Leg : 64 Top/Bottom Interval(mm): 570/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 165.50 Rock Type: IGNEOUS
Core: 14 Sample Midpoint(m) : 170.57 Sect/Pc #: 4/
ROCK = PLAG MODERATELY PHYRIC BASALT;
Texture: MODERATELY PORPHYRITIC,HYALOPILITIC,INTERSERTAL;
Where sampled: NEXT TO GLASSY MARGIN
MARGIN OF SILL,SAMPLED JUST BELOW CHILL MARGIN*
Phenocrysts- PLAGIOCLASE ( 3%)
Size(mm): 0.5-1
APPROX COMP AN58,MICROLITES,SOME ZONED*
Groundmass - OLIVINE
NONE SEEN BUT SOME CPX COULD BE OL AS GRAINS ARE
VERY TINY;
PLAGIOCLASE ( 7%)
Size(mm): 0.05X0.3 Morphology: TINY LATHS
CLINOPYROXENE ( 3%)
Size(mm): 0.05 Morphology: ANHEDRAL
APPROX COMP AUGITE;
OPAQUE MINERALS ( 2%)
Size(mm): <0.1 Morphology: ANHEDRAL
INCLUDES MAGN + ILMENITE;
GLASS ( 80%)
MOSTLY MODERATELY ALTERED BUT SOME FRESH*
Alteration - COMBINATION ( 3%)
Location: VEINLETS
INCLUDES CARB + CLAY.MIN,FOUND IN INTERGRAIN
BOUNDARIES AND IN FRACTURE VEINLETS;
ZEOLITE ( 2%)
Location: VEINLETS
FOUND IN INTERGRAIN BOUNDARIES AND IN FRACTURE
VEINLETS*
Vesicles -
Percent: 0
Leg : 64 Top/Bottom Interval(mm): 440/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 175.44 Sect/Pc #: 1/PCE 1G
ROCK = PLAG-OL MODERATELY PHYRIC BASALT;
Texture: MODERATELY PORPHYRITIC,INTERSERTAL-
INTERGRANULAR;
Where sampled: OTHER
SILL*
Phenocrysts- OLIVINE ( 1%)
Size(mm): 0.5-1 Morphology: ANHEDRAL
PLAGIOCLASE ( 2%)
Size(mm): 0.5-1 Morphology: SUBHEDRAL,TABULAR
Groundmass - OLIVINE
NONE SEEN BUT SOME CPX MAY BE OL;
PLAGIOCLASE ( 30%)
Size(mm): 0.1-0.5 Morphology: SKELETAL,LATHS
CLINOPYROXENE ( 20%)
Size(mm): 0.1-0.4 Morphology: INTERGRANULAR
MAGNETITE ( 1%)
Size(mm): <0.1 Morphology: ANHEDRAL,INTERGRANULAR
Alteration - SMECTITE ( 50%)
Location: INTERSERTAL Replacing: MESOSTASIS
GREEN*
Leg : 64 Top/Bottom Interval(mm): 500/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 175.50 Sect/Pc #: 1/PCE 1I
ROCK = PLAG MODERATELY PHYRIC BASALT
CHILLED;
Texture: MODERATELY PORPHYRITIC,HYALOPILITIC
PILOTAXITIC IN SMALL 4 MM WIDE VEIN OF CHILLED
BASALT;
Where sampled: OTHER
SILL CONTACT WITH CHERTIFIED SEDIMENTS*
Phenocrysts- OLIVINE ( 0.5%)
Size(mm): 0.3 Morphology: SUBHEDRAL
CORRODED + FRESH;
PLAGIOCLASE ( 2%)
Size(mm): 0.5-1.5 Morphology: LATHS
APPROX COMP AN56,MICROLITES,FRESH;
CLINOPYROXENE ( 0.5%)
Size(mm): 0.3 Morphology: SUBHEDRAL
CORRODED-FRESH*
