Petrogenesis of basalts from the FAMOUS area: Mid-Atlantic Ridge

Langmuir, C. H.; Bender, John F.; Bence, A. E.; Hanson, Gilbert N.; Taylor, Stuart Ross

doi:10.1016/0012-821x(77)90194-7

Cited by 609 publications

(229 citation statements)

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“…Therefore the many different melts present at any one time within the melting regime may erupt independently, mix, or react with the mantle through which they pass, in a collection of processes that have been called "dynamic melting" [Langmuir et al, 1977]. The mean composition of the ocean crust, however, will be the mean composition of melts pooled from the melting regime.…”

Section: A Working Modelmentioning

confidence: 99%

“…For example, Figure 6 shows three REE patterns for MORB, one typical of "normal" MORB, one from near a hot spot that is highly "enriched", and one that is transitional. Since the LREE are incompatible, the Rare Earth Elements Transitional T -MORB is from the FAMOUS region [Langmuir et a/., 1977]; Normal N-MORB is from the MAR, between the Atlantis and Hayes Fracture Zones (MAR standard [LDGO, unpublished data] Langmuir et al, 1977). Therefore the LREE depletion of normal MORB requires a LREE depletion of its source.…”

Section: Trace Element Patternsmentioning

confidence: 99%

“…Such studies have identified significant local chemical systematics for both major and trace elements. This chemical variability has been attributed to both magma chamber [Bryan and Moore, 1977;Dungan and Rhodes, 1978] and melting processes [White and Bryan, 1977;Langmuir et al, 1977], although the evidence for variations in the extent of melting has in the past relied almost exclusively on trace element modeling. Klein and Langmuir [1989;hereafter KL89], prompted by the work of Brodholt and Batiza [1989], explored the nature of local chemical variability and how it compares to global variability, using the fractionation-corrected parameters of KL87.…”

Section: Local Variability Of Major Elements In Morbmentioning

confidence: 99%

“…Melt is then continually being removed from the system, but some melt fraction always remains with the residue. This is the "continuous melting" model presented by Langmuir et al [1977] as one aspect of the more complex "dynamic melting," which conceptually included reaction during ascent and a variety of melt extraction processes. Recent literature has used the term dynamic melting for the original continuous melting model [McKenzie, 1985a[McKenzie, , 1985bWill:a -r.s and Gill, 1989;• 20.88-23.02 et al, 1991].…”

Section: The Importance Of Mechanisms Of Melt Extractionmentioning

confidence: 99%

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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

654

390

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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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Section: A Working Modelmentioning

confidence: 99%

Section: Trace Element Patternsmentioning

confidence: 99%

Section: Local Variability Of Major Elements In Morbmentioning

confidence: 99%

Section: The Importance Of Mechanisms Of Melt Extractionmentioning

confidence: 99%

See 2 more Smart Citations

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

654

390

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“…It has been proposed that isotopic and other compositional differences between basalts reflect mineralogical heterogeneity [Langmuir et al, 1977 Hauri [1996]). However, isotopic differences need not be accompanied by substantial differences in mineralogy (compare whole rocks and mineral separates from Okano and Tatsumoto [1996] and Xu et al [1998]), Moreover, variations in the pressures (P) and temperatures (T) of partial melting have a significant impact on basalt composition [Klein and Langmuir, 1987; Kinzler and Grove, 1992b; Kinzler, 1997].…”

Section: Introductionmentioning

confidence: 99%

Melting depths and mantle heterogeneity beneath Hawaii and the East Pacific Rise: Constraints from Na/Ti and rare earth element ratios

Putirka¹

1999

J. Geophys. Res.

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Abstract. Mantle melting calculations are presented that place constraints on the mineralogy of the basalt source region and partial melting depths for oceanic basalts. Melting depths are obtained from pressure-sensitive mineral-melt partition coefficients for Na, Ti, Hf, and the rare earth elements (REE). Melting depths are estimated by comparing model aggregate melt compositions to natural basalts from Hawaii and the East Pacific Rise (EPR). Variations in melting depths in a peridotite mantle are sufficient to yield observed differences in Na/Ti, Lu/Hf, and Sm/Yb between Hawaii and the EPR.Initial melting depths of 95-120 km are calculated for EPR basalts, while melting depths of 200-400 km are calculated for Hawaii, indicating a mantle that is 300øC hotter at Hawaii. Some isotope ratios at Hawaii are correlated with Na/Ti, indicating vertical stratification to isotopic heterogeneity in the mantle; similar comparisons involving EPR lavas support a layered mantle model. Abundances of Na, Ti, and REE indicate that garnet pyroxenite and eclogite are unlikely source components at Hawaii and may be unnecessary at the EPR. The result that some geochemical features of oceanic lavas appear to require only minor variations in mantle mineral proportions (2% or less) may have important implications regarding the efficiency of mantle mixing. Heterogeneity required by isotopic studies might be accompanied by only subtle differences in bulk composition, and material that is recycled at subduction zones might not persist as mineralogically distinct mantle components. IntroductionFundamental questions in the Earth sciences concern the mineralogy of the basalt source region and the temperatures and depths at which basalts form. It has been proposed that isotopic and other compositional differences between basalts reflect mineralogical heterogeneity differentiate between heterogeneity with respect to mineralogy, isotope ratios, or differences in major or minor element composition. To examine issues of heterogeneity and the conditions of partial melting, alkalic and tholeiitic basalts from Hawaii and tholeiites from the EPR are compared. Hawaii is the type example for a mantle plume, while EPR basalts are representative of mid-ocean ridges [Langmuir, 1988]

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Water in Hawaiian peridotite minerals: A case for a dry metasomatized oceanic mantle lithosphere

Peslier

Bizimis

2015

Geochem Geophys Geosyst

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The distribution of water concentrations in the oceanic upper mantle has drastic influence on its melting, rheology, and electrical and thermal conductivities and yet is primarily known indirectly from analyses of OIB and MORB. Here, actual mantle samples, eight peridotite xenoliths from Salt Lake Crater (SLC) and one from Pali in Oahu in Hawaii were analyzed by FTIR. Water contents of orthopyroxene, clinopyroxene, and the highest measured in olivine are 116-222, 246-442, and 10-26 ppm weight H 2 O, respectively. Although pyroxene water contents correlate with indices of partial melting, they are too high to be explained by simple melting modeling. Mantle-melt interaction modeling reproduces best the SLC data. These peridotites represent depleted oceanic mantle older than the Pacific lithosphere that has been refertilized by nephelinite melts containing <5 weight % H 2 O. Metasomatism in the Hawaiian peridotites resulted in an apparent decoupling of water and LREE that can be reconciled via assimilation and fractional crystallization. Calculated bulk-rock water contents for SLC (50-96 ppm H 2 O) are on the low side of that of the MORB source (50-200 ppm H 2 O). Preceding metasomatism, the SLC peridotites must have been even drier, with a water content similar to that of the Pali peridotite (45 ppm H 2 O), a relatively unmetasomatized fragment of the Pacific lithosphere. Moreover, our data show that the oceanic mantle lithosphere above plumes is not necessarily enriched in water. Calculated viscosities using olivine water contents allow to estimate the depth of the lithosphere-asthenosphere boundary beneath Hawaii at 90 km.

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Petrogenesis of basalts from the FAMOUS area: Mid-Atlantic Ridge

Cited by 609 publications

References 54 publications

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

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

Melting depths and mantle heterogeneity beneath Hawaii and the East Pacific Rise: Constraints from Na/Ti and rare earth element ratios

Water in Hawaiian peridotite minerals: A case for a dry metasomatized oceanic mantle lithosphere

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