IODP Expedition 335: Deep Sampling in ODP Hole 1256D

Teagle, D. A. H.; Ildefonse, Benoı̂t; Blum, Peter

doi:10.2204/iodp.sd.13.04.2011

Cited by 11 publications

(13 citation statements)

References 33 publications

(30 reference statements)

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“…The depth interval for each section is cited from Teagle et al [, ]. As bulk rocks from different sections have similar density [ Teagle et al , ], the total mass of each section is proportional to its depth interval that was used to calculate the concentration‐weighted average δ 65 Cu and δ 66 Zn values of bulk oceanic crust at IODP Site 1256.…”

Section: Discussionmentioning

confidence: 99%

“…The oceanic crust at this site formed ~15 Ma ago during an episode of superfast ocean ridge spreading (~220 mm/yr) [ Wilson et al , ]. The 1271.6 m of drilled crustal rocks were recovered at Site 1256 after penetrating ~250 m of sediments [ Wilson et al , ; Teagle et al , , ] (Figure ). As revealed by preliminary downhole stratigraphy established from shipboard core observations and wire line log interpretations onboard [ Wilson et al , , ; Teagle et al , ], the drilled oceanic crust, from top to bottom, consists of (1) the volcanic section (~250–1004.2 m below seafloor, bsf); (2) the lava‐dyke transition zone (1004.2–1060.9 m bsf); (3) the sheeted dyke complex (1060.9–1406.6 m bsf); and (4) the plutonic complex (1406.6–1521.3 m bsf).…”

Section: Geological Background and Sample Descriptionsmentioning

confidence: 99%

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Copper and zinc isotope systematics of altered oceanic crust at IODP Site 1256 in the eastern equatorial Pacific

et al. 2016

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This paper presents the first combined Cu and Zn isotopic study of altered oceanic crust at Integrated Ocean Drilling Program (IODP) Hole 1256D that penetrates a volcanic section, a lava‐dyke transition zone, a sheeted dyke complex, and a plutonic complex. In the volcanic section, all but one rocks have Cu and Zn isotopic compositions similar to fresh mid‐ocean ridge basalt (MORB), reflecting restricted seawater circulation and low oxygen fugacity. Rocks in the transition zone have MORB‐like δ65Cu and δ66Zn, indicating the dominant influence of basalt‐derived Cu and Zn during alteration. Rocks in the dyke complex have more variable δ65Cu (−0.50–0.90‰) and δ66Zn (0.19–0.55‰) and those in the plutonic complex have δ65Cu of −0.43 to 0.20‰ and δ66Zn of 0.21 to 0.41‰. The rocks with heavier δ66Zn and heavier or lighter δ65Cu relative to MORB are characterized by Cu‐Zn depletions, low Li/Yb (<1.0) and low δ18O (<5‰), suggesting that hydrothermal extraction during high temperature alteration of oceanic crust can result in significant Cu and Zn isotope fractionation. Such large Cu and Zn isotopic variations are the results of redox transformation of Cu as well as Cu and Zn isotope fractionation between altered basaltic rocks and dissolved Cu and Zn species in hydrothermal fluids (e.g., [CuCl3]1−, Zn(HS)42−). This work is the first to define the distribution of Cu and Zn isotopes in an intact oceanic crust with concentration‐weighted averages of δ65Cu (0.05 ± 0.03‰) and δ66Zn (0.27 ± 0.01‰). The potential implications of these new observations are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Background and Sample Descriptionsmentioning

confidence: 99%

Copper and zinc isotope systematics of altered oceanic crust at IODP Site 1256 in the eastern equatorial Pacific

et al. 2016

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“…Pilot Hole 1256C cored 250.7 m of sediments and 88.5 m into the basement, that is composed of a 32 m thick lava pond with thin sheet flows above and below (Figure 2) [ Wilson et al , 2003]. The main hole with the deepest penetration, Hole 1256D, lays ∼30 m south of 1256C, started coring at 276 m below seafloor (mbsf) within the uppermost basement and penetrated 1271 m into the oceanic basement completely through the volcanic and dike sections and into the uppermost plutonic rocks (Figure 2) [ Wilson et al , 2006; Teagle et al , 2006, 2012].…”

