MAGNETIC PROPERTIES OF WEAK-MAGNETIC MINERALS OF KRYVBASS IRON QUARTZITES

We present two hypotheses regarding the evolution of Holocene climate in the Northern Rocky Mountains that stem from a previously unpublished environmental magnetic record from Jones Lake, Montana. First, we link two distinct intervals of fining magnetic grain size (documented by an increasing ratio of anhysteretic to isothermal remanent magnetization) to the authigenic production of magnetic minerals in Jones Lake bottom waters. We propose that authigenesis in Jones Lake is limited by rates of groundwater recharge and ultimately regional hydroclimate. Second, at ~8.3 ka, magnetic grain size increases sharply, accompanied by a drop in concentration of magnetic minerals, suggesting a rapid termination of magnetic mineral authigenesis that is coeval with widespread effects of the 8.2 ka event in the North Atlantic. This association suggests a hydroclimatic response to the 8.2 ka event in the Northern Rockies that to our knowledge is not well documented. These preliminary hypotheses present compelling new ideas that we hope will both highlight the sensitivity of magnetic properties to record climate variability and attract more work by future research into aridity, hydrochemical response, and climate dynamics in the Northern Rockies.

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Magnetic Signatures on River Sediments and Agricultural Soils as Proxy Indicators of Anthropogenic-derived Pollution (Case Study: Cikijing River, Rancaekek, West Java)

Jurnal Penelitian Pendidikan IPA ◽

10.29303/jppipa.v7i3.697 ◽

2021 ◽

Vol 7 (3) ◽

pp. 381

Author(s):

Dini Fitriani ◽

Widya Utami ◽

Kartika Hajar Kirana ◽

Eleonora Agustine ◽

Siti Zulaikah

Keyword(s):

Magnetic Properties ◽

Magnetic Susceptibility ◽

Agricultural Soils ◽

River Sediments ◽

Paddy Fields ◽

Composition Analysis ◽

Magnetic Minerals ◽

West Java ◽

Anthropogenic Pollutants ◽

Magnetic Signatures

A number of activities occur around the Cikijing River in Rancaekek area, West Java, such as industrial and domestic activities. The various activities could decrease the quality of the river and surrounding environment due to anthropogenic pollutants that might be produced. Since the Cikijing River is also used as the source of irrigation, paddy fields around the river could be also be affected. The presence of pollutants in river sediments and agricultural soils over a long period could change their magnetic properties. Magnetic susceptibility of Cikijing River sediments and soils of the paddy fields in the surrounding have been examined considering that magnetic properties could represent environmental conditions. The results show that river sediments have magnetic susceptibility (cLF) in range of 356.2-456.3 (×10-8) m3kg-1, whereas soils samples have cLF varying from 94.1 to 347.1 (×10-8) m3kg-1, suggesting domination of ferrimagnetic minerals. The cFD (%) is <4% indicating the anthropogenic origin of magnetic minerals. Electron microscopy images show the imperfect octahedral and spherules shapes of magnetic grains that supports magnetic susceptibility analysis about the source of magnetic minerals. Elemental composition analysis reveals Fe and O’s content as main elements, including minor elements of Ca, Mg, Al. Si, Ti and Cr

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Standard magnetic properties in three mountain lakes of northern Iberia, ¿what is the influence of the major environmental processes?

10.5194/egusphere-egu2020-8417 ◽

2020 ◽

Author(s):

Belén Oliva-Urcia ◽

Ana Moreno ◽

Blas Valero-Garcés

Keyword(s):

