Volcanism and geochemistry in Central America: Progress and problems

Carr, Michael J.; Feigenson, Mark D.; Patino, L. C.; Walker, James A.

doi:10.1029/138gm09

Cited by 145 publications

(197 citation statements)

References 50 publications

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“…2 (upper) mantle (8 þ 1 R A ) contributions [19] to Central American volcanism. Although other studies (see [20,21]) have argued for a plume-like mantle beneath Costa Rica (associated with the Galapagos hotspot), we ¢nd no indication of plume-like He isotope values anywhere along the arc. MORB (mid-ocean ridge basalt)-like and predominantly radiogenic 3 He/ 4 He ratios are found in both Costa Rica and Nicaragua.…”

Section: Resultsmentioning

confidence: 51%

Contrasting He–C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones

Shaw

Hilton

Fischer

et al. 2003

Earth and Planetary Science Letters

166

160

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We report 3 He/ 4 He ratios, relative He, Ne, and CO 2 abundances as well as N 13 C values for volatiles from the volcanic output along the Costa Rica and Nicaragua segments of the Central American arc utilising fumaroles, geothermal wells, water springs and bubbling hot springs. CO 2 / 3 He ratios are relatively constant throughout Costa Rica (av. 2.1U10 10 ) and Nicaragua (av. 2.5U10 10 ) and similar to arcs worldwide (V1.5U10 10 ). N 13 C values range from 36.8x (MORB-like) to 30.1x (similar to marine carbonate (0x)). 3 He/ 4 He ratios are essentially MORBlike (8 þ 1 R A ) with some samples showing evidence of crustal He additions^water spring samples are particularly susceptible to modification. The He^CO 2 relationships are consistent with an enhanced input of slab-derived C to magma sources in Nicaragua ((L+S)/M = 16; where L, M and S represent the fraction of CO 2 derived from limestone and/or marine carbonate (L), the mantle (M) and sedimentary organic C (S) sources) relative to Costa Rica ((L+S)/ M = 10). This is consistent with prior studies showing a higher sedimentary flux to the arc volcanics in Nicaragua (as traced by Ba/La, 10 Be and La/Yb). Possible explanations include: (1) offscraping of the uppermost sediments in the Costa Rica forearc, and (2) a cooler thermal regime in the Nicaragua subduction zone, preserving a higher proportion of melt-inducing fluids to subarc depths, leading to a higher degree of sediment transfer to the subarc mantle. The absolute flux of CO 2 from the Central American arc as determined by correlation spectrometry methods (5.8U10 10 mol/yr) and CO 2 / 3 He ratios (7.1U10 10 mol/yr) represents approximately 14^18% of the amount of CO 2 input at the trench from the various slab contributors (carbonate sediments, organic C, and altered oceanic crust). Although the absolute flux is comparable to other arcs, the efficiency of CO 2 recycling through the Central American arc is surprisingly low (14^18% vs. a global average of V50%). This may be attributed to either significant C loss in the forearc region, or incomplete decarbonation of carbonate sediments at subarc depths. The implication of the latter case is that a large fraction of C (up to 86%) may be transferred to the deep mantle (depths beyond the source of arc magmas). ß

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Section: Resultsmentioning

confidence: 51%

Contrasting He–C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones

Shaw

Hilton

Fischer

et al. 2003

Earth and Planetary Science Letters

166

160

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“…There is no evidence in the lavas erupted throughout this magmatic arc of crustal assimilation in Nicaragua, based on geochemical or isotopic grounds. This was mainly explained by the thin continental crust, and young age of the oceanic crust (Carr et al 2003;Shaw et al 2006). The age trend of the Cenozoic volcanics clearly indicates a trenchward propagation of the extension, similar to the rift structural propagation proposed behind the arc by Mann and Burke (1984).…”

