Mount Vesuvius. This being mixed with lime and rubble, not only furnishes strength to other buildings, but also, when piers are built in the sea, they set underwater.” It was one of the first examples of what is called a “hydraulic cement.” The harbor works at Puteoli were constructed ca 199 BCE with pozzolana cement. Pozzolanic materials by themselves are not cements, but they contain silica (and alumina) in a reactive form. The
The Vesuvius Eruption of 1906: Study of a Volcanic Cycle Eruption of 1906: Study a Volcanic The Vesuvius pozzolana cements of classical antiquity were made simply by mixing volcanic Clouds of gas and ash rise from Vesuvius, April 1906 From 1924 Carnegie Intitute of Washington, pozzolana with lime (CaO, produced by heating limestone). As additives in modern portland cements, pozzolans Maintaining Standards III improve mechanical strength and provide resistance to physical and chemical weathering. Natural pozzolans are not Pozzolana Cement restricted to the ash deposits of Campi Flegrei and Vesuvius. Three distinct pozzolana units are now formally defined in the sequence of volcanic products cross-calibration samples available erupted by the Alban Hills, upon which the town of Rome was (and still is) founded. In commercial building Mike Jackson Last year we carried out an remanent moment determinations, there materials the name is now widely applied IRM interlaboratory cross-calibration exercise was a suprisingly large variation in to volcanic components of suitable Leonardo Sagnotti that involved the 10 labs of the MAG- reported values of anhysteretic suscepti- composition, regardless of their source. Istituto Nazionale di NET consortium, as well as the Bremen bility. We are now making samples of Artificial pozzolans are also used in Geofisica e and IRM labs [Sagnotti et al., 2003; see this material available for wider modern commercial cements; these are Vulcanologia (INGV) also MAG-azine n.3 and 4]. Measure- distribution and additional derived from fly ash, produced by coal- Pierre Rochette ments involved low-field susceptibility, interlaboratory standardization. burning power plants, incineration of Centre Européen de anhysteretic remanence (magnetized at municipal solid waste, etc. Recherche et INGV), and anhysteretic susceptibility The Eternal Cement In modern portland cement the chief d'Enseignement des (i.e., new ARMs magnetized in the other Even before we get to its magnetic raw materials are limestone, chalk, etc. Géosciences de labs). One of the materials we used as a properties, this is rather interesting (which supply lime), and clays or shales l'Environnement standard of comparison was a commer- material. The name pozzolana (a.k.a. (which provide alumina (Al2O3) and (CEREGE) cial Italian cement “pozzolanico,” and pozzuolana) is derived from the Latin Peter Sølheid whereas we found very good interlab pulvis puteolanus (powder from Puteoli, pozzolana IRM consistency in susceptibility and now Pozzuoli, a historical town on the continued on p. 8... 1 Visiting Fellows’ Reports
Low-temperature, high- core taken from the deepest part of the phases is further supported by the HT lake were carried out at the IRM to measurements that show a gradual temperature, and hysteresis characterize the magnetic minerals, the increase in magnetic moment between properties of sediments from carrier of possible magnetic-climatic 300°C and 500°C (Figure 1b), probably Yongxiang Li White Lake, northwestern signatures, in lake sediments. The core due to the transformation of these phases to magnetite. The diverse magnetic Lehigh University New Jersey recovers a ~ 14,000 year record and [email protected] contains a succession from pale grey clay- mineral phases in clay-rich lake rich sediments, through light brownish sediments could result from the fact that Since millennial to decadal climatic marl (calcium carbonate precipitated by detritus came from broad source areas oscillations were recognized as funda- aquatic plants), to dark gyttja (organic- while the ice front retreated. mental features of our climate system, rich mud). Each of these three composi- Marl sediments appear as a there has been growing interest in tional components exhibit different transitional zone between clays and employing multiproxies to reconstruct magnetic properties. gyttja. The magnetic properties also climate change during the Quaternary. The clay-rich sediments occur at the tend to display a transition in magnetic The magnetic variation of lake sedi- base of the core and are characterized by behavior. From the deepest to the ments, used as an independent climatic strong magnetization and pronounced LT shallowest marl in the core, LT experi- proxy, is often attributed to the changes phase transitions. The LT experiments ments indicate that the Verwey transition in climatically-driven detrital input into a show a sharp decrease in SIRM at ~120 K gradually becomes less pronounced in lake. The magnetic mineral - climate (Figure 1a), indicative of magnetite the warming curves. However, the link in organic-rich sediments, however, (Verwey, 1939). The rapid drop in Verwey transition remains recognizable has not been extensively investigated. LTSIRM while warming through ~35 K in cooling curves (Figure 2a), suggesting As part of ongoing interdisciplinary and the lack of changes in the RTSIRM the presence of magnetite. HT experi- work, a magnetic study was conducted during cooling at ~35 K (Figure 1a) ments tend to display a transition in on sediments from White Lake (41.0°N, suggest that some phases such as siderite, magnetic behavior as well. Magnetic 74.8°W), northwestern New Jersey, to ferrihydrite, and ilmenite probably reside moment of marls just above clay shows examine whether the magnetic properties in the clay-rich lake sediments. These a sharp increase while temperature drops of White Lake sediments recorded phases are paramagnetic at room across ~300°C, suggesting some climate change. Low-temperature (LT), temperature and become ferromagnetic at contribution from iron sulphides, high-temperature (HT), and hysteresis low temperature. The presence of these probably pyrrohtite. Marls just below measurements of selected samples from a the gyttja, however, display a gradual
(A) (B)
Figure 1. Low temperature (a) and high temperature (b) properties of the clay-dominated sediments. The sample acquired SIRMs in a 2.5T field at 20K (and 300K) prior to the warming (cooling) process.
(A) (B)
Figure 2. Low temperature (a) and high temperature (b) behaviors of a marl sample. The dash line is the derivative of the cooling curve. The spike at ~120K is interpreted as a Verwey transition indicating the presence of magnetite. 2 (A) (B) (C)
Figure 3. Magnetic properties of gyttja samples. (a) the Verwey transition indicates the presence of magnetite; (b) thermal demagnetization of SIRMs acquired in zero-field cooling (ZFC) and field cooling (FC) show almost no difference in the loss of SIRM around 100K, suggesting that magnetite particles are probably not biogenic (Moskowitz et al., 1993); (c) the magnetic moment increased after thermal treatment, although the magnitude of increase is less than that of the marl- and clay-dominated samples.
increase in magnetic moment while grains dominate the clay-rich sediments; Acknowledgements temperature decreased from 700°C whereas marl and gyttja are dominated I would like to thank the IRM personnel (Figure 2b), indicating virtually no by PSD grains (Figure 4). Although the for their kind and timely help during my contribution from iron sulphides. Day plot shows that both marl and gyttja visit. Discussions with Mike, Qingsong, Siderite was considered an important are indistinguishably dominated by PSD and Christoph Geiss helped interpreta- magnetic phase that may occur in the grains, a difference in magnetic grain tion of the results. marl. The zero field cooling and field size between the marl and gyttja may cooling (ZFC/FC) experiments did not exist because a PSD interpretation in a References show a phase transition at ~38K, Day plot could also be due to a mixture Dekkers, M.J., Mattei, J.L., Fillion, G., diagnostic of the presence of siderite of MD grains and SD/SP grains in and Rochette, P., 1989. Grain size (Housen et al., 1996). The transition in varying proportions. dependence of the magnetic behavior magnetic properties of marl sediments The weak room temperature of pyrrhotite during its low- may be associated with climate change magnetization of gyttja and extensive temperature transition at 34k. during the late Pleistocene-early mineralogical alteration during high Geophysical Research Letters 16, Holocene, when cold climate is gradually temperature experiments make the 855-858. taken over by warm climate. interpretation of its magnetic properties Housen, B.A., Banerjee, S.K., and Gyttja accounts for the top half of the difficult. Detailed interpretation of the Moskowitz, B.M. 1996. Low- core and contains up to ~80% organic minor variations in magnetic properties temperature magnetic properties of materials. The magnetization of gyttja is of the gyttja will need the precise siderite and magnetite in marine generally very weak. The LT measure- chronology data and magnetic data from sediments. Geophysical Research ments of all gyttja samples showed no other cores. At present, both 14C dating Letters 23, 2843-2846. phase transitions in the warming curves, and the magnetic data of the shallow core Moskowitz, B.M., Frankel, R.B., and but the cooling curves did show a faint are still in progress. When these datasets Bazylinski, D.A., 1993. Rock transition at ~120K, which is more are available, the intra-lake correlation magnetic criteria for the detection of prominent in the derivative of a cooling and inter-lake correlation with other biogenic magnetite. Earth and curve (Figure 3a). This transition is independent climatic proxies will be Planetary Science Letters 120, 283- interpreted to indicate magnetite particles made and should shed light on the 300. in gyttja. The ZFC/FC data neither possible magnetic mineral – climate link Verwey, E.J. 1939. Electronic conduction showed a phase transition at ~38 K, in organic rich sediments. The magnetic of magnetite (Fe3O4) and its diagnostic of pyrrhotite (Dekkers et al., results of the deep core obtained at the transition point at low temperatures. 1989), nor exhibited a differential loss in IRM will provide the crucial magnetic Nature 144, 327-328.
