Table T36. Basalt texture types—textural development of metamorphic overprint.
| Texture type |
Reference | Primary igneous features | ||||
|---|---|---|---|---|---|---|
| Thin section |
Core, section, interval (cm) |
Glass | Interstitial clinopyroxene |
Plagioclase hollows |
Fe-Ti oxides |
|
| 1 | Not observed at Site 1256 | Pristine | Fresh | Fresh | All primary | |
| 2 | 109 | 206-1256D-13R-1 (Piece 13, 109–111) | Altered to clay minerals | Fresh | Fresh | All primary |
| 3 | 3 | 312-1256D-173R-2 (Piece 8, 6–10) | All chlorite and oxides | <50% altered to dusty brown fibrous masses | Chlorite and dusty cryptocrystalline material | Mostly primary |
| 4 | 17 | 312-1256D-178R-1 (Piece 3, 31–34) | Tiny fibrous masses and chlorite | >50% altered to dusty brown fibrous masses | Dusty brown material | Mostly primary, tiny secondary grains replacing clinopyroxene |
| 5 | 32 | 312-1256D-192R-1 (Piece 2, 11–13) | Actinolite/Oxide overgrowth | >90% altered to actinolite and oxides | Discrete tiny oxide and actinolite | Mostly primary, abundant tiny secondary grains in altered clinopyroxene |
| 6 | 36 | 312-1256D-196R-1 (Piece 10, 32–33) | Intense actinolite/oxide overgrowth | 100% altered to actinolite and tiny oxide grains | Actinolite/Oxides | Primary grains, large secondary idioblastic grains |
| 7 | 39 | 312-1256D-198R-1 (Piece 4, 46–49) | See notes | 100% altered to actinolite, secondary clinopyroxene and rimmed by tiny oxides | Plagioclase beginning to recrystallize without hollows | No recognizable primary grains, increase in size of secondary grains |
Notes: Variations as observed in microcrystalline to fine-grained rocks of intersertal to variolitic texture. Figure F212 shows representative images of texture Types 2–7.
| Texture type |
Reference | Secondary minerals | ||||
|---|---|---|---|---|---|---|
| Thin section |
Core, section, interval (cm) |
Dusty brown material |
Actinolite | Green hornblende |
Clinopyroxene | |
| 1 | Not observed at Site 1256 | None | None | None | None | |
| 2 | 109 | 206-1256D-13R-1 (Piece 13, 109–111) | None | None | None | None |
| 3 | 3 | 312-1256D-173R-2 (Piece 8, 6–10) | Replacing clinopyroxene | Possibly fibrous material replacing pyroxene | None | None |
| 4 | 17 | 312-1256D-178R-1 (Piece 3, 31–34) | Replacing clinopyroxene | Visible fibers replacing pyroxene and glass | None | None |
| 5 | 32 | 312-1256D-192R-1 (Piece 2, 11–13) | Rare, replacing clinopyroxene | Fibrous, replacing dusty brown material in altered pyroxene | None | None |
| 6 | 36 | 312-1256D-196R-1 (Piece 10, 32–33) | None | Larger, more prismatic, and brown | Sporadically present | None |
| 7 | 39 | 312-1256D-198R-1 (Piece 4, 46–49) | None | Abundant; larger, more prismatic, and brown | Single grains and poikiloblastic clusters | Anhedral grains replacing actinolite, sometimes in patchy domains |
Previous | Close | Next | Top of page