The lower part toward the basaltic substrate has a red color, due to the high iron
content (Vonderhaar et al. 2000) (Fig. 4.13a). The uppermost 4 mm of the crust has
been analyzed in detail. A plane vertical cross section through the crust displays a
clear hierarchical structuring (Fig. 4.13c and d). Parallel to the surface of the crust,
layers of stacked piles are orderly arranged, which are composed of individual
convex units. The width of the stacked piles is approximately 250 mm. HR-SEM
displays that these convex structures appear as wavelike growth lines with borders
that are approximately 250 mm apart (Wang et al. 2009a). The axis of the convex
orientation parallels the surface of the crust (Fig. 4.13c to e).
4.5.3 Growth
Crusts are made from two major building blocks, the negatively charged Mn
oxyhydroxides that bind to hydrated cations (e.g., Ca, Ni, Zn, Pb, etc.) and the
slightly positively charged Fe hydroxides that complex anions (V, As, P, Zr, etc.)
(Halbach et al. 1981; Halbach 1986). Deposition occurs in the mixing zone between
the upper oxygen-minimum zone [OMZ] and the lower oxygen-rich bottom zone
[ORZ] (Koschinsky and Halbach 1995; Koschinsky et al. 1997). The cold oxygenrich Antarctic Bottom Water is richer in reduced Mn(II) species than layers under
the OMZ and contains the oxidized forms of Mn(IV) (Bruland et al. 1994;
Koschinsky and Halbach 1995). In the mixing layer ORZ/OMZ, the crusts are
formed from Mn- and Fe oxyhydroxides/hydroxides via a colloidal state
(Koschinsky and Halbach 1995; Bau et al. 1996; Koschinsky and Hein 2003);
Fig. 4.14.
4.5.4 Coccolithophores
In the photic zone of the oceans, a series calcificating organisms exist, e.g.,
coccolithophores, foraminifera, pteropods, and calcareous dinophytes; however,
most of them dissolve close to their production zone (100 m), while only the
coccolithophores reach the deeper zones of the ocean where the crusts are formed
(Hay 2004). The presence of coccolithophores in crusts had been described by
Cowen et al. (1993). By application of HR-SEM and EDX, those organisms were
demonstrated as candidate bio-seed particles in Co-rich crusts from the Magellan
seamounts (Wang and M€ uller 2009). In those deposits, abundantly fossil individual
coccolith-plates, shed from single-celled coccolithophores have been detected,
that frequently are arranged to coccospheres (Fig. 4.15a–c). It is remarkable
98
X. Wang et al.
content (Vonderhaar et al. 2000) (Fig. 4.13a). The uppermost 4 mm of the crust has
been analyzed in detail. A plane vertical cross section through the crust displays a
clear hierarchical structuring (Fig. 4.13c and d). Parallel to the surface of the crust,
layers of stacked piles are orderly arranged, which are composed of individual
convex units. The width of the stacked piles is approximately 250 mm. HR-SEM
displays that these convex structures appear as wavelike growth lines with borders
that are approximately 250 mm apart (Wang et al. 2009a). The axis of the convex
orientation parallels the surface of the crust (Fig. 4.13c to e).
4.5.3 Growth
Crusts are made from two major building blocks, the negatively charged Mn
oxyhydroxides that bind to hydrated cations (e.g., Ca, Ni, Zn, Pb, etc.) and the
slightly positively charged Fe hydroxides that complex anions (V, As, P, Zr, etc.)
(Halbach et al. 1981; Halbach 1986). Deposition occurs in the mixing zone between
the upper oxygen-minimum zone [OMZ] and the lower oxygen-rich bottom zone
[ORZ] (Koschinsky and Halbach 1995; Koschinsky et al. 1997). The cold oxygenrich Antarctic Bottom Water is richer in reduced Mn(II) species than layers under
the OMZ and contains the oxidized forms of Mn(IV) (Bruland et al. 1994;
Koschinsky and Halbach 1995). In the mixing layer ORZ/OMZ, the crusts are
formed from Mn- and Fe oxyhydroxides/hydroxides via a colloidal state
(Koschinsky and Halbach 1995; Bau et al. 1996; Koschinsky and Hein 2003);
Fig. 4.14.
4.5.4 Coccolithophores
In the photic zone of the oceans, a series calcificating organisms exist, e.g.,
coccolithophores, foraminifera, pteropods, and calcareous dinophytes; however,
most of them dissolve close to their production zone (100 m), while only the
coccolithophores reach the deeper zones of the ocean where the crusts are formed
(Hay 2004). The presence of coccolithophores in crusts had been described by
Cowen et al. (1993). By application of HR-SEM and EDX, those organisms were
demonstrated as candidate bio-seed particles in Co-rich crusts from the Magellan
seamounts (Wang and M€ uller 2009). In those deposits, abundantly fossil individual
coccolith-plates, shed from single-celled coccolithophores have been detected,
that frequently are arranged to coccospheres (Fig. 4.15a–c). It is remarkable
98
X. Wang et al.