Magnetic Properties ◽

Organic Matter ◽

Rock Magnetism ◽

Organic Matter Content ◽

Organic Content ◽

Matter Content ◽

Magnetic Minerals ◽

Magnetic Signal ◽

Subtle Change ◽

Catchment Areas

Paleoenvironmental reconstructions from three mountaineous lakes located in northern Iberia are compared and completed with classical magnetic analyses in order to detect the influence of different processes on the record and preservation of magnetic properties. The lakes are located in the Cantabrian Mountains, Enol Lake, and in the Pyrenees, the Marbor&#233; Lake and Basa de la Mora Lake and share a similar composition of their catchment areas, dominated by limestones. They present other different characteristics, such as in the organic matter content, being Enol the one with the highest organic carbon values. Redox indicator (Mn/Fe) is higher and more variable in Basa de la Mora Lake, whereas in Enol and Marbor&#233; Lakes steadily increases towards the top of the sequences. New and revisited results from sedimentary cores unravel the significance of the magnetic changes respect to the geochemical and sedimentological variations found in the geological record.The magnetic mineralogy present after analyses done in discrete samples (less than 500 mg) is magnetite in all samples, due to a sharp decrease at 120 K (Verwey crystallographic transition) and 580&#186;C (Curie temperature of magnetite) in the thermomagnetic curves performed in the MPMS and the Curie balance respectively. No indication of neither pyrrhotite (phase transition at 35 K) nor siderite is observed. The high temperature thermomagnetic analyses show the presence and creation of magnetite during heating, see an increasing of induced magnetization forming a broad peak above 450&#186;C in the heating curve. In addition, a subtle change in the induced magnetization is observed at around 300&#186;C. All analyses related with coercivity indicate the predominance of low coercitive minerals (&#8220;soft&#8221;) as magnetite is.The combination of geochemical, sedimentological and magnetic proxies suggest that in Enol Lake the magnetic signal may be dominated by the formation of new minerals in relation to redox processes favored by the higher presence of organic matter (6%organic content), whereas in Marbor&#233; Lake, the increase of the magnetic signal toward the top of the sequence seems related to the oxic environment and the preservation of magnetite, since this lake is ultra-oligotrophic. In Basa de la Mora Lake, the source rock seems to play a role in the magnetic signal of the sequence.These results indicate that diagenesis and changes in the redox conditions alter the concentration of magnetic minerals during the Late Pleistocene and Holocene and underlines their value as environmental and paleoclimate archives.AcknowledgementsFunding for this research was provided by the Spanish Inter-Ministry Commission of Science and Technology through MEDLANT (CGL2016-76215-R) and DINAMO 3 (Ref CGL2015-69160-R) projects and by the European Commission (EFA056/15 REPLIM). The Institute for Rock Magnetism (IRM), the Instrumentation and Facilities program of the National Science Foundation of the Earth Science Division and the University of Minnesota are acknowledged for supporting visits and the free use of the facilities at the IRM, together with the both easy-going and expert guidance from the IRM staff.

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Magnetic Properties of a Holocene Sediment Core from the Yeongsan Estuary, Southwest Korea: Implications for Diagenetic Effects and Availability as Paleoenvironmental Proxies

Frontiers in Earth Science ◽

10.3389/feart.2021.593332 ◽

2021 ◽

Vol 9 ◽

Author(s):

Hyeon–Seon Ahn ◽

Jaesoo Lim ◽

Sung Won Kim

Keyword(s):

Grain Size ◽

Magnetic Properties ◽

Magnetic Susceptibility ◽

South Korea ◽

Size Distribution ◽

Sea Level ◽

West Coast ◽

Magnetic Minerals ◽

The West ◽

Saturation Moment

The sensitivity of magnetic properties, which characterize the mineralogy, concentration, and grain size distribution of magnetic minerals, to environmental processes may provide useful information on paleoenvironmental changes in estuarine environments. Magnetic property studies of estuaries are less common than other environments and, due to the west coast of South Korea having an abundance of estuaries, it provides a good place to study these processes. In this study, we analyzed a variety of magnetic properties based on magnetic susceptibility, hysteresis parameters, progressive acquisition of isothermal remanent magnetization and first-order reversal curve data from a Holocene muddy sediment core recovered from the Yeongsan Estuary on the west coast of South Korea. We examined diagenetic effects on magnetic properties and tested their availability as proxies of paleoenvironmental change. The presence of generally low magnetic susceptibility, ubiquitous greigite-like authigenic magnetic component, and very fine magnetic particle occurrence suggested that the analyzed sediments had undergone considerable early diagenetic alteration. Electron microscopic observations of magnetic minerals support this suggestion. Our results confirm that the use of initial bulk susceptibility as a stand-alone environmental change proxy is not recommended unless it is supported by additional magnetic analyses. We recognized the existence of ferromagnetic-based variabilities related to something besides the adverse diagenetic effects, and have examined possible relationships with sea-level and major climate changes during the Holocene. The most remarkable finding of this study is the two distinct intervals with high values in magnetic coercivity (Bc), coercivity of remanence (Bcr), and ratio of remanent saturation moment to saturation moment (Mrs/Ms) that were well coincident with the respective abrupt decelerations in the rate of sea-level rise occurred at around 8.2 and 7 thousand years ago. It is then inferred that such condition with abrupt drop in sea-level rise rate would be favorable for the abrupt modification of grain size distribution toward more single-domain-like content. We modestly propose consideration of the Bc, Bcr, and Mrs/Ms variability as a potential indicator for the initiation/occurrence of sea-level stillstand/slowstand or highstand during the Holocence, at least at estuarine environments in and around the studied area.

