scholarly journals ARCHAEOMAGNETIC STUDIES IN KILNS FROM N. GREECE

2017 ◽  
Vol 43 (4) ◽  
pp. 1888 ◽  
Author(s):  
E. Aidona ◽  
D. Kondopoulou ◽  
M. Alexandrou ◽  
N. Ioannidis
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Archaeological Sites ◽  
Isothermal Remanent Magnetization ◽  
Thermomagnetic Analysis ◽  
Intensity Measurements ◽  
Magnetic Carriers ◽  
Characteristic Component

Archaeomagnetism combines the magnetic properties of baked materials with Archaeology. The archaeomagnetic method can be applied to any kind of permanent - in situ or displaced- burnt structures, such as kilns, ovens, hearths, burnt floors, tiles, bricks and pottery fragments, the latter for intensity measurements only. In this study we present the latest archaeomagnetic results from archaeological sites which are distributed in N. Greece (Polymylos, Sani, Thesssaloniki). The Natural Remanent Magnetization (NRM) and the magnetic susceptibility of the samples have been initially measured. The samples have been subjected to magnetic cleaning (AF and Thermal demagnetizations) and this procedure revealed the characteristic component of the ancient magnetic field. Rock magnetic experiments such as acquisition of the Isothermal Remanent Magnetization (IRM) and thermomagnetic analysis have been performed in pilot samples in order to identify the main magnetic carriers. Finally the secular variation curves for Greece and the SCHA.DIF.3K model were used in order to date these archaeological structures. This dating improved or modified the estimated archaeological ages.

Evidence of Single-Domain Magnetite in the Michikamau Anorthosite

1971 ◽  
Vol 8 (3) ◽  
pp. 361-370 ◽  
Author(s):  
G. S. Murthy ◽  
M. E. Evans ◽  
D. I. Gough
Keyword(s):  
Remanent Magnetization ◽  
Theoretical Models ◽  
Natural Remanent Magnetization ◽  
Single Domain ◽  
Isothermal Remanent Magnetization ◽  
Mineral Separation ◽  
Domain Configuration ◽  
Plagioclase Felspar ◽  
Magnetite Particles ◽  
Theoretical Evidence

The Michikamau anorthosite possesses very stable natural remanent magnetization, some of which resists alternating fields up to 1800 Oe. The rock contains two types of opaque grains, fine opaque needles of order 10 × 0.5 μ in the plagioclase felspar, and large equidimensional magnetite particles. Ore microscope studies suggest, but do not establish, that the needles are composed of magnetite. Saturation isothermal remanence and thermal demagnetization studies indicate magnetite as the carrier of remanent magnetization. In order to distinguish the effects of the large grains from those of the needles, mineral separation was used to show that an artificial specimen of essentially pure plagioclase had very similar isothermal remanent magnetization properties to the whole rock. Both indicated magnetite as the magnetic mineral. Thermoremanent properties of the separated mineral fractions indicated magnetite as the dominant magnetic constituent but showed some evidence of laboratory-produced hematite. Theoretical models of grains elongated along [111] and [110] axes are used to show that magnetite needles can exist in stable single-domain configuration in the size and shape ranges of the needles observed in the Michikamau anorthosite. There is thus considerable experimental and theoretical evidence for the conclusion that the stable remanent magnetization of the Michikamau anorthosite is carried by fine single–domain needles of magnetite in the plagioclase felspar.

Direct determination of the natural remanent magnetization effect in a hole drilled in layered ground from magnetic field and susceptibility logs

Geophysics ◽  
1992 ◽  
Vol 57 (7) ◽  
pp. 872-884 ◽  
Author(s):  
Guy Desvignes ◽  
Véronique Barthes ◽  
Alain Tabbagh
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Direct Determination ◽  
Theoretical Models ◽  
Natural Remanent Magnetization ◽  
Case Examples ◽  
Joint Interpretation ◽  
The Fourier Transform ◽  
Layered Ground

A new method as presented, allows the joint interpretation of both electromagnetic (EM) and magnetic logs in layered ground, based on the fact that the susceptibility responses for these two measurements are linear. Thus we can make use of the classical properties of the Fourier transform to extract from these two signals the magnetic field due to remanent magnetization. Theoretical models show that for a sufficient sample step this remanent magnetization can be recovered, even if the Koenigsberger ratio is of the order of 0.2 and if the thickness of the magnetized layer is of the order of 1 m. The results for two case examples in a sedimentary context are also shown. Despite the difficulties due to experimental procedures, we show that the amplitude of the extracted information is significant in these two cases, even if its variations are somewhat structureless and cannot be easily explained by the geology.

