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Table T5. Summary of the phenocryst and groundmass minerals present in representative thin sections for the different basalt units, Hole 1301B.

Hole: 301-U1301B-
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:











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 (%):
4 2.5 7.9 7 11.8 4.9 8.4 11 2.3 5.2 5.7
Groundmass:











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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