Chemical weathering of basalt in Southwest Iceland; effects of runoff, age of rocks and vegetative/glacial cover

Gíslason, Sigurður R.; Arnórsson, Stefán; Ármannsson, Halldór

doi:10.2475/ajs.296.8.837

Cited by 407 publications

(352 citation statements)

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“…The oldest basalts in the northwest and east are ∼ 13 Ma (Moorbath et al, 1968), whilst the youngest rocks (Quaternary to Recent) are found in the volcanically active zones close to the ridge. The more recently erupted basalts tend to have higher permeabilities, as compaction and the precipitation of secondary minerals reduces the permeability of the older rocks (Sigurdsson and Ingimarsson, 1990;Gislason et al, 1996;Neuhoff et al, 1999). This difference is also reflected in the nature of the water discharge; surface runoff dominates in the older, less permeable areas, whereas there are fewer surface streams in the younger regions, and glacierand spring-fed rivers are more dominant.…”

Section: Geological Setting and Climatementioning

confidence: 94%

“…The annual discharge of Icelandic rivers is 170 km 3 (equating to ∼0.45% of global riverine discharge into the oceans), whilst the total size of the island is 103,000 km 2 , representing ∼0.1% of the global land area drained to the oceans (Gannoun et al, 2006). The flux of suspended load carried by the Icelandic rivers each year is 0.02-0.025 km 3 , which is ∼0.3% of the global annual flux to the oceans (Gislason et al, 1996). Some 11,260 km 2 (∼11%) of the island is under glacial cover, with the largest icecap being the 8300 km 2 Vatnajökull glacier in the southeast.…”

Section: Geological Setting and Climatementioning

confidence: 99%

“…2) has bedrock ages ranging from Quaternary to Recent, and has a number of rivers that are sourced directly from the Vatnajökull glacier. Average physical erosion rates for this area are ∼ 2080 t/km 2 /yr, whilst the average chemical weathering rates are 152 t/km 2 /yr (Gislason et al, 1996;Pogge von Strandmann et al, 2006). The second region in the west of Iceland (Fig.…”

Section: Sample Localitiesmentioning

confidence: 99%

“…Therefore, most of the island (80-85%) is composed of basaltic volcanic rocks, with minor acidic intrusions and volcanoclasitc sediments (Gislason et al, 1996;Jóhannesson and Saemundsson, 1998). The basalts increase in age from the centre of the island towards its western and eastern edges, with the symmetrical zonation following the SW-NE trend of the Atlantic ridge (Fig.…”

Section: Geological Setting and Climatementioning

confidence: 99%

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Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Pearce

Burton

Strandmann

et al. 2010

Earth and Planetary Science Letters

100

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Editor: M.L. DelaneyKeywords: molybdenum (Mo) isotopes basaltic weathering riverine inputs estuarine mixingThe application of the molybdenum (Mo) isotope system as a proxy for determining changes in the redox state of the oceans is predicated on the assumption that the composition of continental input can be characterised from crustal rock types, and remains constant. However, it has recently been shown that the δ 98/95 Mo composition of global rivers varies between 0.15‰ and 2.4‰ and is therefore systematically heavier than the average composition of the continental crust (∼ 0‰ 4‰).Systematic changes in the dissolved Mo-isotope composition are also observed within river catchments, with δ 98/95 Mo values increasing from ∼ 0‰ in glacial rivers (close to the source) to ∼ 1‰ downstream, consistent with Mo-isotopes being fractionated during weathering. Analysis of other riverine phases (bedload, colloids and iron-precipitates) demonstrates that these phases preferentially incorporate light Moisotopes, and remain coupled to the dissolved load during riverine transportation. A δ 98/95 Mo profile through the Borgarfjörður estuary exhibits a predominantly conservative mixing behaviour, but suggests that the release of isotopically light Mo from the particulate and/or colloidal phases may occur in the low salinity part of the estuarine mixing zone.

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Section: Geological Setting and Climatementioning

confidence: 94%

Section: Geological Setting and Climatementioning

confidence: 99%

Section: Sample Localitiesmentioning

confidence: 99%

Section: Geological Setting and Climatementioning

confidence: 99%

See 2 more Smart Citations

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Pearce

Burton

Strandmann

et al. 2010

Earth and Planetary Science Letters

100

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“…Chemical weathering fluxes from rivers draining basaltic terranes are among the highest recorded worldwide (Gislason et al, 1996;Louvat and Allègre, 1997;Dessert et al, 2003Dessert et al, , 2009Das et al, 2005;Pokrovsky et al, 2005Pokrovsky et al, , 2006Eiríksdóttir et al, 2006;Rad et al, 2006;Schopka et al, 2011 etc.). Despite its relative accessibility, there has been little work on chemical weathering fluxes from the Hawaiian archipelago.…”

Section: Introductionmentioning

confidence: 99%

Chemical weathering fluxes from volcanic islands and the importance of groundwater: The Hawaiian example

Schopka

Derry

2012

Earth and Planetary Science Letters

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We investigated the products and rates of chemical weathering on the Hawaiian Islands, sampling streams on Kaua'i and both streams and groundwater wells on the island of Hawai'i. Dissolved silica was used to investigate the flowpaths of water drained into streams. We found that flowpaths exert a major control on the observed chemical weathering rates. A strong link exists between the degree of landscape dissection and flowpaths of water through the landscape, with streams in undissected landscapes receiving water mainly from surface runoff and streams in highly dissected landscapes receiving a considerable fraction of their water from groundwater (springs and/or seepage). Total alkalinity in Hawaiian streams and groundwater is produced exclusively by silicate chemical weathering. We find that fluxes of total alkalinity (often called "CO 2 consumption rate" in the geochemical literature), from the islands are lower than those observed in basaltic regions elsewhere. Groundwater is, overall, the major transport vector for products of chemical weathering from the Hawaiian Islands. On the youngest and largest island, submarine groundwater discharge (SGD) transports more than an order of magnitude more solutes to the ocean than surface water and on the youngest part of the youngest island, SGD is the only link between the terrestrial weathering system and the ocean. These results suggest that groundwater, and particularly SGD, needs to be included in geochemical weathering budgets of volcanic islands.

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Contemporary rates of chemical denudation and atmospheric CO2 sequestration in glacier basins: an Arctic perspective

Hodson

Tranter

Vatne

2000

Earth Surf. Process. Landforms

129

138

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ABSTRACT, whilst the range is 110-13000 kg C km À2 a À1 for the northern hemisphere glacial data set. Transient CO 2 drawdown is therefore usually low in the Svalbard basins unless carbonate or basalt rocks are abundant. The analysis shows that a large area of uncertainty in the transient CO 2 drawdown estimates exists due to the non-stoichiometric release of solute during silicate hydrolysis. Silicate hydrolysis is particularly non-stoichiometric in basins where the extent of glacierization is high, which is most probably an artefact of high flushing rates through ice-marginal and subglacial environments where Kfeldspars are undergoing mechanical comminution.

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Chemical weathering of basalt in Southwest Iceland; effects of runoff, age of rocks and vegetative/glacial cover

Cited by 407 publications

References 0 publications

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Chemical weathering fluxes from volcanic islands and the importance of groundwater: The Hawaiian example

Contemporary rates of chemical denudation and atmospheric CO2 sequestration in glacier basins: an Arctic perspective

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