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A new software, PetroGraph, has been developed to visualize, elaborate, and model geochemical data for igneous petrology purposes. The software is able to plot data on several different diagrams, including a large number of classification and “petrotectonic” plots. PetroGraph gives the opportunity to handle large geochemical data sets in a single program without the need of passing from one software to the other as usually happens in petrologic data handling. Along with these basic functions, PetroGraph contains a wide choice of modeling possibilities, from major element mass balance calculations to the most common partial melting and magma evolution models based on trace element and isotopic data. Results and graphs can be exported as vector graphics in publication-quality form, or they can be copied and pasted within the most common graphics programs for further modifications. All these features make PetroGraph one of the most complete software presently available for igneous petrology research.
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PetroGraph: A new software to visualize, model, and present
geochemical data in igneous petrology
M. Petrelli, G. Poli, D. Perugini, and A. Peccerillo
Department of Earth Sciences, University of Perugia, Piazza Universita`, 1, 06100 Perugia, Italy (
[1] A new software, PetroGraph, has been developed to visualize, elaborate, and model geochemical data
for igneous petrology purposes. The software is able to plot data on several different diagrams, including a
large number of classification and ‘petrotectonic’ plots. PetroGraph gives the opportunity to handle large
geochemical data sets in a single program without the need of passing from one software to the other as
usually happens in petrologic data handling. Along with these basic functions, PetroGraph contains a wide
choice of modeling possibilities, from major element mass balance calculations to the most common partial
melting and magma evolution models based on trace element and isotopic data. Results and graphs can be
exported as vector graphics in publication-quality form, or they can be copied and pasted within the most
common graphics programs for further modifications. All these features make PetroGraph one of the most
complete software presently available for igneous petrology research.
Components: 4646 words, 10 figures, 4 tables.
Keywords: data management; data plotting; geochemical modeling; petrology; software.
Index Terms: 3610 Mineralogy and Petrology: Geochemical modeling (1009, 8410); 1065 Geochemistry: Major and trace
element geochemistry; 1094 Geochemistry: Instruments and techniques.
Received 3 February 2005; Revised 5 May 2005; Accepted 11 May 2005; Published 26 July 2005.
Petrelli, M., G. Poli, D. Perugini, and A. Peccerillo (2005), PetroGraph: A new software to visualize, model, and present
geochemical data in igneous petrology, Geochem. Geophys. Geosyst., 6, Q07011, doi:10.1029/2005GC000932.
1. Introduction
[2] Handling, visualization, and modeling of geo-
chemical data are of fundamental importance in
igneous petrology. Most of these operations can
be performed using a variety of software pack-
ages such as spreadsheet programs (e.g., MS
or Microcal Origin
), interpreted scien-
tific computer languages (e.g., R
or Matlab
or software specifically developed for igneous
petrology such as MinPet
Software Inc. Web site:,
GCDKit [Janousek et al., 2003], IgPet
RockWare Web site:
and PetroPlot [Su et al., 2003]. Moreover, a large
number of codes have been developed [ e.g.,
Wright and Doherty, 1970; Stormer and Nicholls,
1978; Woussen and Coˆte´, 1987; Conrad, 1987;
Holm, 1988, 1990; Nielsen, 1988; Defant and
Nielsen, 1990; Harnois, 1991; Benito and Lo´pez-
Ruiz, 1992; D’Orazio, 1993; Verma et al., 1998;
Keskin, 2002; Spera and Bohrson, 2001] to help
researchers in performing specific geochemical
models. All these software allowed users to
greatly speed up modeling of geochemical data,
but some of them are designed for old MS-DOS
operating systems and cause problems when
loaded into modern MS Windows systems.
Other programs have limited possibility of
geochemical modeling (e.g., MinPet, GCDKit
and PetroPlot). Moreover, problems can arise
when trying to run algorithms available only as
source codes; for example, the mass balance
algorithm by Stormer and Nicholls [1978]
requires a FORTRAN compiler t o be loaded,
and this may cause difficulties for the user if
Published by AGU and the Geochemical Society
Technical Brief
Volume 6, Number 7
26 July 2005
Q07011, doi:10.1029/2005GC000932
ISSN: 1525-2027
Copyright 2005 by the American Geophysical Union 1 of 15
compared to modern object-oriented, user-friendly
3] In this contribution we present a new pro-
gram, PetroGraph (Figure 1), developed with the
aim of giving a complete platform to handle,
visualize and model geochemical data in a user
friendly envi ronment. The program runs under
Windows 98/2000/XP
alone application. The source code is written in
MS Visual Basic 6.0
and is distributed together
with the program. The code is open source and
we invite all users to contribute to the develop-
ment of the software by proposing improvement
or developing new codes. To download the soft-
ware and the tutorial, please go to http://www. (see also ancil-
lary material).
4] In the following sections we present the main
features and potentialities of PetroGraph. The pa-
per is divided into five main sections (Figure 2),
including (1) input of geochemical data, (2) data
visualization, (3) development of geochemical
models, (4) data management, and (5) additional
2. Data Input
[5] Geochemical data can be imported into Petro-
Graph in three file formats (Figure 2a): (1) MS
worksheets, (2) IgPetWin
formatted files,
and (3) PetroGraph (.peg) files.
