Computer Science
Scientific paper
Feb 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981gecoa..45..163m&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 45, Issue 2, pp.163-180
Computer Science
5
Scientific paper
The regular geometry and completeness of the Kiglapait intrusion permit its bulk composition to be obtained by summation, and the composition of successive liquids to be obtained by subtraction. The summations for K and Rb give 1806 and 1.08 ppm, yielding R frsol | K / Rb = 1670 for the intrusion, taken as equal to the parent magma. R increases slightly from this initial value to 2000 at the end of crystallization where MgO approaches zero in the rocks. K and Rb are therefore closely coherent and their distribution coefficients can differ only by a small amount in the Kiglapait system. Apparent feldspar/liquid distribution coefficients (D F/L ) can be estimated from detailed plots of feldspar and liquid compositions against F L . The Kiglapait data imply that these coefficients are linear 1:1 functions of plagioclase composition within experimental error, having values given by D K F / L = 1.42- X An D Rb F / L = 1.13- X An with minimum values of 0.75 and 0.49, respectively. The ratio R F / R L lies in the range of 1.53± 0.03 for the plagioclase composition range X An = 0.34 to 0.67 showing that high-R rocks such as anorthosite crystallized from high- R liquids. The apparent feldspar distribution coefficients are much closer to 1.0 than common literature values. They can be reduced by assuming that the cumulate pile was continuously recharged by the circulating magma until an advanced stage of differentiation was reached, and assuming that alkalies were exchanged to the feldspars from the magma. When such an `aquifer recharge' model is calibrated using olivine-liquid equilibria as a time marker for the liquid, the inferred minimum equilibrium values of the distribution coefficients are D K F / L = 0.42, D Rb F / L = 0.25 at the base of the intrusion. Their variation is given by D K F / L = 1.66-1.88 X An , D Rb F / L = 1.17-1.41 X An , The equilibrium values are considered to be appropriate for deducing liquid compositions in plutonic bodies where alkali exchange can be shown or inferred to have been inhibited, such as in small intrusions. The apparent values are considered to be appropriate, even though they may be artificial, for large intrusions similar to the Kiglapait. The bulk K and Rb concentrations in the Kiglapait intrusion are consistent with a plagioclase-rich abyssal tholeiite magma. Clinopyroxene and olivine fractionation in the mantle may contribute to the production of such high- R magmas.
No associations
LandOfFree
Kiglapait Geochemistry III: Potassium and Rubidium 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 Kiglapait Geochemistry III: Potassium and Rubidium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Kiglapait Geochemistry III: Potassium and Rubidium will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1407728