SIRM at ~110 K (Figure 3b) to suggest a mineralogical constraints for the biogenic origin of magnetite (Moskowitz upcoming detailed interpretation. et al., 1993). High temperature thermo- VF Reports magnetic curves often show a gradual continued on p. 7... increase in magnetic moment during cooling (Figure 3c). This gradual increase in magnetic moment implies that non-magnetic phases probably have been transformed into magnetic minerals. The magnetic susceptibility of gyttja is very weak and the high temperature susceptibility measurements yielded almost only the sample holder’s susceptibility. The signal/noise ratios for most gyttja samples are too low to identify magnetic minerals from their characteristic Curie temperatures. Only a handful of samples showed an overall susceptibility variation pattern that appears to be consistent with their high Figure 4. Hysteresis loop parameters used to estimate grain size. Mr=saturation temperature thermomagnetic curves. The remanence; Ms=saturation magnetization; Bcr=coercivity of remanence; hysteresis loop results show that MD Bc=coercivity. 3 Alteration & Remagnetization magnetization parameters are proposed. A hysteresis shape parameter and a coercivity ratio can be directly calculated Madsen, K. N., Walderhaug, H. and Torsvik, T., 2002, from standard hysteresis and backfield measurements. A Erroneous fold tests as an artifact of alteration chemical transient energy dissipation ratio and the viscosity of IRM, remanent magnetization: Journal of Geophysical Research, require additional measurements, which, however, do not v.107, no.B12, 2369. increase measurement time noticeably. The effectiveness of A laboratory CRM experiment performed on a Silurian lava, these parameters is discussed theoretically and demonstrated with a well-defined single component NRM carried by experimentally. deuterically oxidized titanomagnetite (TM), shows that the CRM acquired has an orientation between parent phase NRM Environmental Magnetism and Paleoclimate and remagnetizing field. Stepwise unfolding of the CRM gave Proxies a syntectonic fold test result. The variation of remanence deflection with angle between H and initial NRM can be CRM Chen, T. H., et al., 2003, Formation mechanism of understood in terms of vector addition of fields or remanence ferromagnetic minerals in loess of China: TEM components. investigation: Chinese Science Bulletin, v.48, no.20, p.2259- 2266. Gillett, S. L., 2003, Paleomagnetism of the Notch Peak Primary magnetite has the morphology and surface contact metamorphic aureole, revisited: Pyrrhotite from characteristics of eolian detrital particles. High-Ti and low-Ti magnetite plus pyrite under submetamorphic conditions: magnetite may be derived from magmatic and metamorphic Journal of Geophysical Research-Solid Earth, v.108, no.B9, rocks, respectively. Nanometer-scale imaging shows partial 2446. pedogenic alteration of primary detrital magnetite to A scattered, two-polarity remagnetization is now thought to pseudomorphic maghemite. Some nanometer scale magnetite reside in metamorphic pyrrhotite, formed in part by in-situ or maghemite particles also formed by pedogenic alteration of reduction of magnetite by pyrite and organic compounds. chlorite. These contain a small amount of P and S, which is Isotopic evidence rules out large-scale introduction of the signal of microbe-mineral interaction. reducing fluids. At higher grades, some pyrrhotite probably also formed by the reaction of pyrite and Fe-bearing silicates. Hanesch, M., Scholger, R. and Rey, D., 2003, Mapping dust Pyrrhotite formation in rocks that are not obviously distribution around an industrial site by measuring metamorphosed shows that the reactions could proceed at magnetic parameters of tree leaves: Atmospheric very low (<200°C) temperatures, the feasibility of which is Environment, v.37, no.36, p.5125-5133. shown by detailed thermodynamic calculations We sampled maple leaves at 102 locations in and around κ, Leoben and determined IRM at 1 Telsa, the S-ratio (IRM- Urbat, M. and Brandau, A., 2003, Magnetic properties of κ 100mT/IRMIT) and the ratio IRM/ . The results showed that marine sediment near the active Dead Dog Mound, Juan one soft ferrimagnetic phase is dominant over the whole de Fuca Ridge, allow to refine hydrothermal alteration investigated area. This finding was corroborated by SEM zones: Physics & Chemistry of the Earth, v.28, no.16-19, analysis of the leaves. A soil κ map shows the same spatial p.701-709. pattern, indicating that the location of the main source has Ubiquitous trace magnetic minerals in these marine sediments been the same over a long time span. are highly sensitive to both temperature and fluid induced post-depositional alteration, allowing for a refined definition of Hu, S., et al., 2003, Magnetic responses to acidification in the lithological alteration zones as well as the establishment of Lake Yangzonghai, SW China: Physics & Chemistry of the additional lateral hydrothermal fluid flow. Earth, v.28, no.16-19, p.711-717. A power plant built in 1960 is close to the lake, and coal The “Acquedotto Claudio” was initiated by Caligola in 38 AD and Anisotropy ashes can be found within the uppermost 12 cm of sediment. Ash collected directly from the power plant is strongly completed by Claudius in 52 AD (it was likely active already in 47 AD). The Fawcett, T. C., Burmester, R. F., Housen, B. A. and Iriondo, magnetic, and its main magnetic content is magnetite. acqueduct had a total length of ca. 69 km, the last 9.5 km of which were built A., 2003, Tectonic implications of magnetic fabrics and However, χ and ARM are very low in the upper 12 cm. Al, a over arches (the initial part was underground). The acqueduct is relatively remanence in the Cooper Mountain pluton, North sensitive indicator for acidification, decreases above 10 cm, Cascade Mountains, Washington: Canadian Journal of and some acidophile diatom species show the reverse pattern. well preserved. Here the height ~17 m and the distance between pillars is 5.5 Earth Sciences, v.40, no.10, p.1335-1356. Thus the lake was acidified after the power plant was built, m. The pillars are made of local tuff blocks (volcanic products from the The magnetic foliation in this pluton typically has a steep dip which caused dissolution of magnetic particles. Alban Hills), slightly cemented. (photo by Leonardo Sagnotti). and a northwest strike; the magnetic lineation plunges moderately to shallowly northwest or southeast. The NRM, Kapicka, A., Jordanova, N., Petrovský, E., and Podrázský, measured to evaluate post-emplacement tilt, has two V., 2003, Magnetic study of weakly contaminated forest components carried by pyrrhotite and magnetite. The soils: Water, Air, and Soil Pollution v.148, p. 31–44. paleomagnetic results and ~47 Ma Ar40-Ar39 ages suggest that Magnetic and magnetomineralogical studies show weak there has been no remagnetization or significant reorientation contamination in the uppermost layer of forest soils from of the pluton since emplacement. Krkonoše (Giant Mountains) National Park in the Czech Republic. Thermomagnetic analysis, acquisition of χ Current Abstracts Hus, J. J., 2003, The magnetic fabric of some loess/ remanence, AF demagnetization of SIRM and fd were palaeosol deposits: Physics & Chemistry of the Earth, v.28, measured in bulk samples and magnetic extracts. XRD and no.16-19, p.689-699. SEM were used to identify ferrimagnetic fractions. A list of current research articles The AMS of deposits from Asia, Europe and Siberia all have a dealing with various topics in the bedding-parallel foliation with low lineation. Lineations in the Kissel, C., Laj, C., Clemens, S. and Solheid, P., 2003, upper part of the Wucheng formation show a preferential Magnetic signature of environmental changes in the last physics and chemistry of magnetism is (prevailing palaeowind?) direction. Soil formation results in 1.2 Myr at ODP site 1146, South China Sea: Marine a regular feature of the IRM Quar- decreasing degree of anisotropy and foliation, and in some Geology, v.201, no.1-3, p.119-132. cases in large deviations of the principal susceptibility A precise age model based on magnetostratigraphy and 18O terly. Articles published in familiar directions caused by bioturbation. The AMS reflects both shows that the studied interval extends to 1.18 Myr. Long- geology and geophysics journals are crystallographic alignment of phyllosilicates and shape term and short-term variations have been documented in the alignment of MD magnetites. magnetic parameters. Except for the most recent 200 kyr, included; special emphasis is given to where the pattern changes, cold/warm periods coincide with current articles from physics, chemis- Zhou, Y., Wu, S. M., Qiu, X. L. and Zhou, P., 2003, Study on low/high magnetic content, and magnetic grains are coarser finite strain and its relationship with magnetic fabric during cold stages and finer during warm periods. This try, and materials-science journals. along Ailao Shan-Red River shear zone: Journal of illustrates changes in the balance between dominant winter Most abstracts are culled from Geophysical Research-Solid Earth, v.108, no.B10, 2479. and summer monsoon activity. Shear strains vary greatly here; ellipticity of amygdules in INSPEC (© Institution of Electrical basalt ranges from 6.79 to 10.47 (corresponding shear strain Liu, Q. S., et al., 2003, An integrated study of the grain- γ = 2.22-2.93), and ellipticity of garnets from 1.56 to 2.95 size-dependent magnetic mineralogy of the Chinese loess/ Engineers), Geophysical Abstracts in xz γ ( xz = 0.45-1.14) in core gneiss. Ferromagnetic minerals paleosol and its environmental significance: Journal of Press (© American Geophysical (mainly PSD and MD Ti-poor magnetite) and hornblende Geophysical Research-Solid Earth, v.108, no.B9, 2437. Union), and The Earth and Planetary dominate the AMS. A poor axial ratio correlation between the Magnetic extracts were divided into two size fractions by magnetic and strain ellipsoids suggests that the finite strain gravitational settling. Hysteresis, low- temperature Express (© Elsevier Science Publish- cannot be evaluated using the magnetic fabric when the latter remanence, SEM and XRD studies show that the loess coarse ers, B.V.), after which they are is a combined result from multiple minerals. particles are MD magnetite with slight oxidation; paleosol coarse particles are also MD magnetite but with a higher subjected to Procrustean editing and Data Processing and Analysis oxidation degree; loess fine particles are PSD magnetite with condensation for this newsletter. An a high oxidation degree; and paleosol fine particles are PSD extensive reference list of articles Borradaile, G. J. and Hamilton, T., 2003, Limestones maghemite. Single domain (SD) and superparamagnetic (SP) distinguished by magnetic hysteresis in three-dimensional