Rare gas systematics on the southernmost Mid‐Atlantic Ridge: Constraints on the lower mantle and the Dupal source

Sarda, Philippe; Moreira, Manuel; Staudacher, Thomas; Schilling, Jean-Guy; Allègre, Claude J.

doi:10.1029/1999jb900282

Cited by 120 publications

(92 citation statements)

References 85 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This peculiar neon signature for MORB is very similar to those observed in the South Atlantic on Shona and Discovery ridge anomalies (Fig. 5.4), except in the latter cases are associated to topographic anomalies (Moreira et al, 1995;Sarda et al, 2000). The second new observation on the neon in MORB is the broad variation of 21 Ne/ 22 Ne ratios for a given 20 Ne/ 22 Ne ratio (for example at 12.5), which was not seen in Sarda et al (1988 29.…”

Section: Figure 55supporting

confidence: 50%

“…W hereas the MORB his togram suggests a well-homogenised mantle and a radiogenic helium isotopic signature, the OIB histogram shows a larger dispersion, and helium isotopic ratios as low as 15,000 (R/ Ra = 50). The tailing of the MORB histogram to low values represents plume-ridge inter actions with Iceland, Saint Paul-Amsterdam, Shona and Discovery topographic anomalies and therefore cannot be considered as "normal MORB" (Poreda et al,1986;Moreira et al, 1995;Graham et al, 1999;Sarda et al, 2000).…”

Section: Helium Isotope Systematics In Oceanic Basaltsmentioning

confidence: 99%

“…Recent studies using step heating or step crushing, and Ne and Ar measurements on single samples have been performed on MORB and OIB and it seems clear that the mantle sources of most hotpots (e.g., Galapagos, Iceland, Hawaii) have 40 Ar/ 36 Ar ratios lower than 10,000, lower than the maximum MORB ratio of ~30,000 (Hiyagon et al, 1992;Honda et al, 1993;Moreira et al, 1995;Valbracht et al, 1997;Sarda et al, 2000;Trieloff et al, 2000;Trieloff et al, 2002;Honda and Woodhead, 2005;Hopp and Trieloff, 2005;Raquin and Moreira, 2009;Mukhopadhyay, 2012), but higher than the atmospheric ratio (299) which is the value that was proposed for the lower mantle by the Paris group in the 1980's. Another interesting approach used to determine the Ar isotopic composition of mantle reservoirs and document the isotopic heterogeneity of vesicles while avoiding atmospheric contamination was developed by Pete Burnard, now in Nancy (France) but who was then in Manchester (UK).…”

Section: Radiogenic Argon In Morb and Oibmentioning

confidence: 99%

“…Modifications to the extraction and purification lines of the mass spectrometers resulted in improvements in blank, CO 2 and 40 Ar ++ corrections and detection limits and better precisions to be obtained. Neon isotopes in South Atlantic samples: Shona and Discovery ridge anomalies (Moreira et al, 1995;Sarda et al, 2000). Neon shows the mixing between MORB and primitive components.…”

Section: The Discovery Of Solar-like Neon In the Mantlementioning

confidence: 99%

See 3 more Smart Citations

Noble gas constraints on the origin and evolution of Earth’s volatiles

Moreira¹

2013

GeochemPersp

Self Cite

108

164

View full text Add to dashboard Cite

Section: Figure 55supporting

confidence: 50%

Section: Helium Isotope Systematics In Oceanic Basaltsmentioning

confidence: 99%

Section: Radiogenic Argon In Morb and Oibmentioning

confidence: 99%

Section: The Discovery Of Solar-like Neon In the Mantlementioning

confidence: 99%

See 2 more Smart Citations

Noble gas constraints on the origin and evolution of Earth’s volatiles

Moreira¹

2013

GeochemPersp

Self Cite

108

164

View full text Add to dashboard Cite

“…Nevertheless the recent extensive studies of isotopes, major and trace elements on MORB glasses have helped to define regional geochemical domains in this region, distinguishing areas influenced by plumes (Shona and Discovery) from the areas where the MORB source is represented by a depleted asthenospheric mantle (Le Roux et al, 2002a;Andres et al, 2002;Douglass et al, 1999;Sarda et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Evidence of primitive melt heterogeneities preserved in plagioclase-hosted melt inclusions of South Atlantic MORB

