apSaturation {GCDkit} | R Documentation |
Calculates apatite saturation temperatures for observed whole-rock major-element compositions. Prints also phosphorus saturation levels for the given major- element compositions and assumed magma temperature.
apSaturation(Si = WR[, "SiO2"], ACNK = WR[, "A/CNK"], P2O5 = WR[, "P2O5"], T = 0)
Si |
SiO2 contents in the melt (wt. %) |
ACNK |
vector with A/CNK (mol %) values |
P2O5 |
vector with P2O5 concentrations |
T |
assumed magma temperature in °C |
* Calculates phosphorus saturation levels following Harrison & Watson (1984):
ln(DP) = (8400 + 26400 (SiO2 - 0.5))/T - 3.1 - 12.4 (SiO2 - 0.5)
P2O5.HW = 42/DP
where 'T
' = absolute temperature (K), 'DP' =
distribution coefficient for phosphorus between
apatite and melt and 'SiO2'
is the weight fraction of silica in the melt, SiO2 wt. %/100.
These formulae were shown to be valid only for metaluminous rocks, i.e. A/CNK < 1, and were modified for peraluminous rocks (A/CNK > 1) by Bea et al. (1992):
P2O5.Bea = P2O5.HW * exp(6429(A/CNK - 1)/(T-273.15))
and Pichavant et al. (1992):
P2O5.PV = P2O5.HW + (A/CNK - 1) exp(-5900/T - 3.22 SiO2 + 9.31)
Note that the phosphorus saturation concentrations are not returned by the function but printed only.
* Calculates saturation temperatures in °C using the observed P2O5 concentrations (Harrison & Watson, 1984):
T.HW = (8400 + 26400 (SiO2 - 0.5))/(ln(42/P2O5) + 3.1 + 12.4(SiO2 - 0.5)) - 273.15
for peraluminous rocks (A/CNK > 1) the equation of Bea et al. (1992)
needs to be solved for 'T
' (in K) by iterations:
P2O5.Bea = 42/(exp(8400 + 26400 (SiO2 - 0.5))/T - 3.1 - 12.4 (SiO2 - 0.5)) * exp(6429(A/CNK - 1)/(T-273.15))
as is that of Pichavant et al. (1992):
P2O5.PV = 42/(exp(8400 + 26400 (SiO2 - 0.5))/T - 3.1 - 12.4 (SiO2 - 0.5)) + (A/CNK - 1) exp(-5900/T - 3.22 SiO2 + 9.31)
Returns a matrix 'results
' with the following columns:
A/CNK |
A/CNK values |
Tap.sat.C.H+W |
saturation T of Harrison & Watson (1984) in °C |
Tap.sat.C.Bea |
saturation T of Bea et al. (1992) in °C, peraluminous rocks only |
Tap.sat.C.Pich |
saturation T of Pichavant et al. (1992) in °C, peraluminous rocks only |
Saturation.r
Vojtěch Janoušek, vojtech.janousek@geology.cz
Bea F, Fershtater GB & Corretge LG (1992) The geochemistry of phosphorus in granite rocks and the effects of aluminium. Lithos 29: 43-56 doi: 10.1016/0024-4937(92)90033-U
Harrison TM & Watson EB (1984) The behavior of apatite during crustal anatexis: equilibrium and kinetic considerations. Geochim Cosmochim Acta 48: 1467-1477 doi: 10.1016/0016-7037(84)90403-4
Pichavant M, Montel JM & Richard LR (1992) Apatite solubility in peraluminous liquids: experimental data and extension of the Harrison-Watson model. Geochim Cosmochim Acta 56: 3855-3861 doi: 10.1016/0016-7037(92)90178-L
data(blatna) accessVar("blatna") apSaturation(T=800)