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Magnetic properties and magnetic minerals morphology of orchards soils Batu Malang

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/311/1/012040 ◽

2019 ◽

Vol 311 ◽

pp. 012040 ◽

Cited By ~ 1

Author(s):

D S Haryati ◽

S Zulaikah ◽

Sunaryono ◽

N Y Daryanti

Keyword(s):

Magnetic Properties ◽

Magnetic Minerals

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Magnetic minerals and magnetic properties of the Siwalik Group sediments of the Karnali river section in Nepal

Earth Planets and Space ◽

10.1186/bf03351645 ◽

2000 ◽

Vol 52 (5) ◽

pp. 337-345 ◽

Cited By ~ 8

Author(s):

Pitambar Gautam ◽

Azumi Hosoi ◽

Kamal Raj Regmi ◽

Dharma Raj Khadka ◽

Yoshiki Fujiwara

Keyword(s):

Magnetic Properties ◽

River Section ◽

Magnetic Minerals ◽

Siwalik Group

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Effect of microwave pre-treatment on the magnetic properties of Ludwigite and its implications on magnetic separation

Metallurgical Research & Technology ◽

10.1051/metal/2018087 ◽

2018 ◽

Vol 116 (1) ◽

pp. 107 ◽

Cited By ~ 2

Author(s):

Yajing Liu ◽

Tao Jiang ◽

Chenhui Liu ◽

Weijun Huang ◽

Junpeng Wang ◽

...

Keyword(s):

Magnetic Properties ◽

Internal Stress ◽

Magnetic Separation ◽

Microwave Radiation ◽

Energy Demand ◽

Active Material ◽

Microwave Treatment ◽

Iron Recovery ◽

Magnetic Minerals ◽

Iron Concentrate

To improve magnetic separation and recovery for Ludwigite, the influences of microwave radiation on the heating characteristics, microstructure, magnetic properties and the magnetic separation of Ludwigite are investigated. The magnetizations of untreated and microwave-treated samples with various microwave powers are analyzed using vibrating sample magnetometer. It is found that magnetite is an active material, while ascharite and serpentine are inactive materials. The heating rate of magnetite is faster than those of ascharite and serpentine, resulting in temperature gradient and internal stress among different components in Ludwigite. The effect of microwave power on the internal stress for mineral phases is positive. The internal stress significantly induces intergranular fractures and facilitates mineral liberation. After microwave treatment from 0 to 4 kW exposed for 40 s, serpentine is dissociated and the crystallinity of magnetite is increased, which leads to the saturation magnetization of samples increasing from 12.39 to 24.51 emu/g. Compared with untreated ore, the energy demand for microwave-treated Ludwigite is only about 0.44 kWh/kg, the grade of iron concentrate of microwave-treated Ludwigite increases from 48.56% to 58.06% and iron recovery increases from 69.44% to 96.35%, respectively. It can be concluded that microwave radiation has a positive effect on magnetic properties of Ludwigite and is conducive to magnetic separation from non-magnetic minerals with low energy consumption, thereby obtaining high iron recovery.

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Magnetic Mineralogy of Speleothems From Tropical-Subtropical Sites of South America

Frontiers in Earth Science ◽

10.3389/feart.2021.634482 ◽

2021 ◽

Vol 9 ◽

Author(s):

Plinio Jaqueto ◽

Ricardo I. F. Trindade ◽

Joshua M. Feinberg ◽

Janine Carmo ◽

Valdir F. Novello ◽

...

Keyword(s):

Magnetic Properties ◽

South America ◽

Remanent Magnetization ◽

Drainage Basin ◽

Environmental Magnetism ◽

Rank Correlation ◽

Natural Remanent Magnetization ◽

Magnetic Minerals ◽

Magnetic Mineralogy ◽

Diverse Range

Fe-bearing minerals are a tiny fraction of the composition of speleothems. They have their origin in the karst system or are transported from the drainage basin into the cave. Recent studies on the magnetism of speleothems focused on the variations of their magnetic mineralogy in specific time intervals and are usually limited to a single sample. In this study, we describe a database of environmental magnetism parameters built from 22 stalagmites from different caves located in Brazil (South America) at different latitudes, comprising different climates and biomes. The magnetic signal observed in these stalagmites is dominated by low-coercivity minerals (∼20 mT) whose magnetic properties resemble those of the magnetite formed in pedogenic environments. Also, a comparison with few samples from soils and the carbonate from cave’s walls shows a good agreement of the magnetic properties of speleothems with those of soil samples, reinforcing previous suggestions that in (sub-)tropical regimes, the dominant magnetic phase in speleothems is associated with the soil above the cave. Spearman’s rank correlation points to a positive strong correlation between magnetic concentration parameters (mass-normalized magnetic susceptibility, natural remanent magnetization, anhysteretic remanent magnetization, and isothermal remanent magnetization). This implies that ultrafine ferrimagnetic minerals are the dominant phase in these (sub-)tropical karst systems, which extend across a diverse range of biomes. Although the samples are concentrated in the savannah biome (Cerrado) (∼70%), comparison with other biomes shows a higher concentration of magnetic minerals in speleothem underlying savannahs and lower concentration in those underlying moist broadleaf forests (Atlantic and Amazon biome) and dry forests (Caatinga). Thus, rainfall, biome, and epikarst dynamics play an important role in the concentration of magnetic minerals in speleothems in (sub-)tropical sites and indicate they can be an important target for paleoenvironmental research in cave systems.

