Paleomagnetism of the middle Cretaceous Iritono granite in the Abukuma region, northeast Japan

Wakabayashi, K.; Tsunakawa, Hideo; Mochizuki, Nobutatsu; Yamamoto, Yuhji; Takigami, Yutaka

doi:10.1016/j.tecto.2006.04.013

Cited by 16 publications

(17 citation statements)

References 32 publications

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“…Mean palaeomagnetic direction for Cretaceous granites of the Abukuma Terrane ( D = 313.5°, I = 54.6°, α 95 = 6.3° and N = 20) is calculated by combining the here presented 12 sites with eight others reported by Ito & Tokieda (1986). This mean is concordant with secondary palaeomagnetic direction ( D = 311.5°, I = 42.8°, α 95 = 3.3° and N = 9) reported by Wakabayahsi et al (2006) from the Cretaceous Iritono granite of the same terrane. Based on these directional similarities, it is suggested that the Cretaceous granite of the Abukuma Terrane was probably subjected to pervasive remagnetization.…”

Section: Discussionsupporting

confidence: 78%

New age constraints on counter-clockwise rotation of NE Japan

Baba¹,

Matsuda

Itaya

et al. 2007

Geophysical Journal International

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S U M M A R YThe Miocene basaltic-andesitic lavas and Cretaceous granites were sampled in the Abukuma Terrane of northeast Honshu for geochronological and palaeomagnetic investigations to determine precise timing of counter-clockwise rotation of NE Japan. Characteristic component with unblocking temperature of 560-590 • C is isolated from 26 sites of the Takadate and Ryozen Formations and 12 sites of the Cretaceous granites. Concordant northwesterly palaeomagnetic directions (D = 265 • -331 • ) are observed in the Cretaceous granites of the Abukuma Terrane. The Cretaceous mean-palaeomagnetic direction from this terrane (D = 313.5 • , I = 54.6 • , α 95 = 6.3 • and N = 20) is almost identical to Oligo-Miocene (33-20 Ma) palaeomagnetic direction reported from the Japan Sea side of NE Japan as well as to the Cretaceous palaeomagnetic direction reported from the Kitakami Terrane. This type of behaviour clearly suggests that the Abukuma Terrane underwent a coherent counter-clockwise rotation as a part of NE Japan after 20 Ma. Conventional potassium (K)-Argon (Ar) dating method performed on the plagioclase grains revealed distinctive ages of 14.44 ± 0.88 and 16.52 ± 0.82 Ma for the Takadate Formation (11 sites) and the Ryozen Formation (eight sites), respectively. This type of behaviour indicates that two independent episodes of volcanic activities were probably responsible for the production of igneous rocks in the Takadate and Ryozen areas. Northerly declination is obtained from the Takadate Formation (D = 355.3 • , I = 39.4 • , α 95 = 11.6 • ), while slightly westerly deflected declination appears in the Ryozen Formation (D = 333.5 • , I = 58.0 • and α 95 = 9.6 • ). The here presented results, therefore, suggest that the province of NE Japan was still experiencing a counter-clockwise rotation at 16.5 Ma, however by 14.4 Ma the rotational motion has completely ceased. Compared with the available palaeomagnetic and geochronological data from SW Japan, rotational motion in both provinces of NE and SE Japan has already been ceased by 14 Ma. Thus any additional evidence regarding the complete cessation of rotational motions in NE Japan will provide a key to understand the timing of opening in the Japan Sea.

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Section: Discussionsupporting

confidence: 78%

New age constraints on counter-clockwise rotation of NE Japan

Baba¹,

Matsuda

Itaya

et al. 2007

Geophysical Journal International

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“…Peaks for quartz, plagioclase feldspar, and magnetite are also recognized. The presence of these minerals in magnetic extracts is likely to be due to the presence of magnetite inclusions [e.g., Wu et al , 1974; Wakabayashi et al , 2006; Tarduno , 2007]. Greigite peaks expected at 52.40° and 47.87° are not obvious.…”

Section: Resultsmentioning

confidence: 99%

Diagenetic alteration of magnetic minerals in Labrador Sea sediments (IODP Sites U1305, U1306, and U1307)

