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Core data from the Ocean Drilling Program legs 101-129
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 019 cm observer code: KOM
core: 001D pieces: 004
rock name: Serpentinized harzburgite (aphyric)
texture: Porphyroclastic
where sampled: Massive Peridotite
grain size: Medium-coarse
***** PHENOCRYSTS *****
***** GROUNDMASS *****
Orthopyroxene present % 1 original % 8 size 0.8-6.4
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Carbonate percent: 1
replacement: Replacing olivine, filling veins
comments :
****** OVERALL COMMENTS ******
Opx is bent into lensoid shape and has sweeping, undulatory extinction. Carbonate
veins (0.04-0.20 mm) are long and branching. They cut serpentine and magnetite
veins, and appear to be the last event in the developement of the rock.
Serpentine veins occur as two types. The first type is 0.8-3.2 mm long, and
0.05-0.15 mm wide, lensoid gashes which are highly birefringent. These veins
crosscut magnetite veins but not carbonate veins. The second type is 0.01-0.5 mm
wide, and is lined with magnetite. These veins cross cut the entire section.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 045 cm observer code: BDC
core: 002D pieces: 010
rock name: Clinopyroxene-bearing serpentinized harzburgite
texture: Porphyroclastic
where sampled: Plutonic intrusion
grain size: Coarse-grained porphyroclasts set in fine grained matrix
***** PHENOCRYSTS *****
Olivine present % ? original % 88.5 size 0.5-1.2
morphology : Hexagonal
comments : Olivine acquired a granoblastic texture during
recrystallization.Mesh texture forms after olivine neoblasts,
composedof lizardite and magnetite.
***** GROUNDMASS *****
? present % ? original % ? size ?
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Carbonate percent: trace
replacement: Veinlets
comments : Associated with talc or by-product of cpx
serpentinization.
****** OVERALL COMMENTS ******
Sequence of events: 1) High temperature plastic deformation. 2) Low temperature
serpentinization; lizardite, biotite, magnetite, and alteration of Cr spinel. 3)
Talc replaces serpentinized pseudomorphs (lining of porphyroclasts). 4)
Chrysotile veins crosscuts every metamorphic mineral. 5) Iron hydroxide alters
magnetite and follows chrysotile veinlets in some places.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 012 cm observer code: RIC
core: 003W pieces: 002
rock name: Serpentinized harzburgite
texture: Porphyroclastic
where sampled: Exterior end of pp/pm minicore
grain size: Coarse
***** PHENOCRYSTS *****
Olivine present % 0 original % 70 size 0.2-0.5
morphology : -
***** GROUNDMASS *****
? present % ? original % ? size ?
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Lizardite percent: 68
replacement: Replacing olivine
comments : Reticulate texture.
****** OVERALL COMMENTS ******
Deformation accompanying serpentinization limited - ?bending of bastites.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 019 cm observer code: RIC
core: 003W pieces: 003
rock name: Altered glassy basalt with zeolite veins
texture: Originally glassy, microlitic, partly spherulitic
where sampled: From cuttings
***** PHENOCRYSTS *****
Olivine present % 0 original % 3 size 0.05-0.3
morphology : Euhedral
comments : Altered to zeolite (single and multi-grain
aggregates).
***** GROUNDMASS *****
Microlites and microphenocrysts (replaced by zeolites).
Plagioclase present % ? original % 2-3 size upto0.2
****** VESICLES *****
Type: Vesicles %: 1
filling : Laumontite(?)
shape : Round
Completely filled with 0.1-0.2 mm zeolite crystals.
****** SECONDARY MINERALIZATION ******
mineral name: Clays percent: 4
replacement: Cpx?
comments : Greenish, moderately birefringent;
chlorite/smectite(?).
****** OVERALL COMMENTS ******
Sequence of open space filling (any one or more may be absent): Very even 10-15
microns pale yellow-green clay (frequently absent). 2) Similarly even 10-30
microns zeolite (only locally present). 3) Fine-grained, almost isotropic zeolite
with abundant inclusions. 4) Blocky, approximately 0.1-0.7 mm zeolite crystals
with abundant inclusions and aggregates of type (1d) clay approximately 10-20
microns. This may also have a radiating appearance. with crystals up to 1 mm long
stilbite(?). 5) Clear, blocky zeolite with at least two cleavages and complex
twinning. Crystals up to 1 by 1.5 mm. Laumontite(?).
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 019 cm observer code: RIC
core: 004W pieces: 003
rock name: Harzburgite
texture: Porphyroclastic
where sampled: Massive peridotite
grain size: Medium to coarse
***** PHENOCRYSTS *****
Olivine present % 35 original % 85 size 0.04-0.20
composition: Fo91
morphology : Xenomorphic
comments : Pseudomorphed by mesh texture serpentine plus
magnetite.Original fragments grains ~0.8 mm.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Lizardite percent: 44
replacement: Olivine
comments : Box and mesh texture serpentine replacing
olivine. Bastite pseudomorphing opx.
Serpentine (chrysotile?) fills some
veins.
****** OVERALL COMMENTS ******
Foliation defined by long axes of elliptical opx and spinel grains. Olivine and
cpx exhibit undulatory extinction indicating that they are internally deformed.