6] MS Excel
worksheets need little formatting
before imported to PetroGraph, as reported in
Figure 2. The arrangement of the worksheet, how-
ever, is not much different from common analytical
outputs. In particular, the first column must contain
the sa mple name, whereas the following three
columns are dedicated to symbol and color man-
agement and to the choice to show (1) or not to
show (0) the sample in the diagrams (see the
tutorial for a detailed explanation of the arrange-
ment of the MS Excel
Figure 1. General screen shot of PetroGraph showing some types of graphs performed by the software. (a) Total
Alkali-Silica, TAS diagram [Le Bas et al., 1986], (b) TiO
versus SiO
binary plot, (c) AFM ternary plot [Kuno,
1968], and (d) Condrite normalized REE diagram [Haskin et al., 1968]. Displayed data are from Pecceril lo et al.
petrelli et al.: petrograph software 10.1029/2005GC000932
[7] A specific code has been written to import
files (.roc format) without modifications
of the original file format.
8] PetroGraph can save data into text files by
applying the .peg extension. These files can be
opened by the software much faster than MS Excel
formatted spreadsheets.
3. Visualization
[9] Once data have been imported, the user can
visualize them (Figure 2b) using three different
types of diagrams commonly used in igneous
petrology: binary, ternary, and spider diagrams
(Figure 1). All diagrams can be easily generated
in few steps. For example, a binary or a ternary
diagram can be created in only 3 steps as de-
scribed in Figure 3. Several options are presented
to the user for each type of diagram. For instance,
data can be plotted in binary diagrams by using
linear and logarithmic scaling; maximum and
minimum values of the axis can be rearranged to
zoom into specific areas of the graphs. In addition,
a large number of symbols and colors can be
selected to visualize data. The most common
Figure 2. PetroGraph block diagram explaining the main features of the program.
petrelli et al.: petrograph software 10.1029/2005GC000932petrelli et al.: petrograph software 10.1029/2005GC000932
normalizations can be chosen for rare earth ele-
ments (REE) normalized diagrams (Figure 4a;
Table 1). For example, REE data can be normal-
ized by Condrite or NASC values by selecting
the relative normalization values in the REE
spiders window (arrow in the REE spiders win-
dow; Figure 4a).
10] Additional spider diagrams can be also per-
formed using several normalizations (Figure 4b;
Table 1). For example, data can be normalized by
primordial mantle [Wood et al., 1979a], mid-ocean
ridge basalts (MORB) [Bevins et al., 1984], and
continental crust [Tayl or and McLennan, 1981;
Weaver and Tarney, 1984] by selecting them in
Figure 3. Screen shot of the program showing the procedure to plot a binary and ternary diagram. (a) Button of
the control bar that opens the ‘binary plot window,’ (b) window that allows the user to customize and plot a binary
diagram, (c) button that allows the user to open (f) the windows in which elements can be easily selected,
(d) example of binary plot, (e) note that name and the coordinate of samples can be displayed on the lower part of
the main windows by tracking on them with the pointer, (g) button of the control bar that opens the ‘triangular plot
window,’ (h) window that allows the user to customize and plot a triangular diagram, and (i) example of a
triangular plot.
petrelli et al.: petrograph software 10.1029/2005GC000932
the relative spider window (arrow in the general
spider window; Figure 4b). An important feature of
PetroGraph is the possibility to generate normali-
zation files that can be used to generate custom
spider diagrams.
11] One of the major tasks in igneous petrology is
rock classification and this can be easily done with
PetroGraph by using a wide choice of classification
diagrams (e.g., Q’-AN OR, TAS, etc.; Table 2);
several ‘petrotectonic’ diagrams (e.g., Nb-Y, Ti-
Zr-Y, etc.; Table 2) can be also generated [Rollison,
1993]. For example, the Total Alkali versus Silica
diagram (TAS) [Le Bas et al., 1986] can be created
simply selecting it from the Diagram section of the
Plot menu (Figure 5).
12] All diagrams can be easily modified by a
mouse double click (Figure 6b) and a cascade
menu containing several options can be opened
by a right click (Figure 6a). All these options allow
the user to generate high-quality graphs that can be
saved to file in publication-ready form in Micro-
metafile format or copied to the clipboard to
Figure 4. Screen shot of the program showing the procedure to plot a spider diagram. (a) Procedure to plot a REE
spider diagram. (b) Procedure t o plot a general spider diagram. Arrow in the REE spiders window: possible
normalizations for REE spiders. Arrow in the general spiders window: possible normalizations for general spiders.
petrelli et al.: petrograph software 10.1029/2005GC000932
be further elaborated in the major vector-graphic
applications (e.g., MS Office
, Corel
4. Modeling of Geochemical Data
4.1. Major Element Modeling
[13] Several modeling approaches by using major
and trace elements, and isotopes are implemented
in PetroGraph (Figure 2c).
14] Major elements are modeled by the mass
balance algorithm [Stormer and Nicholls, 1978].
This approach involves a least squares solution to
a set of linear mass balance equations (one for
each oxide) and the calculations are performed on
data consisting of chemical analyses of igneous
rocks, assumed to represent the composition of
parent and daughter magmas. This computational
approach can be used to test fractional crystalliza-
tion, assimilation, fractional melting, and magma
mixing [e.g., Stormer and Nicholls, 1978]. Mass
balance computations are performed in a user
friendly env ironment (Figure 7) by selecting
‘magmas’ and ‘phas es’ among the samples
belonging to the geochemical data set. Figure 7
shows the procedure to develop a Mass Balance
computation using PetroGraph: first select the
oxides (Figures 7b7e), successively select the
initial and final ‘magmas’ (Figures 7c 7f), then
select the ‘phases’ and finally calculate results
(Figure 7h).
4.2. Trace Element and Isotope Modeling
[15] Trace elements models are divided into three
main sections, involving (1) magma crystallization
processes (Table 3), (2) partial melting (Table 4,
top), and (3) magma mixing (Table 4, bottom).