Kawamura¹,

Ishikawa²,

Torii³

2012

Geochem Geophys Geosyst

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In order to reveal the potential effects of early diagenesis on magnetic minerals in deep‐sea sediments, we studied early diagenetic zones and magnetic mineral characteristics of Lower Pliocene hemipelagic sediment samples from IODP Sites U1305, U1306, and U1307 on Eirik Drift, Labrador Sea. All samples analyzed were unlithified silty clay sediments recovered by a piston corer from depths down to 200 meters composite depth (mcd). Based on shipboard interstitial‐water geochemistry, we divided the sediment column from each site into six early diagenetic zones. Magnetite (Fe3O4) was present at all analyzed depths, whereas maghemite (γFe2O3) was found only above the iron reduction zone. We attribute this to associated changes in interstitial redox conditions, which induced preferential dissolution of maghemitized surfaces on magnetite grains. Mineral magnetic results indicate a general down‐hole change in mean grain size of magnetic minerals. At Site U1307, which has relatively low organic carbon contents, the diagenetic zones occur at greater depths than at the other studies sites. This suggests that interstitial oxygen levels at this site remained high enough to degrade organic matter through oxic bacterial activity, and that detrital magnetic minerals have been preserved even at depth.

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“…Preservation of magnetic mineral inclusions in marine sediments is not surprising. Silicate minerals that host magnetic mineral inclusions occur widely in igneous rocks [e.g., Evans et al, 1968;Evans and Wayman, 1970;Haggerty, 1991;Feinberg et al, 2006;Wakabayashi et al, 2006], so it is to be expected that such particles will occur as detrital grains in sedimentary strata. However, magnetite is a mixed valence iron oxide mineral that is unstable in both oxidizing and reducing sedimentary environments [Roberts, 2015].…”

Section: Widespread Occurrence Of Silicate-hosted Magnetic Inclusionsmentioning

confidence: 99%

Widespread occurrence of silicate‐hosted magnetic mineral inclusions in marine sediments and their contribution to paleomagnetic recording

et al. 2016

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Magnetic mineral inclusions occur commonly within other larger mineral phases in igneous rocks and have been demonstrated to preserve important paleomagnetic signals. While the usefulness of magnetic inclusions in igneous rocks has been explored extensively, their presence in sediments has only been speculated upon. The contribution of magnetic inclusions to the magnetization of sediments, therefore, has been elusive. In this study, we use transmission electron microscope (TEM) and magnetic methods to demonstrate the widespread preservation of silicate‐hosted magnetic inclusions in marine sedimentary settings. TEM analysis reveals detailed information about the microstructure, chemical composition, grain size, and spatial arrangement of nanoscale magnetic mineral inclusions within larger silicate particles. Our results confirm the expectation that silicate minerals can protect magnetic mineral inclusions from sulfate‐reducing diagenesis and increase significantly the preservation potential of iron oxides in inclusions. Magnetic inclusions should, therefore, be considered as a potentially important source of fine‐grained magnetic mineral assemblages and represent a missing link in a wide range of sedimentary paleomagnetic and environmental magnetic studies. In addition, we present depositional remanent magnetization (DRM) modeling results to assess the paleomagnetic recording capability of magnetic inclusions. Our simulation demonstrates that deposition of larger silicate particles with magnetic inclusions will be controlled by gravitational and hydrodynamic forces rather than by geomagnetic torques. Thus, even though these large silicates may contain ideal single‐domain particles, they cannot contribute meaningfully to paleomagnetic recording. However, smaller (e.g., silt‐ and clay‐sized) silicates with unidirectionally magnetized magnetic inclusions can potentially record a reliable DRM.

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Paleomagnetism of the middle Cretaceous Iritono granite in the Abukuma region, northeast Japan

Cited by 16 publications

References 32 publications

New age constraints on counter-clockwise rotation of NE Japan

New age constraints on counter-clockwise rotation of NE Japan

Diagenetic alteration of magnetic minerals in Labrador Sea sediments (IODP Sites U1305, U1306, and U1307)

Widespread occurrence of silicate‐hosted magnetic mineral inclusions in marine sediments and their contribution to paleomagnetic recording

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