Cleavage traces in opx are gently bent.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 111 cm observer code: HEB
core: 005R pieces: 015
rock name: Serpentinized dunite
texture: Granoblastic to cataclastic
where sampled: Plutonic intrusion
grain size: Medium
***** PHENOCRYSTS *****
Olivine present % - original % 95 size 1.5-2.8
morphology : Hexagonal, cubic
comments : Mesh texture of olivine pseudomorphs with
outlineof magnetite at prior margin.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Lizardite percent: 78
replacement: Olivine
comments : Mesh texture of olivine forming cubic to
hexagonal pseudomorphs. Hourglass texture
of amorphous core.
****** OVERALL COMMENTS ******
Sequence of events: 1) Serpentinization (lizardite plus magnetite); low
temperature. 2) Talc; low/medium temperature (?). 3) Chrysotile, plus or minus
magnetite (tensional cracks); low temperature. 4) Shear zones (Antigorite, plus
or minus talc, plus or minus tremolite); low temperature, higher pressure. 5)
Chrysotile, second generation.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0001
hole: 670A top int: 126 cm observer code: RIC
core: 005R pieces: 017
rock name: Serpentinite
texture: Reticulate, veined
where sampled: Exterior end of pp/pm minicore
***** PHENOCRYSTS *****
Olivine present % 0 original %99(?) size ?
morphology : ?
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Lizardite percent: 79
replacement: Olivine
comments : Forms reticulate pattern, with more
birefringent "strands" of network
defining domains 0.2-0.5 mm wide.
****** OVERALL COMMENTS ******
Chrysotile veins are sub-parallel within the slide, but form an oriented
anastomizing network in the hand specimen. Chrysotile continued: reticulate
structure is almost absent, may be developed. This band is up to 2 mm wide each
side.
ODP hard-rock thin section description - verbose form
leg : 109 section: 02 unit/subunit : 0002
hole: 670A top int: 052 cm observer code: EIS
core: 005R pieces: 007
rock name: Serpentinized dunite
texture: Porphyroblastic
where sampled: Peridotite intrusion
grain size: Coarse porphyroblastic
***** PHENOCRYSTS *****
Olivine present % - original % >90 size 1-3(?)
morphology : Polygonal
comments : Mesh texture of olivine pseudomorphs hexagonal
withdiscrete outlines of magnetite.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Chlorite percent: 2
replacement: Antigorite
comments :
****** OVERALL COMMENTS ******
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0003
hole: 670A top int: 004 cm observer code: KOM
core: 006R pieces: 001
rock name: Clinopyroxene-bearing harzburgite
texture: Porphyroclastic
where sampled: Massive peridotite
grain size: Medium-coarse
***** PHENOCRYSTS *****
Olivine present % 20 original % 85 size 0.04-0.4
composition: Fo90
morphology : Anhedral
comments : Undulatory extinction in olivine.
Preserpentinizationolivine fragments 0.4-1.2 mm in size.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Lizardite percent: 64
replacement: Olivine
comments : Mesh texture serpentine replacing
olivine. Bastite pseudomorphs after opx.
****** OVERALL COMMENTS ******
Slight to moderate granulation around opx porphyroblasts.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0004
hole: 670A top int: 043 cm observer code: HEB
core: 007R pieces: 007
rock name: Serpentinite
texture: Cataclastic after porphyroclastic harzburgite, multiple veined alteration assemblage
where sampled: Plutonic intrusion
grain size: Fine
***** PHENOCRYSTS *****
Olivine present % - original % 80 size 1-2
morphology : Polygonal
comments : Mesh texture and hour-glass texture of
lizarditewith magnetite seam.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Chlorite percent: 10
replacement: Antigorite
comments : Magnesium-rich (colorless) with anomalous
copper to blue birefringence.
****** OVERALL COMMENTS ******
Sequence of events: 1) Lizardite plus magnetite after olivine. 2) Chrysotile in
dilation fissures (fibrous). 3) Antigorite (in shear planes). 4) Chlorite plus
tremolite (fibrous, prismatic) partially replace antigorites in lense-shaped
shear planes. 5) Late stage open fissures filled by chrysotile.
ODP hard-rock thin section description - verbose form
leg : 109 section: 01 unit/subunit : 0006
hole: 670A top int: 107 cm observer code: GRO
core: 009R pieces: 014
rock name: Serpentinized peridotite
texture: Cataclastic
where sampled: Probable fault zone
grain size: Fine to coarse
***** PHENOCRYSTS *****
Olivine present % 0 original % 90 size -
morphology : -
comments : Completely altered to serpentine and other
metamorphicminerals.
***** GROUNDMASS *****
- present % - original % - size -
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Chlorite percent: 30
replacement: Olivine
comments : Intergrown with tremolite. Acicular,
micron-sized crystals.
****** OVERALL COMMENTS ******
Primary minerals almost completely reacted by metamorphism. A few relict,
cataclastized orthopyroxene porphyroclasts are surrounded by talc plus serpentine
halos. Patchy areas of lizardite plus magnetite are surrounded by a reaction zone
of tremolite plus chlorite, and cut by chrysotile veins. Some antigorite veins
cut lizardite. Both the serpentine assemblage and the tremolite plus chlorite
have been cataclastically deformed.
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These Web pages are from the Core Data from the Ocean Drilling Program Legs 101-129 CD-ROM produced in 2001 by the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Environmental Satellite, Data, and Information Service, National Geophysical Data Center, and collocated World Data Center for Marine Geology and Geophysics, Boulder. Data were compiled in cooperation with the U.S. Science Support Program, the Joint Oceanographic Institutions, Inc., and the U.S. National Science Foundation. Please see the NGDC privacy, disclaimer, and copyright notices. Additional ocean drilling data are available from NGDC and from the ODP/IODP.
questions to: carla.j.moore@noaa.gov