{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Spear, 1999 diagramas AFM en tiempo real en tu mac

Spear, 1999 diagramas AFM en tiempo real en tu mac - Spear...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Spear Geological Materials Research v.1, n.3, p.1 Copyright '1999 by the Mineralogical Society of America Real-time AFM diagrams on your Macintosh Frank S. Spear Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute Troy, NY 12180 USA <[email protected]> (Received December 15, 1998; Published May 25, 1999) Abstract An algorithm is presented for the calculation of stable AFM mineral assemblages in the KFMASH system based on an internally consistent thermodynamic data set and the petrogenetic grid derived from this data set. The P-T stability of each divariant (three-phase) AFM assemblage is determined from the bounding KFASH, KMASH and KFMASH reactions. Macintosh regions (enclosed areas defined by a sequence of x-y points) are created for each divariant region. The Macintosh toolbox routine °PtInRgn± (point-in-region) is used to determine whether a user- specified P and T falls within the stability limit of each assemblage, and the compositions of minerals in the stable assemblages are calculated and plotted. Implementation of the algorithm is coded in FORTRAN as a module for program Gibbs (Spear and Menard, 1989). Users can calculate individual AFM diagrams at any P-T condition within the limits of the P-T grid, and sequences of AFM diagrams along any P-T path. Diagrams can be saved as PICT images for creating animations. The internally consistent thermodynamic data sets of Holland and Powell (1998) and Spear and Cheney (unpublished) are supported. The algorithm and its implementation provide a useful tool for researchers to explore the implications of a petrogenetic grid and to compare predictions of different thermodynamic data sets. Comparison of natural samples with predictions from the grid can be made if appropriate projections of the natural data into the KFMASH system are made. Results are also useful to students learning to understand petrogenetic grids and the progressive metamorphism of pelitic mineral assemblages. Keywords: AFM diagrams, petrogenetic grid, pelites, pelitic schists, thermodynamics, computing, Gibbs method, education, metamorphic petrology Introduction Since J. B. Thompson introduced the muscovite projection for metapelites over 40 years ago (Thompson, 1957), the AFM diagram (muscovite or Thompson projection) has been used extensively by petrologists for presentation of mineral assemblage and composition data of pelitic schists. Ultimately, the goal of constructing phase diagrams from natural mineral assemblages is to extract P-T information that can then be used to constrain the tectonic and thermal regime during metamorphism. The link between the graphical representation of a natural mineral assemblage (e.g. the AFM diagram) and P-T information is made by constructing petrogenetic grids for the chemical system of interest. The AFM diagram is successful because it is a fairly rigorous representation of the phase relations in the relatively complex system SiO 2 -Al 2 O 3 -MgO-FeO-K 2 O-H 2 O
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Spear Geological Materials Research v.1, n.3, p.2
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 18

Spear, 1999 diagramas AFM en tiempo real en tu mac - Spear...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online