Low 3He/4He ratios in basalt glasses from the western Southwest Indian Ridge (10°-24°E)

Georgen, J. E.; Kurz, Mark D.; Dick, H. J.; Lin, Jian

doi:10.1016/s0012-821x(02)01106-8

Cited by 61 publications

(40 citation statements)

References 63 publications

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“…We argue, following the proposition by Hanyu and Kaneoka (1998) and Georgen et al (2003), that the high diffusion rates of helium preclude survival of He isotope heterogeneities on smaller than km scale-lengths, especially if these heterogeneities represent long-term in-growth within the high temperature convecting mantle. We investigate this question with He diffusion/production modeling, and by consideration of He isotope variability along several wellstudied spreading ridge systems where only N-MORB is sampled.…”

Section: Introductionsupporting

confidence: 53%

“…the southern EPR, see discussion below). Even along the SWIR (Georgen et al, 2003), where the 3 He/ numerically average the profiles in Fig. 2c to determine the 3 He/ 4 He ratios as a function of the scale-length of melt averaging, see Fig.…”

Section: Case A: Recycled Oceanic Crust In An Ambient Dmm Matrixmentioning

confidence: 99%

“…The highest data density is from the long ridge segment between 16°E and 24°E (Georgen et al, 2003), referred to as the orthogonal super-segment. Basalt glass samples from 21 dredge locations along this 490 km super-segment show limited but systematic along-axis 3 He/ 4 He variability, Fig.…”

Section: Case B: the Very-slow-spreading Sw Indian Ridgementioning

confidence: 99%

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Scale length of mantle heterogeneities: Constraints from helium diffusion

Hart

Kurz

Wang

2008

Earth and Planetary Science Letters

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A model of coupled He production/diffusion is used to constrain the question of whether Earth's peridotitic mantle contains ubiquitous mesoscale veins or slabs of other lithologies. The high diffusion rates of helium preclude survival of He isotope heterogeneities on scales smaller than a few tens of meters, especially if they represent long term in-growth of 4 He in the mantle. He variability for these 3 areas is very small, and independent of spreading rate: 0. 13, 0.19 and 0.21 Ra (±1σ). Since these ridges range from ultraslow to very fast-spreading, the variability in size of along-axis magma chambers will lead inevitably to various scales of melt averaging. We conclude that these ridge areas are not sampling mantle that contains enriched veins or recycled oceanic crust slabs of significant size (> tens of meters). It appears difficult to sustain a view of the upper mantle as a ubiquitous mixture of veins and depleted matrix, with MORB always representing an averaging of this mixture.

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Section: Introductionsupporting

confidence: 53%

Section: Case A: Recycled Oceanic Crust In An Ambient Dmm Matrixmentioning

confidence: 99%

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Scale length of mantle heterogeneities: Constraints from helium diffusion

Hart

Kurz

Wang

2008

Earth and Planetary Science Letters

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“…It separates the African and Antarctic plates. It is an ultraslow-spreading ridge ) with a full spreading rate of *13-16 mm/yr (Georgen et al 2003). The average thickness of the crust is 4 km which is much thinner than the average thickness of the ocean crust (about 7 km) (Baker and German 2004).…”

Section: Geological Settingmentioning

confidence: 98%

230Th/238U dating of hydrothermal sulfides from Duanqiao hydrothermal field, Southwest Indian Ridge

Yang

Tao

et al. 2016

Mar Geophys Res

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Duanqiao hydrothermal field is located between the Indomed and Gallieni fracture zones at the central volcano, at 50°28 0 E in the ultraslow-spreading Southwest Indian Ridge (SWIR). Twenty-eight subsamples from a relict chimney and massive sulfides were dated using the 230 Th/ 238 U method. Four main episodes of hydrothermal activity were determined according to the restricted results: 68. 9-84.3, 43.9-48.4, 25.3-34.8, and 0.7-17.3 kyrs. Hydrothermal activity of Duanqiao probably started about 84.3 (±0.5) kyrs ago and ceased about 0.737 (±0.023) kyrs ago. The periodic character of hydrothermal activity may be related to the heat source provided by the interaction of local magmatism and tectonism. The estimated mean growth rate of the sulfide chimney is \0.02 mm/yr. This study is the first to estimate the growth rate of chimneys in the SWIR. The maximum age of the relict chimney in Duanqiao hydrothermal filed is close to that of the chimneys from Mt. Jourdanne (70 kyrs). The hydrothermal activity in Dragon Flag field is much more recent than that of Duanqiao or Mt. Jourdanne fields. The massive sulfides are younger than the sulfides from other hydrothermal fields such as Rainbow, Sonne and Ashadze-2. The preliminarily estimated reserves of sulfide ores of Duanqiao are approximately 0.5-2.9 million tons.

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“…The full spreading rate of the SWIR is about 1.3-1.6 cm/a [6], places SWIR in the category of ultraslowspreading ridges with distinct topographic, tectonic, magmatic and hydrothermal features [7][8][9][10][11]. In recent years, geological and geophysical investigations on the SWIR have become a hot topic in the field of marine geology.…”

mentioning

confidence: 99%

Mineralogical and geochemical features of sulfide chimneys from the 49°39′E hydrothermal field on the Southwest Indian Ridge and their geological inferences

Chen

Huang

et al. 2011

Chin. Sci. Bull.

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, the Chinese research cruise DY115-19 discovered an active hydrothermal field at 49°39′E/37°47′S on the ultraslow spreading Southwest Indian Ridge (SWIR). This was also the first active hydrothermal field found along an ultraslow-spreading ridge. We analyzed mineralogical, textural and geochemical compositions of the sulfide chimneys obtained from the 49°39′E field. Chimney samples show a concentric mineral zone around the fluid channel. The mineral assemblages of the interiors consist mainly of chalcopyrite, with pyrite and sphalerite as minor constitunets. In the intermediate portion, pyrite becomes the dominant mineral, with chalcopyrite and sphalerite as minor constitunets. For the outer wall, the majority of minerals are pyrite and sphalerite, with few chalcopyrite. Towards the outer margin of the chimney wall, the mineral grains become small and irregular in shape gradually, while minerals within interstices are abundant. These features are similar to those chimney edifices found on the East Pacific Rise and Mid-Atlantic Ridge. The average contents of Cu, Fe and Zn in our chimney samples were 2.83 wt%, 45.6 wt% and 3.28 wt%, respectively. The average Au and Ag contents were up to 2.0 ppm and 70.2 ppm respectively, higher than the massive sulfides from most hydrothermal fields along mid-ocean ridge. The rare earth elements geochemistry of the sulfide chimneys show a pattern distinctive from the sulfides recovered from typical hydrothermal fields along sedimentstarved mid-ocean ridge, with the enrichment of light rare earth elements but the weak, mostly negative, Eu anomaly. This is attributed to the distinct mineralization environment or fluid compositions in this area. In 1977 the first hydrothermal black smoker was discovered on the Galapagos Rift by scientists diving in a deep-sea

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Low 3He/4He ratios in basalt glasses from the western Southwest Indian Ridge (10°-24°E)

Cited by 61 publications

References 63 publications

Scale length of mantle heterogeneities: Constraints from helium diffusion

Scale length of mantle heterogeneities: Constraints from helium diffusion

230Th/238U dating of hydrothermal sulfides from Duanqiao hydrothermal field, Southwest Indian Ridge

Mineralogical and geochemical features of sulfide chimneys from the 49°39′E hydrothermal field on the Southwest Indian Ridge and their geological inferences

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