PetroGraph can model mixing [Langmuir et al.,
1978] and Assimilation plus Fractional Crystalli-
zation (AFC) [DePaolo, 1981] processes, using
isotopic data.
16] Trace element and isotope models can be
performed by choosing the model end-members
direc tly from the plotte d samples; this strongly
simplifies the modeling procedure and allows the
user to immediately evaluate if the selected model
is suitable or not for the studied data set. Once a
model has been plotted on a graph, model param-
eters can be readily modified in the appropriate
window that will pop up with a single click of the
mouse directly on the graph. Different models can
be displayed simultaneously either in a single
graph or in different graph windows.
17] Figure 8 reproduces two diagrams extracted
from Peccerillo et al. [2003] and shows, as an
example, how to perform trace element and iso-
tope models with PetroGraph. The models refer to
the origin of peralkaline silicic magmas at
Gedemsa volcano (Central Ethiopian Rift), which
can be generated either by batch melting of a
basaltic rock or by fractional crystallization of a
basaltic parental melt. Trace element and isotope
models reported in Figure 8 show that fractional
crystallization accompanied by little assimilation
of the Precambrian crust is more suitable than
batch-melting to explain sample variability in the
Gedemsa magmatic system (see Peccerillo et al.
[2003] for a detailed discussion of these data)
and these models can be easily developed using
5. Data Management
[18] Data management (Figure 2d) can be per-
formed by using four principal types of operation:
(1) algebraic operations, (2) determination of geo-
chemical parameters or indexes, (3) operation re-
lated to rare earth elements, and (4) operation on
isotopes (Figure 9a).
19] Algebraic operations are the sum, subtraction,
division, multiplication, the elevation to an expo-
Table 1. Normalizations Available in PetroGraph for
REE and General Spider Diagrams
Normalization Source
REE Spiders
Chondrite Haskin et al. [1968]
Chondrite Masuda et al. [1973]
Chondrite Nakamura [1974]
Chondrite Boynton [1984]
Chondrite Sun and McDonough [1989]
NASC Haskin and Frey [1966]
NASC Haskin and Haskin [1966]
General Spiders
Primordial mantle Wood et al. [1979a]
Primordial mantle McDonough et al. [1992]
Primordial mantle Taylor and McLennan [1985]
Condrite Wood et al. [1979b]
MORB Bevins et al. [1984]
Upper cont. crust Taylor and McLennan [1981]
Lower cont. crust Weaver and Tarney [1984]
Average cont. crust Weaver and Tarney [1984]
Average N-type MORB Saunders and Tarney [1984],
Sun [1980]
Average OIB Sun [1980]
Custom spider allows user to generate custom
normalization file
petrelli et al.: petrograph software 10.1029/2005GC000932
nent, and the square root. In addition, it is possible
to convert parts per million (PPM) values to weight
percent (wt%) and vice versa. These operations
allow the user to generate new variables that can be
plotted and elaborated analogously to the original
20] Geochemical para meters and indexes tha t
can be determined by PetroGraph are Total Iron
), Larsen Index, Solidification Index (SI),
CIPW norm, Magnesium Number (Mg#), Alumin-
ium Saturation Index (ASI), and Fe/Mg Ratio.
21] Regarding operations related to REE, Petro-
Graph can calculate the Europium anomaly (Eu/
Eu*), three different normalized REE ratios (La
) and the total sum of REE
22] Regarding isotopes, PetroGraph offers t he
opportunity to use the epsilon notation for Nd
and Hf isotopes and to calculate the percent devi-
ation from present-day chondritic value for
6. Additional Features
[23] Among additional features (Figure 2e), Petro-
Graph offers the opportunity to filter data sets by
applying several kinds of constraints and allows
the user to consult a solid/liquid partition coeffi-
cient database, a useful option when developing
trace element geochemical models.
24] Filters (Figures 9b and 9c) are useful when
only samples with specific compositional charac-
teristics (e.g., only samples with a content of SiO
higher than 50 wt%) are to be selected for plotting
(Figure 9c).
25] A complete data set of partition coefficients is
stor ed in PetroGraph (Figure 10). Data for the
Table 2. Classification and Discriminating Diagrams Performed by PetroGraph
Diagram Source
General Classification Diagrams
) - ANOR] volcanic after Streckeisen and Le Maitre [1979]
] after Peccerillo and Taylor [1976]
] after Middlemost [1975]
[TAS Alkalis - Silica] volcanic after Le Bas et al. [1986]
[TAS Alkalis - Silica] volcanic after Cox et al. [1979]
[TAS Alkalis - Silica] plutonic after Cox et al. [1979]
O Andesite Types] after Gill [1981]
- F/M] after Miyashiro [1974]
AFM after Kuno [1968]
AFM after Irvine and Baragar [1971]
Diagrams for Basalts
[Ta/Yb - Tb/Yb] after Pearce [1982]
[Y - Cr] after Pearce [1982]
[Ti - Zr] after Pearce and Cann [1973]
[Ti - Zr - Y] after Pearce and Cann [1973]
[Ti - Zr - Sr] after Pearce and Cann [1973]
[Nb - Zr - Y] after Meschede [1986]
[Th - Hf - Ta] after Wood [1980]
Diagrams for Granites
[Nb - Y] after Pearce et al. [1984]
[Ta - Yb] after Pearce et al. [1984]
[Rb - (Y + Nb)] after Pearce et al. [1984]
[Rb - (Yb + Ta)] after Pearce et al. [1984]
Mantle End-Members
Sr -
Nd] data from Hart et al. [1992]
Pb -
Nd] data from Hart et al. [1992]
Pb -
Sr] data from Hart et al. [1992]
petrelli et al.: petrograph software 10.1029/2005GC000932
Figure 5. Screen shot of the program showing the procedure to plot classification or ‘petrotectonic’ diagrams.