Section: Geological Setting and Methodsmentioning

confidence: 99%

Downhole variation of lithium and oxygen isotopic compositions of oceanic crust at East Pacific Rise, ODP Site 1256

Gao

Vils

Cooper

et al. 2012

Geochem Geophys Geosyst

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[1] Bulk rock lithium and oxygen isotope compositions from ODP Site 1256 were analyzed to investigate the seawater circulation in the upper oceanic crust formed at the East Pacific Rise (EPR Li principally reflects variations in water-rock ratio (w/r) together with a downhole increase of temperature. Seawater flow in the upper volcanic zone is likely to be channeled with generally small but variable w/r ratios. The w/r ratios increase rapidly with depth in the lower volcanic section into the sheeted dike complex indicating water dominated pervasive hydrothermal flow due to intensive upwelling of hydrothermal fluids.

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“…A characteristic feature of the granoblastic hornfelses at IODP Site 1256 is that they contain intrusions of felsic, evolved plutonic rocks. These are small, irregular patches, veins (~1-2 mm wide), and dikelets (<1.5 cm wide) consisting of oxide gabbro, diorite, tonalite, and trondhjemite (Wilson et al 2006;Teagle et al 2012) with a fine-to medium-grained granular texture. Here, for the comparison to experimental anatectic melts, we focus only on those felsic veins and dikelets of the Hole 1256D drill core characterized as tonalites based on the mineral mode.…”

Section: Felsic Rocks From Iodp Site 1256mentioning

confidence: 99%

Anatexis at the roof of an oceanic magma chamber at IODP Site 1256 (equatorial Pacific): an experimental study

Erdmann

Fischer

France

et al. 2015

Contrib Mineral Petrol

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International audienceReplenished axial melt lenses at fast-spreading mid-oceanic ridges may move upward and intrude into the overlying hydrothermally altered sheeted dikes, resulting in high-grade contact metamorphism with the potential to trigger anatexis in the roof rocks. Assumed products of this process are anatectic melts of felsic composition and granoblastic, two-pyroxene hornfels, representing the residue after partial melting. Integrated Ocean Drilling Program Expeditions 309, 312, and 335 at Site 1256 (eastern equatorial Pacific) sampled such a fossilized oceanic magma chamber. In this study, we simulated magma chamber roof rock anatectic processes by performing partial melting experiments using six different protoliths from the Site 1256 sheeted dike complex, spanning a lithological range from poorly to strongly altered basalts to partially or fully recrystallized granoblastic hornfels. Results show that extensively altered starting material lacking primary magmatic minerals cannot reproduce the chemistry of natural felsic rocks recovered in ridge environments, especially elements sensitive to hydrothermal alteration (e.g., K, Cl). Natural geochemical trends are reproduced through partial melting of moderately altered basalts from the lower sheeted dikes. Two-pyroxene hornfels, the assumed residue, were reproduced only at low melting degrees (<20 vol%). The overall amphibole absence in the experiments confirms the natural observation that amphibole is not produced during peak metamorphism. Comparing experimental products with the natural equivalents reveals that water activity (aH2O) was significantly reduced during anatectic processes, mainly based on lower melt aluminum oxide and lower plagioclase anorthite content at lower aH2O. High silica melt at the expected temperature (1000–1050 °C; peak thermal overprint of two-pyroxene hornfels) could only be reproduced in the experimental series performed at aH2O = 0.1

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IODP Expedition 335: Deep Sampling in ODP Hole 1256D

Cited by 11 publications

References 33 publications

Copper and zinc isotope systematics of altered oceanic crust at IODP Site 1256 in the eastern equatorial Pacific

Copper and zinc isotope systematics of altered oceanic crust at IODP Site 1256 in the eastern equatorial Pacific

Downhole variation of lithium and oxygen isotopic compositions of oceanic crust at East Pacific Rise, ODP Site 1256

Anatexis at the roof of an oceanic magma chamber at IODP Site 1256 (equatorial Pacific): an experimental study

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