Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland

Details Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland

Jan 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007gecoa..71..284a&link_type=abstract

Geochimica et Cosmochimica Acta, Volume 71, Issue 2, p. 284-304.

Other

3

Scientific paper

The concentrations of Mo and W in tholeiite series basaltic to silicic volcanics in Iceland increase with the concentrations of incompatible magmatic elements. In normal Mid Ocean Ridge Basalt (MORB), Mo and W levels are as low as 0.03 and 0.01 ppm but in rhyolites they are up to 4 and 1.3 ppm, respectively. In the slightly evolved Tertiary tholeiites of the main study area of Skagafjördur, northern Iceland, Mo and W concentrations are 1.01 and 0.32 ppm, respectively, on average. Surface waters in this area typically contain <0.5 ppb Mo and <0.1 ppb W. Concentrations are higher in ground waters and, on the whole, they increase with increasing temperature and increasing age of these waters, being as high as ˜100 ppb for Mo and ˜10 ppb for W in the hottest (˜90 °C) and oldest (>10,000 years) waters. In river and ground waters, the average Mo/W ratio is the same as that of the basalt host rock. On the other hand, in peat soil waters, the average Mo/W ratio is higher due to adsorption processes involving W. In river and ground waters, both Mo and W display conservative behavior. Progressive water rock interaction leads to successively lower aquatic B/Mo and B/W ratios. However, the B/Mo and B/W ratios of the most reacted waters are considerably higher than those of the basalt due to non-stoichiometric rock dissolution: B is dissolved preferentially to both Mo and W because B is largely present in a soluble form, but Mo and W are concentrated in the Fe Ti-oxides. These minerals are stable, under both surface and sub-surface conditions, i.e. the waters are over-saturated with respect to these minerals. The main supply of Mo and W to surface waters is from dissolution of plagioclase and pyroxene, as well as volcanic glass. Olivine is not an important source due to its scarcity in the basalts. In <30 °C ground waters, the dominant supply of Mo and W is plagioclase. At higher temperatures pyroxene also contributes, with its contribution increasing with increasing temperature, as deduced from its decreasing stability at higher temperature. Dissolution of basaltic glass produces lower B/Mo and B/W aqueous ratios than dissolution of crystalline basalt.

Affiliated with

Also associated with

No associations

Rating

Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molybdenum and tungsten in volcanic rocks and in surface and <100 °C ground waters in Iceland will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1254539