(a) Procedure to select a diagram; (b) example of a TAS diagram.
petrelli et al.: petrograph software 10.1029/2005GC000932
Figure 6. Screen shot of the program showing options to customize a binary plot. (a) Cascade menu generated by
click of the right mouse button on the diagram; (b) window opened by a double click of the left mouse button on the
diagram to change axis properties.
petrelli et al.: petrograph software 10.1029/2005GC000932
partition coefficient database are from Earth Ref-
erence Data and Models Web site (EarthRef; http://
7. Summary
[26] PetroGraph is a program specifically devel-
oped to visualize, elaborate, and model geochem-
ical data. It runs on Microsoft
Windows 98/2000/
XP platforms and it is written in Visual Basic
With its user friendly design, it is able to plot data
within binary, triangular and spider diagrams with
minimum effort. A large number of classification
and discriminating diagrams can be easily plotted;
several operations can be performed on the original
variables in order to obtain new variables and
geochemical parameters. A large number of geo-
chemical models can be calculated from major and
trace elements, and isotopes. Moreover, Petro-
Figure 7. (a) Mass Balance window and results of the mass balance calculation. (b, c, and d) On the upper part of
the Mass Balance window are reported buttons that open the windows to select (e) oxides, (f) ‘magmas,’ and
(g) ‘phases.’ The computation can be performed by clicking (h) the ‘Calculate’ button. The output is displayed in
the lower part of the window. Results can be also exported into the clipboard or saved as text files. Data and results
reported in the presented example are the same as in the original paper by Stormer and Nicholls [1978]. Detailed
information on step-by-step procedures to perform mass balance computations is reported in the software tutorial.
Table 3. Trace Element Models Involving Crystallization Processes
Model Abbreviation
Equilibrium Crystallization [Wood and Fraser, 1976] EC
Fractional Crystallization [Neuman et al., 1954] FC
Assimilation plus Fractional Crystallization [DePaolo, 1981] AFC
In Situ Crystallization [Langmuir, 1989] In Situ C
Zone Refining [Richter, 1986] ZR
petrelli et al.: petrograph software 10.1029/2005GC000932
10 of 15
Table 4. Trace Element Models Involving Melting and Mixing Processes
Model Abbreviation
Melting Models
Batch Melting [Wood and Fraser, 1976] BM
Non Modal Batch Melting [Wood and Fraser, 1976] nMBM
Fractional Melting [Wood and Fraser, 1976] FM
Mixing Model
Mixing [Langmuir et al., 1978] Mix
Figure 8. Screen shot of the program explaining the potentialities of PetroGraph in performing trace element
modeling. (a) Window that allows the user to customize trace element models. (b) V versus Zr plot in which
Fractional Crystallization (D
= 0.1) and Batch Melting (D
= 0.1) models are reported. It is
clear that Gedemsa rocks’ behavior can be well explained by fractional crystallization, whereas batch melting fails in
accounting for the sample variability. (c) Sr versus
Sr plot reporting the Assimilation and Fractional
Crystallization (AFC) model. Isotopic modeling corroborates the hypothesis indicating that fractional crystallization
couples with moderate assimilation of Precambrian crust can suitably account for Sr isotopic signature of Gedemsa
rocks; model parameters are reported in the graph. Data are from Peccerillo et al. [2003]. Detailed information on
step-by-step procedures to perform geochemical models is reported in the software tutorial.
petrelli et al.: petrograph software 10.1029/2005GC000932
11 of 15
Figure 9. Screen shot of the program showing potentialities of PetroGraph in (a) data management and (b and c) the
data filtering window.
petrelli et al.: petrograph software 10.1029/2005GC000932
12 of 15
Graph produces high-quality graphic outputs
which can be directly used for publication.
[27] We acknowledge the useful suggestions and criticisms of
Yoshiyuki Tatsumi (Associate Editor) and two anonymous
referees. The editorial handling of W. M. White is gratefully
acknowledged. This work was funded by MIUR (G.P., A.P.)
and GNV grants.
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Supplementary resource (1)

... The available chemical data of the Mesozoic basalts of Um Bogma area (Samuel et al., 1999;Samuel et al., 2002) were repurposed, processed and plotted onto appropriate geochemical diagrams using GCDkit software (Janoušek et al., 2006). Fractional crystallization modeling using least squares mass balance solution after Stormer and Nicholls (1978) throughout the Petrograph software of Petrelli et al. (2005) was performed. ...
... Table 4). An attempt to derive the other petrographic types of Gebel El Azraq basalts from the picritic dolerite was made using mass balance calculations of Stormer and Nicholls (1978) throughout the Petrograph software (Petrelli et al., 2005). The results revealed that none of the basaltic types could be derived from the considered picrite. ...
... In terms of normative olivine, plagioclase and clinopyroxene (Fig. 12a), the Gebel Farsh El Azraq basaltic rocks -excluding the picritic dolerite -exhibit sequence of crystallization of olivine + liquid, followed by cotectic crystallization of olivine and plagioclase in their evolution path from olivine-rich basalts to olivine basalts. Of picritic dolerite, it is over-saturated with olivine and plots -as Table 6 Fractional crystallization modeling of Gebel Himayir basaltic rocks, following Stormer and Nicholls (1978) throughout the Petrograph software after Petrelli et al. (2005). ...