maghemite mainly stay in the residues. (primarily about rock magnetism, the projections: Geophysical Research Letters, v.30, no.18, 1973. physics and chemistry of magnetism, We show that limestone samples are simply discriminated in a Liu, X. M., Rolph, T., An, Z. S. and Hesse, P., 2003, new 2D projection produced by projecting hysteresis data Paleoclimatic significance of magnetic properties on the Red Clay underlying the loess and paleosols in China: and some paleomagnetism) is continu- from three dimensions (x, y, z = Mr/Ms, Bcr, Bc) onto a plane containing the M /M axis. The orientation of the plane is Palaeogeography Palaeoclimatology Palaeoecology, v.199, ally updated at the IRM. This list, r s controlled by its x-axis that is defined by a suitably selected no.1-2, p.153-166. This widespread Miocene-Pliocene (7.2-2.5 Ma) aeolian with more than 5200 references, is Bcr/Bc ratio, most often in the magnetite PSD range, 2 < (Bcr/ B ) < 4. deposit comprises highly-developed soils and interbedded available free of charge. Your c layers of reddish loess-like material, interpreted to represent contributions both to the list and to Fabian, K., 2003, Some additional parameters to estimate climatic fluctuations. Magnetite, maghemite and hematite domain state from isothermal magnetization measure- (and possibly goethite) are present, and there are good the Abstracts section of the IRM χ ments: Earth & Planetary Science Letters, v.213, no.3-4, correlations among , SP content, and Rb:Sr ratio, an Quarterly are always welcome. p.337-345. independent weathering index. More work to deconvolve the 4 For quantitative analysis of domain state, four new isothermal climatic record of the Red Clay may extend the record of Krasa, D., Heunemann, C., Leonhardt, R. and Petersen, N., paleomonsoon evolution back into the late Miocene. Catling, D. C. and Moore, J. A., 2003, The nature of coarse- 2003, Experimental procedure to detect multidomain grained crystalline hematite and its implications for the remanence during Thellier-Thellier experiments: Physics & Muxworthy, A. R., Matzka, M., Davila, A. F. and Petersen, early environment of Mars: Icarus, v.165, no.2, p.277-300. Chemistry of the Earth, v.28, no.16-19, p.681-687. N., 2003, Magnetic signature of daily sampled urban The Mars Global Surveyor spacecraft has detected deposits of A new reliability test detects the presence of MD particles by atmospheric particles: Atmospheric Environment, v.37, coarse-grained, gray crystalline hematite in Sinus Meridiani, verifying the law of additivity of pTRMs. Additivity holds for no.29, p.4163-4169. Aram Chaos, and Vallis Marineris. The topography and the regular pTRMs (i.e. cooling from TC to T1) for both SD and In samples collected in Munich over a 160-day period, mass- collapsed nature of the chaotic terrain favor a hydrothermally MD particles, whereas it fails for pTRM* (heating from 20°C dependent magnetic parameters varied in a complicated way charged aquifer as the original setting where the hematite to T1) in the case of MD particles. Thellier experiments, based governed by both the meteorological conditions and the formed. The coexistence of factors required to form the gray on pTRM*, fail with MD carriers. Experiments covering the particulate matter (PM) loading rate, whereas mineralogy/ hematite deposits would also have produced a favorable grain size range 23 nm to 12.1 µm show a significant error for grain-size-dependent parameters displayed little variation. The environment for primitive life, including liquid water, electron all samples with grain sizes >0.7 µm, but our experiment is 3+ signal was dominated by fine (<100 nm ) magnetite-like grains donors (H2), and electron acceptors (Fe ). able to detect this failure. thought to be derived primarily from vehicles. Such small grains are particularly dangerous to humans. There was also Kopp, R. E. and Humayun, M., 2003, Kinetic model of Kruiver, P. P., Krijgsman, W., Langereis, C. G. and Dekkers, evidence that the magnetite-like grains were covered with an carbonate dissolution in Martian meteorite ALH84001: M. J., 2002, Cyclostratigraphy and rock-magnetic oxidised rim. Geochimica et Cosmochimica Acta, v.67, no.17, p.3247-3256. investigation of the NRM signal in late Miocene The magnetites and sulfides in the rims of carbonate globules palustrine-alluvial deposits of the Librilla section (SE Oldfield, F., et al., 2003, The late-Holocene history of in ALH84001 have been claimed as evidence of past life on Spain): Journal of Geophysical Research, v.107, no.B12, Gormire Lake (NE England) and its catchment: a Mars. Model calculations indicate that the rims could have 2334. multiproxy reconstruction of past human impact: formed in < 50 yr of exposure to small amounts of aqueous A refined magnetostratigraphy shows that the sedimentary Holocene, v.13, no.5, p.677-690. fluids at ambient temperatures, more likely in the modern cycles reflect climatic precession. Two intervals of complex Magnetic measurements, XRF and organic biogeochemical Martian or terrestrial atmospheres than in an ancient Martian NRM behavior were identified, showing normal and reversed analyses provide evidence for changes in sediment atmosphere. A terrestrial origin is supported by anticorrelated overprints. Fuzzy c-means cluster analysis on a geochemical composition and source and for catchment erosion over the variations of radiocarbon with δ13C, indicating solution- data yields a three-cluster model that roughly describes last 3500 years. Interpretation of the magnetic record is precipitation reactions immediately after initial fall (~13,000 yr lithology. Remarkably, all the samples with a normal overprint complicated by the presence of biogenic magnetite and ago) and again during recent exposure prior to collection. belong to one particular cluster. The reversed overprints, authigenic greigite and by probable magnetite dissolution. however, do not show any relation to the cluster partition. Magnetic indications of catchment erosion are nevertheless McKay, C. P., Friedmann, E. I., Frankel, R. B. and Bazylinski, clearly distinguishable, especially in the record of the D. A., 2003, Magnetotactic bacteria on Earth and on Magnetic Microscopy and Spectroscopy antiferromagnetic minerals haematite and goethite. Mars: Astrobiology, v.3, no.2, p.263-270. There are credible arguments for both the biological and non- Kasama, T., Golla-Schindler, U. and Putnis, A., 2003, High- Retallack, G. J., Sheldon, N. D., Cogoini, M. and Elmore, R. biological origin of the magnetite in ALH84001, and we resolution and energy-filtered TEM of the interface D., 2003, Magnetic susceptibility of early Paleozoic and suggest that more studies of ALH84001, extensive laboratory between hematite and ilmenite exsolution lamellae: Precambrian paleosols: Palaeogeography simulations of non-biological magnetite formation, as well as Relevance to the origin of lamellar magnetism: American Palaeoclimatology Palaeoecology, v.198, no.3-4, p.373-380. further studies of magnetotactic bacteria on Earth will be Mineralogist, v.88, no.8-9, p.1190-1196. In deposits pre-dating the evolution of rooted land plants, root required to further address this question. Magnetite grains The interfaces between fine-scale exsolution lamellae have traces cannot be used for recognizing paleosols. Magnetic produced by bacteria could provide one of the few inorganic been studied by TEM, to investigate the lamellar magnetism susceptibility peaks are useful supporting evidence for traces of past bacterial life on Mars that could be recovered hypothesis for the unusual properties of an igneous rock from paleosols that are red and oxidized, but not for those with from surface soils and sediments. Rogaland, Norway. The interfaces between the coarse reduction spots, iron-manganese nodules or other evidence of hematite and ilmenite lamellae (length >1 µm) and their hosts gleization. These ancient paleosols have much lower χ than Newsom, H. E., et al., 2003, Paleolakes and impact basins have some interface dislocations to relieve elastic coherency comparable Quaternary units, due in part to burial in southern Arabia Terra, including Meridiani Planum: strain, but very fine lamellae (length <50 nm) have no interface recrystallization of fine-grained ferrimagnets, and in part to a Implications for the formation of hematite deposits on dislocations and are perfectly coherent. These results are in lower level of susceptibility-enhancing microbial activity. Mars: Journal of Geophysical Research-Planets, v.108, accord with the predictions of Monte Carlo simulations of the no.E12, 8075. exsolution process and with the hypothesis that coherent and Watkins, S. J. and Maher, B. A., 2003, Magnetic Our discovery of a chain of paleolake basins and channels sharp structural and compositional interfaces are the origin of characterisation of present-day deep-sea sediments and along the southern margin of the hematite deposits in lamellar magnetism. sources in the North Atlantic: Earth & Planetary Science Meridiani Planum supports the possible role of water in the Letters, v.214, no.3-4, p.379-394. formation of the hematite and other layered materials in the Kawakami, T., et al., 2003, Mössbauer spectroscopy of North Atlantic surface-sediment magnetic data show distinct region. The hematite may have formed by direct precipitation pressure-induced phase transformation from maghemite spatial patterns related to sediment sources and transport from lake water, as coatings precipitated from groundwater, or to hematite: Journal of the Physical Society of Japan, v.72, pathways, especially of windblown dust and ice-rafted debris by oxidation of preexisting iron oxide minerals. Stratigraphic no.10, p.2640-2645. (IRD). The spatial distributions of the IRD-dominated relationships indicate that the formation of channels in the Using a diamond anvil cell, 57Fe Mössbauer spectroscopy has sediments substantiate those mapped previously using region occurred over much of Mars’ history. been carried out on maghemite, γ-Fe O , under high pressure lithological tracers, provide additional spatial information on 2 3 up to 30GPa. Maghemite transforms to hematite, α-Fe O , sediment sources and pathways, and suggest that deep water Treiman, A. H., 2003, Submicron magnetite grains and 2 3 with a wide coexistent pressure range. The onset of phase currents are less significant than proposed in controlling carbon compounds in martian meteorite ALH84001: transformation is 14 GPa and complete transformation to present-day sediment mineralogy and distribution. Inorganic, abiotic formation by shock and thermal hematite is found at 26GPa. The pressure-induced metamorphism: Astrobiology, v.3, no.2, p.369-392. transformation is irreversible and hematite is preserved at Xiong, S. F., et al., 2002, Northwestward decline of We propose that the carbonate globules in ALH84001 