Wedge {GCDkit} | R Documentation |
Implementation of Wedge diagrams after Ague (1994) and Bucholz and Ague (2010) used for judging the mobility of elements or oxides in course of various geochemically open-system processes such as alteration or partial melting.
Wedge(x = "Ti", y = NULL, protolith = NULL, outline = "chull", smoothness = 10, plotAltered = TRUE, xmin = 0, ymin = 0, xmax = NULL, ymax = NULL, fun = NULL)
x |
a single geochemical species presumably immobile during the given rock transformation. |
y |
list of elements/oxides for plotting, separated by commas. |
protolith |
Boolean search pattern to specify the protolith samples in the data file. |
outline |
method for contouring the clusters of protolith and product compositions, see Details. |
smoothness |
smoothness (vs. speed of computation) of teh contours, if |
plotAltered |
logical; should be the altered analyses plotted or just contoured? |
xmin, xmax |
(optional) limits for shared x axes of the individual plots. |
ymin |
(optional) minimum for all of the y axes of the plots. |
ymax |
(optional) upper limits for each of the y axes of the plots. |
fun |
panel function to be applied to each of the individual plots. |
Wedge diagrams (Ague 1994) enable qualitative treatment of losses/gains of geochemical species (elements or oxides) during open-system geological processes, such as alteration, metamorphism or partial melting. As such they represent a viable alternative to the isocon plots (Grant 1986, 2005) or concentration ratio diagrams (Ague 1994). However, the Wedge diagrams have an advantage in that they take into account the overall variability of the whole dataset (both of the putative protolith and the altered product) and not just a selected whole-rock pair.
Wedge diagrams are simple binary plots of a potentially mobile element j versus a reference (immobile) element i. The compositionally heterogeneous protolith samples yield a cloud of points. The outer edges of this cloud define a wedge-shaped region that converges towards the origin.
As shown by Bucholz and Ague (2010), the altered samples that plot above and to the left of this wedge are thought to have gained the mobile species j, whereas those falling below and to the right suffered its loss. The samples that remain in the wedge but moved upwards are thought to record residual enrichment, and those shifted downwards to have underwent a residual dilution.
The samples defining the protolith variation can be selected based
on combination of three searching mechanisms
(by sample name/label, range or a Boolean condition) - see
selectSamples
for details.
Implemented are two methods for outlining the
clusters of the protolith and altered compositions
(as specified by the argument 'outline'
),
convex hull (chull) and contour (contour). For the latter,
the shape of the contours drawn can be controlled using the parameter
smoothness. The higher it is, the smoother contours result.
See contourGroups
and chullGroups
for further details.
Optionally, the individual data points for the altered samples may be replaced by contours portraying their density, if plotAltered = FALSE.
Parameters xmin, xmax, ymin and ymax are passed to the function plotWithLimits
used for the actual data plotting.
Optionally, panel function specified by fun with two arguments, xlab and ylab, is applied to each of the plots.
Returns a matrix 'results
' of slopes of tie-lines from individual
protolith samples to the origin
(with a component for each diagram, i.e. for each species evaluated).
Lines of maximum and minimum slopes are those which are plotted as dashed lines,
thus defining the wedge of the protolith variation (see Details).
Isocon.r
This function uses the plates concept. The individual plots can be selected and their
properties/appearance changed as if they were stand alone Figaro-compatible plots.
See Plate
, Plate editing
and
figaro
for details.
Vojtěch Janoušek, vojtech.janousek@geology.cz
Ague JJ (1994) Mass transfer during Barrovian metamorphism of pelites, south-central Connecticut; I, Evidence for changes in composition and volume. Amer J Sci 294: 989-1057 doi: 10.2475/ajs.294.8.989
Bucholz CE, Ague JJ (2010) Fluid flow and Al transport during quartz-kyanite vein formation, Unst, Shetland Islands, Scotland. J Metamorph Geol 28: 19-39 doi: 10.1016/0009-2541(67)90004-6
Grant JA (1986) The isocon diagram - a simple solution to Gresens equation for metasomatic alteration. Econ Geol 81: 1976-1982 doi: 10.2113/gsecongeo.81.8.1976
Grant JA (2005) Isocon analysis: a brief review of the method and applications. Phys Chem Earth (A) 30: 997-1004 doi: 10.1016/j.pce.2004.11.003
Gresens RL (1967) Composition-volume relationships of metasomatism. Chem Geol 2: 47-55 doi: 10.1016/0009-2541(67)90004-6
Ague, isocon, Plate, Plate editing, chull, contour contourGroups chullGroups, plotWithLimits
data(sazava) accessVar("sazava") Wedge("Ti","SiO2,FeOt,MgO,CaO,Na2O,K2O", protolith="Intrusion=\"Sazava\"","chull") # Using the default precision of 10 Wedge("Ti","Zr,Nb,Sr,Rb,Ba",protolith="Intrusion=\"Sazava\"","contour") Wedge("Ti","Zr,Nb,Sr,Rb,Ba",protolith="Intrusion=\"Sazava\"","contour",smoothness=10) Wedge("Ti","Zr,Nb,Sr,Rb,Ba",protolith="Intrusion=\"Sazava\"","contour",smoothness=100)