Groundmass - OLIVINE ( 0%)
PLAGIOCLASE ( 5%)
Size(mm): <0.1
QUENCHED;
CLINOPYROXENE ( 3%)
Morphology: ANHEDRAL
OPAQUE MINERALS ( 1%)
INCLUDES MAGN + ILMENITE,CONCENTRATED ALONG FLOW
LINES;
GLASS ( 85%)
FRESH-MINOR ALTERATION*
Alteration - COMBINATION ( 3%)
Location: FRACTURES
INCLUDES CARB + CLAY.MIN + ZEOLITES,FOUND IN
INTERGRAIN BOUNDARIES AND MICROFRACTURES,MINOR*
Leg : 64 Top/Bottom Interval(mm): 680/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 175.68 Sect/Pc #: 1/PCE 1K
ROCK = APHYRIC BASALT;
Texture: APHYRIC,HYALOPILITIC-INTERSERTAL
SOME DISCRETE AREAS APPROACHING PILOTAXITIC;
Where sampled: OTHER
UPPER SILL MARGIN*
Groundmass - OLIVINE ( 5%)
Size(mm): <0.4 Morphology: ANHEDRAL
FRESH;
PLAGIOCLASE ( 30%)
Size(mm): 0.3-1.5 Morphology: LATHS
APPROX COMP AN40?,MICROLITES;
CLINOPYROXENE ( 5%)
Size(mm): 0.4 Morphology: ANHEDRAL
FRESH;
OPAQUE MINERALS ( 1%)
Size(mm): <0.2
INCLUDES MAGN + ILMENITE;
GLASS ( 49%)
MOSTLY FRESH-LITTLE ALTERED*
Alteration - CARBONATE ( 0%)
NONE SEEN;
COMBINATION ( 10%)
Location: INTERGRANULAR
INCLUDES CLAY.MIN + ZEOLITES,FOUND IN INTERGRAIN
BOUNDARIES*
Vesicles -
Percent: 0
Leg : 64 Top/Bottom Interval(mm): 760/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 177.26 Sect/Pc #: 2/PCE 1N
ROCK = PLAG MODERATELY PHYRIC BASALT
THIS THIN SECTION (A) CONTAINS THE MARGIN OF
EARLIER BASALT WITH LATER BASALT QUENCHED AGAINST
IT;
Texture: MODERATELY PORPHYRITIC,PILOTAXITIC,SPHERULITIC-
INTERGRANULAR
PILOTAXITIC FLOW TEXTURE,SPHERULITIC ZONE (APPROX
3 MM WIDE) GRADES INTO VARIOLITIC BASALT (GRADES
FROM 0.3-0.6 MM DEPENDING ON POSITION RELATIVE TO
CONTACT);
Where sampled: OTHER
SILL RIM ADJACENT TO EARLIER BASALT*
Phenocrysts- OLIVINE ( 0%)
NONE SEEN BUT SEE ALTERATION CODES;
PLAGIOCLASE ( 2-5%)
Size(mm): 0.2-1.0 Morphology: ELONGATE LATHS
PHENOS + MICROPHENOS,CLEARLY DISTINGUISHED IN
CHILLED ZONE*
Groundmass - OLIVINE ( 0%)
NONE SEEN BUT MAY BE ALTERED;
PLAGIOCLASE ( 25%)
Size(mm): <0.5 Morphology: SKELETAL
CLINOPYROXENE ( 30%)
Size(mm): 0.01-0.4 Morphology: ANHEDRAL,GRANULAR
OPAQUE MINERALS ( 3%)
Size(mm): <0.2 Morphology: DISSEMINATED-ANHEDRAL
MICROCRYST GROUNDMASS ( 30%)
COMPRISES OP.MINS + PYX + ?GLASS*
Alteration - CLAY MINERALS ( 3%)
Replacing: OL
0.5-1 MM PSEUDOMORPHS;
CLAY MINERALS ( 10%)
Location: INTERGRANULAR Replacing: MESOSTASIS
Vesicles -
Percent: 0
