Abyssal peridotites, very slow spreading ridges and ocean ridge magmatism

Dick, H. J.

doi:10.1144/gsl.sp.1989.042.01.06

Cited by 471 publications

(452 citation statements)

References 75 publications

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“…ite at 350øC, compared with titanire and clinopyroxene at 400øC. In general, these alteration assemblages are consistent with observations of serpentinized MOR peridotites [Dick, 1989 Table 3a and the mineral densities, the approximate volume of the fresh peridotite may be calculated and compared to the final volume of the alteration products. In these simulations, the serpentinization of the peridotites resulted in volume increases from 2 to 23%.…”

Section: Rock Alterationsupporting

confidence: 85%

Distinguishing ultramafic‐from basalt‐hosted submarine hydrothermal systems by comparing calculated vent fluid compositions

Wetzel¹,

Shock²

2000

J. Geophys. Res.

147

106

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Section: Rock Alterationsupporting

confidence: 85%

Distinguishing ultramafic‐from basalt‐hosted submarine hydrothermal systems by comparing calculated vent fluid compositions

Wetzel¹,

Shock²

2000

J. Geophys. Res.

147

106

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“…Physical models predict spreading rate-dependencies on the pattern of melt and mantle flow [e.g., Scott and Stevenson, 1989;Spiegelman and McKenzie, 1987], which may influence the composition of melt formed and the volume of melt segregated to form the oceanic crust. It has been suggested that spreading rate correlates with crustal thickness for ridges far from hot spots [Reid and Jackson, 1981], with basalt major element composition [Bass, 1971;Morel and Hekinian, 1980], with isotopic heterogeneity [Cohen and O'Nions, 1982;Batiza, 1984], with gravity characteristics [Small and Sandwell, 1989], and with certain aspects of tectonic and magmatic segmentation [Schouten et al, 1985;Dick, 1989;Sinton et al, 1991]. We have found that the local vectors of compositional variability exhibit a striking contrast between slow-and fast-spreading ridges.…”

Section: Significance Of Spreading Ratementioning

confidence: 58%

Petrological Systematics of Mid-Ocean Ridge Basalts: Constraints on Melt Generation Beneath Ocean Ridges

Langmuir

Klein

Plank

2013

Mantle Flow and Melt Generation at Mid-Ocean Ridges

653

385

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Mid-ocean ridge basalts (MORB) are a consequence of pressure-release melting beneath ocean ridges, and contain much information concerning melt formation, melt migration and heterogeneity within the upper mantle. MORB major element chemical systematics can be divided into global and local aspects, once they have been corrected for low pressure fractionation and interlaboratory biases. Regional average compositions for ridges unaffected by hot spots ("normal" ridges) can be used to define the global correlations among normalized Na20, FeO, TiO2 and Si02 contents, CaO/Al203 ratios, axial depth and crustal thickness. Back-arc basins show similar correlations, but are offset to lower FeO and TiO2 contents. Some hot spots, such as the Azores and Galapagos, disrupt the systematics of nearby ridges and have the opposite relationships between FeO, Na 20 and depth over distances of 1000 km.Local variations in basalt chemistry from slow-and fast-spreading ridges are distinct from one another. On slow-spreading ridges, correlations among the elements cross the global vector of variability at a high angle. On the fast-spreading East Pacific Rise (EPR), correlations among the elements are distinct from both global and slow-spreading compositional vectors, and involve two components of variation. Spreading rate does not control the global correlations, but influences the standard deviations of axial depth, crustal thickness, and MgO contents of basalts.Global correlations are not found in very incompatible trace elements, even for samples far from hot spots. Moderately compatible trace elements for normal ridges, however, correlate with the major elements. Trace element systematics are significantly different for the EPR and the mid-Atlantic Ridge (MAR). Normal portions of the MAR are very depleted in REE, with little variability; hot spots cause large long wavelength variations in REE abundances. Normal EPR basalts are significantly more enriched than MAR basalts from normal ridges, and still more enriched basalts can erupt sporadically along the entire length of the EPR. This leads to very different histograms of distribution for the data sets as a whole, and a very different distribution of chemistry along strike for the two ridges. Despite these differences, the mean Ce/Sm ratios from the two ridges are identical.Existing methods for calculating the major element compositions of mantle melts [Klein and Langmuir, 1987;McKenzie and Bickle, 1988;Niu and Batiza, 1991] are critically examined. New quantitative methods for mantle melting and high pressure fractionation are developed to evaluate the chemical consequences of melting and fractionation processes and mantle heterogeneity. The new methods rely on new equations for partition coefficients for the major elements between mantle minerals and melts. The melting calculations can be used to investigate the chemical compositions produced by small extents of melting or high pressures of melting that cannot yet be determined experimentally. Application of the new models to the ...

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“…7. The association with refractory lithosphere comprising harzburgite tectonites and dunite in contrast to the more fertile abyssal lherzolites commonly found with oceanic crust [e.g., Dick, 1989;Dick and Bullen, 1984]. 8.…”

Section: Rapid Extension Of Upper Plate Into Gapmentioning

confidence: 99%

“…8. Mineral compositions in the lavas and mantle tectonites that are refractory compared to those found in oceanic basalts and abyssal peridotites, e.g., Cr spinels with high Cr/Al ratios and low Mg/Fe ratios [Cameron, 1985;Crawford et al, 1989;Dick, 1989;Dick and Bullen, 1984;Umino et al, 1990] Cohen and O'Nions, 1982;Hamelin et al, 1984Hamelin et al, , 1981Hanan and Schilling, 1989;Ito et al, 1987;Jacobsen and Wasserburg, 1979;McCulloch and Cameron, 1983;McCulloch et al, 1980McCulloch et al, , 1981Noiret et al, 1981;Sun, 1980]. [7] These geochemical signatures result from processes or conditions that are unique to subduction zones or that are enhanced within the subduction zone environment.…”

Section: Rapid Extension Of Upper Plate Into Gapmentioning

confidence: 99%

Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

Shervais

2001

Geochem Geophys Geosyst

449

275

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[1] Abstract: Suprasubduction zone (SSZ) ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites. This sequence includes the following: (1) birth, which entails the formation of the ophiolite above a nascent or reconfigured subduction zone; this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex; (2) youth, during which is continued melting of refractory asthenosphere (depleted during birth) occurs in response to fluid flux from the subducting slab, with extensional deformation of the older plutonic suite, eruption of refractory lavas, and the intrusion of wehrlite-pyroxenite; (3) maturity, with the onset of semistable arc volcanism, typically calc-alkaline, as the subduction zone matures and stabilizes, and the intrusion of quartz diorite and eruption of silicic lavas; and (4) death, which is the sudden demise of active spreading and ophiolite-related volcanism, which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis; expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites; (5) resurrection, with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction. The early stages (1± 3) may be diachronous, and each stage may overlap in both time and space. The existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the SSZ tectonic setting.

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Abyssal peridotites, very slow spreading ridges and ocean ridge magmatism

Cited by 471 publications

References 75 publications

Distinguishing ultramafic‐from basalt‐hosted submarine hydrothermal systems by comparing calculated vent fluid compositions

Distinguishing ultramafic‐from basalt‐hosted submarine hydrothermal systems by comparing calculated vent fluid compositions

Petrological Systematics of Mid-Ocean Ridge Basalts: Constraints on Melt Generation Beneath Ocean Ridges

Birth, death, and resurrection: The life cycle of suprasubduction zone ophiolites

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