FLUID INCLUSION DATA REDUCTION AND INTERPRETATION USING MacFlinCor ON THE MACINTOSH

Philip E. Brown and Steffen G. Hagemann

The University of Wisconsin-Madison, Department of Geology and Geophysics, Madison, WI 53706, USA

pbrown@geology.wisc.edu

MacFlinCor was developed to process laboratory data gathered on fluid inclusions and to calculate P-T isochores for geologically important fluids composed of H2O, CO2, CH4, N2, and salts (Brown and Hagemann 1994; 1995). Within the program, interactive diagrams are available to describe those chemical systems which cannot be adequately constrained numerically. The user can choose from among multiple published equations of state describing fluid behavior and can easily compare the results obtained by using different equations. Once the basic fluid parameters are established, the program allows the data to be manipulated to permit the determination of, for example, P-T conditions or the evaluation of pressure corrections.

MacFlinCor was developed in HyperCard which operates on the model of index cards with each card providing an entry in a simple but powerful database. This approach is ideal for working with fluid inclusions because each "card" in a data "stack" can be used to record all the information about a single inclusion. Nine of the 41 cards are tailored to specific chemical systems for which sufficient experimental data is available to attempt to interpret laboratory observations on individual fluid inclusions. These cards serve as templates that are created and copied automatically from MacFlinCor into a user's data stack by clicking "Create" on the Index card (Fig. 1).

Index Card (17k)

Fig. 1 Initial Index card of a newly created data stack.

Each of the data cards (eg. Fig. 2) has essentially the same screen layout. In the upper left corner, a popup menu permits the choice of an equation of state for the chemical system at hand. This list of equations is the same on most of the cards with those that are not applicable to the chosen chemical system grayed out (Fig. 3). Below this is a large area designed for two purposes. The first use is as a notebook for recording observations in the laboratory during heating and freezing runs. Secondly, clicking on the "Graphic" button above the text box causes the text to be temporarily hidden and to be replaced by a white board upon which simple sketches of the inclusion in question, its relationship to fractures and other inclusions, and other data can be recorded. HyperCard provides a set of drawing tools that are adequate for simple illustrative purposes. This graphic becomes a permanent part of the data record for an inclusion.

H2O-NaCl (25k)

Fig. 2 Card for the system H2O-NaCl-[KCl].

         

Fig. 3 Equations of State.          Fig. 4 Systems menu.

The most complicated system that can be approximately modeled using experimental phase equilibria (H2O-CO2-CH4-NaCl) can be accessed from the popup menu (Fig. 4) on the Index card. The output area on Figure 5 presents data for both the aqueous and carbonic phases as well as the bulk inclusion. It is not possible to calculate numerically the methane content of the carbonic phase in an inclusion - this must be done graphically. Therefore upon clicking the "Σ" button, the user is taken, in this example, to an interactive figure in the MacFlinCor stack that has been modified from Thiery et al. (1994). This figure permits the bulk molar volume and XCH4 in the carbonic phase to be derived from microthermometric data. The bulk density allows the reasonably well known isochores for pure CO2 to be applied to the mixed CO2-CH4 system. On returning from the CO2-CH4 card, the remaining calculations are automatically made on the data card.

H2O-CO2-CH4-NaCl (21k)

Fig 5 Data card for inclusion fluids in the system H2O-CO2-CH4-NaCl.

Returning to the Index Card, a list of data cards present in the stack can be made on the right hand portion of the card (Fig. 1). Data from the stack can be exported to a tab delimited file which can be read and manipulated by spreadsheet or statistical programs.

References

Brown, P.E. and Hagemann, S.G. (1994) MacFlinCor: A computer program for fluid inclusion data reduction and manipulation. In De Vivo and Frezzotti (eds) Fluid Inclusions in Minerals: Methods and Applications, VPI Press, 231-250.

Brown, P.E. and Hagemann, S.G. (1995) The program MacFlinCor and its application to geobarometry in Archean lode-gold deposits. Geochim. Cosmochim. Acta (in press).

Thiery R., Kerkhof A.M. Van Den and Dubessey J. (1994) vX properties of CH4-CO2 and CO2-N2 - Modeling for fluid inclusions (T<31°ree;C, P<400 bar). European J. Mineral. v. 6, 753-771.