Leg : 64 Top/Bottom Interval(mm): 761/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 177.26 Sect/Pc #: 2/PCE 1N
ROCK = APHYRIC BASALT TO DOLERITE
THIS THIN SECTION (B) IS ABOVE THE CONTACT BETWEEN
THE EARLIER AND LATER BASALT;
Texture: APHYRIC,COARSE,INTERGRANULAR-SUBOPHITIC;
Where sampled: OTHER
SILL INTERIOR ADJACENT TO LATER INTRUSION*
Groundmass - OLIVINE ( 0%)
NONE SEEN BUT SEE ALTERATION CODES;
PLAGIOCLASE ( 50%)
Size(mm): 0.3-2 Morphology: LATH-SHAPED
CLINOPYROXENE ( 20%)
Size(mm): 0.5-2 Morphology: ANHEDRAL
INTERGRANULAR AND SUBOPHITIC,ENCLOSING PLAG,APPROX
COMP AUGITE;
MAGNETITE ( 3%)
Size(mm): 0.1-0.2 Morphology: ANHEDRAL-SUBHEDRAL
ILMENITE ( <1%)
Size(mm): 0.01X0.3 Morphology: ELONGATE
Alteration - CLAY MINERALS ( 5%)
Replacing: OL
PSEUDOMORPHS AFTER OL?;
CLAY MINERALS ( 20%)
Location: INTERGRANULAR Replacing: MESOSTASIS
Leg : 64 Top/Bottom Interval(mm): 1140/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 175.00 Rock Type: IGNEOUS
Core: 15 Sample Midpoint(m) : 179.14 Sect/Pc #: 3/PCE 1L
ROCK = GABBRO;
Texture: OPHITIC;
Where sampled: SILL INTERIOR*
Groundmass - OLIVINE ( 5%)
Size(mm): 0.5-1 Morphology: SUBHEDRAL-ANHEDRAL
XTLS SHOW ALTERATION RIMS;
PLAGIOCLASE ( 40%)
Size(mm): 0.5-2 Morphology: TABLETS,LATHS
APPROX COMP AN40;
CLINOPYROXENE ( 15%)
Size(mm): 0.5-4 Morphology: SUBHEDRAL-ANHEDRAL
AGGREGATES;
OPAQUE MINERALS ( 5%)
Size(mm): 0.2-0.5 Morphology: SUBHEDRAL-ANHEDRAL
INCLUDES MAGN + ILMENITE;
MICROCRYST GROUNDMASS ( 30%)
IN POCKETS,SOMEWHAT ALTERED BUT RELATIVELY FRESH*
Alteration - COMBINATION ( 5%)
Location: INTERGRAIN
Location: BOUNDARIES
INCLUDES CLAY.MIN + ZEOLITES;
OTHER ( 1%)
Replacing: OL,CPX
REDDISH BROWN PSEUDOMORPHS AFTER OL + CPX*
Vesicles -
Percent: 0
Leg : 64 Top/Bottom Interval(mm): 1200/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 184.50 Rock Type: IGNEOUS
Core: 16 Sample Midpoint(m) : 185.70 Sect/Pc #: 1/PCE 1M
ROCK = PLAG-OL MODERATELY PHYRIC BASALT;
Texture: MODERATELY PORPHYRITIC,VARIOLITIC;
Where sampled: SILL INTERIOR*
Phenocrysts- OLIVINE ( 5%)
Size(mm): 0.4-1.0 Morphology: SUBHEDRAL-EUHEDRAL
INTERGROWN OR CONCENTRATED AS GLOMEROCRYSTS WITH
PLAG,MOSTLY ALTERED;
PLAGIOCLASE ( 5%)
Size(mm): 0.5-1.5 Morphology: THIN LATHS
APPROX COMP AN55-60,FRESH,INTERGROWN OR
CONCENTRATED AS GLOMEROCRYSTS WITH OL*
Groundmass - OLIVINE ( 0%)
