Depth trends in magnetic properties in an area of prolonged cold seawater drawdown in uppermost Troodos-type oceanic crust

1987 ◽  
Vol 24 (5) ◽  
pp. 941-952 ◽  
Author(s):  
James M. Hall ◽  
Charles Walls ◽  
Mark Williamson ◽  
Bing-Xi Wang
Keyword(s):  
Magnetic Properties ◽  
Low Temperature ◽  
Curie Temperature ◽  
Sedimentary Cover ◽  
Drill Core ◽  
Secondary Minerals ◽  
Troodos Ophiolite ◽  
Core Section ◽  
Discontinuous Nature ◽  
Magnetization Behaviour

Study of the oxide minerals and measurements of the magnetic properties of about 100 samples distributed over a 475 m continuous drill-core section from the uppermost part of an extrusive sequence of the Troodos, Cyprus, ophiolite close to 35°02′N, 33°11′E, in the vicinity of Malounda, yields the following principal results: (1) Low-temperature alteration is intense to a depth of 260 m, below which it is relatively much subdued. (2) Saturation magnetization, natural remanence intensity, and initial susceptibility all increase continuously with depth throughout the section. (3) Curie temperature decreases with depth to 260 m, below which a change in the style of the thermal decay of magnetization behaviour takes place. (4) Pillowed and massive flows differ in their magnetic properties.The results are consistent with the downwards decrease in low-temperature alteration also noted by K. Gillis from the distribution of secondary minerals. The downwards variations in magnetic properties closely follow in both sense and magnitude the trends observed in DSDP hole 417A, where marked downwards decrease in low-temperature alteration also occurs. This comparison and the discontinuous nature of the lower units of the Troodos sedimentary cover in the vicinity of hole CY-1 support the interpretation of the upper, reddened facies of the Troodos extrusive sequence as being due to prolonged drawdown of cold seawater and suggest that the magnetization of at least the upper part of the Troodos ophiolite is a reliable guide to ocean crust magnetization.

scholarly journals Magnetic Properties of Layered Heisenberg Ferromagnets

1993 ◽  
Vol 46 (4) ◽  
pp. 571 ◽  
Author(s):  
A Du ◽  
GZ Wei
Keyword(s):  
Magnetic Properties ◽  
Low Temperature ◽  
Curie Temperature ◽  
Temperature Region ◽  
Asymptotic Form ◽  
Interlayer Coupling ◽  
Arbitrary Spin ◽  
Spin Fluctuations ◽  
Asymptotic Expressions ◽  
Double Time

The double-time-temperature spin Green's function method is used to study the magnetic properties of layered ferromagnets with arbitrary spin S, within Tyablikov's decoupling approximation. According to the extent to which interlayer coupling suppresses twodimensional spin fluctuations, we divide the low-temperature region into two new ones, and give the asymptotic expressions for magnetisation and susceptibility over different temperature regions, including the low-temperature region, the vicinity of the Curie temperature and the high-temperature region. We also give the Curie temperature in an asymptotic form when inter layer coupling is weak.

Magnetic Nanostructures Fabricated by Electrochemical Synthesis

2007 ◽  
Vol 121-123 ◽  
pp. 839-842 ◽  
Author(s):  
K. Keshoju ◽  
X. Gu ◽  
A.T. Kumar ◽  
L. Sun
Keyword(s):  
Thin Film ◽  
Magnetic Properties ◽  
Low Temperature ◽  
Curie Temperature ◽  
Magnetic Nanostructures ◽  
Cost Effective ◽  
Remnant Magnetization ◽  
Saturation Field ◽  
Alloy Electrodeposition ◽  
Nanoporous Structures

Electrochemical processing is a cost effective and low-temperature approach suitable for the fabrication of certain unique nanostructures that are difficult to obtain by other methods. Here we report on the synthesis of nanowires and nanoporous structures with the intention to control the magnetic properties of conventional materials. Nanowires with variable sizes (diameter 15 nm - microns, and length up to 100 microns) have been fabricated by template assisted electrodeposition. Utilizing a combined alloy electrodeposition and electrochemical dealloying approach, porous nanostructures with controlled pore size and porosity have also been synthesized. Magnetization, Curie temperature, coercivity, saturation field, and remnant magnetization of these magnetic nanostructures exhibit much wider tunibility compared to bulk and thin film samples.

