Petrology of Lavas from the Lamont Seamount Chain and Adjacent East Pacific Rise, 10  N

Allan, James F.; Batiza, Rodey; Perfit, Michael R.; Fornari, Daniel J.; Sack, Richard O.

doi:10.1093/petrology/30.5.1245

Cited by 145 publications

(121 citation statements)

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“…While this fact has been known from some of the earliest work on MORB [Kay et al, 1970;Allan et al, 1989;Langmuir et al, 1986;Donnelly et al, 2004;Cousens et al, 1995;Niu et al, 1999], the concept of a depleted upper mantle similar to previous N-MORB estimates remains ingrained. This is reflected, for example, in the common practice of normalizing trace element data to the Sun and McDonough [1989] N-MORB composition.…”

Section: Plume-influenced Morb Versus E-morbmentioning

confidence: 76%

The mean composition of ocean ridge basalts

Gale

Dalton

Langmuir

et al. 2013

Geochem. Geophys. Geosyst.

142

317

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[1] The mean composition of mid-ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. "ALL MORB" is the total composition of the crust apart from back-arc basins, N-MORB the most likely basalt composition encountered along the ridge >500 km from hot spots, and D-MORB the depleted end-member. ALL MORB and N-MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back-arc spreading centers requires higher extents of melting and greater concentrations of fluid-mobile elements, reflecting the influence of water on back-arc petrogenesis. The average data permit a re-evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 AE 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and 143 Nd/ 144 Nd ratio of ALL MORB and N-MORB provide constraints on the hypothesis that Earth has a non-chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.

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Section: Plume-influenced Morb Versus E-morbmentioning

confidence: 76%

The mean composition of ocean ridge basalts

Gale

Dalton

Langmuir

et al. 2013

Geochem. Geophys. Geosyst.

142

317

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“…Before the report of U1349 type basalt, the most depleted MORB sample was reported to be depleted basalts from Lamont seamounts and adjacent East Pacific Rise (Allan et al, 1989).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Formation and evolution of Shatsky Rise oceanic plateau: Insights from IODP Expedition 324 and recent geophysical cruises

Sager

Sano

Geldmacher

2016

Earth-Science Reviews

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“…This is a common feature in overlying lava flows [Alabaster et al, 1982;Umino et al, 1990]. Intermediate to fast spreading ridges such as the EPR and Costa Rica Rift also yield aphyric dikes and lavas [Dick et al, 1992;Allan et al, 1989]. In contrast, lava flows from slow spreading ridges like the Mid-Atlantic Ridge show bimodal phenocryst abundance with peaks at less than 10 vol% and more than 18 vol% [Bryan and Moore, 1977;Hekinian, 1982;Hodges, 1978;O'Donell and Presnall, 1980;Sato et al, 1978;Shipboard Scientific Party, 1988].…”

Section: Petrographymentioning

confidence: 99%

Along‐strike variation of the sheeted dike complex in the Oman Ophiolite: Insights into subaxial ridge segment structures and the magma plumbing system

Umino

Miyashita

Hotta

et al. 2003

Geochem Geophys Geosyst

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[1] Along-strike variations of the 60-km-long sheeted dike complex in the northern Oman Ophiolite were studied in order to understand the shallow magma plumbing system beneath the fossil fast spreading ridge. The presence of numerous dikes intruding into the layered gabbro defines the northern end of the paleoridge segment at Wadi Fizh. The postulated segment center is located at Wadi Thuqbah, which has a thicker Mono transition zone than elsewhere along the fossil segment. Aphyric dikes predominate in the sheeted dikes, of which 99% are simple, while multiple and composite dikes are few. The thickness of 1511 dikes ranges from <1 cm to >13 m, with an average thickness of 71.3 cm. Restored dike trends in the 30-km-long northern half of the dike complex display the NS trending north domain and NNE-NS trending south domain bordered at the south of Wadi Bani Umar al Gharbi. In the domain boundary, dikes gradually change strikes or are mutually intrusive. Dike thickens northward with the largest peak along Wadi Fizh at the northern end of the paleoridge segment and a small peak at Wadi Bani Umar al Gharbi. Most dikes have a bulk Mg# of 55-66, which overlaps the majority of MORB. Less common, highly evolved dikes with Mg# 34-40 characterize the north domain. Thicker dikes (>3 m) tend to have high Mg#, while thinner dikes (<2 m) are highly variable in Mg#. The regional variations of the dike trends and the whole rock compositions can be explained by the secular variation in the structures of the paleoridge segment comparable to a third-order segment of the present mid-ocean ridge system spanning a few tens of thousands of years. Initially, the segment-long melt lens developed along the paleoridge axis, which fed long and thick dikes with high Mg#. With decreasing supply of magma, the melt lens split up into the north and south smaller lenses bordered by a DEVAL that fed thinner dikes intruding into the former thick dikes. Cut-off of the northern melt lens from the magma source changed the melt composition to highly evolved, low-Mg# magmas, which subsequently intruded as short evolved dikes. Meanwhile, the main melt lens in the segment center continued feeding the high-Mg# dikes which were maintained by the larger melt lens size and intermittent magma supply from deep magma chambers.

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Petrology of Lavas from the Lamont Seamount Chain and Adjacent East Pacific Rise, 10 N

Cited by 145 publications

References 0 publications

The mean composition of ocean ridge basalts

The mean composition of ocean ridge basalts

Formation and evolution of Shatsky Rise oceanic plateau: Insights from IODP Expedition 324 and recent geophysical cruises

Along‐strike variation of the sheeted dike complex in the Oman Ophiolite: Insights into subaxial ridge segment structures and the magma plumbing system

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