580
Frederichs et al.
1.0
0.16...,-------,--1-----'
•
• Maher 1988
•
• Hartstra 1982a, b
0.12 •
0.8
~ o
(f)' 0.6
';2'"
-- 0.08
' "
';2
•
••
•
•
0.4
0.04
0.00 +----.---r"T"T"T"TTIr---....,.-,rrTTT'TT--r-T""r ...... -.,.,j10
100
0.01
0.1
10
(a)
% Magnetite
(b)
Grain-Size [J.lm]
Fi g. 4. ( a) S -0.3 T index for mixtures of hematite and different grain -sized magnetite (Bloemendal et al. 1992). (b)
Magnetite grain-size dependence of the Mar/Msir ratio (anhysteretic remanent magnetization to isothermal
saturation remanent magnetization).
as small SD particles have higher remanences.
Ferrimagnetic minerals are largely saturated in
fields of about 0.3 T, while antiferromagnetic minerals need several Tesla to reach Mrs' Hard isothermal remanent magnetization
Mhir = 0.5· (Msir + M-03T)
relates to high-coercive remanences encompassing primarily the concentration of antiferrornagnetic
minerals (Stoner et al. 1996). Only SD and small
PSD particles acquire a significant anhysteretic
remanent magnetization (Banerjee 1981) and are
therefore quantified by Mar'
Mineralogy Dependent Parameters
The ratio Knf IK estimates the contribution of paramagnetically bound iron and diamagnetic compounds to susceptibility separating distinctly different depositional regimes.
The ratio of high- (hematite, goethitc) to lowcoercive «titano-)magnetite) mineral concentrations is expressed as
S-03T = 0.5· (I + M-03T /Msir)
varying non-linearly from 0 to 1 (Fig. 4a). Because
of much lower specific magnetizations S-03T
allows a reliable assessment of relative antiferromagnetic mineral concentrations only if their fraction exceeds about 80% (Bloemendal ct al. 1992).
Coercivity Parameters
Be is a measure of bulk magnetic stability (coercivity) and particularly sensitivc to grain-size and
magnetomineralogy. Other than the following three
parameters, Be is affected by (super-)paramagnetic
and diamagnetic components.
Bcr quantifies the coercivity of remanence
carrying particles.
B 1I2 (M ar ) and B 1I2 (M ir ) selectivity for mineralogy and grain-size is equivalent to that of Mar
and M ir .
Grain-Size Sensitive Parameters
The ratios Mrs IMs and Bcr/Bc depend on the
dominant (titano-)magnetite domain state and therefore grain-size (Wasilewski 1973). With decreasing grain-size Mrs/M s varies between about 0.01
and 0.5, Bcr IBc between about 10 and 1 (> 1 0 if a
considerable SP fraction is present). Both parameters are commonly combined in a diagram (Fig. 5;
Day et al. 1977).
Due to the predominant contribution of small
PSD/SD particies to anhysteretic remanent mag-
Frederichs et al.
1.0
0.16...,-------,--1-----'
•
• Maher 1988
•
• Hartstra 1982a, b
0.12 •
0.8
~ o
(f)' 0.6
';2'"
-- 0.08
' "
';2
•
••
•
•
0.4
0.04
0.00 +----.---r"T"T"T"TTIr---....,.-,rrTTT'TT--r-T""r ...... -.,.,j10
100
0.01
0.1
10
(a)
% Magnetite
(b)
Grain-Size [J.lm]
Fi g. 4. ( a) S -0.3 T index for mixtures of hematite and different grain -sized magnetite (Bloemendal et al. 1992). (b)
Magnetite grain-size dependence of the Mar/Msir ratio (anhysteretic remanent magnetization to isothermal
saturation remanent magnetization).
as small SD particles have higher remanences.
Ferrimagnetic minerals are largely saturated in
fields of about 0.3 T, while antiferromagnetic minerals need several Tesla to reach Mrs' Hard isothermal remanent magnetization
Mhir = 0.5· (Msir + M-03T)
relates to high-coercive remanences encompassing primarily the concentration of antiferrornagnetic
minerals (Stoner et al. 1996). Only SD and small
PSD particles acquire a significant anhysteretic
remanent magnetization (Banerjee 1981) and are
therefore quantified by Mar'
Mineralogy Dependent Parameters
The ratio Knf IK estimates the contribution of paramagnetically bound iron and diamagnetic compounds to susceptibility separating distinctly different depositional regimes.
The ratio of high- (hematite, goethitc) to lowcoercive «titano-)magnetite) mineral concentrations is expressed as
S-03T = 0.5· (I + M-03T /Msir)
varying non-linearly from 0 to 1 (Fig. 4a). Because
of much lower specific magnetizations S-03T
allows a reliable assessment of relative antiferromagnetic mineral concentrations only if their fraction exceeds about 80% (Bloemendal ct al. 1992).
Coercivity Parameters
Be is a measure of bulk magnetic stability (coercivity) and particularly sensitivc to grain-size and
magnetomineralogy. Other than the following three
parameters, Be is affected by (super-)paramagnetic
and diamagnetic components.
Bcr quantifies the coercivity of remanence
carrying particles.
B 1I2 (M ar ) and B 1I2 (M ir ) selectivity for mineralogy and grain-size is equivalent to that of Mar
and M ir .
Grain-Size Sensitive Parameters
The ratios Mrs IMs and Bcr/Bc depend on the
dominant (titano-)magnetite domain state and therefore grain-size (Wasilewski 1973). With decreasing grain-size Mrs/M s varies between about 0.01
and 0.5, Bcr IBc between about 10 and 1 (> 1 0 if a
considerable SP fraction is present). Both parameters are commonly combined in a diagram (Fig. 5;
Day et al. 1977).
Due to the predominant contribution of small
PSD/SD particies to anhysteretic remanent mag-