were decompression process. The magnetization direction stays magnetic susceptibility for the red clay deposit in the deposited from hydrothermal water, without biological nearly parallel after maghemite transforms to hematite. This Chinese Loess Plateau: Geophysical Research Letters, v.29, mediation. Thereafter, an impact shock event raised its strong orientation of magnetization does not appear on no.24, 2002GL015808. temperature nearly instantaneously to 500-700K, decomposing compression of original hematite, and is therefore due to the Magnetic susceptibility in the Miocene-Pliocene red clay Fe-rich carbonate and producing magnetite and other minerals. transformation. deposits shows a clear systematic decrease from the southeast Carbon-bearing gas from the carbonate decomposition reacted (Lingtai section) to the northwest (Baishui section). This with water to produce organic matter via Fischer-Tropsch-like Klausen, S. N., et al., 2003, An inelastic neutron scattering suggests that the climatic controls (probably precipitation) had reactions, catalyzed by the magnetite. study of hematite nanoparticles: Journal of Magnetism & a northwestward-decreasing gradient during the red clay Magnetic Materials, v.266, no.1-2, p.68-78. deposition, similar to the present pattern, implying that the Magnetic Field Records and Paleointensity Neutron scattering studies in nanocrystalline hematite at influence of the East Asian summer monsoon on the Chinese temperatures from 5 to 325 K show that the particles are Loess Plateau has persisted from at least 6 Ma. Methods canted antiferromagnetic (weakly ferromagnetic) at Dunlop, D. J. and Yu, Y. J., 2003, Testing an inverse Thellier temperatures at least down to 5 K. The data and their Extraterrestrial Magnetism method of paleointensity determination: Journal of temperature dependence can with good agreement be Geophysical Research-Solid Earth, v.108, no.B9, 2447. interpreted on the basis of the Neel-Brown theory for Barber, D. J. and Scott, E. R. D., 2003, Transmission Inverse TRM (ITRM) can be produced in nature if a superparamagnetic relaxation and a model for the collective electron microscopy of minerals in the martian meteorite magnetite-bearing meteorite warms through the Verwey magnetic excitations. Allan Hills 84001: Meteoritics & Planetary Science, v.38, transition (TV = 120 K) in the Earth’s field. A new inverse no.6, p.831-848. Thellier method of paleointensity determination uses cooling- Sandhu, A., Masuda, H. and Oral, A., 2003, Room TEM, X-ray microanalysis, and electron diffraction show temperature scanning micro-Hall probe microscopy under heating steps below room temperature T0. In our experiments, magnetite crystals that are epitaxially oriented at voids and extremely large pulsed magnetic fields: IEEE Transactions NRM was an ITRM produced by warming from 30 K to T0, microfractures, clearly formed in situ. Fully embedded, faceted for magnetites of 0.065, 0.2, 1, 3, 6, 9, 17, 20 and 135 µm and on Magnetics, v.39, no.5 Part 2, p.3462-3464. magnetites are topotactically oriented on carbonate so that two gabbros containing elongated SD magnetite. SD samples The versatility of a room-temperature scanning Hall probe their oxygen layers are aligned. All magnetite and periclase had quasi-linear inverse Arai plots but other samples had microscope system with an integrated minicoil capable of crystals probably formed by exsolution from carbonate convex-down curves, resembling Arai plots for TRM in MD generating pulsed magnetic fields up to 2.9 T was following impact-induced thermal decomposition. Any grains. However, the inverse Thellier method may have more demonstrated by imaging magnetic structures on the surface of magnetites that existed in the rock before shock heating could linear behavior if the NRM is a TRM because the greater 1.4-MB floppy disks. Vibration isolation between the sample not have preserved evidence for biogenic activity. resistance of TRM to LTD should offset the too-rapid decay of and minicoil enabled extremely fast measurements, using a ITRM in zero-field steps. GaAs-AlGaAs micro-Hall probe sensor located at a height of Brearley, A. J., 2003, Magnetite in ALH 84001: An origin 0.5 µm above-the sample surface. by shock-induced thermal decomposition of iron Frank, U., Schwab, M. J. and Negendank, J. F. W., 2003, carbonate: Meteoritics & Planetary Science, v.38, no.6, Results of rock magnetic investigations and relative Magnetic Petrology and Anomaly Sources p.849-870. paleointensity determinations on lacustrine sediments TEM studies show that the carbonate fragments embedded from Birkat Ram, Golan Heights (Israel): Journal of Alva-Valdivia, L. M., et al., 2003, Integrated magnetic within feldspathic glass contain myriad, nanometer-sized Geophysical Research-Solid Earth, v.108, no.B8, 2379. studies of the El Romeral iron-ore deposit, Chile: magnetite particles with cuboid, irregular, and teardrop Relative paleointensity (RPI) was estimated by normalizing the implications for ore genesis and modeling of magnetic morphologies, frequently associated with voids. The fragments NRM intensity after demagnetization at 20 mT (JNRM(20 mT)) by anomalies: Journal of Applied Geophysics, v.53, no.2-3, of carbonate must have been incorporated into the melt at different concentration parameters. The MDF of the NRM is p.137-151. temperatures of ~900°C, well above the upper thermal stability coherent with the RPI estimates, indicating that a sedimentary CRM seems to be present in most of investigated ore and limit of siderite. These observations suggest that most, if not effect has not sufficiently been removed. The RPI variation, wall-rock samples, substituting completely or partially the all, of the fine-grained magnetite associated with Fe-bearing however, correspond to archeomagnetic records from Bulgaria original TRM. Magnetite (or Ti-poor titanomagnetite) and carbonate in ALH 84001 could have been formed as result of and Greece. A second normalization, based on the linear the thermal decomposition of the siderite and is not due to relationship between RPI and MDF(NRM), improved the biological activity. records. abstracts 5 continued on p. 6... titanohematite are commonly found in the ores. Magmatic In normalized vector plots of AF demagnetization of ...abstracts titanomagnetite, found in igneous rocks, shows trellis texture, orthogonal pARMs, LTD-treated samples showed universal Peters, C. and Dekkers, M. J., 2003, Selected room which is compatible with high temperature (deuteric) oxy- improvement in the degree of independence, greatest for temperature magnetic parameters as a function of continued from p. 5 exsolution processes. Hydrothermal alteration in ore deposits synthetic SD and PSD magnetites and natural lake sediments, mineralogy, concentration and grain size: Physics & is indicated by goethite and hematite oxide minerals. and to a lesser degree for synthetic MD magnetite, granites, Chemistry of the Earth, v.28, no.16-19, p.659-667. and gabbros. In general, LTD provides a better resolution of A data set of room temperature magnetic parameters for iron Arkani-Hamed, J., 2003, Thermoremanent magnetization of superimposed vectors in multicomponent remanence. The oxides and sulphides, compiled from the literature, shows that the Martian lithosphere: Journal of Geophysical Research- direction of the original remanence is perfectly recovered. hematite and in particular goethite are recognised by their χ Planets, v.108, no.E10, 5114. However, the pARM overprint is not perfectly resolved, high HCR. The ratio MRS/ is high for pyrrhotite, intermediate This model assumes that the upper part of the lithosphere especially for overprinting coercivities <40 mT, where the for greigite and maghemite, and very low for acquired TRM early in Mars’ history in the presence of a core deviation is 10° or more. (titano)magnetite. From the concentration-dependent χ χ χ field, whereas the lower part has been gradually magnetized by parameters , MRS and ARM, displayed the least grain-size the magnetic field of the upper part as it has cooled below TC. Mineral & Rock Magnetism dependence, and is therefore the best indicator of If the Martian lower lithosphere is more magnetic than concentration. All minerals except goethite showed a µ Earth’s, e.g., by an order of magnitude, the secondary γ decrease in HC and MRS/MS for d>1 m. Assessment of Caizer, C., 2003, Saturation magnetization of - Fe2O3 magnetization can be significant, although still weaker than the nanoparticles dispersed in a silica matrix: Physica B, v.327, domain state was complicated by the similar properties of primary magnetization of the upper part. In all models no.1, p.27-33. very small and large grains. considered the primary magnetization is ~20-30 A/m and has MS increases by 69.7% on cooling from 300 to 77 K for non- the dominant contribution to the observed magnetic interacting nanoparticles of γ - Fe O (0.68 vol%) isolated in an Mineral Physics & Chemistry anomalies. 2 3 amorphous SiO2 matrix. This is much higher than the corresponding increase for the bulk ferrite, which is only 9.5% Cudennec, Y. and Lecerf, A., 2003, Study of the formation Gac, S., Dyment, J., Tisseau, C. and Goslin, J., 2003, Axial in the same temperature range. We attribute the anomalous processes of iron oxy-hydroxides; hypotheses of topotactic magnetic anomalies over slow-spreading ridge segments: increase to low-T ferromagnetic ordering of a paramagnetic transformations: Comptes Rendus Chimie, v.6, no.4, p.437- insights from numerical 3-D thermal and physical surface layer, with spins aligned by superexchange interaction. 444. modelling: Geophysical Journal International, v.154, no.3, This amounts to an increase in the effective magnetic diameter Goethite, α-FeO(OH), is the most stable iron oxy-hydroxide. p.618-632. of the particles from 10.20 to 11.76 nm at low temperatures. It can be formed directly from trivalent iron solutions or from The axial magnetic anomaly along Mid-Atlantic Ridge ‘white rust’ Fe(OH)2 by oxidation of divalent iron. segments is systematically twice as high at segment ends Delius, H., Brewer, T. S. and Harvey, P. K., 2003, Evidence Lepidocrocite, γ-FeO(OH), can be obtained at room compared with segment centres, due to: (1) shallower Curie for textural and alteration changes in basaltic lava flows temperature by fast oxidation of divalent iron in a ‘green rust’ isotherm at segment centres, (2) higher Fe-Ti content at using variations in rock magnetic properties (ODP Leg precursor phase, containing also trivalent iron and chloride segment ends and/or (3) serpentinized peridotites at segment 183): Tectonophysics, v.371, no.1-4, p.111-140. ions. Based on a structural study and a comparison of crystal ends. 3-D numerical modeling suggests that, in the case of In subaerial basalts, χ and NRM are typically high in the altered structures of these different phases, we propose possible aligned and slightly offset segments, a combination of (2) and flow top, and lower in the less-altered massive flow interior. In topotactic reactions. (3) dominate; for greater offsets, serpentinized peridotites at contrast, submarine lava flows typically display the opposite segment ends can account for the observations. pattern. It is concluded that rate of cooling and degree of Demianets, L. N., Pouchko, S. V. and Gaynutdinov, R. V.,