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Sinai Mesozoic basalts are restricted in its southwestern portion at Um Bogma area, where they occur as intra-continental fissure-fed sills, dykes, plugs and lava flows, following mainly the older structural and crustal weaknesses planes. During Late Paleozoic - Middle to Late Triassic, Egypt had witnessed sporadic tectonic disturbances and faulting activities accompanied by volcanisms. Faulting activity continued during Early to Middle Jurassic and was associated with crustal stretching and basaltic volcanism. At Um Bogma area, southwestern Sinai Peninsula, Middle Triassic, and Early Jurassic basaltic exposures intruded/extruded the Carboniferous sandstones. The main Mesozoic basalts outcrop at Gebel Farsh El Azraq - Gebel Himayir area, where they were successfully discriminated from their surrounding country rocks using Landsat-8 dataset. The Mesozoic basaltic rocks are the least reflective rocks and exhibit a characteristic spectral curve, compared to their country rocks. Landsat-8 bands 7, 5, 3 in RGB and Principal Component Analyses (PCA) technique were used in lithological discrimination of the Mesozoic basalts and their surrounding Late Neoproterozoic basement rocks and Phanerozoic sedimentary succession. Accordingly, a new geological map was produced for the study area. Petrography and geochemistry of these basalts were addressed. Characteristically they contain substantial MgO contents (22.24 to 7.09 wt%) and exhibit low TiO2 (1.56–0.77 wt%) and P2O5 (0.30–0.15 wt%) contents. Geochemically, they pertain to the low P2O5 –TiO2 continental tholeiitic to transitional basalts and point out to enriched MORB magma sources. They suggest derivation from spinel-garnet lherzolite source by moderate non-modal partial melting (ca 20–30%). Their petrogenesis was discussed and fractional crystallization odeling was performed as a plausible mechanism to be accounted for their evolutions.
... Plagioclase and clinopyroxene (phenocrysts and microlites) compositions within the matrix (An 51-90 ; Wo 28-46 En 35-51 Fs [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] ) and enclaves (An ; Wo [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] En 34-51 Fs 12-23 ) in FL samples overlap ( Supplementary Fig. 1). Enclave hosted olivine crystals are more fayalitic (Fo ) than matrix microlites (Fo [68][69][70][71][72][73] ). ...
... Incompatible elements Ba and La increase with increasing Zr. A fractional crystallisation trend was modelled using Petrograph software 34 (Fig. 4). FL MI and glasses fit well with the modelled fractional crystallisation trend, indicating crystallisation-controlled melt evolution. ...
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Although rare, basaltic Plinian eruptions represent a considerable volcanic hazard. The low viscosity of crystal-poor basaltic magma inhibits magma fragmentation; however, Las Sierras-Masaya volcano, Nicaragua, has produced multiple basaltic Plinian eruptions. Here, we quantify the geochemistry and volatile concentrations of melt inclusions in samples of the Fontana Lapilli and Masaya Triple Layer eruptions to constrain pre-eruptive conditions. Combining thermometry and geochemical modelling, we show that magma cooled to ~1000 °C prior to eruption, crystallising a mush that was erupted and preserved in scoriae. We use these data in a numerical conduit model, which finds that conditions most conducive to Plinian eruptions are a pre-eruptive temperature <1100 °C and a total crystal content >30 vol.%. Cooling, crystal-rich, large-volume basaltic magma bodies may be hazardous due to their potential to erupt with Plinian magnitude. Rapid ascent rates mean there may only be some minutes between eruption triggering and Plinian activity at Masaya.
... Os elementos-traços e os elementos terras raras (ETR) foram analisados por espectrômetro de massa em plasma indutivamente acoplado (inductively coupled plasma mass spectrometry -ICP-MS), após fusão utilizando metaborato/tetraborato de lítio e digestão em ácido nítrico, sendo que para os metais Cu, Ni, Pb e Zn a digestão foi por água régia. O tratamento dos dados geoquímicos e a construção de diagramas foram realizados com emprego do programa PETROGRAPH versão 2 beta dic2007 (Petrelli et al., 2005). ...
Entre as rochas da Formação Ponta Grossa, aflorantes no município de Rio Verde de Mato Grosso, é registrada a presença de camadas constituídas predominantemente por apatita, não fossilíferas, que ocorrem como estratos destacados intercalados em folhelhos cinzas-escuros a pretos. Petrograficamente, essa rocha fosfática apresenta estrutura sutilmente laminada e não são observadas feições indicativas de algas, restos fósseis ou de estruturas orgânicas. Possui teores de P2O5 variando entre 12,96 e 23,35%, teores de CaO variando entre 19,85 e 33,04%, e possui alta concentração de elementos terras raras (ETR) em relação à média da crosta continental superior. Essa ocorrência não possui evidências de ação biogênica — o que é confirmado pela microscopia eletrônica — e possui relictos de oxi-hidróxidos, preferencialmente de ferro, com pequena quantidade de manganês, sugerindo origem pela dessorção de fosfato por comportamento redox a partir desses relictos. As condições de formação dessas fosforitas — se não condicionadas a aporte externo de oxi-hidróxidos de ferro pela proximidade da costa, por ambientes deltaicos ou por contribuições hidrotermais e/ou vulcânicas — colocam as camadas fosfáticas de Rio Verde de Mato Grosso, Mato Grosso do Sul, em condições de ambiente marinho plataformal raso, com profundidade entre 200 e 300 m, de águas frias e com baixa salinidade, preferencialmente anóxico, e suscetível a estabelecimento de zona de ressurgência.
