Leg : 7 Top/Bottom Interval(mm): 960/ 970 Describer: Heath, R.
Hole: 66 Top of Core Depth(m) : 187.00 Rock Type: HYALOCLASTITE
Core: 9 Sample Midpoint(m) : 187.97 Sect/Pc #: 1/
ROCK = BENTONITE
ALTERED HYALOCLASTITE,THIN SECTION DATA IN SMEAR
SLIDE DATA BASE*
Leg : 7 Top/Bottom Interval(mm): 500/ 0 Describer: Heath, R.
Hole: 66 Top of Core Depth(m) : 187.00 Rock Type: IGNEOUS
Core: 9 Sample Midpoint(m) : 190.50 Sect/Pc #: 3/
ROCK = BASALT;
Texture: FINE-GRAINED*
Phenocrysts- PLAGIOCLASE
Size(mm): TO .7 Morphology: EUHEDRAL
RARE,SCATTERED,USUALLY RIMMED BY A .01-.03MM ZONE
OF MORE CALCIC COMPOSITION,SLIGHT REPLACEMENT OF
GRAIN MARGINS AND CLEAVAGE PLANES BY
MONTMORILLONITE HAS TAKEN PLACE*
Groundmass - PLAGIOCLASE ( 40%)
Size(mm): .05-.25 Morphology: ACICULAR MICROLITES
MESHWORK OF RANDOMLY ORIENTED PLAG SEPARATED BY
.01-.03MM CLOTS OF PALE GREEN OR BROWNISH GREEN
MONTMORILLONITE AND FERRO-MANGANESE AND FE-OXIDES-
EITHER DIFFUSE PATCHES OR STUBBY PRISMS OR
ACICULAR NEEDLES .01-.03MM LONG;
PYROXENE (10-20%)
PREVIOUSLY DESCRIBED NEEDLES OCCUR IN
INTERPENETRATING SETS IN ALTERED PYX;
GLASS (40-50%)
MOST OF MONTMORILLONITE AND FE-OXIDES FORMED FROM
ORIGINAL GLASS.BOUNDARY BETWEEN DARKER RIND AND
LIGHTER CORE OF THE SECTIONED FRAGMENT IS MARKED
BY A .25MM BAND OF FELDSPAR MICROLITES AND
MONTMORILLONITE,WITH A MUCH LOWER THAN AVERAGE
CONTENT OF METAL OXIDES. THE RIND IS DISTINGUISHED
BY ABUNDANT IRON(AND MANGANESE?)OXIDES,BROWN OR
GREENISH BROWN MONTMORILLONITE,AND LARGE PATCHES
(UP TO .3MM ACROSS) OF MICROLITE-FREE DEVITRIFIED
GLASS(NOW VERY FINELY XTLLINE(2MM)MOSAICS OF
GREENISH-BROWN MONTMORILLONITE).WITHIN .5MM OF THE
EDGE OF THE ROCK,THE FELDSPAR MICROLITES(LARGELY
REPLACED BY BROWN,IRON-STAINED MONTMORILLONITE)
ARE ORIENTED PARALLEL TO THE SURFACE.THE WHITE
MATERIAL ON EXPOSED FACES,MENTIONED IN THE MACRO
DESCRIPTION,APPEARS TO BE ALMOST COLORLESS,FINELY
ACICULAR MONTMORILLONITE? WITH APPROX 20% .002-
.005MM IRON OR FERROMANGANESE PARTICLES.NO
ZEOLITES COULD BE IDENTIFIED.THE PRESENCE OF
FELDSPAR MICROLITES IN THE WHITE MATERIAL SUGGESTS
THAT IT IS LEACHED BASALT RATHER THAN A SECONDARY
COATING*
Alteration - ZEOLITE ( 0%)
MONTMORILLONITE
FERROUS OXIDE
Vesicles -
Size(mm): .05-.15
Location: THROUGHOUT
Filling: MONTMORILLONITE
SMALL INFILLED VESICLES ARE COMMON THROUGHOUT THE
ROCK.THE FILLING IS ALMOST INVARIABLY
MONTMORILLONITE USUALLY AS A MOSAIC OF SMALL
AGGREGATES OR SPHERULES(.01-.02MM DIAMETER)OF VERY
FINE ACICULAR XTLS BUT ALSO AS LARGER RADIATING
ACICULAR XTLS OR VERMIFORM MASSES OF ACICULES.