alteration are the main factors influencing the magnetization 2003, Fe2O3 single crystals: hydrothermal growth, crystal Magnetization & Demagnetization Processes and, hence, the distribution of iron oxides. chemistry and growth morphology: Journal of Crystal Growth, v.259, no.1-2, p.165-178. Ozima, M. and Funaki, M., 2003, Hemoilmenite as a carrier Frederichs, T., von Dobeneck, T., Bleil, U. and Dekkers, M. J., Optical and AFM study of the {h k i l} faces of of SRTRM in dacitic pumice from Akagi, Ontake and 2003, Towards the identification of siderite, rhodochrosite, hydrothermally-grown hematite single crystals show two Sambe Volcanoes, Japan: Earth & Planetary Science and vivianite in sediments by their low-temperature main mechanisms of growth: layer-by-layer growth and island Letters, v.213, no.3-4, p.311-320. magnetic properties: Physics & Chemistry of the Earth, v.28, growth. Large flat terraces with height h 100-150 nm, width Dacite pumice samples from Akagi Volcano acquire an intense no.16-19, p.669-679. d ~10000 nm are observed on the {1 1 2 0} surface. Terraces self-reversed TRM (SRTRM). Bitter patterns of the oriented Natural samples of siderite (FeCO3), rhodochrosite (MnCO3), are composed from steps of h~15-65, d~100-1200 nm, hemoilmenite crystals from both the Haruna and Akagi and vivianite ([Fe3(PO4)2].8 H2O), authigenic sedimentary consisting of globules with rounded or elongated shapes and volcanoes indicate that ordered ferrimagnetic and disordered minerals that are paramagnetic at room temperature, were typical heights of 0.5-5 nm and lengths of 30-60 nm. weak-ferromagnetic phases are inter-grown in relatively measured at low-T in an MPMS. Below their Neel comparable amounts, with an irregular texture. This pattern is temperatures, siderite (37 K) and rhodochrosite (34 K) acquire Froese, E., 2003, Point defects in pyrrhotite: Canadian consistent with rapid quenching of these pumices. We a strong spin-canted remanence (~0.4 Am2/kg) from cooling in Mineralogist, v.41, no.Part 4, p.1061-1067. conclude that not only the chemical composition of the a 5 T magnetic field. Different ratios of FC and ZFC The nature of point defects in pyrrhotite can be determined hemoilmenite, but also the cooling rate control SRTRM remanences allow a discrimination between the two minerals. from measurements of composition and the corresponding
acquisition. Vivianite also shows metamagnetism below 5 K in 5 T fields fugacity of S2 by examining reaction equilibria written to and a ‘two-stage’ increase in susceptibility between 2 and 12 K involve perfectly ordered FeS, species deduced from point
Spassov, S., et al., 2003, A lock-in model for the complex attributed to successive short- and long-range magnetic defects, and S2. This approach is illustrated using the Matuyama-Brunhes boundary record of the loess/ ordering. Shifting of the Neel points to lower temperatures experimental data at 1257 K. In S-rich pyrrhotite, the palaeosol sequence at Lingtai (Central Chinese Loess occurs with element substitution and non-stoichiometry, predominant defect is produced by vacancies on Fe sites; in Plateau): Geophysical Journal International, v.155, no.2, common in sedimentary environments. Fe-rich pyrrhotite, the predominant defect consists of Fe p.350-366. atoms on S sites. The MBB at Lingtai occurs in L8 and is characterized by Goya, G. F., Berquo, T. S., Fonseca, F. C. and Morales, M. P., α multiple polarity flips. The NRM is mainly carried by two 2003, Static and dynamic magnetic properties of spherical Liu, H., et al., 2003, Static compression of -Fe2O3: linear coexisting phases, one with higher coercivity (dominant in magnetite nanoparticles: Journal of Applied Physics, v.94, incompressibility of lattice parameters and high-pressure loess layers and thought to be detrital), and one with lower no.5, p.3520-3528. transformations: Physics & Chemistry of Minerals, v.30,
coercivity (prevailing in palaeosols and probably formed in situ Magnetic behavior of Fe3O4 nanoparticles changes with average no.9, p.582-588. α by (bio-)chemical processes). A dual lock-in model, with the particle size
harder component physically locked shortly after deposition, as MS, hyperfine parameters, HC, and Verwey transition are heated diamond anvil cell remains in the corundum structure
and the softer component locking chemically at greater depth, observed in 150 nm particles. For decreasing particle size, TV up to 50 GPa, but with a coexisting high-pressure phase is able to explain the observed rapid multiple polarity flips and shifts down to ~20 K for
to a blocked state at TB~45 K, which depends on the applied 50 GPa. Analysis of linear compressibilities suggests that the
Walton, D., 2002, Conditions for ferromagnetic resonance field. Dynamic ac susceptibility measurements show a thermally high-pressure phase above 50 GPa is of the Rh2O3 (II)
in nanoparticles and microwave magnetization: activated Arrhenius-Neel dependence of TB on frequency for structure. Geophysical Research Letters, v.29, no.24, 2002GL016049. the 5 nm particles. Microwaves are absorbed by generating spin-waves, a very Pasternak, M. P., et al., 2003, Pressure-induced efficient way to raise the temperature of ferromagnetic Gregorova, D., Hrouda, F. and Kohut, M., 2003, Magnetic coordination crossover in magnetite; the breakdown of particles in a non-magnetic matrix. Since microwaves are susceptibility and geochemistry of Variscan West the Verwey-Mott localization hypothesis: Journal of essentially only absorbed by the magnetic grains the matrix Carpathian granites: implications for tectonic setting: Magnetism & Magnetic Materials, v.265, no.2, p.L107-L112. remains cool which eliminates the problem of mineral Physics & Chemistry of the Earth, v.28, no.16-19, p.729-734. Temperature-dependent 57 Fe Mössbauer spectroscopy to 40 alteration. A key factor is the size of the magnetic particles. Granites usually display a bimodal distribution of χ, with modes GPa shows that magnetite undergoes a coordination Spin waves whose wavelength exceeds about twice the size of on the order of 10-5-10-4 SI and 10-3-10-2 SI, respectively crossover (CC), whereby charge density is shifted from the particle are not possible so the dispersion relations for corresponding to ilmenite-bearing (S-type) and magnetite- octahedral to tetrahedral sites and the spinel structure thus small particles are cutoff at the corresponding wave-vector. bearing (I-type) granite. In the West Carpathians, isotope changes from inverse to normal with increasing pressure and geochemistry discriminates an older peraluminous group (350- decreasing temperature. The CC transition takes place almost
Yu, Y., Dunlop, D. J. and Ozdemir, O., 2003, Testing the 330 Ma) of two-mica granites and granodiorites, carrying exactly at the Verwey transition temperature (TV = 122 K) at
independence law of partial ARMs: implications for monazite and ilmenite; and a younger metaluminous to ambient pressure. While TV decreases with pressure the CC- paleointensity determination: Earth and Planetary Science subaluminous group (310-300 Ma) of biotite tonalites and transition temperature increases with pressure, reaching 300K Letters, v.208, (1-2), p. 13-26. granodiorites, carrying allanite and magnetite. Magnetic at 10GPa. The independence of pARMs was tested by AF demagnetizing susceptibilities of both sets are in general rather low, on the orthogonal pARMs whose blocking field intervals do not order of 10-4, in apparent contradiction with the granite origin Sanders, J. P. and Gallagher, P. K., 2003, γ overlap with each other. Experimentally the two pARMs as revealed geochemically. Unusual redox conditions controlled Thermomagnetometric evidence of -Fe2O3 as an demagnetized independently for SD grains but not for MD and by the tectonic setting are possible explanations of this intermediate in the oxidation of magnetite: PSD grains. Experimentally and in numerical simulations, discrepancy. Thermochimica Acta, v.406, no.1-2, p.241-243. when a total ARM (simulating primary remanence in a field The oxidation of magnetite to hematite was followed by
Ha) was orthogonally overprinted by pARM (simulating Miranda, J. M., et al., 2002, Study of the Saldanha Massif thermogravimetry (TG), both with and without a small
remagnetization in Hb), estimation of the intensity of Hb was (MAR, 36° 34 ‘ N): Constrains from rock magnetic and magnetic field gradient imposed upon the sample. The results
relatively successful but the intensity of Ha was always geophysical data: Marine Geophysical Researches, v.23, no.4, clearly indicate the formation of a strongly magnetic
underestimated. Conversely, the direction of Ha was preserved p.299-318. intermediate during oxidation, confirming the speculation that γ but the direction of Hb was spurious. These violation of pARM These basalt samples have magnetic minerals of SD grain size, -Fe2O3 is an intermediate in this process. independence imply that the conventional criteria in pseudo- typical of rapid cooling. Thermomagnetic study distinguishes Thellier paleointensity determination require modification. between three different stages of low temperature oxidation: van der Zee, C., Roberts, D. R., Rancourt, D. G. and Slomp, the presence of titanomagnetite, titanomagnetite and C. P., 2003, Nanogoethite is the dominant reactive Yu, Y., Dunlop, D. J. and Ozdemir, O., 2003, On the titanomaghemite, and exclusively of titanomaghemite. Based on oxyhydroxide phase in lake and marine sediments:
resolution of multivectorial remanences: Earth and established empirical relationships between TC and degree of Geology, v.31, no.11, p.993-996. 6 Planetary Science Letters, v.208, (1-2), p. 27-39. oxidation, the latter is tentatively deduced for all samples. Reactive ferric oxides and oxyhydroxides are usually quantified by selective chemical extractions that are not Fabian, K., 2003, Statistical theory of weak field Szotek, Z., et al., 2003, Ab initio study of charge order in 57 mineral specific. We have used cryogenic Fe Mössbauer thermoremanent magnetization in multidomain particle Fe3O4: Physical Review B, v.6805, no.5, 4415. spectroscopy to show that the reactive iron oxyhydroxide ensembles: Geophysical Journal International, v.155, no.2, We present a self-interaction corrected local spin-density study phase in a large variety of lacustrine and marine environments p.479-488. of the electronic structure and possible charge order of α is nanophase goethite ( -FeOOH), rather than the assumed A non-equilibrium statistical theory of MD TRM describes magnetite Fe3O4. The issue of charge order in magnetite is surface-complex-stabilized, two-line ferrihydrite and thermal magnetization changes as continuous inhomogeneous explored in both cubic and orthorhombic structures, the latter accompanying mixture of clay and oxyhydroxide Fe-bearing Markov processes. From three very general physical being an approximation to the true, low-temperature, phases. properties of TRM, the linearity of TRM with field is derived monoclinic structure. We find that the Verwey charge ordered for generic MD particle ensembles. The general validity of phase is not the ground-state solution for this compound either Ziemniak, S. E. and Castelli, R. A., 2003, Immiscibility in Thellier’s law of additivity of partial TRM’s in weak fields is in cubic or orthorhombic structure. We conclude that the
the Fe3O4-FeCr2O4 spinel binary: Journal of Physics & established and a method for proving a large class of similar structural distortions, more than localization/delocalization Chemistry of Solids, v.64, no.11, p.2081-2091. additivity laws is developed. The theory allows consistent correlations, are responsible for the charge disproportionation A recent thermodynamic model of mixing in spinel binaries, treatment of blocking and unblocking of remanence in in the low-temperature phase. based on changes in cation disordering between tetrahedral multidomain particle ensembles and naturally explains and octahedral sites, gives poor agreement with measured apparent differences between blocking and unblocking Synthesis and Properties of Magnetic consolute solution temperature and solvus for the Fe O - temperatures. 3 4 Materials FeCr2O4 system under conditions where incomplete mixing occurs. A revised model including (1) ordering of magnetic Morup, S., 2003, Spin-canting and transverse relaxation at moments of cations in the tetrahedral sublattice antiparallel to surfaces and in the interior of ferrimagnetic particles: Fu, Y. Y., et al., 2003, Synthesis of large arrays of aligned α-Fe O nanowires: Chemical Physics Letters, v.379, no.3-4, the moments of those in the octahedral sublattice and (2) pair- Journal of Magnetism & Magnetic Materials, v.266, no.1-2, 2 3 wise electron hopping between octahedral site Fe3+ and Fe2+ p.110-118. p.373-379. α Synthesized -Fe2O3 nanowire arrays are comprised of perfect ions predicts a consolute solution temperature (Tcs) = 600°C Analytical expressions for the magnetic energy and the spin- and a solvus at 500°C of n = 0.05 and 0.70 for the Fe (Fe canting angles in some simple ferrimagnetic bulk and surface single crystals with diameters of 20-40 nm and lengths of 2-5 1- µm. The high surface density of the nanowires (108-109 cm-2) nCrn)2O4 spinel binary. structures are presented. It is shown that the energy barriers separating different spin-canted states often will be very small. is considered to be responsible for the aligned growth. The size of the α-Fe O nanowires may be tailored to required Modeling and Theory Therefore, the spin canting may be static only at very low 2 3 temperatures and dynamic at higher temperatures. The dimension by adjusting the flowing rate of the gases as well as calculations elucidate the field dependence of the canting the time and temperature of reaction, offering opportunities Carvallo, C., Muxworthy, A. R., Dunlop, D. J. and Williams, for both fundamental research and technological applications. W., 2003, Micromagnetic modeling of first-order reversal angles, the high-field susceptibility of complex magnetic materials, the high-frequency susceptibility of diamagnetically curve (FORC) diagrams for single-domain and pseudo- Itoh, H. and Sugimoto, T., 2003, Systematic control of size, single-domain magnetite: Earth & Planetary Science substituted ferrites, and the apparently temperature- independent relaxation phenomena at very low temperatures. shape, structure, and magnetic properties of uniform Letters, v.213, no.3-4, p.375-390. magnetite and maghemite particles: Journal of Colloid & A conjugate-gradient micromagnetic model yields a FORC Interface Science, v.265, no.2, p.283-295. diagram with a single peak at H for individual elongated SD. Muxworthy, A., Williams, W. and Virdee, D., 2003, Effect of c As an application of the gel-sol method especially developed For a vortex PSD grain we observe multiple FORC peaks. In a magnetostatic interactions on the hysteresis parameters of single-domain and pseudo-single-domain grains: Journal for the synthesis of general monodisperse particles in large 2x2x2 array of elongated SD particles, a secondary branch on quantities, uniform hematite (α-Fe O ), magnetite (Fe O ), and of Geophysical Research-Solid Earth, v.108, no.B11, 2517. 2 3 3 4 the reversal curves appears if the spacing D between particles maghemite (γ-Fe O ) particles, precisely controlled in size, A three-dimensional micromagnetic study shows that 2 3 is less than about twice the particle length L. This feature aspect ratio, and internal structure, have been prepared. translates into the appearance of one negative and three interactions can strongly affect the magnetic characteristics of positive peaks on the FORC diagram. For a 3x3x3 array of assemblages of ideal SD grains and cubic grains between 30- 250 nm in size. For example, assemblages of interacting SD Lian, S. Y., et al., 2003, Convenient synthesis of single particles, we again observe several secondary branches when crystalline magnetic Fe O nanorods: Solid State grains can plot in the traditional MD area of the Day plot. For 3 4 D<2L, leading to the appearance of multiple peaks on the Communications, v.127, no.9-10, p.605-608. FORC diagram. Splitting of the central peak on the H axis grains > 100 nm in size, interactions can have the opposite u Uniform single-crystal magnetic Fe O nanorods synthesized in when particles interact could explain the vertical spread of effect, and can cause the hysteresis parameters to shift toward 3 4 the SD region of the Day plot. The SD/MD transition size a solution-phase approach have average diameters of ca. 80 FORC distributions of natural interacting samples. µ increases as the interaction spacing is decreased. nm and lengths of up to 2 m. The composition of the nanorods is appraised by X-ray photoelectron spectroscopy Davila, A. F., Fleissner, G., Winklhofer, M. and Petersen, N., Shcherbakov, V. P. and Sycheva, N. K., 2003, Mathematical (XPS). TEM images show that the magnetite particles are 2003, A new model for a magnetoreceptor in homing homogenous and have the shape of rods. pigeons based on interacting clusters of superparamag- modeling of biased hysteresis loops in the presence of exchange anisotropy at an interface: Izvestiya-Physics of netic magnetite: Physics & Chemistry of the Earth, v.28, Vargas, J. M., et al., 2003, Structural, magnetic, and no.16-19, p.647-652. the Solid Earth, v.39, no.8, p.685-692. A rigorous theory of biased hysteresis loops in exchange- Mössbauer characterization of size-controlled iron-iron Potentially magnetoreceptive nerve cells comprise chain-like oxide nanoparticles obtained by chemical methods: IEEE aggregates with up to 20 closely spaced clusters of SP coupled ferro-antiferromagnetic bilayers shows that domain wall creation decreases the loop bias field H by two orders of Transactions on Magnetics, v.39, no.5 Part 2, p.2681-2683. magnetite. Experiments on SP model systems simulate the bs magnitude, bringing H into agreement with observed values. Size-controlled Fe nanoparticles have been obtained by behaviour of the aggregates in varying magnetic fields. bs thermal decomposition of Fe(CO) in organic solution. The H value is shown to reach a few hundreds of oersted for 5 Magnetic-field induced interactions between the clusters in an bs Samples with different sizes, in the 6-12 nm range, have been aggregate gives rise to attractive and repulsive forces between solid-state exsolution structures in bilayers of the maghemite- hematite and hemoilmenite-hemoilmenite (with different Ti characterized by high-resolutibn TEM, XRD, Mössbauer the clusters. The resulting stress on the surrounding cellular spectroscopy, and magnetization measurements. All samples structures varies with field direction and intensity. concentrations) types if the ferromagnetic phase is SD. The bias can be extremely small (~1 Oe) for MD particles. present narrow size distributions and superparamagnetic behavior. Exposure to air leads to the formation of a
polycrystalline phase, mainly Fe3O4.
sealed in quartz capsules of 3 cm and anisotropy dominates above 540-560C annealed for 3 hr at 700C to stabilize the while magnetostrictive anisotropy Temperature dependence of magnetic properties. The quartz capsules controls hysteresis properties below 120 ...VF Reports were unsealed just prior to hysteresis K. Titanomagnetite-bearing oceanic continued from p. 3 magnetic hysteresis measurements. The second set of powders basalts show quite different behavior is 0.5% volume dispersions of with much higher coercivity, resulting unannealed magnetite in a matrix of CaF . from prominent magnetostrictive Knowledge of the temperature 2 Yongjae Yu dependence of hysteresis properties is The third set is bulk magnetites. anisotropy. While many factors such as Scripps Institution of useful in deciphering dominant anisot- Natural samples were also studied: composition, field-treatment, grain Oceanography ropy and/or changes in domain states. CG (Cordova Gabbro, ON, Canada); KM shape and size, and stress affect UC San Diego Although the low-temperature hysteresis (Kometsuka basalts, Mt. Aso, Japan); hysteresis properties at various tempera- [email protected] properties of titanomagnetites have been MORB 1-7 (zero-age mid-oceanic ridge ture ranges, a dominant anisotropy was extensively studied, the high-temperature basalts, East Pacific Rise); sbg (subma- better recognized when remanence ratio hysteresis properties of rine basaltic glass, ODP 807C}; and TG- was plotted against coercivity. (titano)magnetites have been relatively A, TG-B (Tudor Gabbro, ON, Canada). I appreciate Mike Jackson, Jim less studied. Hysteresis properties have been Marvin, and Peat Solheid of the I used seven synthetic magnetite measured at a series of temperatures Institution for Rock Magnetism (IRM) powders whose mean grain sizes range between 20 K and 600C in the peak field for their help with the measurements. from single domain (SD; 65 nm) to small of 1 T (field increments were 10 mT). Jeff S. Gee generously donated a large multidomain (MD; 16.9 µm). For each The signal averaging time was usually set collection of MORBs for use in this grain size, three sets of powders were to 200 ms, but 1 s was used for weak study. Lisa Taxue and Bruce M. prepared. The first set of powders is samples. Moskowitz shared fruitful discussions. 