NONE SEEN;
PLAGIOCLASE ( 20%)
Size(mm): <0.4 Morphology: SKELETAL
MICROLITES;
CLINOPYROXENE ( 20%)
Size(mm): <0.2 Morphology: SKELETAL GROWTHS,WHEATSHEAF,
Morphology: DENDRITIC
PERCENTAGE QUESTIONABLE;
OPAQUE MINERALS ( 4%)
Size(mm): <0.1
INCLUDES MAGN + ILMENITE,DISSEMINATED*
Alteration - CLAY MINERALS ( 40%)
Location: MESOSTASIS Replacing: MESOSTASIS
IDENTITY OF ALTERATION IS QUESTIONABLE*
Leg : 64 Top/Bottom Interval(mm): 1240/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 184.50 Rock Type: IGNEOUS
Core: 16 Sample Midpoint(m) : 187.24 Sect/Pc #: 2/PCE 2D
ROCK = DOLERITE OR GABBRO
MOST OF SLIDE HAS BEEN LOST DURING THIN SECTION
PREPARATION AND HENCE PERCENTAGES CANNOT BE
ESTIMATED,COARSE DOLERITE TO MICROGABBRO;
Texture: COARSE,SUBOPHITIC;
Where sampled: OTHER
SILL INTERIOR*
Groundmass - PLAGIOCLASE
Size(mm): 1-3 Morphology: LATH-SHAPED,TABULAR
CLINOPYROXENE
Size(mm): 1-2 Morphology: IRREGULAR,INTERGRANULAR-
Morphology: SUBOPHITIC
MAGNETITE
Size(mm): <0.3 Morphology: CUBOID,AMORPHOUS
Alteration - CLAY MINERALS
Replacing: OL
PSEUDOMORPHS,PROBABLY REPLACING OL*
Leg : 64 Top/Bottom Interval(mm): 320/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 184.50 Rock Type: IGNEOUS
Core: 16 Sample Midpoint(m) : 187.82 Sect/Pc #: 3/PCE 3A
ROCK = PLAG MODERATELY PHYRIC BASALT;
Texture: MODERATELY PORPHYRITIC, SERIATE, COARSE-GRAINED,
INTERGRANULAR-INTERSERTAL;
Where sampled: OTHER
SILL INTERIOR*
Phenocrysts- PLAGIOCLASE ( 5%)
Size(mm): 1-2 Morphology: TABULAR-LATH SHAPED
GENERALLY RESORBED,APPROX COMP AN60-65*
Groundmass - OLIVINE ( 0%)
NONE POSITIVELY IDENTIFIED BUT SEE ALTERATION
CODES;
PLAGIOCLASE ( 40%)
Size(mm): 0.5-2 Morphology: LATH SHAPED,SKELETAL
CLINOPYROXENE ( 20%)
Size(mm): 0.1-0.7 Morphology: IRREGULAR,GRANULAR,ANHEDRAL,
Morphology: INTERGRANULAR
APPROX COMP AUGITE?;
MAGNETITE ( 2-3%)
Size(mm): <0.1 Morphology: CUBOID,AMORPHOUS
ILMENITE ( <2%)
Morphology: ELONGATE,DENDRITIC
DIMENSIONS ARE 0.5 X <0.1*
Alteration - CLAY MINERALS ( 30%)
Location: INTERGRANULAR Replacing: MESOSTASIS
CLAY MINERALS ( 5%)
Replacing: OL
PSEUDOMORPHS*
Leg : 64 Top/Bottom Interval(mm): 250/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 194.00 Rock Type: IGNEOUS
Core: 17 Sample Midpoint(m) : 194.25 Sect/Pc #: 1/PCE 2B
ROCK = BASALT VEIN
HOST ROCK DESCRIBED SEPARATELY IN NEXT THIN