Magnetic characteristics of Luna 16 and 20 samples

1977 ◽  
Vol 284 (1319) ◽  
pp. 151-156 ◽  
Keyword(s):  
Grain Size ◽  
Iron Content ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Magnetic Behaviour ◽  
Heavy Fraction ◽  
Magnetic Characteristics ◽  
Iron Particles ◽  
Isothermal Remanent Magnetization ◽  
Rock Fragments

The natural remanent magnetization of rock fragments L2015,3,1 and L2015,3,11 was found to be < 3.5 x 10 -7 and < 40 x 10 -6 G cm 3 g -1 respectively. The former sample, from isothermal remanent magnetization (i.r.m.) measurements, contained very little iron, while the latter sample had a much higher iron content and exhibited i.r.m. characteristics similar to breccia samples from Apollo missions. Susceptibility and i.r.m. measurements have shown that Luna 16 fines contain about four times as much iron as Luna 20 samples and that the light fractions from the density separations contain about twice as much iron as the heavy fraction. Like the Apollo fines, the magnetic behaviour of Luna 16 and 20 fines is dominated by small iron particles, most of which are superparamagnetic and of grain size less than about 13 nm.

Paleomagnetism of the Keweenawan Chipman Lake and Seabrook Lake carbonatite complexes, Ontario

1992 ◽  
Vol 29 (6) ◽  
pp. 1215-1223 ◽  
Author(s):  
D. T. A. Symons
Keyword(s):  
Magnetic Field ◽  
Remanent Magnetization ◽  
Pole Position ◽  
Alteration Zone ◽  
Contact Aureole ◽  
Isothermal Remanent Magnetization ◽  
Abitibi Subprovince ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Host Rocks

The Chipman Lake complex crops out as a series of carbonatite and related alkalic mafic dikes in the Wabigoon Subprovince of the Superior Province, whereas the Seabrook Lake complex crops out as an alkalic syenite – carbonatite stock in the Abitibi Subprovince. Paleomagnetic analysis was done on specimens from 23 and 19 sites located in and around the Chipman Lake and Seabrook Lake complexes, respectively, using detailed alternating-field and thermal step demagnetization and isothermal remanent magnetization tests. Contact tests with adjacent Archean host rocks show that both complexes retain a primary characteristic remanence (ChRM). The Chipman Lake's ChRM is retained in 11 dikes with normal polarity and one dike with reversed polarity and at one site with normal polarity and one site with reversed polarity from the fenite alteration zone. Its ChRM gives a pole position at 186°E, 38°N (dp = 7°, dm = 11°), which corresponds to a Keweenawan age of 1098 ± 10 Ma, suggesting that younger K–Ar amphibole ages do not date emplacement. The ChRM of the host rock, the Chipman Lake diorite stock, gives a pole at 49°E, 51°N (dp = 8°, dm = 13°), showing that it is not part of the Keweenawan complex but may be a 2.45 Ga Matachewan intrusive. The Seabrook Lake complex's ChRM is found at six normal polarity sites from within the complex and at four normal and three reversed polarity sites from within the fenitized Archean granite and Matachewan diabase of the contact aureole. It gives a pole position at 180°E, 46°N (dp = 11°, dm = 17°), which corresponds to a Keweenawan age of 1103 ± 10 Ma, agreeing with K/Ar biotite ages. The paleomagnetic data indicate that no significant motion on the Kapuskasing Structural Zone occurred after emplacement of the complexes excluding minor vertical uplift of less than about 4 km, and that there were multiple polarity transitions of a symmetric Earth's magnetic field during Keweenawan time.

scholarly journals Application of the pseudo-Thellier technique to a paleomagnetic record from lake El Trébol (Patagonia, Argentina)

2008 ◽  
Vol 47 (4) ◽  
pp. 319-327
Author(s):  
C. S. G. Gogorza ◽  
S. Torcida ◽  
A. M. Sinito ◽  
M. A. E. Chaparro
Keyword(s):  
Magnetic Susceptibility ◽  
Error Estimates ◽  
Sediment Core ◽  
Standard Method ◽  
Remanent Magnetization ◽  
Reasonable Agreement ◽  
Natural Remanent Magnetization ◽  
Isothermal Remanent Magnetization ◽  
Low Field ◽  
Relative Paleointensity

The pseudo-Thellier technique was applied to obtain relative paleointensity determinations using a sediment core from Lake El Tre?bol (Patagonia, Argentina). Measurements of intensity of natural remanent magnetization left (NRMleft) after AF demagnetization versus intensity of anhysteric remanent magnetization gained (ARMgained) at the same peak were carried out on a set of samples. Two versions of a jackknife resampling scheme were used to get error estimates on the paleointensity. The pseudo-Thellier paleointensity records were compared with the authors previous results where the remanent magne- tization at 20mT (NRM20mT) has been normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the satu- ration of the isothermal remanent magnetization at 20mT (SIRM20mT) and the low field magnetic susceptibility (k) (Gogorza et al., 2006). The pseudo-Thellier record shows a reasonable agreement with the standard method of normalization (NRM20mT/ ARM20mT).

