Table T5. Summary of the phenocryst and groundmass minerals present in representative thin sections for the different basalt units, Hole 1301B.
Hole: | 301-U1301B- | |||||||||||
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Core, section, interval (cm): | 1R-1, 14–18 | 1R-1, 118–121 | 2R-1, 4–8 | 12R-1, 31–33 | 15R-4, 66–68 | 16R-1, 83–85 | 18R-2, 92–94 | 19R-1, 132–134 | 21R-2, 126–128 | 26R-1, 41–43 | 35R-2, 107–109 | 36R-2, 102–104 |
Depth (mbsf): | 351.20 | 351.20 | 357.10 | 428.90 | 448.10 | 453.20 | 472.30 | 476.10 | 491.56 | 515.50 | 565.07 | 574.70 |
Basalt unit: | 1A | 1B | 1C | 2A | 4C | 5 | 6 | 7A | 7B | 7C | 8B | 8C |
Rock type: | Breccia | Massive basalt | Pillow basalt | Massive basalt | Massive basalt | Pillow basalt | Massive basalt | Pillow basalt | Pillow basalt | Pillow basalt | Massive basalt | Pillow basalt |
Texture: | Brecciated | Intersertal | Hyalophitic | Intersertal | Intersertal | Intersertal | Intergranular | Intersertal | Hyalophitic | Hyalophitic | Hyalophitic | Intersertal |
Maximum groundmass grain size: | Clay to pebbles | Microcrystalline | Microcrystalline | Fine grained | Fine grained | Microcrystalline | Fine grained | Microcrystalline | Microcrystalline | Microcrystalline | Fine grained | Microcrystalline |
Vesicles (%): | NA | 2 | 2.3 | 2.7 | Trace | 2.7 | 13.3 | 1.3 | Trace | 2.8 | 2.1 | 0.9 |
Phenocrysts: |
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Plagioclase (%) | — | 3 | 1.2 | 3.1 | 3 | 5.4 | 3.7 | 1.8 | 5.4 | 1.1 | 3.5 | 3.6 |
Morphology | Euhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral | Euhedral to subhedral | Euhedral |
Size range (mm) | — | 0.4–1.4 | 1.2–2.0 | 1.2–2.5 | 0.7–2.8 | 0.2–4.5 | 1.2–2.5 | 1.5–3.8 | 0.8–2.7 | 1–3.3 | 0.8–2.2 | 1.2–4.0 |
Olivine (%) | — | Trace | 0.5 | 3.6 | 3 | 3 | 1.2 | 1.6 | 2.1 | 1.2 | Trace | 0.3 |
Morphology | — | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Subhedral |
Size range (mm) | — | 0.2–0.5 | 1–1.5 | 0.8–1.6 | 0.5–1.0 | 0.5–1.0 | 0.6–1.2 | 0.8–1.5 | 0.6–1.2 | 0.8–1.2 | 0.8–1.2 | 1.2–5.5 |
Clinopyroxene (%) | — | 1 | 0.8 | 1.2 | 1 | 3.4 | — | 5 | 3.5 | — | 1.7 | 1.8 |
Morphology | — | Anhedral | Euhedral to anhedral | Euhedral to anhedral | Euhedral to anhedral | Euhedral to anhedral | — | Anhedral | Euhedral to anhedral | — | Euhedral to anhedral | Euhedral to anhedral |
Size range (mm) | — | 0.2–0.5 | 1.5–2.5 | 0.8–2.2 | 0.4–1 | 0.5–1.0 | — | 1–2.5 | 0.8–3.8 | — | 0.8–3 | 0.5–0.8 |
Total phenocryst (%): |
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4 | 2.5 | 7.9 | 7 | 11.8 | 4.9 | 8.4 | 11 | 2.3 | 5.2 | 5.7 |
Groundmass: |
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Plagioclase (%) | Trace | 38 | 15.5 | 34.2 | 37 | 28.3 | 32.9 | 29.2 | 12.7 | 11.7 | 16.8 | 20.6 |
Morphology | Euhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral | Euhedral to subhedral | Euhedral to subhedral |
Size range (mm) | <0.2 | <0.4 | <0.8 | <1.0 | <0.5 | <0.8 | <1.0 | <0.5 | <0.7 | <0.2 | <0.7 | <0.4 |
Olivine (%) | — | Trace | 1.6 | 12.5 | Trace | 5 | 17.4 | 3.8 | 2.1 | 2.4 | 1.8 | 3.8 |
Morphology | — | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral to subhedral | Euhedral | Euhedral to subhedral | Euhedral to subhedral |
Size range (mm) | — | <0.2 | <0.8 | <0.8 | <0.5 | <0.4 | <1.0 | <0.3 | <0.7 | <0.2 | <0.7 | <0.3 |
Clinopyroxene (%) | — | 20 | 3.3 | 35.5 | 10 | 19.6 | 31 | 10.7 | 6.7 | 5 | 5.9 | 9 |
Morphology | — | Anhedral | Euhedral to anhedral | Anhedral | Anhedral | Anhedral | Anhedral | Anhedral | Anhedral | Euhedral to anhedral | Anhedral | Subhedral to anhedral |
Size range (mm) | — | <0.2 | <0.8 | <0.6 | <0.4 | <0.5 | <0.8 | <0.3 | <0.7 | <0.1 | <0.7 | <0.4 |
Mesostasis (%): | — | 36 | 74.8 | 7.2 | 46 | 32.6 | 1.7 | 51.6 | 67.5 | 75.8 | 68.2 | 59.1 |
Note: NA = not applicable, — = not observed.
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