COMAGMAT-NET 3.3 (1997)

User's Manual
Alexey Ariskin and Pavel Plechov

Vernadsky Institute, Moscow, Russia
Moscow State University, Moscow, Russia

Petrological Significance .......................... 1.1

Mineral-melt geothermometers ....................... 2.1
Trace element partitioning ......................... 2.2
Solving Equilibrium Problem ........................ 2.3


Access to COMAGMAT-NET ............................. 3.1

Starting the Program ............................. 4.1
Main Petrological Functions ................... 4.2
Data INPUT ......................................... 4.3
Define Conditions .................................. 4.4
Calculations ......................................... 4.5


Basic Plot Procedure ..................................... 5.1
Additional graphics ...................................... 5.2


Basic Format ......................................... 6.1
Getting Files .......................................... 6.2



Welcome to Comagmat-NET 3.3 (1997) program! This is a network version of COMAGMAT-3.0 (1992-1995), a popular package of phase equilibria models widely distributed among igneous petrologists and geochemists (Ariskin et al., 1993; Ariskin and Nielsen, 1993). The COMAGMAT programs have been constrained in the Vernadsky Institute (Moscow, Russia) by over 20 years of field works, petrography, geochemistry and computer simulating the formation process of differentiated sills and volcanic series occurred in Eastern Siberia, Karelia, Kamchatka, and Mid-Ocean Ridge systems (Ariskin et al., 1988-1995; Barmina et al., 1989,1992; Frenkel et al., 1989). This program is designed to be simple and intelligible at every stage of petrological calculations with the input and output files organized to be user friendly. The COMAGMAT programs operate in a sophisticated environment and provide a graphics support making it useful for beginners and dabblers.
1.1. Petrological Significance
The COMAGMAT model is a series of linked programs developed to calculate phase equilibria for dry and hydrous natural magmas crystallizing in the range of pressures from 1 atm to 10-12 kbar and including both open (12 oxygen buffers) and closed system fractionation with respect to oxygen. The modeling process may be calculated for systems ranging from basalts to dacites, with modeled major elements including Si - Ti - Al - Fe(tot) - Mg - Ca - Na -K and P, where Fe(tot) is assumed to be divided to Fe2+ and Fe3+ species (Nikolaev et al., 1996). Moreover, COMAGMAT allows the user to simulate behaviour of 20 trace elements, including Mn, Ni, Co, Cr, V, Sc, Sr, Ba, Rb, Cu, and REE. The modeled minerals include olivine (Fo-Fa solution), plagioclase (An-Ab), 3 pyroxenes (augite, pigeonite, and ortho- pyroxene: En-Fs-Wo plus Al and Ti), ilmenite (Ilm-Hem), and magnetite (Mt- Ulv). The results of the program are in the form of calculated liquid lines of descent, plus the equilibrium mineral proportions and compositions. The phase equilibria calculations form the core of a model that allows the user to simulate processes ranging from simple isobaric crystallization to polybaric fractionation.
2.1. Mineral-melt geothermometers
The building blocks of COMAGMAT are a set of empirically calibrated expressions that are used to calculate equilibrium temperatures and phase relations. These expressions describe mineral-melt equilibria for major and trace elements in terms of pressure, temperature, oxygen fugacity and liquid composition (Ariskin et al., 1987, 1993; Ariskin and Barmina, 1990). These mineral-melt geothermometers have been calibrated using an earlier version of the INFOREX database which now includes information on over 11,000 melting experiments published in 235 works (Ariskin et al., 1992, 1996, Meshalkin and Ariskin, 1996, 1997). Applying these geothermometers to the initial database liquid compositions, one can invert these calculations to estimate mineral-melt equilibria temperatures: comparison of the calculated and experimental temperatures indicate an accuracy of 10-15oC (Ariskin et al., 1987,1993). Similar comparisons of the calculated and experimental mineral compositions indicate that Fo, An, En and Wo contents can be predicted within 1-3 mol%. Note, that the best fit with experimental data can be obtained if apply the COMAGMAT mineral-melt expressions to tholeiitic and transitional systems ranging from magnesium basalts to dacites.
2.2. Trace element partitioning
One of the major advantages of COMAGMAT is the linkage between the major and trace element systematics. Calculation of the major element mineral-melt equilibria controlled parameters, such as temperature and fractionating mineral proportions, allows us to constrain the trace element systematics based on the values of the single component distribution coefficients: such an approach is used to calculate the behaviour of 20 trace elements - Mn, Ni, Co, Cr, V, Sc, Sr, Ba, Rb, Cu plus REE (Barmina et al., 1989,1992).
2.3. Solving Equilibrium Problem
The problem of the calculation of mineral-melt equilibrium at a given set of independent parameters of state is equivalent to the search for an extreme of one of the thermodynamic potentials. To address the problem we take advantage of numerical solutions of nonlinear empirical equations that describe mineral-melt equilibria and mass action law, combined with the mass balance constraints for a whole system composition (Frenkel and Ariskin, 1984). This approach combines the basic empirical and thermodynamic considerations into a hybrid algorithm allowing one to simulate the differentiation of multiply saturated magmas step by step, as the total percent crystallized is increased (Ariskin et al., 1993).
3.1. Access to COMAGMAT-NET
The COMAGMAT-3.3 programs operate under any UNIX SVR4. It uses the Perl interface to FORTRAN-based core and SQL-database (Postgres-95) for data manipulation. For access to Comagmat-net is required a any frame-capable Web Browser (Netscape-2.x or later, MSIE-3.0 or later). All users data is contained in SQL-database and user can edit his database records. Each record is protected by users computer IP-address. For access to Comagmat-net interface user can click here or load the "" page in his WWW-browser.