COMBINATIONS OF MOSAICS GRADING INWARDS TO
ACICULES OCCUR NEAR THE EDGES OF THE ROCK.IN
HEAVILY STAINED AREAS VESICLES LINED WITH
RADIATING MONTMORILLONITE AND INFILLED WITH RED-
BROWN IRON-OXIDES OR IRON STAINED MONTMORILLONITE
ARE COMMON*
Leg : 7 Top/Bottom Interval(mm): 0/ 0 Describer: Heath, R.
Hole: 66 Top of Core Depth(m) : 192.00 Rock Type: IGNEOUS
Core: 10 Sample Midpoint(m) : 192.10 Sect/Pc #: CC/
ROCK = PLAG SPARSELY PHYRIC BASALT
ALTERED BASALT;
Texture: SPARSELY PHYRIC,FINE-GRAINED
INDISTINGUISHABLE FROM BASALT PEBBLES IN 9-3-50*
Phenocrysts- PLAGIOCLASE
Size(mm): .35 Morphology: SUBHEDRAL-EUHEDRAL
RARE,SCATTERED THROUGH THE GROUNDMASS.TWINNED,
USUALLY PARTLY ALTERED TO MONTMORILLONITE ALONG
THE EDGES AND CLEAVAGE PLANES.THE CORES OF THE
GRAINS ARE >AN55(BY MICHEL-LEVY METHOD)BUT TOO
FEW OBSERVATIONS COULD BE MADE TO YIELD AN
ACCURATE COMPOSITION.MOST OF THE PHENOS HAVE
CORRODED EDGES OR RIMS OF MORE CALCIC COMPOSITION
(APPROX .02MM THICK)*
Groundmass - PLAGIOCLASE (30-40%)
Size(mm): .05-.15 Morphology: ACICULAR LATHS
ROCK IS BASICALLY A MESHWORK OF PLAG ENCLOSING
BLEBS OF IRON-OXIDES AND FINELY ACICULAR
MONTMORILLONITE IS AFTER CPX(RARE XTLLITES
SURVIVE)BUT MOST IS AN ALTERATION PRODUCT OF GLASS
AS IS THE IRON-OXIDE COMPONENT.IN PLACES THE
MICROLITES OF PLAG FORM SWIRLS AND EDDIES,
GENERALLY APPROX 2MM ACROSS SEVERAL 0-5MM BANDS
OF ALIGNED XTLS,PRESUMABLY MARKING THE TERMINAL
STAGES OF VISCOUS SHEAR ARE ALSO PRESENT.IN
GENERAL,HOWEVER,THE MICROLITES ARE RANDOMLY
ARRANGED WITH FLOW BANDING A MINOR FEATURE;
PYROXENE
Size(mm): .25 Morphology: EUHEDRAL
ALMOST COLORLESS.THE ONLY DIFFERENCE BETWEEN THE
RIM AND CORE AREAS OF THE ROCK APPARENT IN THIN
SECTION IS THE CONCENTRATION OF FERRO-MANGANESE
OXIDES(THESE ARE BLACK AND OPAQUE IN CONTRAST TO
THE RED-BROWN TRANSLUCENT IRON-OXIDES OF THE
ALTERED GROUNDMASS).THE RIM AREAS CONTAIN APPROX
20% OF .005-.01MM BLEBS(LOCALLY OBLITERATING ALL
BUT THE PLAG LATHS IN THE DENDRITES MENTIONED
ABOVE)AS WELL AS STAINED(BROWN)MONTMORILLONITE.
THE CORE AREAS RARELY CONTAIN MORE THAN 10% OF
FERRO-MANGANESE OXIDES,BUT ARE USUALLY RICHER IN
BROWN IRON-OXIDES THAN THE RIM AREAS;
DEVITRIFIED GLASS
ALSO PRESENT IN THE RIM AREAS,BUT NOT THE CORES
ARE IRREGULAR PATCHES OF YELLOW-BROWN,MICROLITE-
FREE DEVITRIFIED GLASS UP TO .25MM ACROSS.THESE
ARE NOW MOSAICS OF FINELY XTLLINE MONTMORILLONITE,
AND RARELY INCLUDE .005MM GRAINS OF IRON OXIDES*
Alteration - CHLORITE ( 0%)
MONTMORILLONITE
NUMEROUS SPHERICAL MASSES OF RADIATING ACICULAR
PALE GREEN MONTMORILLONITE WHICH PROBABLY MARK
FINE VESICLES IN THE ORIGINAL ROCK;
FERROUS OXIDE
FERROUS MN OXIDE
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