pyrolite.geochem.magma

Submodule for calculating and modelling melt chemistry. Includes common functions for predicting and accounting for melt evolution.

pyrolite.geochem.magma.FeAt8MgO(FeOT: float, MgO: float) → float

To account for differences in the slopes and curvature of liquid lines of descent as a function of parental magma composition [1] [2] (after [3]).

Parameters:

• FeOT (float) – Iron oxide content.

• MgO (float) – Magnesium oxide content.

References

[1]

Castillo PR, Klein E, Bender J, et al (2000). Petrology and Sr, Nd, and Pb isotope geochemistry of mid-ocean ridge basalt glasses from the 11°45’N to 15°00’N segment of the East Pacific Rise. Geochemistry, Geophysics, Geosystems 1:1. doi: 10.1029/1999GC000024

[2]

Klein EM, Langmuir CH (1987). Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness. Journal of Geophysical Research: Solid Earth 92:8089–8115. doi: 10.1029/JB092iB08p08089

[3]

Langmuir CH, Bender JF (1984). The geochemistry of oceanic basalts in the vicinity of transform faults: Observations and implications. Earth and Planetary Science Letters 69:107–127. doi: 10.1016/0012-821X(84)90077-3

pyrolite.geochem.magma.NaAt8MgO(Na2O: float, MgO: float) → float

To account for differences in the slopes and curvature of liquid lines of descent as a function of parental magma composition [4] [5] (after [6]).

Parameters:

• Na2O (float) – Iron oxide content.

• MgO (float) – Magnesium oxide content.

References

[4]

Castillo PR, Klein E, Bender J, et al (2000). Petrology and Sr, Nd, and Pb isotope geochemistry of mid-ocean ridge basalt glasses from the 11°45’N to 15°00’N segment of the East Pacific Rise. Geochemistry, Geophysics, Geosystems 1:1. doi: 10.1029/1999GC000024

[5]

Klein EM, Langmuir CH (1987). Global correlations of ocean ridge basalt chemistry with axial depth and crustal thickness. Journal of Geophysical Research: Solid Earth 92:8089–8115. doi: 10.1029/JB092iB08p08089

[6]

Langmuir CH, Bender JF (1984). The geochemistry of oceanic basalts in the vicinity of transform faults: Observations and implications. Earth and Planetary Science Letters 69:107–127. doi: 10.1016/0012-821X(84)90077-3

pyrolite.geochem.magma.SCSS(df, T, P, kelvin=False, grid=None, outunit='wt%')

Obtain the sulfur content at sulfate and sulfide saturation [7] [8].

Parameters:

• df (pandas.DataFrame) – Dataframe of compositions.

• T (float | numpy.ndarray) – Temperature

• P (float | numpy.ndarray) – Pressure (kbar)

• kelvin (bool) – Whether temperature values are in kelvin (True) or celsuis (False)

• grid (None, 'geotherm', 'grid') – Whether to consider temperature and pressure as a geotherm (geotherm), or independently (as a grid, grid).

Returns:

sulfate, sulfide – Arrays of mass fraction sulfate and sulfide abundances at saturation.

Return type:

numpy.ndarray, numpy.ndarray

Notes

For anhydrite-saturated systems, the sulfur content at sulfate saturation is given by the following:

\[\begin{split}\begin{align} ln(X_S) = &10.07 - 1.151 \cdot (10^4 / T_K) + 0.104 \cdot P_{kbar}\\ &- 7.1 \cdot X_{SiO_2} - 14.02 \cdot X_{MgO} - 14.164 \cdot X_{Al_2O_3}\\ \end{align}\end{split}\]

For sulfide-liquid saturated systems, the sulfur content at sulfide saturation is given by the following:

\[\begin{split}\begin{align} ln(X_S) = &{-1.76} - 0.474 \cdot (10^4 / T_K) + 0.021 \cdot P_{kbar}\\ &+ 5.559 \cdot X_{FeO} + 2.565 \cdot X_{TiO_2} + 2.709 \cdot X_{CaO}\\ &- 3.192 \cdot X_{SiO_2} - 3.049 \cdot X_{H_2O}\\ \end{align}\end{split}\]

References

[7]

Li, C., and Ripley, E.M. (2009). Sulfur Contents at Sulfide-Liquid or Anhydrite Saturation in Silicate Melts: Empirical Equations and Example Applications. Economic Geology 104, 405–412. doi: gsecongeo.104.3.405

[8]

Smythe, D.J., Wood, B.J., and Kiseeva, E.S. (2017). The S content of silicate melts at sulfide saturation: New experiments and a model incorporating the effects of sulfide composition. American Mineralogist 102, 795–803. doi: 10.2138/am-2017-5800CCBY

Todo

• Produce an updated version based on log-regressions?

• Add updates from Smythe et al. (2017)?