0.5% by volume dispersions of magnetite For synthetic samples and gabbros, in a matrix of CaF . These were vacuum- shape anisotropy dominates most 2 temperature ranges. However, exchange 7 The Colosseum is another enduring pozzolana and masonry structure, and we and is probably due to the same may also mention the aqueducts. phenomena: incomplete saturation in 2.5 Although the early ones (such as the Pont T at 20 K, and more efficient magnetiza- du Gard) were made of massive cut stone tion by cooling in a strong field. This blocks, remarkably and laboriously fitted FC-ZFC behavior is distinctly different together with no mortar, the later ones from that of stoichiometric magnetite, (e.g., Merida) were made elegantly and where the differences in intensity economically from continuous pozzolana (attributable to anisotropy induced by concrete cores, with facings of stone or field-cooling) disappear abruptly on brick. warming through the Verwey transition at TV~120 K. Magnetic Composition of Pozzolana The room-temperature hysteresis Cements loop in a maximum field of 1 T (Fig 1a) But let’s get to the point. One of the shows a small curvature even near the characteristics of our pozzolana cement peak field, indicating not-quite-complete The Pantheon in Rome, with its 43-m-diameter pozzolanic concrete saturation. Measurements in higher dome that makes it suitable for use as an interlab standard is that it is quite strongly fields, up to 2.5 T, show that indeed the high-field slope continues to decrease ...pozzolana silica (SiO )). Crushing and “burning” magnetic. Hysteresis measurements (Fig 2 slightly, even above 2 T. Thus a small continued from p. 1 (heating to ~1500° C) these produces a 1a) show a saturation magnetization 2 amount of hard antiferromagnetic mixture of di-, tri- and tetra-calcium around 0.6 to 0.7 Am /kg, equivalent to a magnetite/maghemite content of nearly material is also present. The tempera- silicates, aluminates and aluminoferrites. ture dependence of the high-field When these are subsequently mixed with 1% by mass. Although portland cements nearly all contain some iron (typically susceptibility (Fig 3b) shows that it is water, the hydration reaction forms a dominantly paramagnetic in origin, and colloidal gel of calcium-alumininum 0.5-5%), it is likely that the majority of this magnetically-ordered phase origi- the values indicate that the paramagnetic silicate hydrate, with high internal iron content is <1% by mass. M and surface forces that bind it together with nates in the pozzolanic ash in the mixture; S both volcanic ash [e.g., Heider et al., MR are nearly independent of tempera- other building materials. ture below 300 K. The burning or calcination that 1993; Rosenbaum et al., 1993; Pawse et al., 1998; Evans, 1999] and industrial fly renders the raw ingredients reactive Magnetic Kinetics: Frequency- and occurs naturally in pozzolans. As ash [e.g., Dekkers & Pietersen, 1992; Gomes et al., 1999; Hanesch & Petersen, Rate-Dependent Behavior Vitruvius puts it, “therefore the fire and In contrast to the brute simplicty of vapor of flame within, flowing through 1999; Hower et al., 1999] often contain abundant fine-particle ferrimagnets. In strong-field measurements, interlab the cracks, makes that earth light. And calibration of weak-field remanence the tufa which is found to come up there our pozzolana cement samples, a dominantly single-domain and pseudo- properties is made more interesting/ is free from moisture. Therefore when difficult by the sensitivity of the three substances formed in like manner single-domain state is indicated by the M /M ratio of about 0.3. magnetization process to a variety of by the violence of fire come into one R S The ferrimagnetic phase in these factors. For example, there is a mixture, they suddenly take up water and surprisingly strong dependence of both cohere together. They are quickly pozzolana cements appears to be dominantly oxidized magnetite or pTRM and pARM intensities on prior hardened by the moisture and made “conditioning” of the sample [e.g., solid, and can be dissolved neither by the maghemite, as shown by the Curie waves nor the power of water.” temperature exceeding 600° C (Fig 1b), The Pantheon in Rome, one of the and by the absence of any low-tempera- landmarks in the history of architecture, ture transitions (Fig 3, 4). Although is equally a triumph of engineering and maghemite is unstable and inverts to applied materials science. Its hemi- hematite at high temperatures, fine- spheric dome, 43 meters in diameter, has grained maghemites survive to tempera- stood for nearly two millennia, and was tures exceeding 700° C [Özdemir and until modern times the largest in the Banerjee, 1984; Özdemir, 1990; de Boer world. The structure is built primarily of and Dekkers, 1996]. Mössbauer concrete, with pozzolana both in the spectroscopy of bulk pozzolana cement 2+ aggregate blocks and in the mortar powder shows sextets of both Fe and 3+ binding the blocks together. The Fe in magnetically-ordered phases, in a aggregate materials were assembled with proportion roughly halfway between a gradation in density: heavy travertine in those of stoichiometric magnetite and the foundation and walls, proceeding to maghemite (Fig 2). lighter materials such as pumice at the The low-temperature remanence top, and culminating in the great open characteristics (Fig 3a) strongly resemble oculus. Over the centuries a series of those of oxidized synthetic fine-grained radial cracks has developed, extending (~50 nm) magnetite (e.g. the Wright 4000 from the base of the dome upward sample in the Rock Magnetic Bestiary towards the oculus, caused by the
0.25 0.70 6.00E-08 0.24 pozzolana cement powder 0.60 0.23 LT and RT remanence 5.00E-08
0.22 FC 0.50 ZFC pozzolana cement powder 4.00E-08 0.21 high-field measurements /kg] RTSIRM 2 /kg] 0.40 /kg] 2 0.20 3 Ms 3.00E-08
0.19 [m
M [Am 0.30 Mr hf χ
M [Am Xhf 0.18 2.00E-08 0.20 0.17
0.16 0.10 1.00E-08 0.15 0 50 100 150 200 250 300 0.00 0.00E+00 0 50 100 150 200 250 300 Temperature [K] T [K]
Fig 3. (a, left) Low-temperature cycling of room-temperature SIRM (RTSIRM, circles), and zero-field warming curves for remanences acquired by field- cooling (FC, diamonds, cooled in 2.5 T) and isothermally in 2.5 T at 20 K after zero-field cooling (ZFC, squares). (b, right) Parameters of low-temperature χ hysteresis loops, measured to maximum fields of 2.5 T: saturation remanence (Mr, squares); high-field slope ( hf, circles) and saturation magnetization (Ms, diamonds) were calculated at each temperature for field intervals 1-1.5 T, 1.5-2T, and 2-2.5T; inequality of the three values shows degree of non-linearity, due to incomplete ferromagnetic saturation and/or partial paramagnetic saturation at the lowest temperatures. pozzolana 9 continued on p. 10... 4.65E-06 5.0E-06 2.0E-07 80 A/m 4.60E-06 4.5E-06 1.8E-07 k' 1 Hz 4.55E-06 pozzolana cement powder AC frequency- and amplitude-dependence 4.0E-06 1.6E-07 k' 3 Hz 4.50E-06 k' 10 Hz 3.5E-06 1.4E-07 k' 32 Hz 4.45E-06 k' 100 Hz 1.2E-07 χ 3.0E-06 " [m k' 317 Hz /kg]
3 pozzolana cement powder 4.40E-06 /kg] k' 997 Hz 3 300 K 2.5E-06 1.0E-07 3 /kg]
[m AC frequency- and temperature- k'' 1 Hz χ 4.35E-06 k' 16 A/m ' [m dependence k'' 3 Hz χ 8.0E-08 k' 24 A/m 2.0E-06 k'' 10 Hz 4.30E-06 k' 80 A/m k'' 32 Hz 1.5E-06 6.0E-08 k' 159 A/m k'' 100 Hz 4.25E-06 k' 239 A/m 1.0E-06 4.0E-08 4.20E-06 5.0E-07 2.0E-08 4.15E-06 1 10 100 1000 0.0E+00 0.0E+00 0 50 100 150 200 250 300 frequency [Hz] Temperature [K] Fig 4. (a, left) Room-temperature frequency- and amplitude-dependence of ac susceptibility; the former is ~2.8% per decade, and the latter is
insignificant. (b, right) Temperature- and frequency-dependence (Hac=80 A/m). Paramagnetic susceptibility becomes significant only at the lowest temperatures. The strong frequency dependence above 30 K, and the quasi-linear increase in susceptibility with temperature, indicate a relatively broad distribution of SP grainsizes.
activation theories of Néel [1949] and samples are available in Sagnotti et al. 8.5E-05 Egli & Lowrie [2002] predict decreases [2003] and in this article. On request, of 6-11% per decade for SD assemblages. 8.0E-05 we will send you a solid 2x2x2-cm cube For this reason, one might also expect a of pozzolana cement, and/or a small vial 7.5E-05 similar dependence of χ on AF fre- a of uncured powder suitable for measure- quency. The Schoenstedt instrument at 7.0E-05 ment in various instruments. You can IRM operates at 397 Hz, and the DTech use these to compare the behavior of 6.5E-05 2G-inline at 137 Hz, nearly 3 times slower. For a /kg]
3 your magnetizing and measurement 2G-independent decay rate of 0.1 µT/half-cycle, each
[m 6.0E-05 other instruments to those of the previously- a χ 2G-CEREGE-inline instrument completes 500,000 cycles tested labs. We are particularly Schoenstedt-CEREGE 5.5E-05 during the decay from a peak of 100 mT, interested in further work illuminating Schoenstedt-IRM but the DTech takes a leisurely 61 5.0E-05 Dtech-IRM the intricate dependence of anhysteretic minutes to complete the process, whereas susceptibility on details of the magnetiz- 4.5E-05 the Schoenstedt speeds through in 21 ing process, and would like to see minutes. Ergo, kinetics should yield measurements made using a wide variety 4.0E-05 somewhat higher ARMs from the DTech, 0.1 1 10 100 1000 of approaches and instruments. decay rate [µT/half-cycle] for the same AC and DC fields. Interest- If you would like to receive a ingly, however, we find just the opposite, pozzolana cement specimen, send your µ Fig 5. Anhysteretic susceptibilities (100 mT AC, 50 T DC) despite careful calibration of AC and DC request to the IRM ([email protected]). In determined for a set of pozzolana cement samples in the MAG-NET fields. order to maximize distribution effi- interlab calibration study (solid symbols) and in subsequent Which brings us back to the idea of ciency, we would like to receive requests measurements at CEREGE (open symbols, black lines) and at IRM preconditioning. Because of differences no later than March 1, 2004, after which (gray). There is a trend of decreasing χ with increasing AF decay in ARM circuitry, the Schoenstedt and A we will begin sending the specimens. rate; for the magnetizers at IRM the average drop is about 4% per DTech instruments handle the DC field Please indicate whether you need a solid decade. In-line magnetizers, where the decay rate is governed by differently: in the former the DC field is cube or powder. field geometry and translation speed, produce systematically lower on during both the ramping up and The same material that holds ARMs. The differences between the IRM and CEREGE Schoenstedt ramping down of the AC field; in the together the ancient structures of the results may be due in part to the use of different