The Rb/Sr geochronology of the Archean Chibougamau pluton, Quebec

1980 ◽  
Vol 17 (6) ◽  
pp. 776-783 ◽  
Author(s):  
C. Brooks
Keyword(s):  
Close Agreement ◽  
Major Element ◽  
Volatile Content ◽  
Zircon Age ◽  
Rock Samples ◽  
Earth’S Mantle ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Selection Of

The U–Pb zircon age for the Chibougamau pluton is some 200 Ma older than the published Rb–Sr total-rock age. However, application of sample rejection techniques based on petrography, volatile content, and major-element chemistry to published and new Rb–Sr data, permits a selection of less altered total-rock samples which define an age in close agreement with the zircon age. These data suggest that the Chibougamau pluton crystallized with a uniform initial-Sr ratio equivalent to values for the surrounding metavolcanics and by inference Earth's mantle at 2.7 Ga.

Major element chemistry of the geothermal sea-water at Reykjanes and Svartsengi, Iceland

1978 ◽  
Vol 42 (322) ◽  
pp. 209-220 ◽  
Author(s):  
Stefán Arnórsson
Keyword(s):  
Ground Water ◽  
Major Element ◽  
Sea Water ◽  
Geothermal Water ◽  
Ionic Exchange ◽  
Geothermal Waters ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Geothermal Fields ◽  
Reykjanes Peninsula

SummaryHigh-temperature geothermal fields in Iceland represent localized anomalies of hot, altered rock in the uppermost part of the crust, which coincide with points of maximum tectonic/magmatic activity. These points correspond to the intersection of oblique fault swarms to the plate boundaries. Geothermal activity under mid-ocean ridges follows probably similar tectonic/magmatic anomalies.Due to high permeability sea-water invades the bed-rock of the Reykjanes Peninsula, Iceland, and is overlain by a variably thick lens of dilute ground water of meteoric origin. The variable degree of salinity of geothermal waters in the Reykjanes Peninsula has resulted from different degree of mixing of fresh ground water with the underlying sea-water-ground-water in the downflow zones around the geothermal fields. At Reykjanes the geothermal water represents heated sea-water without any freshwater mixing. The difference in the composition of sea-water or sea-water/fresh water mixtures and the geothermal waters is due to basalt/water interaction at elevated temperatures. The major-element chemistry of the geothermal water represents an equilibrium composition at the relevant aquifer temperatures. The activities of silica, calcium, sulphate, and carbonate are thus limited by the solubilities of quartz, anhydrite, and calcite. Fluoride activity is thought to be controlled by an ionic exchange reaction where it substitutes for hydroxyl groups in phyllosilicates. The ratios of individual cations and hydrogen ion are governed by ionic exchange equilibria with hydrothermal minerals, probably smectite and chlorite. The equilibrium pH for the Reykjanes and Svartsengi geothermal waters is 5·5 and 5·1 respectively. Sea-water will become somewhat acid upon heating to more than about 300 °C and equilibration with basalt, the acidity increasing with temperature.

Determination of major element chemistry in terrestrial waters from Antarctica by ion chromatography

1996 ◽  
Vol 739 (1-2) ◽  
pp. 257-263 ◽  
Author(s):  
K.A Welch ◽  
W.B Lyons ◽  
E Graham ◽  
K Neumann ◽  
J.M Thomas ◽  
...  
Keyword(s):  
Ion Chromatography ◽  
Major Element ◽  
Major Element Chemistry ◽  
Element Chemistry

Geologic control of Sr and major element chemistry in Himalayan Rivers, Nepal

2000 ◽  
Vol 64 (15) ◽  
pp. 2549-2566 ◽  
Author(s):  
N.B. English ◽  
J. Quade ◽  
P.G. DeCelles ◽  
C.N. Garzione
Keyword(s):  
Major Element ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Himalayan Rivers
Sign in / Sign up

Export Citation Format

Share Document