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.

Hydrothermal Sr contamination of the Dippin sill, Isle of Arran, Western Scotland

1984 ◽  
Vol 48 (348) ◽  
pp. 311-322 ◽  
Author(s):  
A. P. Dickin ◽  
C. M. B. Henderson ◽  
F. G. F. Gibb
Keyword(s):  
Stable Isotope ◽  
Hydrothermal Alteration ◽  
Closed System ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Drill Core ◽  
Sr Isotope ◽  
Core Section ◽  
High Silica ◽  
Isotope Measurements

Abstract The Dippin sill, which is emplaced into the Triassic sediments of SE Arran, is an alkaline basic sheet which displays pronounced hydrothermal alteration. The 40-m-thick sill has suffered pervasive contamination with radiogenic Sr, introduced from the Triassic sediments by hydrothermal fluids. Stable isotope measurements suggest that fluids were of meteoric origin, but were restricted to a small closed-system circulation. Initial 87Sr/86Sr ratios in the sill were raised from an original value of 0.7032 to a maximum of 0.7091, contamination being especially pronounced near the contacts at Dippin Head itself (localities 12 and 14) and in a drill core section through the sill above Dippin. Hydrothermal Sr was incorporated into an early-formed high-CaO, high-Sr analcime, which replaced unstable high-silica nepheline in interstitial patches. However, this high-CaO analcime, along with plagioclase, was later replaced by a low-CaO, low-Sr analcime, allowing Sr leaching from the margins of the sill. Hydrothermal fluids are thought to have migrated up to 1 km laterally, up the dip of the sill, mainly via tension joints forming in the cooling intrusion. Pooling of hot fluids at the upper end of the sill probably raised water/rock ratios in this region and allowed greater Sr contamination during mineralogical alteration. The undersaturated mineralogy of the sill accounts for its pervasive hydrothermal Sr contamination, which contrasts markedly with the relatively undisturbed Sr isotope compositions of Hebridean granites involved in hydrothermal systems.

Magnetic Properties of the Cylindrical Ising Nanowire: A Monte Carlo Simulation Study

SPIN ◽  
2017 ◽  
Vol 07 (04) ◽  
pp. 1750011 ◽  
Author(s):  
A. Jabar ◽  
R. Masrour ◽  
M. Hamedoun ◽  
A. Benyoussef
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Magnetic Properties ◽  
Crystal Field ◽  
Remanent Magnetization ◽  
Hysteresis Loops ◽  
Core Shell ◽  
Monte Carlo Simulation Study ◽  
The Core ◽  
Magnetic Nanowire

A cylindrical ferrimagnetic magnetic nanowire system of core and shell layers has been investigated using Monte Carlo simulation. Critical temperature is obtained for different values of exchange couplings at the core–shell interface, at shell–shell and core–core. The total magnetization has been the determinate for different values of crystal field. Hysteresis loop, coercive field and remanent magnetization of a core and shell layers are obtained using the Monte Carlo simulation. A number of characteristic behaviors are found, such as the occurrence of single and triple hysteresis loops for appropriate values of crystal field, temperatures values and exchange interaction values.

scholarly journals Atmospheric CO2 Concentration During the Last Glaciation

1984 ◽  
Vol 5 ◽  
pp. 160-164 ◽  
Author(s):  
B. Stauffer ◽  
H. Hofer ◽  
H. Oeschger ◽  
J. Schwander ◽  
U. Siegenthaler
Keyword(s):  
Ice Core ◽  
Co2 Concentration ◽  
Temporal Variations ◽  
Air Bubbles ◽  
The Core ◽  
Last Glaciation ◽  
Time Period ◽  
Core Section ◽  
Glacier Ice ◽  
Short Time

Analyses of atmospheric air extracted from air bubbles in polar glacier ice provide a measure of past CO2concentrations and their temporal variations. Earlier measurements have shown that the atmospheric CO2concentration was significantly lower during the late Wisconsin stage and that the change from low to high CO2concentration occurred in a relatively short time period.We measured the CO2concentration of ice samples from the deep ice core recently drilled at Dye 3 (south Greenland). The core section investigated represents ice from about 40 to 30 ka BP. The air extracted from the ice samples shows large variations of CO2concentration which are correlated with δ18O values of the ice samples. A probable explanation of the results is that corresponding changes of the atmospheric CO2concentration occurred during that glacial period. These changes could have had a significant influence on the climate. Possible reasons for the variations of the atmospheric CO2concentration are discussed.