... Patterns of incompatible trace elements of low mobility (Fig. 5) suggest that the progressive enrichment associated with SiO 2 wt.% incre-ment (Fig. 4) is compatible with fractional crystallization connecting the basic and the silicic volcanic rocks in the CACB, whereas in the basalts their contrasting enrichment might result from different degrees of mantle partial melting. We employed trace element modeling based on the systematics of Cocherie (1986), by using the set of geochemical models included in the software PetroGraph (Petrelli et al., 2005), to investigate the petrogenesis of the silicic rocks from both stages of the CACB. The paired evolution in the concentration of two trace elements, from the original composition in the initial liquid (i), results in at least four main patterns for the residual liquids and corresponding solid phases (Fig. 11a). ...
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The Ediacaran Campo Alegre-Corupá Basin in South Brazil developed in two stages, the synorogenic passive rift (Basin Stage ∼605–590 Ma) and the post-collisional caldera volcano (Caldera Stage ∼583–577 Ma), respectively. Volcanic rocks from the Basin Stage show a bimodal compositional spectrum with dominant basalt and subordinate silicic rocks. The basaltic rocks are transitional to mildly alkaline, exhibiting Ocean Island Basalt-like (OIB-like) trace element enrichment patterns, with depletion in Nb and Ta, however, and crustal-like Sr-Nd isotopic signatures, suggesting that they were derived from low degrees (∼5%) of partial melting of an enriched lithospheric mantle source. The silicic rocks are transitional to mildly alkaline trachydacites associated with subordinate rhyolites, exhibiting trace element compositions typical of A2-type granitoids, produced by fractional crystallization of the coeval basalts in the Moho. Volcanic rocks from the Caldera Stage are constituted mainly by alkaline trachytes and rhyolites, occurring primarily as pyroclastic sequences coupled to minor effusive lava flows and domes, also exhibiting trace element compositions typical of A2-type granitoids. They are associated with subordinated effusive transitional to mildly alkaline basalts with Island Arc Basalt-like (IAB-like) trace element signatures. Compared to the Basin Stage, the basalts from the Caldera Stage result from higher degrees (∼15 %) of partial melting of possibly the same enriched lithospheric-mantle sources during the lithospheric root collapse of a cratonic terrane. The silicic rocks from the Caldera Stage are also derived from the coeval basalts by fractional crystallization in the Moho. However, an additional stage of differentiation in the upper crust is required to explain their silica-enriched compositions and eruptive styles. Results from this study support a connection between the silicic volcanic rocks from the Caldera Stage and the plutonic bodies from the nearby A-type Graciosa Province. Lu-Hf isotopes from detrital zircon suggest an Andean arc-type tectonic setting during the Paleoproterozoic (∼2,185 Ma) history of the Luis Alves Terrane (LAT) basement. This tectonic setting was responsible for the arc-like signatures of the intraplate lithospheric-derived rocks of both bimodal volcanic sequences. Crustal-like Sr-Nd-Hf isotopic characteristics result from a protracted isotope evolution of their enriched mantle sources, and each tectono-magmatic stage results from a different extensional setting, which has implications for the metacratonization of the LAT.
... The end members of the three component mixing models are: depleted mantle (DM), altered oceanic crust (AOC), and Sediments (Hauff et al., 2003;Plank, 2014). The mixing trends are calculated using the geochemical modeling software by Petrelli et al. (2005). ...
Continental rifts result from the simultaneous action of shallow processes such as the thinning of the lithosphere, and deeper processes related to the dynamics of the mantle. The role of these deeper processes may change over time as a function of the type of rifting, e.g., subduction-related rift vs plume-related rifts, and the pre-rift geodynamics. During the Cretaceous, the Songliao Basin (NE China) was affected by continental rifting accompanied by discontinuous stages of volcanism. The relative role of the asthenospheric and lithospheric mantle associated with the Songliao Basin rift volcanism, its evolution with time, and the origin of the felsic rocks are still debated problems due to the lack of comprehensive studies. Here, we present a critical review of the available geochronological and geochemical data (major, trace elements, and Sr-Nd isotopes) and show that the Songliao rift Cretaceous volcanism developed between 133 Ma and 102 Ma in five main stages: Stage I (133–129 Ma), Stage II (124–118 Ma), Stage III (117–113 Ma), Stage IV (115–106 Ma), and Stage V (105–102 Ma). While magmas with an alkaline, intraplate affinity characterize all the Stages, magmas with a subalkaline (calc-alkaline) signature erupted in Stages II and III. Mafic and intermediate rocks are always present, whereas felsic magmas have been found in the last three Stages. Based on the major, trace elements and Nd-Sr isotopic compositions, the general evolution of volcanism is dominated by crystal fractionation processes. Evidence of assimilation of upper crust material is restricted to the more evolved rocks (SiO2>57 wt%). The alkaline mafic rocks derived from a veined asthenospheric mantle modified by melts deriving from the sediments of the Paleo-Pacific slab or associated with pre-rifting, Jurassic, collisional subduction processes related to the closing of the Mongol–Okhotsk Ocean. The source of the Songliao rift subalkaline rocks is the sub-continental lithospheric mantle metasomatized by fluids released from the dehydration of the subducting Paleo-Pacific slab. The release of fluids from the sediments subducted during the Jurassic Mongol–Okhotsk collision may also have played a role. The Songliao Basin Cretaceous rift may be classified as a subduction-related rift caused by the eastward roll-back of the west-dipping Paleo- Pacific slab, a process initiated after the Jurassic collisional phase in NE China. Within the wider geodynamic frame of the eastern Asian block, the 133–102 Ma volcanism of the Songliao rift suggests a transition from a lithospheric mantle responsible for the pre-140 Ma NE China, Mongolia, and Russia volcanism to an asthenospheric mantle source of the post-107 Ma magmatism. This is also suggested by the fact that the Songliao rift magmatism shows compositional features consistent with the contribution of both the lithospheric and asthenospheric mantle. The Songliao rift volcanism would be therefore associated with a passive rifting process, where the progressive removal of the lithosphere below East Asia, which is due to eastward rollback of the Pacific oceanic plate, caused an upwelling of asthenospheric material, finally involved in the post-102 Ma magmatism in the NE China block.