4.1. Starting the Program
For first start of Comagmat software, click here and follow the instructions. Each screen contains some input fields and submit buttons. You could use only navigation buttons in the document body ("Get Values", "Yes", "No" etc.). Don't use "Back" or "Forward" buttons on the Browser panel.
If you have the last visited record, you can choose the record by the comment from this table.

Define Conditions ?................................. 4.3
Data INPUT ? ....................................... 4.4
Calculations ? ..................................... 4.5

4.2. Main Petrological Functions.
There are 3 main modes in COMAGMAT-NET that may be used in solving more general petrological problems. They are given in the first active box and can be selected. We remove the "Layered intrusion" petrological option from network version,
because in this version we can use only one data record simultaneously.
* Thermometry of Mineral-Melt Equilibria allows one to calculate mineral-melt equilibria temperatures for the melt (inclusion) compositions that are supposed to be saturated with a mineral. That solid phase may be selected directly from the screen. Now is supported Olivine, Plagioclase, Augite, LowPyroxene, Ilmenite and Magnetite mineral-melt equilibria.
The next 2 routine have common peculiarities in specifying the model
* Simulating Equilibrium Crystallization
* Simulating Fractional Crystallization
Next request is regarding a possibility to change a species of low-Ca pyroxene to be simulated (this version of COMAGMAT enables to calculate simultaneously only one high-Ca and one low-Ca pyroxene). To do that move highlighted field to Opx or Pigeonite. Note, that for tholeiitic and related systems you should select Pig while for the calc-alkaline melts Opx is more reliable phase. This option is not actual for Mineral-Melt Equilibrium calculation.
After definition of required fields user should press "Get Values" button.

4.3 Data INPUT
The next step is filling of the start melt composition request. The fill-in form contains 10 petrochemical input fields. User should enter the start melt composition to this form and click to the "Get Values" button. If any field is not filled, the program accept it as "0.00".
The last variable parameter in this screen is H2O content in the initial melt. Really it only a first very primitive attempt to account for water presence as a factor decreasing mineral-melt equilibria temperature in a different degree for different minerals.
Note, that the COMAGMAT program includes a special subroutine to simulate water solubility as a function of temperature, pressure and SiO2 content (see "Subroutine Solub" in Program Listing of Ariskin et al., 1992b). The simulating process will be ceased if a current H2O content in the liquid is more than the model calculated solubility.
After that, user should enter the comment, reference, his name and his mail. It is optional fill-in form, but the time-to-live of the record without this attributes is 24 hours and if you fill this form, the time-to-live of the record is one year. Next time, you can edit or recalculate this record.
Then, user should enter the trace elements composition. By default, all trace element content is 1. It is convinient for trace component trends research.