et al. 2006

View full text Add to dashboard Cite

Melt inclusions contained in plagioclase and olivine phenocrysts have been studied in tholeiitic basalts from the Shona ridge-centered hot spot region, South Atlantic Ocean. Two types of primitive melt inclusions exist within a hand sample, Normal-Mid Ocean Ridge Basalt (N-MORB) and Enriched-Mid Ocean Ridge Basalt (E-MORB) as defined by trace elements. The N-MORB melt inclusions have low (La/Sm) n (0.54-0.72), high Zr/Nb (22-44) and depleted Light Rare Earth Element (LREE) patterns, whereas the E-MORB melt inclusions have high (La/Sm) n (0.79-1.09), low Zr/Nb (12-21) and flat LREE. The composition of melt inclusions has been modified by post-entrapment crystallization of the host phase, but this effect is considered relatively small and does not affect the incompatible trace element ratios. The matrix glasses have mildly E-MORB compositions that lie between the two different types of melt inclusions, suggesting that they are produced by mixing of primary magmas of E-MORB and N-MORB type.The N-MORB primitive melt inclusions are geochemically similar to Indian and other South Atlantic N-MORB in having high Ba/Nb ratios (4-10), but for the first time much more extreme values are found (8-18). The reason for this anomalous enrichment can be related to the presence of old pelagic sediments in a regionally depleted asthenosphere.The melt inclusions of this study display positive anomalies of Sr and Eu, the first time that have been recorded in the South Atlantic. Their characteristics could be explained by partial melting of mantle containing recycled oceanic crust.

show abstract

Deep plume origin of the Louisville hotspot: Noble gas evidence

Hanyu

2014

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Noble gas compositions have been reported for basaltic core samples from Louisville seamounts recovered during IODP Expedition 330. The in-vacuum crushing techniques were employed to extract noble gases from fresh olivine phenocrysts and submarine glasses with ages between 50 and 74 Ma.Stepwise crushing tests confirmed the extraction of magmatic noble gases from the olivine samples with minimal release of posteruption radiogenic nuclides; however, this was not always the case for the glass samples. The 3 He/ 4 He ratios of the studied samples range from a value similar to those of mid-ocean ridge basalts (MORB) to slightly elevated ratios up to 10.6 Ra. These ratios are not as high as those observed in other ocean island basalts, suggesting that the Louisville mantle plume was weak or the samples represent late-stage magmatic activity of the seamounts. However, two Louisville seamount basalts exhibit a primordial Ne isotopic signature that can be clearly discriminated from MORB Ne ratios. The He and Ne isotopic compositions of the Louisville seamount basalts can be explained by the mixing of less degassed mantle and depleted upper mantle with different He/Ne ratios. The presence of the less degassed mantle component in the source of the Louisville seamounts documents a deep origin of their mantle plume.

show abstract

Rare gas systematics on the southernmost Mid‐Atlantic Ridge: Constraints on the lower mantle and the Dupal source

Abstract: Abstract. Concentrations and isotopic compositions ofIn the former case, a maximum subduction age of 500 Ma can be calculated. In the latter case, the sublithospheric mantle should have a 4øm/36Ar ratio 2-5 times lower than the convective mantle and a 238U/3He ratio 2-3 times higher.

Cited by 120 publications

References 85 publications

Noble gas constraints on the origin and evolution of Earth’s volatiles

Noble gas constraints on the origin and evolution of Earth’s volatiles

Evidence of primitive melt heterogeneities preserved in plagioclase-hosted melt inclusions of South Atlantic MORB

Deep plume origin of the Louisville hotspot: Noble gas evidence

Contact Info

Product

Resources

About