Excess 3He in the sea: Evidence for terrestrial primodal helium

Clarke, W. B.; Beg, Mirza Arshad; Craig, H.

doi:10.1016/0012-821x(69)90093-4

Cited by 338 publications

(194 citation statements)

References 19 publications

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“…On the basin scale, the distribution of terrigenic helium along 9 • 30 ′ N is dominated by a plume with a core depth between 2000 and 2500 m (Fig. 1, shading (Clarke et al, 1969), are marked with black dots and the corresponding station numbers are printed above the panel. Above the crest depth of the EPR, density contour levels were chosen to be uniformly spaced in depth.…”

Section: Large-scale Contextmentioning

confidence: 99%

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Thurnherr

Ledwell

Lavelle

et al. 2011

Deep Sea Research Part I: Oceanographic Research Papers

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1ABSTRACT. Topography has a strong effect on the physical oceanography over the flanks and crests of the global mid-ocean ridge system. Here, we present an analysis of the hydrography and circulation near the crest of the East Pacific Rise (EPR) between 9 • and 10 • N, which coincides with an integrated study site (ISS) of the RIDGE2000 program. The analysis is based primarily on survey and mooring data collected during the LADDER project, which aimed to investigate oceanographic and topographic influences on larval retention and dispersal in hydrothermal vent communities. Results indicate that the yearly averaged regional mean circulation is characterized by a westward drift of 0.5-1 cm·s −1 across the EPR axis and by north-and southward flows along the western and eastern upper ridge flanks, respectively. The westward drift is part of a basin-scale zonal flow that extends across most of the Pacific ocean near 10 • N, whereas the meridional currents near the ridge crest are a topographic effect. In spite of considerable mesoscale variability, which dominates the regional circulation and dispersal on weekly to monthly time scales, quasi-synoptic surveys carried out during the mooring deployment and recovery cruises indicate subinertial circulations that are qualitatively similar to the yearly averaged flow but associated with significantly stronger velocities. Weekly averaged mooring data indicate that the anticyclonically sheared along-flank flows are associated with core speeds as high as 10 cm·s −1 and extend ≈10 km off axis and 200 m above the ridge-crest topography. Near the northern limit of the study region, the Lamont Seamount Chain rises from the western ridge flank and restricts along-EPR flow to five narrow passages, where peak velocities in excess of 20 cm·s −1 were observed. Outside the region of the ridge-crest boundary currents the density field over the EPR near 10 • N is characterized by isopycnals dipping into the ridge flanks. Directly above the EPR axis the ridge-crest boundary currents give rise to an isopycnal dome. During times of strong westward cross-EPR flow isopycnal uplift over the eastern flank causes the cross-ridge density field below the doming isopycnals to be asymmetric, with higher densities over the eastern than over the western flank.

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Section: Large-scale Contextmentioning

confidence: 99%

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Thurnherr

Ledwell

Lavelle

et al. 2011

Deep Sea Research Part I: Oceanographic Research Papers

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“…Since the discovery of excess 3He in deep Pacific waters [Clarke et al, 1969], helium isotope data have been used to study the circulation of various ocean water masses [Craig, 1990a;Jean-Baptiste et al, 1991a;Jenkins, 1998;Lupton, 1998; with improved data quality and quantity and with the knowledge that mantle helium is also present. Although the abundance of U and Th in oceanic crust is relatively low (compared to continental crust), this flux amounts to approximately 10% of the total terrestrial 4He degassing flux [Torgersen, 1989].…”

Section: Introductionmentioning

confidence: 99%

Crustal helium in deep Pacific waters

Well¹,

Lupton²,

Roether³

2001

J. Geophys. Res.

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“…0148-0227/79/009B-1422$01.00 that a significant flux of 3 He is being injected into the Pacific cir· culation by the spreading activity of the East Pacific Rise system {Clarke et at., 1969, 1970. In the Gulf of California, helium injection at spreading centers should produce even higher concentrations because of the confined geometry of the basins.…”

Section: Introductionmentioning

confidence: 99%

Helium‐3 in the Guaymas Basin: Evidence for injection of mantle volatiles in the Gulf of California

Lupton¹

1979

J. Geophys. Res.

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Helium isotope measurements in six major basins in the Gulf of California show that the deep Guaymas Basin has 3 He/ 4 He 65· 70% higher than atmospheric helium, clear evidence of mantle helium injection. Smaller 3 He excesses observed in the Carmen and Farallon basins may be derived from this Guaymas Basin anomaly. The 3 He concentrations in the Mazatlan Basin in the mouth of the Gulf of California are similar to average eastern Pacific values, indicating that the Gulf does not provide a significant flux of 3 He into the general Pacific circulation . On the basis of temperature and salinity measurements an upper limit of 0.28oC can be placed on the amount of geothermal heating observed in any of the basins. The isotopic ratio of the injected Guaymas Basin helium is found to be 3 He/ 4 He = (1 .10 ± 0.06) X w-5 , almost identical to the helium signature observed at the Galapagos Rift but somewhat lower than the average rat io in oceanic basalt glasses.

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Excess 3He in the sea: Evidence for terrestrial primodal helium

Cited by 338 publications

References 19 publications

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Crustal helium in deep Pacific waters

Helium‐3 in the Guaymas Basin: Evidence for injection of mantle volatiles in the Gulf of California

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