... Multi-trace element distribution patterns with depletion of Nb, Ta, Ti and slight negative Eu anomalies in the spider and REE graphics (Fig. 7) mainly indicate fractionation of plagioclase and Ti-magnetite. To quantify the crystal fractionation process, major elements have been modeled using the mass balance algorithm (i.e., XLFRAC code) by Stormer and Nicholls (1978) with an Excel-based program designed by Petrelli et al. (2005). The XLFRAC modeling results (S. ...
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Voluminous moderate- to high-magnesian [Mg# = molar Mg/(Mg + Fe²⁺) = 44–64] andesitic and dacitic rocks with high silica (mostly 61–66 wt%) adakitic affinity (Y = 13–22, Yb = 1.3–2.1, Sr/Y = 18–44, La/Yb = 10–25) and common mafic magmatic enclaves (MMEs) are first reported in the Keçiboyduran stratovolcano (KSV) from the Cappadocia volcanic province (CVP), Central Anatolia, Turkey. We present comprehensive whole-rock geochemistry and Sr–Nd–Pb isotope data, mineral chemical compositions and ⁴⁰Ar–³⁹Ar ages for KSV samples. Based on the volcanostratigraphy and ⁴⁰Ar–³⁹Ar dating results, two successive eruption ages of 2.2–1.6 Ma (stage I: amphibole-rich) and 1.6–1.2 Ma (stage II: pyroxene-rich) were established for the KSV, corresponding to the Gelasian and Calabrian stages of Early Pleistocene, respectively. Textural and geochemical evidence indicates that the KSV magnesian andesites–dacites are products of a hybrid magma formed by mixing between mantle-derived mafic and crust-derived felsic magmas with further fractionation and minor contamination during magma storage and ascent. Our new data, combined with previous geological and geophysical results suggest that parental magnesian mafic melts of the KSV rocks originated from a heterogenous mantle source generated through the metasomatism of mantle wedge material by subducted sediment-derived melts, and then partially melted through asthenospheric upwelling in response to slab break-off. The mafic magma underplated the overlying lower crust, resulting in its partial melting to generate crustal felsic magma. Both magmas mixed at lower crustal levels creating MME-rich hybrid magmas. Subsequently, the hybrid magmas were emplaced at different depths of the crust (c. 4–11 and 11–15 km for the stage I and II, respectively), where they crystallized at moderate temperatures (c. 1180–840 °C) and under relatively high oxygen fugacity (LogƒO2 = − 11.4 to − 9.2), water-rich (H2Omelt = 5.6–3.6 wt%) and polybaric (~ 1.2 to 5.1 kbars) conditions, and underwent fractionation of primarily amphibole ± pyroxene causing adakitic affinity. We propose a new petrogenetic model for the early Quaternary magnesian/adakitic andesites/dacites of the CVP in a post-subduction tectonic setting. Our results provide robust evidence for slab break-off of the eastern Cyprus oceanic lithosphere and put further constraints on the tectonic evolution of the eastern Mediterranean collision zone during the Early Quaternary.
«Geochemical functions» is a new free Add-In to MS Excel for geochemists and mineralogists. It implements useful functions for routine operations in geochemical and mineralogical calculations: abundance normalization, calculations of empirical formula coeffi cients from chemical and EMPA analyses, statistical operations with partial and unequal data.
Geochemical Functions is a new Add-Ins for Microsoft Excel. The Add-ins includes several functions to automatize the routine operations used commonly in mineralogical and geochemical data processing, such as abundance normalization, calculation of mineral formulas, and statistical treatment of analyses. The add-ins is free for noncommercial use with obligatory reference to the program and article. The file to install the Geochemical Functions may be downloaded from the web-site of the Vernadsky Institute GEOKHI_ Zaitsev.xla. The same functions are available in the MS-Excel template
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For estimating major elemental geochemistry of sedimentary packages, various Weathering Indices (WIs) are utilized by researchers involved in geochemical evolution of sediments. Through developing a computer program, GeoChem, based on ‘R’ programming environment, we intend to simplify the evaluation and implementation of various Weathering Indices (WIs), including CIW, CPA, PIA, CIX, CIA, WIP, R, ICV, V, MWPI and STI. Additionally, it generates plots of input data used to quantify chemical weathering of clastic sediments in various compositional space diagrams, such as Al2O3 – CaO – Na2O, Al2O3 – K2O – CaO – Na2O, Al2O3 – CaO + Na2O – K2O, Al2O3 – CaO + Na2O + K2O – Fe2O3 + MgO and M – F – W compositional space diagram. Using GeoChem, one can do all the calculations and artwork associated with the finished report without having to use Microsoft Excel, CorelDraw or similar software. Input data source files and output calculations results data files are in CSV format. Data plots are produced in vector as well as in raster formats, providing additional flexibility to the user. Also, we are trying to figure out the associated statistical parameters, their correlation and specially restricting the major elemental geochemistry in a variety of compositional space diagrams to constrain sediment and rock composites, demonstrating chemical weathering profiles and mineralogical composition of the parent rock. By altering different arguments in the code, the ‘R’ programming environment allows the investigator to change the code, depending on the dataset under consideration and the user requirement to generate user-defined, customized plots. To demonstrate the applicability of the tool, its performance was tested, evaluating the major elemental geochemical data of diverse geological settings and sedimentary provenance different in kind. For the same, sediments selected include channel, suspended and overbank sediments of the Peninsular rivers of Ganga basin; Surma group and Barail group of sandstones; lake sediments of Manasbal, Kashmir; Mizoram Foreland Basin, India.
