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Core data from the Ocean Drilling Program legs 101-129
ODP hard-rock thin section description - verbose form
leg : 111 section: 01 unit/subunit : 0151
hole: 504B top int: 006 cm observer code: CMS
core: 142R pieces: 001
rock name: Moderately plagioclase clinopyroxene phyric basalt
texture: Intergranular, subophitic
where sampled: Unit 151
grain size: Fine
***** PHENOCRYSTS *****
Plagioclase present % 8 original % 8 size 0.2-2.0
composition: An 54
morphology : Euhedral, tabular
comments : Occur as glomerocrysts and single crystals.
Sometimestogether with cpx. Strained (wavy extinction).
***** GROUNDMASS *****
Replaced in part by chlorite(?), clays.
Plagioclase present % 35 original % 41 size 150microns
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Clays percent: 9
replacement: Plag.
comments : Plag replaced, especially in vugs.
****** OVERALL COMMENTS ******
Although the rock is generally fine grained, it has a patchy appearance with
patches or "vugs" up to 2 mm in which alteration minerals, chlorite, magnetite,
and clays, are concentrated. Magnetite concentration in the matrix occurs around
radiating plag laths and may represent devitrification of original glassy
mesostasis.
ODP hard-rock thin section description - verbose form
leg : 111 section: 01 unit/subunit : 0152
hole: 504B top int: 009 cm observer code: DIV
core: 142R pieces: 001
rock name: Highly plagioclase clinopyroxene olivine phyric basalt
texture: Chilled margin, hypohyaline
where sampled: Chilled margin, unit 152
grain size: Glass + phenocrysts. Hyaline.
***** PHENOCRYSTS *****
Olivine present % 5 original % 9 size <0.5-2.5
composition: Fo 85
morphology : Euhedral-subhedral
comments : Altered to 1) Mixed-layer clays + talc +
magnetite;2) Chlorite + talc + magnetite + actinolite.
***** GROUNDMASS *****
Now smectite + chlorite + oxides.
Glass present % 0 original % 53 size ?
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Clays percent: 25
replacement: Ol, matrix
comments : ~ 2% replacing ol.
****** OVERALL COMMENTS ******
Phenocrysts of plag, plag + cpx, and plag + ol commonly occur in glomerocrysts.
Cpx + ol are resorbed in places. Plag + cpx commonly have glass inclusions, 40-80
microns. Ol alteration occcured first along crystal margins and then along
fractures. Phenocrysts are often broken. Chilled margin: Pyrite intergrown with
chalcopyrite, chalcopyrite inclusions in pyrite, pyrite intergrown with
magnetite, small pyrrhotite inclusions in pyrite. Thin section is taken at
contact between two basaltic dike units. Unit 152 is clearly chilled compared to
unit 151. Unit 152 shows altered glassy contact, 2 mm wide, grading into altered
glassy mesostasis with microlites of plag. Oxide + smectite + chlorite
alteration. Intrusion permissive since no rip-ups of older unit in chill. Cpx in
reaction relationship with glass; resorbed margins and numerous glass inclusions.
Plag phenocrysts (core An 65) show normal zoning towards outside third of
crystals. Also have glass inclusions in centers.
ODP hard-rock thin section description - verbose form
leg : 111 section: 01 unit/subunit : 0151
hole: 504B top int: 009 cm observer code: CMS
core: 142R pieces: 001
rock name: Moderately plagioclase clinopyroxene phyric basalt
texture: Subophitic (diabasic)
where sampled: Contact unit 151
grain size: Fine to aphanitic
***** PHENOCRYSTS *****
Plagioclase present % 6 original % 6 size 0.3-1.0
composition: An 45
morphology : Euhedral-subhedral
comments : Zone Marginal 1/10 of crystals. Glomerocrysts.
***** GROUNDMASS *****
Altered in part to clays (+/- talc?).
Plagioclase present % 45 original % 50 size <0.1-0.5
****** VESICLES *****
Type: Vesicles %: 0
****** SECONDARY MINERALIZATION ******
mineral name: Clays percent: 6
replacement: Cpx, plag
comments : Alteration predominantly of groundmass
cpx, and some plag.
****** OVERALL COMMENTS ******
Unit 151. This thin section is problably not representative of the unit. Thre
is no record of ol phenocrysts which are described in the lithological
description. Likewise for cpx. Plag phenocrysts problably underestimated in
lithological description. In so far as plag concerned, almost seriate
porphyritic since maximum groundmass plag is larger than minimum phenocryst. See
111-504B-142R-1 (Piece 1A, 6-8 cm). Note: patchy clots of oxides + chlorite +
clays +/- actinolite may represent altered areas of finer groundmass.
ODP hard-rock thin section description - verbose form
leg : 111 section: 01 unit/subunit : 0153
hole: 504B top int: 101 cm observer code: DIV
core: 142R pieces: 015
rock name: Moderately plagioclase clinopyroxene olivine phyric basalt basaltic
texture: Cataclatsic (30-40% clasts)
where sampled: Contact between dike + breccia unit 153
grain size: Very fine to fine
***** PHENOCRYSTS *****
Olivine present % <1 original % <1 size
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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