An oxygen isotopic profile through the upper kilometer of the oceanic crust, DSDP Hole 504B

Alt, Jeffrey C; Muehlenbachs, Karlis; Honnorez, J.

doi:10.1016/0012-821x(86)90106-8

Cited by 208 publications

(160 citation statements)

References 35 publications

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“…Lower δ 13 C values tend to occur in vesicles with higher CO 2 / 3 He although there is not a strong correlation (Fig. 7d) suggesting that there may be some δ 13 C heterogeneity in the contaminant (Alt et al 1986;Staudigel et al, 1995;Kelley and Früh-Green, 2001). …”

Section: Evolution Of Vesicle Gasmentioning

confidence: 95%

“…The speciation and isotopic composition of carbon in oceanic crust is probably stratified. The top 10s to 100s of metres of the most thoroughly characterised oceanic crust, from hole DSDP Holes 417, 418 (Atlantic Ocean) and 504B (Pacific Ocean), host carbonate with marine δ 13 C values (~ 0‰ ± 2‰; Alt et al, 1986;Staudigel et al 1995). Rocks from greater depths, however, which are likely to represent wall rocks where magma is stored, contain CO 2 and CH 4 with a range of carbon concentrations and isotope ratios.…”

Section: Evolution Of Dissolved Volatilesmentioning

confidence: 99%

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Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Macpherson

Hilton

Mertz

et al. 2005

Geochimica et Cosmochimica Acta

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Section: Evolution Of Vesicle Gasmentioning

confidence: 95%

Section: Evolution Of Dissolved Volatilesmentioning

confidence: 99%

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Macpherson

Hilton

Mertz

et al. 2005

Geochimica et Cosmochimica Acta

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“…Strontium data from Table 1 (whole rocks = solid circles; secondary minerals are labeled) and various sources Friedrichsen, 1982, 1987;Barrett, 1983;Hart and Mottl, 1983;Friedrichsen, 1985;Staudigel and Hart, 1985;Kawahata et al, 1987;Kusakabe et al, 1989;Shimizu et al, 1989). Oxygen data from Table 1 (solid circles), Alt et al (1986bAlt et al ( , 1989bAlt et al ( , 1995, and Nesbitt et al (1987). S data from Alt et al (1989aAlt et al ( , 1995, Zuleger et al (1995), and Bach et al (this volume).…”

Section: Methodsmentioning

confidence: 99%

“…Hblde = hornblende. Data from this work and Alt et al (1985Alt et al ( , 1986aAlt et al ( , 1986bAlt et al ( , 1995.…”

Section: Site 504mentioning

confidence: 99%

Stable and Strontium Isotopic Profiles through Hydrothermally Altered Upper Oceanic Crust, Hole 504B

Alt¹,

Teagle²,

Bach³

et al. 1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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Leg 148 penetrated 111m farther into Hole 504B, to a total depth of 2111 meters below seafloor (mbsf), and recovered diabase dikes similar to the immediately overlying rocks. Secondary mineralogy and whole-rock oxygen and strontium isotopic compositions were determined for samples from Leg 148. In addition, strontium isotopic analyses were performed on previously recovered samples of the lower dikes (1550-2000 mbsf). Trends observed in the lower dikes (1550-2000 mbsf) continue in the Leg 148 section (2000-2111 mbsf). These include the local presence of magnesiohornblende and secondary calcic plagioclase and high Ti contents of amphiboles. Cu, Zn, and S contents of the more altered rocks are low, and whole-rock δ 18 θ values of 33%350°C) and greater extents of recrystallization than in the upper dikes. All of the data for the new Leg 148 section are consistent with the rocks being a continuation of a subsurface reaction zone, where metals and sulfur are leached from the crust by hydrothermal fluids and transported to form metal sulfide mineralizations on or within the crust or vent into seawater.Sr contents of the lower sheeted dikes (1550-2111 mbsf) are generally 48-62 ppm, and whole-rock 87 Sr/ 86 Sr ratios range from 0.70265 to 0.70304, only slightly elevated relative to fresh MORB values. The rocks were altered by seawater-derived hydrothermal fluids, with little change in the Sr concentrations of the rocks. Although amphibole is the most abundant secondary phase, the Sr isotopic composition of the rocks is probably dominated by the abundance of secondary plagioclase. The 87 Sr/ 86 Sr ratios of hydrothermal fluids were higher than measured in variably recrystallized (10%-80%) whole rocks. The seawater component of hydrothermal fluids increased through time, as documented by 87 Sr/ 86 Sr ratios of 0.7028-0.7034 for amphibole and chlorite, to 0.7035-0.7038 for vein epidotes. The latter values record the composition of upwelling black smoker-type endmember hydrothermal fluids at Site 504.The low 87 Sr/ 86 Sr ratios for the lower dikes differ from the uniformly high ratios of the thoroughly recrystallized sheeted dikes from the Troodos ophiolite. The oceanic dikes interacted with much smaller volumes of seawater than the ophiolitic rocks and apparently to a lesser extent. These differences are in some way related to the contrasting tectonic setting, mineralogy, and chemical composition of ophiolites compared to in situ ocean crust.