Low-temperature metamorphism and secondary components in the Portage Lake Volcanics: a reassessment

1993 ◽  
Vol 30 (7) ◽  
pp. 1404-1414 ◽  
Author(s):  
Huiling Li ◽  
S. Beske-Diehl
Keyword(s):  
Magnetic Properties ◽  
Hydrothermal Alteration ◽  
Remanent Magnetization ◽  
Drill Core ◽  
Upper Peninsula ◽  
The Core ◽  
Time Period ◽  
Core Section ◽  
Order Of Magnitude ◽  
A Minor

We studied the effects of hydrothermal alteration on magnetic properties of the magnetite and hematite components in the 1.1 Ga Portage Lake Volcanics, Upper Peninsula, Michigan. Results show the importance of the intensity and direction of the hematite magnetization in the detection of secondary magnetite overprints in basalts. We collected samples from 20 flows in two stratigraphic sections, one from outcrops and the other from drill core. The remanence unblocked below 590 °C during thermal demagnetization is considered to be due to magnetite, and that unblocked between 610–690 °C is considered to be due to hematite. Hematite remanent intensities in the flow interiors are an order of magnitude less intense than those of magnetite, and correlate with magnetite intensities from the top of the volcanics to the lower prehnite–pumpellyite zone (5.5 km depth) in the outcrop section and to the epidote–pumpellyite zone (7.0 km depth) in the core section. These magnetic properties are very similar to those of Recent Icelandic basalt flows. Below these depths, magnetite intensities decrease until they are equal to hematite intensities. Hematite remanent intensities do not consistently increase with depth, suggesting that secondary hematite produced during hydrothermal alteration is a minor contributor to hematite intensities. The magnetite directions become distinct from the hematite directions in the prehnite–pumpellyite zone (6.2 km depth). This difference in directions indicates an unresolved secondary overprint formed during hydrothermal alteration. We conclude that the magnetite component carries a secondary overprint; a conclusion that contrasts with that of a previous study. Thermo-viscous remanent magnetization obtained over a time period of 1–10 Ma near 300 °C would be enough to account for much of the secondary component.

scholarly journals Influence of non-magnetic Cu on enhancing the low temperature magnetic properties and Curie temperature of FeCoNiCrCu(x) high entropy alloys

2020 ◽  
Vol 182 ◽  
pp. 99-103 ◽  
Author(s):  
Varun Chaudhary ◽  
Vishal Soni ◽  
Bharat Gwalani ◽  
R.V. Ramanujan ◽  
Rajarshi Banerjee
Keyword(s):  
Magnetic Properties ◽  
Low Temperature ◽  
Curie Temperature ◽  
High Entropy Alloys ◽  
High Entropy

Tracing the SW border of the Svecofennian Domain in the Baltic Sea region: evidence from petrology and geochronology from a granodioritic migmatite

2021 ◽  
Author(s):  
Evgenia Salin ◽  
Jeremy Woodard ◽  
Krister Sundblad
Keyword(s):  
Baltic Sea ◽  
Short Distance ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
Drill Core ◽  
The Baltic Sea ◽  
Baltic Sea Region ◽  
Drill Site ◽  
Southwestern Margin ◽  
The Baltic

AbstractGeological investigations of a part of the crystalline basement in the Baltic Sea have been performed on a drill core collected from the depth of 1092–1093 m beneath the Phanerozoic sedimentary cover offshore the Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with the SIMS U–Pb zircon method. Inherited zircon cores from this migmatized granodioritic orthogneiss have an age of 1854 ± 15 Ma. Its chemical composition and age are correlated with the oldest generation of granitoids of the Transscandinavian Igneous Belt (TIB), which occur along the southwestern margin of the Svecofennian Domain in the Fennoscandian Shield and beneath the Phanerozoic sedimentary cover on southern Gotland and in northwestern Lithuania. It is suggested that the southwestern border of the Svecofennian Domain is located at a short distance to the SW of the investigated drill site. The majority of the zircon population shows that migmatization occurred at 1812 ± 5 Ma, with possible evidence of disturbance during the Sveconorwegian orogeny.

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