Section: Nicaragua Subduction Zonementioning

confidence: 87%

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Ramos¹

2009

Geological Journal

227

139

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The analyses of the main parameters controlling the present Chile-type and Marianas-type tectonic settings developed along the eastern Pacific region show four different tectonic regimes: (1) a nearly neutral regime in the Oregon subduction zone; (2) major extensional regimes as the Nicaragua subduction zone developed in continental crust; (3) a Marianas setting in the Sandwich subduction zone with ocean floored back-arc basin with a unique west-dipping subduction zone and (4) the classic and dominant Chile-type under compression. The magmatic, structural and sedimentary behaviours of these four settings are discussed to understand the past tectonic regimes in the Mesozoic Andes based on their present geological and tectonic characteristics. The evaluation of the different parameters that governed the past and present tectonic regimes indicates that absolute motion of the upper plate relative to the hotspot frame and the consequent trench roll-back velocity are the first order parameters that control the deformation. Locally, the influences of the trench fill, linked to the dominant climate in the forearc, and the age of the subducted oceanic crust, have secondary roles. Ridge collisions of seismic and seismic oceanic ridges as well as fracture zone collisions have also a local outcome, and may produce an increase in coupling that reinforces compressional deformation. Local strain variations in the past and present Andes are not related with changes in the relative convergence rate, which is less important than the absolute motion relative to the Pacific hotspot frame, or changes in the thermal state of the upper plate. Changes in the slab dip, mainly those linked to steepening subduction zones, produce significant variations in the thermal state, that are important to generate extreme deformation in the foreland.

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“…Guatemala and Costa Rica data are from Fischer et al (2002) and Zimmer et al (2004). Selected Ba/La data are from Patino et al (2000) and Carr et al (2003). Open symbols represent geothermal gases and filled symbols are volcanic gases.…”

Section: Nitrogen Flux and Mass Balancementioning

confidence: 99%

Tracing nitrogen in volcanic and geothermal volatiles from the Nicaraguan volcanic front

Elkins

Fischer

Hilton

et al. 2006

Geochimica et Cosmochimica Acta

114

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We report new chemical and isotopic data from 26 volcanic and geothermal gases, vapor condensates, and thermal water samples, collected along the Nicaraguan volcanic front. The samples were analyzed for chemical abundances and stable isotope compositions, with a focus on nitrogen abundances and isotope ratios. These data are used to evaluate samples for volatile contributions from magma, air, air-saturated water, and the crust. Samples devoid of crustal contamination (based upon He isotope composition) but slightly contaminated by air or air-saturated water are corrected using N 2 /Ar ratios in order to obtain primary magmatic values, composed of contributions from upper mantle and subducted hemipelagic sediment on the down-going plate. Using a mantle endmember with d 15 N = À5& and N 2 /He = 100 and a subducted sediment component with d 15 N = +7& and N 2 /He = 10,500, the average sediment contribution to Nicaraguan volcanic and geothermal gases was determined to be 71%. Most of the gases were dominated by sediment-derived nitrogen, but gas from Volcán Mombacho, the southernmost sampling location, had a mantle signature (46% from subducted sediment, or 54% from the mantle) and an affinity with mantle-dominated gases discharging from Costa Rica localities to the south. High CO 2 /N 2 exc. ratios (N 2 exc. is the N 2 abundance corrected for contributions from air) in the south are similar to those in Costa Rica, and reflect the predominant mantle wedge input, whereas low ratios in the north indicate contribution by altered oceanic crust and/or preferential release of nitrogen over carbon from the subducting slab. Sediment-derived nitrogen fluxes at the Nicaraguan volcanic front, estimated by three methods, are 7.8 · 10 8 mol N/a from 3 He flux, 6.9 · 10 8 mol/a from SO 2 flux, and 2.1 · 10 8 and 1.3 · 10 9 mol/a from CO 2 fluxes calculated from 3 He and SO 2 , respectively. These flux results are higher than previous estimates for Central America, reflecting the high sediment-derived volatile contribution and the high nitrogen content of geothermal and volcanic gases in Nicaragua. The fluxes are also similar to but higher than estimated hemipelagic nitrogen inputs at the trench, suggesting addition of N from altered oceanic basement is needed to satisfy these flux estimates. The similarity of the calculated input of N via the trench to our calculated outputs suggests that little or none of the subducted nitrogen is being recycled into the deeper mantle, and that it is, instead, returned to the surface via arc volcanism.

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Volcanism and geochemistry in Central America: Progress and problems

Cited by 145 publications

References 50 publications

Contrasting He–C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones

Contrasting He–C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

Tracing nitrogen in volcanic and geothermal volatiles from the Nicaraguan volcanic front

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