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“…rocks underwent hydration. The alteration could potentially be a result of the high permeability of young seafloor allowing sea-water to penetrate and hydrothermally react with the rocks, or of submarine weathering (Gregory & Taylor, 1981;Stakes & O'Neil, 1982;Alt, Muehlenbachs & Honnorez, 1986). Alternatively, the greenschist metamorphic event may have involved hydration (as in the case of alteration of meta-gabbro) or dehydration (deserpentinization).…”

Section: A Major and Trace Element Geochemistrymentioning

confidence: 99%

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

et al. 1996

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-The six exposures of the Upper tectonic Unit of the Cycladic Massif occurring on the island of Tinos are shown to comprise a metamorphosed dismembered ophiolite complex. The common stratigraphic section consisting of tens-of-metres-thick tectonic slices of mafic phyllites overlain by serpentinites and gabbros is considered to have been derived by a combination of thrusting during obduction and subsequent attenuation by low-angle normal faults. All rock types show evidence of a phase of regional greenschistfacies metamorphism, which in the case of the phyllites is accompanied by penetrative deformation. The greenschist-facies metamorphism in gabbros is preceded by high temperature sea-floor amphibolite-facies alteration, whereas in the serpentinites, the antigorite + forsterite greenschist-facies assemblage overprinted an earlier low temperature lizardite serpentinite. Trace element patterns of the mafic phyllites and a harzburgitic origin of meta-serpentinites suggest a supra subduction zone (SSZ) affinity for the ophiolitic suite. 5"O values of phyllites, gabbros and serpentinites range from 6 to 15%o. Model calculations indicate that such values are consistent with low temperature (50-200 °C) alteration of parent rocks by sea-water at varying water/rock ratios. This would agree with the early low temperature mineralogy of the serpentinites, but the early high temperature alteration of the gabbros would require the presence of "O-enriched sea-water.The following overall history is suggested for Tinos ophiolitic slices.(1) Oceanic crust was generated at a supra-subduction zone spreading centre with high temperature alteration of gabbros. (2) Tectonic disturbance (its early hot stages recorded in an amphibolitic shear zone at the base of serpentinites) brought the already cooled ultramafics into direct contact with sea-water and caused low-7* serpentinization. (3) Tectonism after cooling involved thrusting which caused repetition and inversion of the original order of the oceanic suite. (4) Regional metamorphism of all the ophiolite components at greenschist-facies conditions (~450 °C) overprinted the early alteration mineralogy. It was probably induced by continued thrusting and piling up of nappes. The Tinos ophiolite, dated as late Cretaceous and genetically related to other low pressure rock-units of the same age in the Aegean, differs in age and degree of dismemberment and metamorphism from ophiolites in mainland Greece.

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An oxygen isotopic profile through the upper kilometer of the oceanic crust, DSDP Hole 504B

Cited by 208 publications

References 35 publications

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Sources, degassing, and contamination of CO2, H2O, He, Ne, and Ar in basaltic glasses from Kolbeinsey Ridge, North Atlantic

Stable and Strontium Isotopic Profiles through Hydrothermally Altered Upper Oceanic Crust, Hole 504B

The tectono-metamorphic evolution of a dismembered ophiolite (Tinos, Cyclades, Greece)

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