Preliminary absolute paleointensity estimation from a single volcanic-glass grain extracted from an unwelded pyroclastic flow

2020 ◽  
Author(s):  
Yuhji Yamamoto ◽  
Hiromi Takeda ◽  
Masahiko Sato ◽  
Hiroshi Kawabata
Keyword(s):  
Pyroclastic Flow ◽  
Remanent Magnetization ◽  
Volcanic Glass ◽  
Volcanic Eruptions ◽  
Natural Remanent Magnetization ◽  
Primary Component ◽  
Pyroclastic Flows ◽  
Isothermal Remanent Magnetization ◽  
Inflection Points ◽  
Stable Characteristic

&lt;p&gt;Many pyroclastic flows are distributed around Japan. They usually involve volcanic-glass grains. These grains are considered to form at the timing of volcanic eruptions and are expected to have magnetic inclusions consisting of tiny single (titano)magnetites with recording the paleomagnetic field. We have extracted single volcanic-glass grains of pumice-type with a diameter of 0.60-0.84 mm from an unwelded part of the Ito pyroclastic flow deposits (A-Ito, 26-29 ka; Machida and Arai, 2003), Kyusyu, Japan. A series of rock- and paleomagnetic measurements have been made on the grains.&lt;/p&gt;&lt;p&gt;Sixty-seven out of 88 grains had detectable intensities of natural remanent magnetization. Some of such grains were further investigated. Results of low-temperature magnetometry exhibited inflection points at 105-120 K, suggesting magnetite as a main remenence carrier. Stepwise alternating field demagnetization revealed an existence of stable characteristic remanence (ChRM) which was interpreted to be a primary component.&amp;#160;&lt;/p&gt;&lt;p&gt;Tsunakawa-Shaw method (Tsunakawa and Shaw, 1994; Yamamoto et al., 2003), one of the latest absolute paleointensity (API) techniques to date, was applied to selected grains having stable ChRMs. On the application we newly included measurements related to an isothermal remanent magnetization (IRM). Four successful results were obtained by an adoption of IRM corrections, giving an average API value of about 25 &amp;#956;T. This corresponds to a virtual axial dipole moment (VADM) of about 50 ZAm&lt;sup&gt;2&lt;/sup&gt;, which is consistent with the contemporaneous VADM of the sedimentary record (PISO-1500; Channell et al., 2009).&amp;#160;&lt;/p&gt;

IN‐SITU DETERMINATION OF THE REMANENT MAGNETIC VECTOR OF TWO‐DIMENSIONAL TABULAR BODIES

Geophysics ◽  
1966 ◽  
Vol 31 (5) ◽  
pp. 949-962 ◽  
Author(s):  
H. P. Ross ◽  
P. M. Lavin
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Potential Fields ◽  
Small Samples ◽  
Magnetic Survey ◽  
Two Dimensional ◽  
Magnetic Vector ◽  
Gravity And Magnetic

Recent studies have shown that many rocks of the earth’s crust have a substantial component of remanent magnetization. Extensive sampling is required to determine adequately the remanent vector from small samples. A field technique has been developed (and tested on model data) for the in‐situ determination of the resultant (induced+remanent) magnetic vector of bulk volumes of rock, using a combined analysis of the gravity and magnetic fields of a disturbing body (Poisson’s Theorem). The potential fields are sampled adequately at a limited expenditure of time and effort in the field by utilizing the geometry of two‐dimensional bodies. The major limitation to the analysis is the removal of regional gradients and the estimation of the base levels of anomalies. Combined gravity and magnetic surveys were conducted over six diabase bodies in the Triassic Basin of Pennsylvania. The results of these surveys indicate a resultant direction of magnetization given approximately by: declination 2° W, inclination 41 degrees below the horizon. The corresponding direction of natural remanent magnetization has a declination of 1° W and an inclination of 28 degrees. The ratio of remanent to induced magnetization for the diabase is approximately two. These results have been used to provide a better interpretation of magnetic survey data over a magnetite deposit in the Triassic Basin.