4.4. Define Conditions
The next screen involves both pressure and redox routines that should be specified with definition of the values of main variables peculiar to those conditions. First of all, it is necessary to select what kind of the effect of pressure (isobaric or polybaric) on phase equilibria you wish simulate in the calculations. Move highlighted field to a pressure routine.
It is obvious that the first routine is not need in a special comment (you should only define the total pressure from the screen), but polybaric mode deserves a notice. The most reliable results the high pressure model gives in the range as much as 10-12 kbar, while more elevated pressures also can be modelled. The main problem here is correct parameters to simulate low-Ca pyroxenes precipitation and absence in the COMAGMAT model of the high-temperature Spinel crystallization. New geothermometers for the mineral-melt equilibria are now in development. The Decompression (Polybaric) Crystallization is modelled in COMAGMAT system by means of monotonous decreasing the total pressure from an initially given P to a final value PminP-YP with a constant pressure increment YP per each 1% of the system crystallized. It results in specific liquid line of descent that are principally different from the isobaric ones but may be more corresponded to the natural petrochemical trends observed in basaltic series (Ariskin, Barmina, 1992).
After defining the pressure parameters the user must specify the model redox conditions. The COMAGMAT program allows us to simulate crystallizing systems that are either closed or open with respect to oxygen. The first case is peculiar for the systems where fO2 is controlled internally by mineral-melt equilibria and reactions in the liquid phase, first of all the Fe2+/Fe3+ relations. The latter is supposed to be the main factor controlling the oxygen fugacity in a closed system. So, one should specify the initial Fe2+/FeO(tot) ratio in the melt to simulate the closed respect to O2 crystallization.
To model the open to O2 system crystallization, the user should select an oxygen buffer. A special table including 12 different oxygen buffers will appear on the screen, so that one can select the redox conditions by movement of highlighted field:
IW : Myers,Eugster,1983
WM : Myers,Eugster,1983
IM : Huebner J.S.,1971
MH : Myers,Eugster,1983
QFM : Myers,Eugster,1983
IQF : Myers,Eugster,1983
NNO : Huebner J.S.,1971
CCO : Myers,Gunter,1979
COC>5kb: Woermann et al.,1977
COC<5kb: French B.H., 1966
GRA : Ulmer, Luth, 1991
ARB : Arbitrary buffer
The Menu Manager allows to make changes not only in petrological parameters but also in precision of calculations. The default values of calculating temperature and phase compositions can be changed in the "Advanced Options" screen:
Temperature accuracy,C 1.0
Phase compositions, mol.% 0.1
set of trace elements 1
crystal increment,% 1
break point of calculation,% 50
Of course, it is no real absolute accuracy of simulation, but only precision of the convergence for the main computation iteration loops. Nevertheless, in same cases if you faced a trouble in modeling any compositions for a given conditions a slight modifications in the precision parameters may help to calculate more evolved liquid line of descent. However, we don't recommend to use the operation often.

4.5. Calculations
Just after starting the program reads Data input and runs the simulation subroutine that is corresponded to one of the main routines selected. During the modeling process the equilibrium state information is accumulating in the output file. I
One can track each step of the calculations (corresponding to a given crystal increment) on the screen while the calculations are accumulating in the computer memory. It is taken 0.3-0.5 sec to simulate crystallization for a one initial composition to a bulk crystallinity of 70-80%. The fractionation process is simulating markedly fast than the equilibrium crystallization. In some cases (especially if you gave an extremely high extent of equilibrium crystallization or try to model advanced precipitation of magnetite) the simulating process may be ceased earlier than you were indicated in the calculation options. Usually, it is due to a of the scheme used in the algorithm. Corresponding diagnostics will be appeared on the screen. In that case, try to change slightly input parameters (e.g., to decrease the crystallization increment or alter initial composition as for a component in the scale of 0.05-0.10 wt.%). If it does not help to advance the simulation you should stop the calculations.
A system of graphics support of the COMAGMAT calculations has been developed independently on the and "comagmat" program. It involves the Graphics Manager that permits ..............
5.1. Basic Plot Procedure
5.2. Additional graphics


6.1. Basic Format
6.2. Getting Files ?

The main reasons hat can result in troubleshouting the program is connected with the fact that the program has a lot of different modes and can operate in a wide range of natural compositions, so that we simply could not forsee all possible nonstandard situations. Nevertheless a special system of diagnostic with comments is present (see Section 3.5). We would be also grateful if you were fixed the troubleshouting parameters and sent the information to us.

