Rock-Magnetic Investigation of Basalts from the Southern Kerguelen Plateau (Leg 120)

Helder, Franz; Geiss, C. E.; Dunlop, David J.; Inokuchi, Hiroo

doi:10.2973/odp.proc.sr.120.127.1992

Cited by 3 publications

(3 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…is shown in all samples (Figure 2), which also suggests the presence of maghemite (e.g., Heider et al, 1992 and 3b), which corresponds to the Néel temperature of goethite (e.g., Bocquet and Kennedy, 1992;Özdemir and Dunlop, 1996). The intensity of the high coercivity component is higher at station 44 than the other stations (Figure 3c).…”

Section: Concentrations Of Total Organic Carbon (Toc) Andmentioning

confidence: 72%

“…Coercivity spectra are shown with respect to temperature for the 0-0.07 T, 0.07-0.3 T, and 0.3-2.5 T components. The Néel temperature of goethite at 120°C, the thermal decomposition of (titano-)maghemite at around 300-400°C, the Curie point of magnetite at 580°C, titanium-poor maghemite at 620°C (Heider et al, 1992), and the Néel temperature of hematite (Ht) at 675°C. the Verwey transition of magnetite (Verwey, 1939).…”

Section: Concentrations Of Total Organic Carbon (Toc) Andmentioning

confidence: 99%

See 1 more Smart Citation

Magnetic properties in nearshore marine sediments off southern Chile

Kawamura

Ishikawa

Kurasawa

2016

JAMSTEC Rep. Res. Dev.

View full text Add to dashboard Cite

In order to determine magnetic mineral distributions in nearshore marine sediments off southwestern Chile, chemical analysis of bottom waters and rock magnetic characterization of surface sediments were performed. The samples analyzed are terrigenous and calcareous sediments recovered with a multiple corer at five stations. Calcareous sediments occur at stations with highly dissolved oxygen catchment in the bottom waters. Concentration-dependent magnetic parameters of calcareous sediment samples show relatively low values, and their magnetic grain sizes are coarse. Higher values of concentration-dependent magnetic parameters are recognized, and fine grain magnetic minerals are distributed in silty and sandy clay sediments. Magnetic mineralogy of the sediment samples reflects not only lithology but also redox conditions in the overlying bottom waters. Thermo-magnetometry results suggest that magnetite (Fe 3 O 4), hematite (αFe 2 O 3), (titano)maghemite (γFe 2 O 3), and goethite (αFeOOH) are common in sediment samples at all stations. Higher coercivities and total organic carbon (TOC) values are also observed at oxic stations, suggesting the presence of goethite and (titano)maghemite. In general, higher TOC contents in sediments lead anoxic conditions due to organic matter decomposition, therefore goethite and (titano)maghemite are unstable. Despite higher TOC contents in this sediment sample, such magnetic minerals can present. This implies that the magnetic minerals are kept in oxic conditions.

show abstract

Section: Concentrations Of Total Organic Carbon (Toc) Andmentioning

confidence: 72%

Section: Concentrations Of Total Organic Carbon (Toc) Andmentioning

confidence: 99%

Magnetic properties in nearshore marine sediments off southern Chile

Kawamura

Ishikawa

Kurasawa

2016

JAMSTEC Rep. Res. Dev.

View full text Add to dashboard Cite

show abstract

“…Estas amostras representam um dique de granodiorito que também apresentou a componente B. Entretanto, os dados de mineralogia magnética mostram que o seu principal portador magnético é a maghemita, que se forma pela oxidação da magnetita em baixas temperaturas, sugerindo uma origem secundária para a magnetização destas rochas, adquirida em tempos mais recentes. Entretanto, estudos mostram que a oxidação de grãos de domínio simples de magnetita e titanomagnetita (portadores de MTR), produzindo maghemita ou titanomaghemita, geram uma magnetização remanescente química (MRQ) que permanece paralela a MTR inicial, portada pelo mineral de origem, não importando a direção do campo magnético que atua durante a oxidação (Heider & Dunlop, 1987;Özdemir & Dunlop, 1985;Johnson & Merrill, 1974;Heider et al, 1992). Segundo Johnson & Heider (1974), este paralelismo entre a MRQ e a MTR pode estar relacionado à anisotropia de forma que domina o crescimento da MRQ ou ainda a interações de troca positivas que ocorrem entre a magnetita e a maghemita durante a oxidação.…”

Section: )unclassified

Estudo Paleomagnético da Suíte Paleoproterozóica Colíder e Máficas Associadas, Sudoeste do Cráton Amazônico

Santos¹

View full text Add to dashboard Cite

_______________________________________________________ This work presents a paleomagnetic study perfomed on felsic volcanic rocks of the Colider Suite (5 oriented cores and 42 oriented hand samples, 12 sites), Flor da Serra and Guadalupe mafic rocks (75 oriented cores and 3 oriented hand samples, 11 sites). These units are situated in the northern Mato Grosso State (southwestern Amazonian Craton), close to the Alta Floresta, Colider, Terra Nova, and Matupá cities. The Colider Suite rocks have been dated by the U-Pb (zircon) method, and ages vary between 1.80 and 1.78 Ga. Radiometric determinations are not yet available for the Guadalupe Intrusive. Two very stable magnetization components were isolated after AF and thermal demagnetization: northern (southern) directions with moderate to steep downward (upward) inclinations (component B-Dm=187.4°, Im=50.9°, N=16 α95=11.3°, K=11.7) were isolated for most Colider Suite rocks and associated mafic rocks. Northern upward direction with moderate inclination (component A-Dm=356.5°, Im=47.6°, N=3, α95=15.8°, K=61.9) was found for the Guadalupe gabbro and other two mafic dikes. Rock magnetism experiments show that the magnetization is carried by hematite, which is probably primary in origin, in the felsic rocks. In the mafic rocks the main magnetic carrier is Ti-poor titanomagnetite in the PSD magnetic structure. Two paleomagnetic poles were determined for these components, which are located at 289.4°E,-65.4°N (α95=12.9°) (SC pole, Colider Suite) and 298.8°E, 50.4°N (α95=15.1°) (IG pole, Guadalupe Intrusive). An age of 1.780 ± 7 Ma is attributted to pole SC (quality factor Q=5), which is considered a key pole for the Amazon Craton. Paleogeographic reconstructions using Paleoproterozoic key poles suggest 65 xviii Sumário _______________________________________________________ Agradecimentos iii Resumo vi Abstract viii Lista de Figuras x Lista de Tabelas xvii Capitulo 1: Introdução Capitulo 2: Contexto Geológico 2.1. O conceito de Cráton 2.2. Aspecto Geológico do Cráton Amazônico 2.3. Contexto Geológico Regional 2.4. Geologia Local 2.4.1. Suíte Colíder 2.4.2. Intrusivas Máficas Guadalupe 2.4.3. Suíte Intrusiva Flor da Serra 2.4.4. Dados Geocronológicos 2.5. Localização da Área de Estudo 2.6. Análise Petrográfica

show abstract

Untitled

Muxworthy

Heider

2001

Studia Geophysica Et Geodaetica

View full text Add to dashboard Cite

Rock-Magnetic Investigation of Basalts from the Southern Kerguelen Plateau (Leg 120)

Cited by 3 publications

References 22 publications

Magnetic properties in nearshore marine sediments off southern Chile

Magnetic properties in nearshore marine sediments off southern Chile

Estudo Paleomagnético da Suíte Paleoproterozóica Colíder e Máficas Associadas, Sudoeste do Cráton Amazônico

Untitled

Contact Info

Product

Resources

About