Magnetic Properties of Coring Samples from Aceh Basin West Off Sumatera Island

2014 ◽  
Vol 896 ◽  
pp. 434-439
Author(s):  
Eddy Z. Gaffar
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Magnetic Polarity ◽  
Isothermal Remanent Magnetization ◽  
Reverse Polarity ◽  
Geologic Time ◽  
The Third ◽  
Geologic Time Scale ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Three oriented core samples was taken by Japanese MIRAI Research Vessel in Aceh Basin west of the Sumatera Island. 927 small box samples from 3 coring samples was measure. Core bottom ages of three cores are in the last glacial maximum (around 19 kyBP). We measured Natural Remanent Magnetization (NRM), NRM after Alternating Field Demagnetization up to 800 Oe. Measurement of NRM have done by 2G Enterprice Squid, Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization (ARM) on Paleomagnetic Laboratory of Geological Survey of Japan. Result of NRM after Alternating Field Demagnetization shows that there are reverse polarizaty magnetizations. This reverse polarity seems not usual since in Geologic Time Scale 1989 showed that the first reversal polarity was between Brunches Normal Epoch and Jaramillo Epoch beginning at 0.75 Ma There are some possibility of reverse polarity events contained in the three cores mentioned above. The first possibility is the result of the tsunami so that the sediment that settles on the Aceh Basin was a sediment that remain turbid flows that enable magnetic recording on magnetic sediment did not follow directions when he formed so that it seems a polarity reverse polarity when only superficial. The second possibility is indeed occurs under reverse polarity at age 700.000 years. Research in Argentina, South America show that between 11 thousand to two thousand years ago there was an excursion from the magnetic polarity produces some reverse polarity at the time (Nami, 1999). The third possibility was circular variation magnetic.

Viscosité magnétique potentielle, aimantation détritique et viscosité réelle d'un sédiment lacustre quaternaire

1987 ◽  
Vol 24 (9) ◽  
pp. 1903-1912 ◽  
Author(s):  
Daniel Biquand ◽  
François Sémah
Keyword(s):  
Remanent Magnetization ◽  
Rock Magnetism ◽  
Viscosity Index ◽  
Natural Remanent Magnetization ◽  
Blocking Temperature ◽  
Magnetic Viscosity ◽  
Paleomagnetic Study ◽  
Temperature Spectra

The magnetic viscosity of sediments, as indicated by thermal demagnetization of natural remanent magnetization (NRM), depends on two main parameters: (i) the specific magnetic viscosity of the material and (ii) the efficiency of the primary magnetization process. In an attempt to determine the relative importance of these two variables, we studied a Lower Pleistocene lacustrine sequence bearing a primary reversed detrital remanent magnetization (DRM).Using natural samples and small cores made of crushed sediment, our study is based on the thermodynamic theory of rock magnetism developed by L. Néel, who established an equivalence between time and temperature, that is, between viscous remanent (VRM) and thermoremanent (TRM) magnetization processes. The determination of the blocking temperature spectra from 20 to 152 °C allows us to calculate the maximum theoretical VRM acquired in situ at each horizon, while the detailed thermal study of the NRM permits an appraisal of the DRM quality. This leads us to define a geological viscosity index, which accounts, in a rather convincing manner, for the behaviour of the samples observed during the classical paleomagnetic study. For the section studied, it appears that the variations of this index are closely correlated with the efficiency of the DRM acquisition process.

THERMOMAGNETIC ANALYSIS AND ORE GENESIS

1967 ◽  
Vol 4 (6) ◽  
pp. 1119-1125
Author(s):  
E. J. Schwarz
Keyword(s):  
Remanent Magnetization ◽  
Rock Magnetism ◽  
Thermal Conditions ◽  
Natural Remanent Magnetization ◽  
Ore Deposits ◽  
Ore Genesis ◽  
Thermomagnetic Analysis ◽  
Stable Part ◽  
Physical Changes ◽  
Genesis Of Ore Deposits

The potential of rock magnetism in studies on the genesis of ore deposits is examined. It is suggested that techniques based on magnetic properties other than the direction of the stable part of the natural remanent magnetization might prove usefully applicable. More specifically the analysis of the type of remanent magnetization in ores and their wall rocks is suggested as a worthwhile approach in the study of ore genesis. Other methods suggested are based on the occurrence of chemical or physical changes affecting ferromagnetic minerals in ores during heating. It may be possible to relate the results of such experiments to the thermal conditions prevailing at the time of either formation of minerals in ore deposits or acquisition of stable remanent magnetization.

Sign in / Sign up

Export Citation Format

Share Document