Al'meev R.R., Ariskin A.A. (1996) Mineral-melt equilibria in a hydrous basaltic system: computer modelling. Geochem. Intern., 34 (7): 563-573.
Ariskin A.A., Barmina G.S., Frenkel M.Ya. (1987) Computer simulation of basalt magma crystallization at a fixed oxygen fugacity. Geochem. Intern., 24 (6): 85-98.
Ariskin A.A., Barmina G.S., Frenkel M.Ya., Yaroshevsky A.A. (1988) Simulating low-pressure tholeiite-magma fractional crystallization. Geochem. Intern., 25 (4): 21-37.
Ariskin A.A., Barmina G.S. (1990) Equilibria thermometry between plagioclases and basalt or andesite magmas. Geochem. Intern., 27 (10):129-134.
Ariskin A.A., Frenkel M.Ya., Tsekhonya T.I. (1990). High-pressure fractional crystallization of tholeiitic magmas. Geochem. Intern., 27 (9): 10-20.
Ariskin A.A., Bouadze K.V., Meshalkin S.S., Tsekhonya T.I. (1992) Inforex: A database on experimental studies of phase relations in silicate systems. Amer. Miner., 77 (5/6): 668-669.
Ariskin A.A., Frenkel M.Ya., Barmina G.S., Nielsen R.L. (1993) COMAGMAT: a Fortran program to model magma differentiation processes. Computers and Geosciences, 19: 1155-1170.
Ariskin A.A., Nielsen R.L. (1993) Application of computer simulation of magmatic processes to the teaching of petrology. Journal of Geol. Education, 41: 438-441.
Ariskin A.A., Barmina G.S., Ozerov A.Yu., Nielsen R.L. (1995) Genesis of high-alumina basalts from Klyuchevskoi Volcano. Petrology, 3 (5): 449-472.
Ariskin A.A., Barmina G.S., Meshalkin S.S., Nikolaev G.S., Almeev R.R. (1996) INFOREX-3.0: A database on experimental phase equilibria in igneous rocks and synthetic systems.II.Data description and petrological applications. Computers and geosciences, 22 (10): 1073-1082.
Barmina G.S., Ariskin A.A., Frenkel M.Ya. (1989) Petrochemical types and crystallization conditions of the Kronotsky Peninsula plagiodolerite (Eastern Kamchatka). Geochem. Intern., 26 (9): 24-37.
Barmina G.S., Ariskin A.A., Kolesiov G.M. (1992) Simulating the REE spectra of hypabyssal rocks in the Kronotsky series, Eastern Kamchatka. Geochem. Intern., 29(3): 45-54.
Frenkel M.Ya., Yaroshevsky A.A., Ariskin A.A., Barmina G.S., Koptev-Dvornikov E.V., Kireev B.S. (1989) Convective-cumulative model simulating the formation process for stratified intrusions In: Magma-crust interactions and evolution. Theophrastus Publications, S.A., Athens-Greece, p. 3-88.
Frenkel M.Ya., Ariskin A.A. (1984) A computer algorithm for equilibration in a crystallizing basalt magma. Geochem. Intern., 21 (5): 63-73.
Meshalkin S.S., Ariskin A.A. (1996) INFOREX-3.0: A database on experimental phase equilibria in igneous rocks and synthetic systems. I. Datafile and management system structure. Computers and Geosciences, 22 (10): 1061-1071.
Nikolaev G.S., Borisov A.A., Ariskin A.A. (1996) Calculation of the ferric-ferrous ratio in magmatic melts: testing and additional calibration of empirical equations for various magmatic series. Geochem. Intern., 34 (8): 641-649.

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