specimens, and in latter the DC field is only switched on Eternal City can also help tie together part to the use of mu-metal shielding and DC coils at IRM, whereas after the peak AC amplitude has been the worldwide set of laboratories the CEREGE ARMs were imparted in the terrestrial field. reached, remaining on during the decay. working on rock- and mineral magne- It seems that the additional application of tism, and help ensure greater consis- the DC field during ramp-up in the tency of data, procedures and analyses. Schoenstedt may outweigh the kinetic systems is therefore not constant, but disadvantage of its higher frequency. ...pozzolana References and Information Sources changes with time, position and However this is not easy to test, since it continued from p. 9 amplitude; the in-line decay rates in Fig requires changing the way the instruments Brachfeld, S., 1999, Separation of geomag- 5 are averages, calculated by the method work. netic paleointensity and paleoclimate of Brachfeld [1999]. signals in sediments: examples from Dunlop and Yu [2003] have Further Interlab Comparisons and North America and Antarctica, Thesis observed experimentally that ARM Calibrations (Ph. D.), University of Minnesota. intensities diminish with increasing Previous interlaboratory calibration de Boer, C. B., and Dekkers, M. J., 1996, decay rate for SD and PSD assemblages, studies [Snowball et al., 1994; Sagnotti et Grain-size dependence of the rock but increase for MD grains, mimicking al., 2003] have been conducted as blind magnetic properties for a natural maghemite: Geophysical Research the dependence of TRM on cooling rate tests, with “expected” values unknown to Letters, v. 23, no. 20, p. 2815-2818. and grain size. The decrease is attributed the participants. Here we propose a more Dekkers, M. J., and Pietersen, H. S., 1992, to less complete equilibration with the open approach for follow-up studies. Magnetic properties of low-Ca fly ash: a 10 bias field at higher decay rates; thermal Detailed experimental data for these p. 255-9. Geophysical Journal International, v. Gomes, S., et al., 1999, Characterization of 132, p. 712-720. magnetite in silico-aluminous fly ash by Rosenbaum, J. G., 1993, Magnetic grain-size Volta, Alessandro SEM, TEM, XRD, magnetic susceptibil- variations through an ash-flow sheet: b. Feb 18, 1745, Como, Lombardy [Italy] ity, and Mössbauer spectroscopy: Cement influence on magnetic properties and d. March 5, 1827, Como and Concrete Research, v. 29, p. 1705- implications for cooling history: Journal 1711. of Geophysical Research B: Solid Earth, Alessandro Giuseppe Antonio Anastasio Volta is Hanesch, M., and Petersen, N., 1999, v. 98, p. 11,715–11,727. remembered for his 1775 development of the Magnetic properties of a recent Sagnotti, L., Rochette, P., Jackson, M., electrophorus, a device for generating static parabrown-earth from Southern Vadeboin, F., Dinares-Turell, J., and electricity, and especially for invention by 1800 Germany: Earth and Planetary Science Winkler, A., 2003, Inter-laboratory of the “voltaic pile,” the first electric battery. Letters, v. 169, no. 1-2, p. 85-97. calibration of low-field magnetic and Following the discovery by his friend Luigi Heider, F., Körner, U., and Bitschene, P., anhysteretic susceptibility measurements: Galvani of the effects of dissimilar metals in 1993, Volcanic ash particles as carriers of Physics of the Earth & Planetary contact with animal nerve tissue, it was contro- remanent magnetization in deep-sea Interiors, v. 138, no. 1, p. 25-38. sediments from the Kerguelen Plateau: Shcherbakov, V. P., Shcherbakova, V. V., versial whether the fundamental phenomenon Earth and Planetary Science Letters, v. Vinogradov, Y., and Heider, F., 2001, involved inherent animal electricity or metallic 118, p. 121-134. Thermal stability of pTRMs created from origins. In honor of Volta’s demonstration that Halgedahl, S. L., 1993, Experiments to different magnetic states: Physics of the electricity could be generated inorganically, the investigate the origin of anomalously Earth and Planetary Interiors, v. 126, no. unit of electrical potential was named for him in elevated unblocking temperatures: 1, p. 59-73. 1881. Volta was also the discoverer of methane Journal of Geophysical Research B: Snowball, I., C. Hunt, and B. Moskowitz, gas, which he isolated in 1778. Solid Earth, v. 98, p. 22,443–22,460. 1994, Initial inter-laboratory calibration Hower, J. C., et al., 1999, Petrology, effort: A lesson in trial and error?: IRM mineralogy, and chemsitry of magneti- Quarterly, v. 4, n. 1. cally-separated fly ash: Fuel, v. 78, p. Worm, H.-U., 1998, On the superparamag- 197-203. netic-stable single domain transition for rapid tool for Fe-assessment and a survey Néel, L., 1949, Théorie du traînage magnetite, and frequency dependence of for potentially hazardous elements: magnétique des ferromagnétiques en susceptibility: Geophysical Journal Materials Research Society Symposium grains fins avec applications aux terres International, v. 133, p. 201-206. Proceedings, v. 245, p. 37–47. cuites: Annales de Géophysique, v. 5, p. Yu, Y., Dunlop, D. J., and Ozdemir, O., 2002, Dunlop, D J, and Y. Yu, 2003, The depen- 99–136. Partial anhysteretic remanent magnetiza- dence of anhysteretic remanent Özdemir, Ö. 1990, High-temperature tion in magnetite. 2. Reciprocity: Journal magnetization on alternating field decay hysteresis and thermoremanence of of Geophysical Research, v. 107, no. rate: Fundamental origin and paleomag- single-domain maghemite: Physics of the B10, 2245, doi:10.1029/2001JB001269. netic applications: Eos Trans. AGU, Earth and Planetary Interiors, v. 65, p. 84(46), Fall Meet. Suppl., Abstract 125–136. http://www.geo.uu.nl/~magnet/MAGazine/ GP31A-06, 2003 Özdemir, Ö., and Banerjee, S. K., 1984, High Magazine.htm Egli, R., and Lowrie, W., 2002, Anhysteretic temperature stability of maghemite (γ- http://www.globalcolleges.com/spain/ remanent magnetization of fine magnetic Fe2O3): Geophysical Research Letters, v. aqueduct-merida.jpg particles: Journal of Geophysical 11, p. 161–164. http://www.chass.utoronto.ca/~wulfric/varia/ Research-Solid Earth, v. 108, no. B2, p. Pawse, A., Beske-Diehl, S., and Marshall, S. photos-fr/pont-du-gard1.jpg art. no. 2209. A., 1998, Use of magnetic hysteresis http://www.unf.edu/classes/freshmancore/ Evans, M. E., 1999, Magnetoclimatology: a properties and electron spin resonance core1images/pantheon.jpg test of the wind-vigour model using the spectroscopy for the identification of http://kevino.net/images/kevino.net/p-rome- 1980 Mount St. Helens ash: Earth and volcanic ash: a preliminary study: pantheon--2.jpg Planetary Science Letters, v. 172, no. 3,
New and Recent Visiting Vincent Chevrier, CEREGE, Weather- Fellows palaeoceanography and palaeoclimate. ing of iron rich phases in a Martian Donald Thieme, University of Georgia, atmosphere. 2003B Environmental magnetism of Jennifer Inwood, University of Sue Beske-Diehl, Michigan Tech Susquehanna Valley alluvium. Plymouth, Rock magnetic characteriza- University, Environmental signal in rock David Williamson, CEREGE, Magnetic tion of the carriers of stable, pre- magnetic properties of Lake Superior enhancement in volcanic ash soils from deformational magnetizations in a sediments. the tropics: glass dissolution, Tethyan ophiolite (Hatay, Turkey). Claire Carvallo, University of Toronto authigenesis of (ultra)fine iron oxides, or Adrian Muxworthy, University of at Mississauga, Characterization of N- wet deposition? Edinburgh, Understanding MD rema- type titanomaghemite in submarine basalt Yongjae Yu, Scripps Institution of nence: Viscous magnetization of MD from Koko seamount, and FORC Oceanography, Magnetic properties of magnetite and Assessing magnetostatic diagrams of submarine basalts and chromite. interactions between different mineral elongated SD natural samples. phases. Yongxiang Li, Lehigh University, Do 2004A Anne-Lise Salomé, Institut de Physique magnetic properties of sediments from Milagrosa Aldana, Universidad Simón du Globe de Paris (IPGP), Characteriza- White Lake, northwestern New Jersey, Bolívar, Identification of magnetic tion of magnetic mineralogy for sands/ indicate climate changes? authigenesis in drill-cuttings from rocks from La Martinique Island and for Stephanie Maes, University of Wiscon- Venezuelan oil fields. lacustrines sediments from Lebanon. sin-Madison, Separating complex Laurent Carporzen, Institut de Xixi Zhao, University of California anisotropies with high-field AMS: Physique du Globe de Paris (IPGP), Santa Cruz, Rock magnetic investigation Insizwa complex, South Africa. Superparamagnetic magnetite contribu- of serpentinized peridotite from the Robert Musgrave, Monash University, tion to the magnetic properties of Newfoundland Margin, ODP Leg 210. Rock-magnetic signature of the bacterial shocked rocks from the Vredefort response to gas hydrate: implications for Meteorite Crater. 11 The Institute for Rock Magnetism is press), or if you have any suggestions http://www.th.physik.uni-frankfurt.de/~jr/gif/phys/volta.jpg dedicated to providing state-of-the-art to improve the newsletter, please facilities and technical expertise free of notify the editor: charge to any interested researcher who Mike Jackson applies and is accepted as a Visiting Institute for Rock Magnetism Fellow. Short proposals are accepted University of Minnesota semi-annually in spring and fall for work 291 Shepherd Laboratories to be done in a 10-day period during the 100 Union Street S. E. following half year. Shorter, less formal Minneapolis, MN 55455-0128 visits are arranged on an individual basis phone: (612) 624-5274 through the Facilities Manager. fax: (612) 625-7502 The IRM staff consists of Subir e-mail: [email protected] Banerjee, Professor/Director; Bruce www.geo.umn.edu/orgs/irm/irm.html Moskowitz, Professor/Associate Director; Jim Marvin, Senior Scientist; Mike Jackson, Senior Scientist and Facility Manager, and Peat Sølheid, Scientist. I Funding for the IRM is provided by the National Science Foundation, the W. M. Keck Foundation, and the University of Minnesota. The IRM Quarterly is published four The U of M is committed to the policy times a year by the staff of the IRM. If that all people shall have equal access to you or someone you know would like to its programs, facilities, and employment be on our mailing list, if you have without regard to race, religion, color, VOLTA something you would like to contribute sex, national origin, handicap, age, (e.g., titles plus abstracts of papers in veteran status, or sexual orientation.
Collector’s Series #25
In the “Park of acqueducts” in Roma, where there are preserved some of the highest and longest ancient acqueducts, the most spectacular is this one, built under Caligola and Claudius (38-52 AD). (photo by Leonardo Sagnotti).
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