Geochemical Evidence of Continental Fluid Circulation in the Peru Subduction Zone

Dia, Aline

doi:10.1180/minmag.1994.58a.1.119

Cited by 1 publication

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References 3 publications

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“…In the Paita area, chemical analyses indicate that a unique continental source is providing most of the fluids expelled at venting sites (Dia et al 1993). The variations in potassium and trace metal (manganese and lithium) concentrations that exist are assumed to be due to differences in plumbing systems and not to different origins of the fluid (Dia et al 1994); they may influence the distribution of the Vesicomyidae along the margin, however. Sibuet et al (1990), Henry et al (1992) and Lallemant et al (1994) suggested that species composition and clam density are related to the temperature gradient in the Nankai accretionary wedge.…”

Section: Vesicomyid Species Distributionmentioning

confidence: 99%

Structure and distribution of cold seep communities along the Peruvian active margin:relationship to geological and fluid patterns

Olu¹,

Duperret²,

Sibuet³

et al. 1996

Mar. Ecol. Prog. Ser.

105

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Exploration of the northern Peruvian subduction zone with the French submersible 'Nautile' has revealed benthlc communities dominated by new species of vesicomyid bivalves (Calyptogena spp and Ves~comya sp) sustained by methane-nch fluid expulsion all along the continental margin, between depths of 5140 and 2630 m Videoscoplc studies of 25 dives ('Nautiperc cruise 1991) allowed us to describe the distribution of these biological conlnlunities at different spahal scales At large scale the communities are associated with fluid expuls~on along the major tectonic features (scarps, canyons) of the margln At a smaller scale on the scarps, the distribuhon of the communities appears to be controlled by fluid expulsion along local fracturatlon features such as joints, faults and small-scale scars Elght dlves were made at one particular geological structure the Middle Slope Scarp (the scar of a large debns avalanche) where numerous clam beds have been discovered The spatial dlstnbution of the chemosynthetic communities on thls scarp indicates extensive fluid expulsion, but the low clam densities and low fauna1 diversity in clam beds and the presence of dead beds suggest fluld expulsion is temporally irregular An exceptionally large clam field was observed at the bend of this scarp at the intersection of 2 faults It extends for about 1000 m2 with the biomass of b~valves as hlgh as 30 kg m-' wet weight without shells A strong and regular fluid flow, estimated at 400 m yr-l, is requlred at this locatlon to generate such a hlgh chemosynthetic pnmary production Temperature anomalies In the sediment were measured in s~t u in the main fleld and compared to clam denslty The dlstnbution of the bivalves at the metre scale 1s likely related to local vanations In fluid flow and in fluid expulsion patterns controlled by the nature of the subsurface sediment Exceptionally large and densely dlstnbuted serpuhds (Neoverm~ha n sp) were arranged in clumps of 20 to 30 m', and covered 200 m2 of the fleld Their abundance may be related to the filtration of chemoautotrophic free-living bacteria Another 22 non-syinbiotic species displaying varlous trophic strategies have been sampled or observed, and 5 are still undescnbed new specles The resulting community structure is more complex than In other subduction systems descnbed so far KEY WORDS: Cold seeps. Subduction zones. Peruvian margin Spatial distribution. Community structure O Inter-Research 1996 Resale of full article not permitted

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Section: Vesicomyid Species Distributionmentioning

confidence: 99%