SECTION,GROUNDMASS IS TOO FINE-GRAINED TO BE
CLEARLY DISTINGUISHED--VERY IRON RICH--APPEARS
QUITE ALTERED;
Texture: PORPHYRITIC,ALMOST HYALOPILITIC;
Where sampled: OTHER
VEIN CUTTING BASALT*
Phenocrysts- OLIVINE ( 5%)
Size(mm): 0.3-0.8 Morphology: SUBHEDRAL-EUHEDRAL
BADLY ALTERED,GENERALLY INTERGROWN WITH PLAG;
PLAGIOCLASE ( 10%)
Size(mm): 0.5-1.0 Morphology: ELONGATE,TABULAR
APPROX COMP AN60-70,ONE XTL IS A LARGE RESORBED
ZONED PHENOCRYST OVER 3 MM ACROSS (NOT ALL
PRESERVED IN THIN SECTION)*
Alteration - COMBINATION ( 3%)
Location: VEINS
INCLUDES CARB + CLAY.MIN;
CLAY MINERALS (20-30%)
Location: MESOSTASIS Replacing: OL
PERCENTAGE QUESTIONABLE*
Leg : 64 Top/Bottom Interval(mm): 260/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 194.00 Rock Type: IGNEOUS
Core: 17 Sample Midpoint(m) : 194.26 Sect/Pc #: 1/PCE 2B
ROCK = DOLERITE
HOST ROCK OF VEIN DESCRIBED IN PREVIOUS THIN
SECTION;
Texture: PORPHYRITIC-INTERGRANULAR;
Where sampled: OTHER
SILL INTERIOR (ADJACENT TO BASALTIC VEIN)*
Phenocrysts- PLAGIOCLASE ( 15%)
Size(mm): 0.5-1.5 Morphology: LATH-SHAPED,TABULAR
APPROX COMP AN50-60*
Groundmass - OLIVINE
Size(mm): <0.3 Morphology: ROUNDED
PERCENTAGE QUESTIONABLE--MAY BE CPX;
PLAGIOCLASE ( 40%)
Size(mm): 0.4-1.0 Morphology: SKELETAL,LATHS
CLINOPYROXENE ( 10%)
Size(mm): 0.5-0.7 Morphology: SKELETAL
APPROX COMP ?AUGITE,OPTICALLY INTERGRANULAR-
CONTINUOUS AGGREGATES;
MAGNETITE ( 3%)
Size(mm): <0.2 Morphology: AMORPHOUS BLOBS
Alteration - CARBONATE ( 5%)
Location: VEINS
CLAY MINERALS ( 30%)
Location: MESOSTASIS Replacing: MESOSTASIS,OL
POSSIBLY REPLACING OL?*
Leg : 64 Top/Bottom Interval(mm): 1150/ 0 Describer: Saunders, A.
Hole: 481A Top of Core Depth(m) : 194.00 Rock Type: IGNEOUS
Core: 17 Sample Midpoint(m) : 195.15 Sect/Pc #: 1/PCE 2N
ROCK = PLAG MODERATELY PHYRIC BASALT;
Texture: PORPHYRITIC,INTERGRANULAR-INTERSERTAL;
Where sampled: OTHER
SILL INTERIOR*
Phenocrysts- OLIVINE ( 0%)
NONE SEEN BUT SEE ALTERATION CODES;
PLAGIOCLASE ( 5%)
Size(mm): 1.5-3 Morphology: LATH-SHAPED,TABULAR
LATH SHAPED AND (MORE RARELY) LARGER RESORBED
TABULAR XTLS*
Groundmass - OLIVINE ( 0%)
NONE SEEN;
PLAGIOCLASE ( 45%)
Size(mm): 0.5-2 Morphology: LATH-SHAPED
CLINOPYROXENE ( 35%)
Size(mm): <0.5 Morphology: ANHEDRAL
APPROX COMP ?AUGITE,INTERGRANULAR;
MICROCRYST GROUNDMASS ( 10%)
Morphology: AMORPHOUS-CRYPTOCRYSTALLINE
