rtSaturation {GCDkit}R Documentation

Rutile saturation (Hayden + Watson 2007)

Description

Calculates rutile saturation temperatures for the observed major-element data and Ti concentrations. Also returns Ti saturation levels for the given major-element compositions and assumed magma temperature.

Usage

rtSaturation(cats=milli,T=0,P=0,Ti=filterOut(WR,"Ti",1))

Arguments

cats

numeric matrix; whole-rock data recast to millications

T

assumed temperature of the magma in °C

P

assumed pressure in kbar, Ryerson & Watson (1987) model only

Ti

numeric vector with Ti concentrations in ppm

Details

Ryerson & Watson (1987) have first formulated rutile saturation model for melts ranging in composition from basalt to rhyodacite. The distribution of TiO2 between rutile and liquid was given as:

DTiO2 = exp(-3.16+9373/T+0.026*P-0.152*FM)

where 'T' is the absolute temperature (K) of the magma, 'P' pressure (kbar) and 'FM' is a melt composition parameter:

FM = 1/Si*(Na+K+2(Ca+Mg+Fe))/Al

.

The Ti saturation level then would be:

Ti.sat.RW = 599342.9/DTiO2 (ppm)

In turn, when the rutile saturation was reached, the magma temperature (in °C) can be calculated as:

TRt.sat.C.RW<-9373/(3.16+ln(100/TiO2)-0.026*P+0.152*FM)-273.15

The Ti solubility in rutile-saturated hydrous siliceous melts was revisited by Hayden & Watson (2007). According to these authors, it can be expressed as:

Ti.sat.HW = 10^(7.95 - 5305/T + 0.124 FM) (ppm)

where 'T' is the absolute temperature (K) of the magma, and 'FM' is the melt composition parameter defined above.

The temperature (in °C) for rutile-saturated magma can be calculated as:

TRt.sat.C.HW = 5305/(7.95 -log(Ti) + 0.124 FM) - 273.15

Using these formulae, the function 'rtSaturation' calculates the rutile saturation levels, Ti activities and rutile saturation temperatures following both models.

The formulation of Ryerson & Watson (1987) may be more suitable for basic rocks, whereas the more recent model of Hayden & Watson (2007) seems to be appropriate for siliceous magmas. Please note also that the latter does not take into account effects of pressure (having been calibrated at 1 GPa; Hayden & Watson 2007).

Value

Returns a matrix 'results' with the following columns:

FM

melt composition parameter

Ti

observed Ti concentrations

Ti.sat.RW

saturation levels of Ti for assumed temperature, Ryerson & Watson (1987)

aTi.RW

activity of Ti (ratio of Ti/Ti.sat), Ryerson & Watson (1987)

TRt.sat.C.RW

rutile saturation temperatures in °C, Ryerson & Watson (1987)

Ti.sat.HW

saturation levels of Ti for assumed temperature, Hayden & Watson (2007)

aTi.HW

activity of Ti (ratio of Ti/Ti.sat), Hayden & Watson (2007)

TRt.sat.C.HW

rutile saturation temperatures in °C, Hayden & Watson (2007)

Plugin

Saturation.r

Author(s)

Vojtěch Janoušek, vojtech.janousek@geology.cz

References

Ryerson FJ, Watson EB (1987) Rutile saturation in magmas; implications for Ti-Nb-Ta depletion in island-arc basalts. Earth Planet Sci Lett 86: 225-239 doi: 10.1016/0012-821X(87)90223-8

Hayden LA, Watson EB (2007) Rutile saturation in hydrous siliceous melts and its bearing on Ti-thermometry of quartz and zircon. Earth Planet Sci Lett 258: 561-568 doi: 10.1016/j.epsl.2007.04.020

Examples

    data(sazava)
    accessVar("sazava")

    rtSaturation(T=800,P=3)

[Package GCDkit version 6.1 Index]