|
Core, section,
interval (cm) |
Description
|
Alteration
|
XRD identification
|
|---|---|---|---|
| 183-1137A- |
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|
| 25R-4, 100-115 | Aphyric basalt, vesicular (20%-25%; 0.1-0.5 mm), incompletely crystallized. Groundmass with microdoleritic texture. Phenocrysts of long lathe of plagioclase (andesine; 0.1-0.3 mm). Dark brown volcanic glass with opaque dust and clinopyroxene. | Moderate (30%-35%); vesicles completely or partly infilled by clay minerals, zeolites, and carbonate. Oxidation of basalt is ~30%. |
|
| 27R-1, 100-105 | Sparsely plagioclase microphyric basalt, vesicular (5%-10%; up to 2-4 mm), incompletely crystallized. Groundmass of vitrophyric-microlitic texture. Phenocrysts of crystals of plagioclase (<1%; 0.5-0.6 mm). | ~25%-30%; clinopyroxene completely replaced by chlorite; plagioclase is partly replaced with chlorite; vesicles infilled zonally (from walls to center of vesicles) with smectite, zeolite, and trace of chlorite, carbonate is located in center. Oxidation of basalt is low (~5%). | Smectite |
| 29R-1, 38-43 | Sparsely olivine-plagioclase microphyric basalt, weakly vesicular (1%; 0.1-0.3 mm), incompletely crystallized. Groundmass of intergranular, partly microdoleritic, texture. Microphenocrysts of single tabular crystals of plagioclase (andesine; to 0.2-0.4 mm) and olivine. Groundmass of plagioclase lathe (50%), isometric clinopyroxene crystals (30%-35%), opaque minerals, and interstitial glass (5%-10%). | ~20%; olivine and interstitial glass completely replaced by smectite and chlorite; vesicles infilled with smectite and chlorite. Oxidation of basalt is low (~5%). | Smectite |
| 29R-3, 5-9 | Olivine-clinopyroxene-plagioclase phyric basalt, vesicular (10%-15%; 1-2 to 5 mm), incompletely crystallized. Groundmass with vitrophyric-microlitic texture. Phenocrysts (5%-10%) of olivine (0.2-0.7 mm), clinopyroxene (0.2-1 mm), and plagioclase (up to 1.3-1.5 mm). Groundmass of plagioclase lathe (50%), clinopyroxene, and dark brown interstitial glass. | ~15%-20%; olivine and interstitial glass completely replaced by smectite and chlorite; vesicles infilled with smectite and chlorite, with admixture of zeolites and carbonate. Oxidation of basalt is low (~5%). |
|
| 32R-3, 71-76 | Clinopyroxene-plagioclase glomerophyric basalt, massive. Phenocrysts of clinopyroxene (0.2-0.5 mm) and plagioclase (labradorite and andesine) (to 0.3-1.2 mm). Groundmass of plagioclase lathe (45%-50%), clinopyroxene (30%-35%), opaque minerals (5%), and interstitial glass (10%). | 10%-15%; olivine replaced by smectite, chlorite, and oxidized Fe, interstitial glass replaced by smectite and chlorite. Oxidation of basalt is low (~2%). | Smectite and defective chlorite in trace amounts |
| 32R-7, 46-50 | The sample is similar to Sample 183-1137A-32R-3, 71-76 cm. | 10%-15%; olivine completely replaced by smectite, chlorite, and oxidized Fe, interstitial glass replaced by smectite and chlorite. Oxidation of basalt is low (~2%). | Smectite |
| 34R-3, 18-23 | Contact of tuff and basalt: |
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1. Sparsely plagioclase microphyric basalt, weakly vesicular (single vesicles), incompletely crystallized. Groundmass demonstrates microlitic texture. Microphenocrysts of plagioclase (<5%; to 0.1-0.55 mm). Groundmass represented by glass and long lathe of plagioclase. | Moderate (~30%); microphenocrysts replaced completely by opaque minerals and traces of chlorite; interstitial glass replaced by chlorite and smectite and opaque minerals. Groundmass plagioclase replaced by albite; single vesicles infilled with opaque minerals and chlorite. Oxidation of basalt is moderate (~10%). | Smectite and hydromica, chlorite, and swelling chlorite in trace amounts |
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2. Crystal-lithoclastic tuff, vesicular. | Moderate (~30%). Oxidation of basalt is moderate (~10%). | Smectite and hydromica and quartz in trace amounts |
| 37R-5, 73-79 | Sparsely plagioclase microphyric basalt, highly vesicular (~50%; 1-5 mm), incompletely crystallized, with microlitic texture in groundmass. Microphenocrysts of plagioclase (<5%) represented by tabular crystals (0.1-0.3 mm). Groundmass represented by interstitial glass and long plagioclase lathe. | High (~60%); vesicles infilled (from wall to center) with brown-yellow chlorite, brown-green chlorite with zeolites (natrolite and tomsonite), and green clay minerals with traces of zeolites; microphenocrysts of plagioclase partly replaced by albite and chlorite; interstitial glass replaced by opaque minerals and chlorite. Oxidation of basalt is strong (total ~40% of rock). |
|
| 39R-2, 114-119 | Aphyric basalt, incompletely crystallized, brecciated rock, with microlitic, partly hyaline, texture of groundmass. | ~35%; secondary minerals represented by chlorite smectite, and zeolites. Oxidation of basalt is low (total ~3%-5% of rock). |
|
| 39R-3, 6-14 | Sparsely plagioclase microphyric basalt, weakly vesicular, incompletely crystallized, with microlitic texture. Microphenocrysts of plagioclase (<5%) represented by tabular crystals (0.2-1.2 mm). Groundmass of plagioclase lathe, microlathe of clinopyroxene, opaque minerals, and interstitial glass. | Moderate (~30%); interstitial glass replaced by chlorite and smectite; single vesicles infilled (from wall to center) with chlorite and smectite. Oxidation of basalt is low (total ~2% of rock). | Smectite |
| 43R-2, 84-92 | Dacitic tuff. Matrix contains baked ashes. | Very high (80%); secondary minerals represented by chlorite and carbonate. Oxidation of basalt is moderate (total ~10%-15% of rock). | Smectite and quartz in trace amounts with 10% of mica layers |
| 45R-1, 121-126 | Plagioclase phyric basalt, vesicular (10%-15%), incompletely crystallized, with microlitic, partly intersertal, texture. Microphenocrysts of plagioclase (10%) are represented by tabular crystals. Groundmass of plagioclase, clinopyroxene, and interstitial glass. | Moderate to high (~40%); olivine completely replaced by chlorite, plagioclase replaced by K-feldspar (adularia?), smectite, chlorite, and carbonate; interstitial glass completely replaced by chlorite and smectite and oxidized Fe; single vesicles infilled with chlorite, smectite, zeolites, and carbonate. Oxidation of basalt is moderate (total ~10%-15% of rock). | Smectite and swelling chlorite and hydromica in trace amounts |
Note: XRD = X-ray diffraction.