biogenic matter and in fecal pellets that rapidly fall to
the seafloor; their dissolution on the seafloor and in
transit is likely the dominant control on the barium
concentration in the deep ocean. Within the sediment
and in ferromanganese deposits, barite can form
authigenically as discrete particles and diagenetically
as replacement of biogenic skeletal remains (Figure 8).
Authigenic Silicates
Zeolites Low-temperature alteration of basalt and
metastable volcanic glasses on pillow rims, in layers,
and dispersed throughout deep-sea sediments can
produce a variety of diagenetic alteration phases.
(Low temperature is defined as ranging from modern
ambient seafloor conditions, or near 01C to up to
1501C, the low-temperature metamorphism limit.)
These include X-ray-amorphous palagonite, the
zeolites phillipsite, clinoptilolite, analcite (plus several
others of rarer occurrence), smectites, and authigenic
K-feldspar (Table 1). Phillipsite is a hydrated
potassium- and sodium-rich aluminosilicate that
forms elongated and sometimes twinned crystals from
8 to 250mm length with numerous inclusions that
indicate rapid growth. Oxygen isotope values of 34%
for phillipsite indicate formation in the marine
environment at modern seafloor temperatures.
Phillipsite appears metastable on geological
timescales, becoming rarer beyond Cenozoic age. The
mineral is found globally at the sediment–sea water
interface and continues to grow within the sediment
column until it dissolves and disappears in the deepest
(A)
(B)
(C)
(D)
Figure 8 Photograph of barite crystals inside a ferromanganese nodule. (A) Scanning electron micrograph of foraminifera shell walls
that have been replaced by barite. (B) Barium elemental X-ray map produced by EMP. (C) Magnification of (A) showing individual
barite crystals. (D) Elemental spectrum of the barite crystals: S Ka at 2300 eV; Ba La, b, g at 4460 eV. (After Lalou C, Brichet E,
Poupeau G, Romany P and Jehanno C (1979) Growth rates and possible age of a North Pacific manganese nodule. In Bischoff JL and
Piper DZ (eds) Marine Geology and Oceanography of the Central Pacific Manganese Nodule Province, pp. 815–834. New York and
London: Plenum Press.)
332 AUTHIGENIC DEPOSITS
the seafloor; their dissolution on the seafloor and in
transit is likely the dominant control on the barium
concentration in the deep ocean. Within the sediment
and in ferromanganese deposits, barite can form
authigenically as discrete particles and diagenetically
as replacement of biogenic skeletal remains (Figure 8).
Authigenic Silicates
Zeolites Low-temperature alteration of basalt and
metastable volcanic glasses on pillow rims, in layers,
and dispersed throughout deep-sea sediments can
produce a variety of diagenetic alteration phases.
(Low temperature is defined as ranging from modern
ambient seafloor conditions, or near 01C to up to
1501C, the low-temperature metamorphism limit.)
These include X-ray-amorphous palagonite, the
zeolites phillipsite, clinoptilolite, analcite (plus several
others of rarer occurrence), smectites, and authigenic
K-feldspar (Table 1). Phillipsite is a hydrated
potassium- and sodium-rich aluminosilicate that
forms elongated and sometimes twinned crystals from
8 to 250mm length with numerous inclusions that
indicate rapid growth. Oxygen isotope values of 34%
for phillipsite indicate formation in the marine
environment at modern seafloor temperatures.
Phillipsite appears metastable on geological
timescales, becoming rarer beyond Cenozoic age. The
mineral is found globally at the sediment–sea water
interface and continues to grow within the sediment
column until it dissolves and disappears in the deepest
(A)
(B)
(C)
(D)
Figure 8 Photograph of barite crystals inside a ferromanganese nodule. (A) Scanning electron micrograph of foraminifera shell walls
that have been replaced by barite. (B) Barium elemental X-ray map produced by EMP. (C) Magnification of (A) showing individual
barite crystals. (D) Elemental spectrum of the barite crystals: S Ka at 2300 eV; Ba La, b, g at 4460 eV. (After Lalou C, Brichet E,
Poupeau G, Romany P and Jehanno C (1979) Growth rates and possible age of a North Pacific manganese nodule. In Bischoff JL and
Piper DZ (eds) Marine Geology and Oceanography of the Central Pacific Manganese Nodule Province, pp. 815–834. New York and
London: Plenum Press.)
332 AUTHIGENIC DEPOSITS