"""
Functions for calcuating indexes of chemical alteration.
"""
import pandas as pd
from ..util.log import Handle
from ..util.meta import update_docstring_references
logger = Handle(__name__)
[docs]@update_docstring_references
def CIA(df: pd.DataFrame):
"""
Chemical Index of Alteration (molecular) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Nesbitt HW, Young GM (1984). Prediction of some weathering trends of plutonic
and volcanic rocks based on thermodynamic and kinetic considerations.
Geochimica et Cosmochimica Acta 48:1523–1534.
doi: `10.1016/0016-7037(84)90408-3 <https://dx.doi.org/10.1016/0016-7037(84)90408-3>`__
"""
return 100 * df.Al2O3 / (df.Al2O3 + df.CaO + df.Na2O + df.K2O)
[docs]@update_docstring_references
def CIW(df: pd.DataFrame):
"""
Chemical Index of Weathering (molecular) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Harnois L (1988). The CIW index: A new chemical index of weathering.
Sedimentary Geology 55:319–322. doi:
`10.1016/0037-0738(88)90137-6 <https://dx.doi.org/10.1016/0037-0738(88)90137-6>`__
"""
return 100.0 * df.Al2O3 / (df.Al2O3 + df.CaO + df.Na2O)
[docs]@update_docstring_references
def PIA(df: pd.DataFrame):
"""
Plagioclase Index of Alteration (molecular) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Fedo CM, Nesbitt HW, Young GM (1995).
Unraveling the effects of potassium metasomatism
in sedimentary rocks and paleosols, with implications for paleoweathering
conditions and provenance. Geology 23:921–924.
doi: `10.1130/0091-7613(1995)023<0921:UTEOPM>2.3.CO;2 <https://dx.doi.org/10.1130/0091-7613(1995)023<0921:UTEOPM>2.3.CO;2>`__
"""
return 100.0 * (df.Al2O3 - df.K2O) / (df.Al2O3 + df.CaO + df.Na2O - df.K2O)
[docs]@update_docstring_references
def SAR(df: pd.DataFrame):
"""
Silica-Alumina Ratio (molecular)
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
"""
return df.SiO2 / df.Al2O3
[docs]@update_docstring_references
def SiTiIndex(df: pd.DataFrame):
"""
Silica-Titania Index (molecular) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Jayawardena U de S, Izawa E (1994).
A new chemical index of weathering for metamorphic silicate rocks in
tropical regions: A study from Sri Lanka.
Engineering Geology 36:303–310.
doi: `10.1016/0013-7952(94)90011-6 <https://dx.doi.org/10.1016/0013-7952(94)90011-6>`__
"""
# may need to recalculate titania from titanium ppm
si_ti = df.SiO2 / df.TiO2
si_al = df.SiO2 / df.Al2O3
al_ti = df.Al2O3 / df.TiO2
return si_ti / (si_ti + si_al + al_ti)
[docs]@update_docstring_references
def WIP(df: pd.DataFrame):
"""
Weathering Index of Parker (molecular) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Parker A (1970). An Index of Weathering for Silicate Rocks.
Geological Magazine 107:501–504.
doi: `10.1017/S0016756800058581 <https://dx.doi.org/10.1017/S0016756800058581>`__
"""
return 2 * df.Na2O / 0.35 + df.MgO / 0.9 + 2 * df.K2O / 0.25 + df.CaO / 0.7
[docs]@update_docstring_references
def IshikawaAltIndex(df: pd.DataFrame):
"""
Alteration Index of Ishikawa (wt%) [#ref_1]_
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
References
----------
.. [#ref_1] Ishikawa Y, Sawaguchi T, Iwaya S, Horiuchi M (1976).
Delineation of prospecting targets for Kuroko deposits based on
modes of volcanism of underlying dacite and alteration halos.
Mining Geology 27:106-117.
"""
return 100 * (df.K2O + df.MgO) / (df.K2O + df.MgO + df.Na2O + df.CaO)
[docs]@update_docstring_references
def CCPI(df: pd.DataFrame):
"""
Chlorite-carbonate-pyrite index of Large et al. (wt%) [#ref_1]_.
Parameters
----------
df : :class:`pandas.DataFrame`
DataFrame to calculate index from.
Returns
--------
:class:`pandas.Series`
Alteration index series.
Notes
-----
Here FeO is taken as total iron (FeO+Fe2O3).
References
----------
.. [#ref_1] Large RR, Gemmell, JB, Paulick, H (2001). The alteration box
plot: A simple approach to understanding the relationship between
alteration mineralogy and lithogeochemistry associated with
volcanic-hosted massive sulfide deposits.
Economic Geology 96:957-971.
doi:`10.2113/gsecongeo.96.5.957 <http://dx.doi.org/10.2113/gsecongeo.96.5.957>`__
"""
if "FeO" in df.columns:
ccpi = 100 * (df.MgO + df.FeO) / (df.MgO + df.FeO + df.Na2O + df.K2O)
elif "Fe2O3" in df.columns and "FeO" in df.columns:
ccpi = (
100
* (df.MgO + df.FeO + df.Fe2O3)
/ (df.MgO + df.FeO + df.Fe2O3 + df.Na2O + df.K2O)
)
return ccpi