Basalts from the Northern Part of the Rift Zone of the Mid-Atlantic Ridge

Muir, I. D.; Tilley, C. E.; Scoon, J. H.

doi:10.1093/petrology/5.3.409

Cited by 197 publications

(51 citation statements)

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“…The groundmass olivine is more iron-rich and has a composition of Fo 80 . These iron contents are comparable to olivine compositions of tholeiitic-type basalts reported by Muir and Tilley (1964).…”

Section: Olivinesupporting

confidence: 88%

“…In three samples, two analyses are given, partially indicating grain-to-grain variability. The pyroxenes range in composition from typical augite to subcalcic augite and resemble the trend of pyroxene compositions of the Mid-Atlantic Ridge (Muir and Tilley, 1964). Like these pyroxenes, the 157-49-2(55-65), 159-BIT, and 163-29-4(67) specimens are notable for their high Al contents.…”

Section: Pyroxenementioning

confidence: 75%

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Petrology and Geochemistry of DSDP Leg 16 Basalts, Eastern Equatorial Pacific

Yeats¹,

Forbes²,

Heath³

et al. 1973

Initial Reports of the Deep Sea Drilling Project

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Basalts cored on DSDP Leg 16 fall into two groups. Those from the west flank of the East Pacific Rise (DSDP 159-163) are geochemically homogeneous tholeiites. In contrast, the Panama Basin samples (DSDP 155-158) range from alkali basalts to tholeiites and may have formed over a mantle "hot spot" rather than at a mid-ocean ridge. Based on core relationships, all the Leg 16 basalts are extrusive.DSDP 163 penetrated 18 meters of basalt made up of seven cooling units with chilled glassy margins. Even in this Campanian (Cretaceous) sequence, severe alteration affects only the uppermost few centimeters. Sideromelane appears particularly resistant to low-temperature alteration. Microprobe analyses of spheroidal "globules" (probably spherulites) at the inner margins of sideromelane masses show bimodal chemical compositions: reddish spherulites are enriched in Na2θ, A1 2 O 3 and SiC>2, whereas opaque ones are enriched in MgO and FeO relative to glass. The bulk composition of the "globular" zone is the same as that of the bulk rock, pointing to partitioning in situ.

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Section: Olivinesupporting

confidence: 88%

Section: Pyroxenementioning

confidence: 75%

Petrology and Geochemistry of DSDP Leg 16 Basalts, Eastern Equatorial Pacific

Yeats¹,

Forbes²,

Heath³

et al. 1973

Initial Reports of the Deep Sea Drilling Project

View full text Add to dashboard Cite

show abstract

“…As has been known for 50 years, MORB are predominately hypersthene-normative tholeiites of comparatively uniform composition (e.g., Engel et al, 1965;Muir and Tilley, 1964). Compared to tholeiitic basalts from other tectonic environments, MORB are, on average, poorer in K 2 O, TiO 2 , and FeO.…”

Section: 1 Major Elementsmentioning

confidence: 98%

Composition of the Oceanic Crust

White

Klein²

2014

Treatise on Geochemistry

193

160

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“…This global coverage is made up of a large number of investigations, representing more than two decades of studies of the local compositional variations among MORB recovered from individual ridge segments [e.g. Muir et al, 1964]. Such studies have identified significant local chemical systematics for both major and trace elements.…”

Section: Local Variability Of Major Elements In Morbmentioning

confidence: 99%

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

Langmuir

Klein

Plank

2013

Geophysical Monograph Series

665

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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Basalts from the Northern Part of the Rift Zone of the Mid-Atlantic Ridge

Cited by 197 publications

References 0 publications

Petrology and Geochemistry of DSDP Leg 16 Basalts, Eastern Equatorial Pacific

Petrology and Geochemistry of DSDP Leg 16 Basalts, Eastern Equatorial Pacific

Composition of the Oceanic Crust

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

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