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Some magnetic properties of Athabasca Oil Sand samples, Alberta, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e84-030 ◽

1984 ◽

Vol 21 (3) ◽

pp. 278-283 ◽

Cited By ~ 6

Author(s):

Brooks B. Ellwood ◽

S. George Pemberton

Keyword(s):

Magnetic Properties ◽

Remanent Magnetization ◽

Magnetic Measurements ◽

Magnetic Fabric ◽

Oil Sand ◽

Magnetic Minerals ◽

Remanent Magnetism ◽

Sand Core ◽

Bitumen Content ◽

High Concentrations

A number of induced and remanent magnetic measurements have been performed on 55 cubic samples, each 8 cm3, from a single segment of Athabasca Oil Sand core. Samples are representative of four major lithofacies types, which have been classified in the following manner: facies A—laminated, bitumen-free sediments; facies B—bioturbated (laminae are biologically disrupted to some degree), bitumen-free sediments; facies C—bioturbated sediments with moderate bitumen content; and facies D—massive sand, bitumen-rich sediments. Samples of facies D are divided into subfacies D1 and D2, based upon extremely high percentage values of anisotropy of magnetic susceptibility (AMS) observed for D2 samples. Magnetic fabric ranges progressively from undisturbed in samples of facies A to anomalous, considered highly disturbed, for samples of facies D2. Only samples of facies D record a stable remanent magnetization and, since the magnetic fabric is anomalous, it is inferred that the remanent magnetism may also be anomalous. It is concluded that zone D2 may result from locally high concentrations of authigenic magnetic minerals such as maghemite or siderite. Such D2 zones may prove to be useful stratigraphic markers in bitumen-saturated samples in which sedimentary structures are usually obscure.

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Rock magnetic properties, magnetic susceptibility, and organic geochemistry comparison in core LZ1029-7 Lake El'gygytgyn, Far Eastern Russia

Climate of the Past Discussions ◽

10.5194/cpd-8-4565-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 4565-4599 ◽

Cited By ~ 4

Author(s):

K. J. Murdock ◽

K. M. Wilkie ◽

L. L. Brown

Keyword(s):

Magnetic Properties ◽

Magnetic Susceptibility ◽

Organic Carbon ◽

Magnetic Measurements ◽

Organic Geochemistry ◽

Magnetic Minerals ◽

Rock Magnetic Properties ◽

Anoxic Environments ◽

Lake El’Gygytgyn ◽

Order Of Magnitude

Abstract. Susceptibility measurements performed on initial short (3–16 m) cores taken from Lake El'gygytgyn exhibited a large range in values. This observation led to the suggestion of widespread magnetite dissolution within the sediments due to anoxic conditions within the lake. Rock magnetic properties and their comparison with magnetic susceptibility, Total Organic Carbon (TOC), and bulk δ13Corg proxies in core LZ1029-7 provide an insight into the character of the magnetic minerals present within the lake and can further the understanding of processes that may be present in the newer long core sediments Susceptibility measurements (χ) of discrete samples corroborate the two order of magnitude difference seen in previous continuous susceptibility measurements (κ), correlating high values with interglacial periods and low values with glacial intervals. Hysteresis parameters defined the majority of the magnetic material to be magnetite of PSD size. TOC values increase while δ13Corg values decrease in one section of LZ1029-7, which is defined as the Last Glacial Maximum (LGM), and help confine the age of the core to approximately 62 kyr. Increases in TOC during the most recent glacial interval suggest increased preservation of organic carbon during these times High TOC and low magnetic susceptibility during the LGM support the theory of perennial ice cover during glacial periods, which would lead to lake stratification and therefore anoxic bottom water conditions. Low temperature magnetic measurements also confirmed the presence of magnetite, but also indicated titanomagnetite, siderite and/or rhodochrosite, and vivianite were present. The latter three minerals are found only in anoxic environments, and further support the notion of magnetite dissolution.

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