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 Atmospheric CO2 Concentration During the Last Glaciation

1984 ◽  
Vol 5 ◽  
pp. 160-164 ◽  
Author(s):  
B. Stauffer ◽  
H. Hofer ◽  
H. Oeschger ◽  
J. Schwander ◽  
U. Siegenthaler
Keyword(s):  
Ice Core ◽  
Co2 Concentration ◽  
Temporal Variations ◽  
Air Bubbles ◽  
The Core ◽  
Last Glaciation ◽  
Time Period ◽  
Core Section ◽  
Glacier Ice ◽  
Short Time

Analyses of atmospheric air extracted from air bubbles in polar glacier ice provide a measure of past CO2 concentrations and their temporal variations. Earlier measurements have shown that the atmospheric CO2 concentration was significantly lower during the late Wisconsin stage and that the change from low to high CO2 concentration occurred in a relatively short time period.We measured the CO2 concentration of ice samples from the deep ice core recently drilled at Dye 3 (south Greenland). The core section investigated represents ice from about 40 to 30 ka BP. The air extracted from the ice samples shows large variations of CO2 concentration which are correlated with δ18O values of the ice samples. A probable explanation of the results is that corresponding changes of the atmospheric CO2 concentration occurred during that glacial period. These changes could have had a significant influence on the climate. Possible reasons for the variations of the atmospheric CO2 concentration are discussed.

The Mid-Atlantic Ridge near 45° N. XIII. Magnetic properties of basalt bore-core

1970 ◽  
Vol 7 (6) ◽  
pp. 1515-1527 ◽  
Author(s):  
J. Brooke ◽  
E. Irving ◽  
J. K. Park
Keyword(s):  
Magnetic Properties ◽  
Coercive Force ◽  
Physical Properties ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
The Core ◽  
Mid Atlantic Ridge ◽  
Technical Interest

Three bore-cores containing basalts have been obtained from the Mid-Atlantic Ridge at 45° N. The material is fresh and ideal for the study of physical properties. The drilling record and the nature of the core itself suggest that much of the basalt is from detached boulders, although one core may be in situ. In one core, variations in coercivity by a factor 2 occur within a distance of 5 cm. The coercive force spectra of anhysteretic and natural remanent magnetization are similar, but there are small differences due to secondary components which are used to predict correctly the polarity of 11 out of 12 specimens studied. This result may be of technical interest only since there is no guarantee that the material is in situ.

Magnetic Properties of Fe3O4/CoFe2O4 Composite Nanoparticles with Core/Shell Architecture

2020 ◽  
Vol 65 (10) ◽  
pp. 904
Author(s):  
V. O. Zamorskyi ◽  
Ya. M. Lytvynenko ◽  
A. M. Pogorily ◽  
A. I. Tovstolytkin ◽  
S. O. Solopan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Spinel Ferrite ◽  
Composite Nanoparticles ◽  
Core Shell ◽  
Cofe2o4 Nanoparticles ◽  
Core Diameter ◽  
The Core ◽  
Shell Particles ◽  
Interface Parameters ◽  
Shell Composite

Magnetic properties of the sets of Fe3O4(core)/CoFe2O4(shell) composite nanoparticles with a core diameter of about 6.3 nm and various shell thicknesses (0, 1.0, and 2.5 nm), as well as the mixtures of Fe3O4 and CoFe2O4 nanoparticles taken in the ratios corresponding to the core/shell material contents in the former case, have been studied. The results of magnetic research showed that the coating of magnetic nanoparticles with a shell gives rise to the appearance of two simultaneous effects: the modification of the core/shell interface parameters and the parameter change in both the nanoparticle’s core and shell themselves. As a result, the core/shell particles acquire new characteristics that are inherent neither to Fe3O4 nor to CoFe2O4. The obtained results open the way to the optimization and adaptation of the parameters of the core/shell spinel-ferrite-based nanoparticles for their application in various technological and biomedical domains.

Investigation of the Structure and Magnetic Properties of Bulk Amorphous FeCoYB Alloy

2017 ◽  
Vol 68 (9) ◽  
pp. 2162-2165 ◽  
Author(s):  
Katarzyna Bloch ◽  
Mihail Aurel Titu ◽  
Andrei Victor Sandu
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Hyperfine Field ◽  
Irreversible Processes ◽  
Magnetization Process ◽  
Casting Method ◽  
The Core ◽  
Injection Casting ◽  
Core Losses ◽  
Microstructural Studies

The paper presents the results of structural and microstructural studies for the bulk Fe65Co10Y5B20 and Fe63Co10Y7B20 alloys. All the rods obtained by the injection casting method were fully amorphous. It was found on the basis of analysis of distribution of hyperfine field induction that the samples of Fe65Co10Y5B20 alloy are characterised with greater atomic packing density. Addition of Y to the bulk amorphous Fe65Co10Y5B20 alloy leads to the decrease of the average induction of hyperfine field value. In a strong magnetic field (i.e. greater than 0.4HC), during the magnetization process of the alloys, where irreversible processes take place, the core losses associated with magnetization and de-magnetization were investigated.

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