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Table of Contents
doi:10.2204/iodp.pr.312.2006
Table T2. Key parameters for Hole 1256D and preliminary subdivisions of the upper oceanic crust at Site 1256 adopted for Expeditions 309 and 312.
Location: 6°44.163'N, 91°56.061'W
Water depth (m): 3634.7
Sediment thickness (m): 250
16-in casing string (m): 269.5
Interval in Hole 1256D drilled during
ODP Leg 206: 752 mbsf, 502 msb
IODP Expedition 309: 1255.1 mbsf, 1005.1 msb
IODP Expedition 312: 1507.1 mbsf, 1257.1 msb
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Top core, section,
interval (cm)
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Lavas
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Lava Pond
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206-1256D-2R-1, 0
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1256D-1
(1256C-1 through 18)
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~250
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Massive ponded lava including overlying sheet flows.
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Inflated Flows
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206-1256D-13R-1, 0
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1256D-2
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350.3
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Massive sheet and pillowed flows with rare inflation features.
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Sheet and massive flows
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206-1256D-43R-1, 0
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1256D-16
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533.9
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Sheet flows with subordinate massive flows.
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Transition zone
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309-1256D-117R-1, 85
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1256D-40
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1004.2
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Sheet flows with breccias, rare dikes, and alteration at (sub-) greenschist facies conditions.
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Sheeted dike complex
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Upper dikes
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309-1256D-129R-1, 0
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1256D-44a
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1060.9
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Massive basalts, common subvertical intrusive contacts. Elevated VP and TC.
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Granoblastic dikes
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312-1256D-192R-1, 0
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1256D-78
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1348.3
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Granoblastic texture; equant grains; secondary clinopyroxene, orthopyroxene, plagioclase, hornblende, magnetite, and illite.
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Plutonic section
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Gabbro 1
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312-1256D-213R-1 (Piece 13, 52)
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1256D-81
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1406.62
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Medium-grained gabbroic rocks intrude overlying dikes: gabbro, disseminated oxide gabbro, patchy gabbro, and quartz-rich oxide diorite.
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Upper dike screen
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312-1256D-225R-1 (Piece 1, 0)
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1256D-90
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1458.9
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Fine-grained to cryptocrystalline basalt dike. Highly altered, granoblastic texture, secondary clinopyroxene, orthopyroxene, plagioclase, mt, illite, and hornblende.
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Gabbro 2
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312-1256D-230R-1 (Piece 5, 15)
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1256D-91
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1483.1
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Plutonic rock intrudes upper and lower dike screens; medium-grained gabbro, oxide-bearing quartz gabbro, oxide gabbro, orthopyroxene-bearing gabbro, trondjhemite; leucocratic-gabbro; all highly altered; stoped basalt.
Gabbronorite of uncertain origin.
Late dike Unit 95 at 1502.6 mbsf.
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