1
The Solid Phase of Marine Sediments
6
volume of the clay particles significantly as it
goes into or out of the clay structure. All in all,
hydration can vary the volume of a clay particle
by 95 %.
Kaolinite is the most important clay mineral of
the two-layer group, also referred to as the 7-Ångstrom clay minerals (Fig. 1.4), which consist of
interlinked tetrahedron-octahedron units. Illite
and the smectites which have the capacity to bind
water by swelling belong to the group of threelayered minerals, also referred to as 10-Ångstrom
clay minerals. They are made of a combination of
two tetrahedrally and one octahedrally coordinated sheets. Four-layer clay minerals, also known
as 14-Ångstrom clay minerals, arise whenever a further autonomous octahedral layer emerges between
the three-layered assemblies. This group comprises
the chlorites and an array of various composites.
Apart from these types of clay minerals, there
is a relatively large number of clay minerals that
possess a mixed-layered structure made up of a
composite of different basic structures. The result
is a sheet by sheet chemical mixture on the scale
of the crystallite. The most frequent mixed-layer
structure consists of a substitution of illite and
smectite layers.
relative
importance
idealized composition
Quarz
+++
SiO 2
Calcite
+
CaCO 3
Dolomite
+
(Ca,Mg)CO 3
Feldspars
Plagioclase
++
(Na,Ca)[Al(Si,Al)Si 2 O 8 ]
Orthoclase
++
K[AlSi 3 O 8 ]
Muscovite
++
KAl 2 [(AlSi 3 )O 10 ](OH) 2
C l a y m i n e r a l s
Kaolinite
+++
Al 2 Si 2 O 5 (OH) 4
Mica Group
e.g. Illite
+++
K 0.8-0.9 (Al,Fe,Mg) 2 (Si,Al) 4 O 10 (OH) 2
Chlorite Groupe
e.g. Chlorite s.s.
+++
(Mg 3-y Al 1 Fe y )Mg 3 (Si 4-x Al)O 10 (OH) 8
Smektite Groupe
e.g. Montmorillonite
+++
Na 0.33 (Al 1.67 Mg 0.33 )Si 4 O 10 (OH) 2 •nH 2 O
H e a v y m i n e r a l s , e. g.
Amphiboles
e.g. Hornblende
+
Ca 2 (Mg,Fe) 4 Al[Si 7 ,Al 22 ](OH) 2
Pyroxene
e.g. Augite
+
(Ca,Na)(Mg,Fe,Al)[(Si,Al) 2 O 6 ]
Magnetite
-
Fe 3 O 4
Ilmenite
-
FeTiO 3
Rutile
-
TiO 2
Zircon
-
ZrO 2
Tourmaline
-
(Na,Ca)(Mg,Fe,Al,Li) 3 Al 6 (BO 3 ) 3 Si 6 O 18 (OH) 4
Garnet
e.g. Grossular
-
Ca 3 Al 2 (SiO 4 ) 3
Table 1.1 Mineralogy and relative importance of main lithogeneous sediment components.
The Solid Phase of Marine Sediments
6
volume of the clay particles significantly as it
goes into or out of the clay structure. All in all,
hydration can vary the volume of a clay particle
by 95 %.
Kaolinite is the most important clay mineral of
the two-layer group, also referred to as the 7-Ångstrom clay minerals (Fig. 1.4), which consist of
interlinked tetrahedron-octahedron units. Illite
and the smectites which have the capacity to bind
water by swelling belong to the group of threelayered minerals, also referred to as 10-Ångstrom
clay minerals. They are made of a combination of
two tetrahedrally and one octahedrally coordinated sheets. Four-layer clay minerals, also known
as 14-Ångstrom clay minerals, arise whenever a further autonomous octahedral layer emerges between
the three-layered assemblies. This group comprises
the chlorites and an array of various composites.
Apart from these types of clay minerals, there
is a relatively large number of clay minerals that
possess a mixed-layered structure made up of a
composite of different basic structures. The result
is a sheet by sheet chemical mixture on the scale
of the crystallite. The most frequent mixed-layer
structure consists of a substitution of illite and
smectite layers.
relative
importance
idealized composition
Quarz
+++
SiO 2
Calcite
+
CaCO 3
Dolomite
+
(Ca,Mg)CO 3
Feldspars
Plagioclase
++
(Na,Ca)[Al(Si,Al)Si 2 O 8 ]
Orthoclase
++
K[AlSi 3 O 8 ]
Muscovite
++
KAl 2 [(AlSi 3 )O 10 ](OH) 2
C l a y m i n e r a l s
Kaolinite
+++
Al 2 Si 2 O 5 (OH) 4
Mica Group
e.g. Illite
+++
K 0.8-0.9 (Al,Fe,Mg) 2 (Si,Al) 4 O 10 (OH) 2
Chlorite Groupe
e.g. Chlorite s.s.
+++
(Mg 3-y Al 1 Fe y )Mg 3 (Si 4-x Al)O 10 (OH) 8
Smektite Groupe
e.g. Montmorillonite
+++
Na 0.33 (Al 1.67 Mg 0.33 )Si 4 O 10 (OH) 2 •nH 2 O
H e a v y m i n e r a l s , e. g.
Amphiboles
e.g. Hornblende
+
Ca 2 (Mg,Fe) 4 Al[Si 7 ,Al 22 ](OH) 2
Pyroxene
e.g. Augite
+
(Ca,Na)(Mg,Fe,Al)[(Si,Al) 2 O 6 ]
Magnetite
-
Fe 3 O 4
Ilmenite
-
FeTiO 3
Rutile
-
TiO 2
Zircon
-
ZrO 2
Tourmaline
-
(Na,Ca)(Mg,Fe,Al,Li) 3 Al 6 (BO 3 ) 3 Si 6 O 18 (OH) 4
Garnet
e.g. Grossular
-
Ca 3 Al 2 (SiO 4 ) 3
Table 1.1 Mineralogy and relative importance of main lithogeneous sediment components.