DARK MESOSTASIS CONTAINING ABUNDANT DISSEMINATED
OP.MINS (ILMENITE XTLALLITES AND MAGN),OCCURS
INTERSERTALLY TO PLAG*
Alteration - CLAY MINERALS ( 5%)
Replacing: OL
SMALL (1 MM) AGGREGATES WHICH MAY BE REPLACING OL*
Leg : 64 Top/Bottom Interval(mm): 690/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 346.00 Rock Type: IGNEOUS
Core: 33 Sample Midpoint(m) : 346.69 Sect/Pc #: 1/PCE 1
ROCK = APHYRIC BASALT;
Texture: APHYRIC,PILOTAXITIC,SPHERULITIC IN CONTACT;
Where sampled: GLASSY MARGIN AND NEXT TO GLASSY MARGIN
UPPER CHILLED CONTACT OF SILL*
Phenocrysts- PLAGIOCLASE
Size(mm): 0.8-1.5 Morphology: TABULAR
RESORBED,INCLUDED IN GROUNDMASS*
Groundmass - OLIVINE ( <1%)
Morphology: ANHEDRAL
TINY ANHEDRAL GRAINS;
PLAGIOCLASE ( 2%)
Size(mm): 0.2-3 Morphology: LATHS,TABULAR
APPROX COMP AN40,TINY LATHS TO PHENOS--TABULAR
LYING IN GLASS;
CLINOPYROXENE ( <1%)
Morphology: ANHEDRAL
TINY ANHEDRAL GRAINS;
OPAQUE MINERALS ( 2%)
INCLUDES MAGN + ILMENITE;
GLASS ( 95%)
DEVITRIFIED,FRESH WITH WHEAT-SHEAVE STRUCTURES AND
SPHERULITES*
Alteration - COMBINATION ( <1%)
Replacing: CPX
INCLUDES CLAY.MIN + ZEOLITES,PSEUDOMORPHS AFTER
CPX;
CALCITE
Location: VESICLES
Vesicles -
Size(mm): 2
Percent: 5
Location: RANDOM
Filling: MESOSTASIS,
Shape: SPHERICAL
Filling: CALCITE
Leg : 64 Top/Bottom Interval(mm): 900/ 0 Describer: Fornari, D.
Hole: 481A Top of Core Depth(m) : 346.00 Rock Type: IGNEOUS
Core: 33 Sample Midpoint(m) : 346.90 Sect/Pc #: 1/PCE 5
ROCK = APHYRIC BASALT;
Texture: APHYRIC,HYALOPILITIC,VESICULAR;
Where sampled: OTHER
JUST BELOW CHILLED MARGIN OF SILL*
Groundmass - OLIVINE ( 2%)
Size(mm): 0.1-0.3 Morphology: ANHEDRAL
PLAGIOCLASE ( 15%)
Size(mm): 0.1-1 Morphology: LATHS
LATHS AND MICROLITES,SOME ZONED;
CLINOPYROXENE ( 3%)
Size(mm): 0.1-0.3 Morphology: ANHEDRAL
OPAQUE MINERALS ( 3%)
INCLUDES MAGN + ILMENITE;
MICROCRYST GROUNDMASS ( 65%)
MESOSTASIS,GLASS + CRYPTXLN + PLAG + CPX + MOSTLY
OL,FRESH*
Alteration - CARBONATE ( 0%)
NONE SEEN;
COMBINATION ( 5%)
Location: INTERGRAIN
Location: BOUNDARIES,
Location: VESICLES
INCLUDES CLAY.MIN + ZEOLITES*
Vesicles -
Size(mm): 0.5-1.5
Percent: 5
Filling: CLAY.MIN
Shape: ELLIPSOID-
Shape: ROUND
CRUDELY ELLIPSOID TO COARSELY ROUND,THINLY LINED
WITH CLAYS AND HAVING PERIPHERAL PILOTAXITIC
ILMENITES*
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