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CWS is an open-source application developed for calculating chemical weathering indices using major elemental geochemical data of clastic sediments and for generating associated plots. Chemical weathering indices include Chemical Index of Weathering (CIW), Chemical Index of Weathering without CaO (CIW′; expressed as CIW*), Chemical Proxy of Alteration (CPA), Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), Modified Chemical Index of Alteration (CIX), Index of Compositional Variability (ICV) and Weathering Index of Parker (WIP). Also, hierarchical charts, histogram, boxplots, scatter matrices, correlation matrices, heatmap with related data tables are included along with the statistical measures of weathering indices and their correlation with Al2O3/TiO2. Additionally, it generates plots of input data used to quantify chemical weathering of clastic sediments in various compositional space diagrams, such as A - CN - K, A - CNK - FM and M - F - W compositional space diagram. Using CWS, one can do all the calculations and artwork associated with the finished report without having to use Microsoft Excel, CorelDraw or similar software. Input data source files and output calculations results data files are both in CSV format (Comma Separated Value). HTML files can be exported for plots generated by CWS. As an example of the capability of CWS to evaluate chemical weathering, we evaluated Surma and Barail sandstones from the Mizoram Foreland Basin in North-eastern India, Manasbal Lake sediments from Kashmir; channel, suspended and overbank sediments of the Peninsular rivers of Ganga basin.
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ABSTRACT Volcanic arc basalts are all characterized by a selective enrichment in incompatible elements of low ionic potential, a feature thought to be due to the input of aqueous fluids from subducted oceanic crust into their mantle source regions. Island are basalts are additionally characterized by low abundances [for a given degree of fractional crystallization) of incompatible elements of high ionic potential, as feature for which high degrees ot'melting, stability of rninor residual oxide phases, and remelting of depleted mantle are all possible explanations. Calc-alkaline basalts and shoshonites are additionally characterised by enrichment of Th, P and the light REE in addition to elements of low ionic potential, a feature for which one popular explanation is th contamination of their mantle source regions by a melt derived from subducted sediments. By careful selection of variables, discrimination diagrams can be drawn which highlight these various characteristics and therefore enable volcanic arc basalts to he recognized in cases where geological evidence is ambiguous. Plots of Y against Cr, K[Yb, Ce/Yb, or Th/Yb against Ta/Yb, and Ce/Sr against Cr are all particularly successful and can be modelled in terms of vectors representing different petrogenctic processes. An additional plot of Ti/Y against Nb/Y is useful for identifying 'anomalous' volcanic arc settings such as Grenada and parts of the Aleutian arc. Intermediate and acid rocks from volcanic are settings can also be recognized using a simple plot of Ti against Zr. The lavas from the Oman ophiolite complex provide a good test of the application of these techniques. The results indicate that the complex was made up of back-arc oceanic crust intruded by the products of volcanic arc magmatism.
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SUMMARY: Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (≤1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (≤2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by
The author offers an overview of the complex phenomenon of andesite genesis to help clarify the long-standing problem and to identify profitable areas for future research. It is considered that conventional explanations better account for more of the data than do the more elegantly simple theories produced by plate tectonic theory. -R.A.H.
Results of analyses on composite samples of igneous and sedimentary rocks and chondritic meteorites, obtained by an improved analytical procedure, are reported. The relative rare-earth abundances in composite samples of shales, metamorphosed shales, basalts, rhyolites, and granites are remarkably similar to each other, but small differences are apparent, even among the heavier rare earths. Eu and Ce show “anomalous” abundances in several of the samples. A new value for the average Gd content of chondritic meteorites leads to the conclusion that common crustal rocks are deficient in Eu, relative to the other rare earths.
The uniformity of rare earth element patterns in sedimentary rocks is used to provide estimates for the composition of the Post-Archean upper crust. This approximates to granodiorite. The island-arc model for continental growth is used to provide a total crustal composition, from which the upper crust is derived by partial melting, leaving a depleted lower crust. The Archean sedimentary rock patterns reveal a different composition for the upper crust in that era. They closely resemble those of present- day island-arc suites, which the composition of the Archean crust is inferred to be less fractionated, with much less development of high-level granodiorites. Continental evolution appears to be episodic, rather than uniform, with a major period of production of differentiated upper crust at about 2.5 aeons, long recognized as the Archean-Protoerozoic boundary.-from Author
Compared with volcanic rocks, plutonic rocks have cooled more slowly, under greater pressure and in the more protracted presence of volatiles. All three factors combine to influence the structure, texture and mineralogy of plutonic rocks but it is usually assumed that rate of cooling exerts the more important influence on the development of primary structure and texture while pressure and volatile content predominate in determining mineralogical features. Thus we may observe that in a body of magma of sufficiently low viscosity, the slower the cooling rate the greater will be the opportunity for crystals of different densities and sizes to move relative to one another and for that movement to be influenced by currents within the magma or flow of the magma itself. On the other hand we may note that increased pressure imposes different sets of mineral equilibria leading, for instance, to the suppression of the incongruent melting of enstatite, and that the maintenance of a high volatile content (under elevated pressure) will favour the stability of hydrous minerals both as primary phases and secondary replacements of other primary phases, and will also be a control in sub-solidus changes such as exsolution.