The purpose of SmNdMin is to investigate a possible source of error inherent, and often ignored, in geochronologic data where metamorphic porphyroblasts and their host rock (as opposed to whole rock) have been chemically and isotopically analyzed. The program is customized for the Sm-Nd geochronometer and to accommodate garnet analyses where Nd and Sm compositional data are available, but may be used for similar geochronometers and similar host-mineral relationships. Minimally, garnet core, garnet rim, and host-rock analyses are needed for Sm concentration, Nd concentration, and 143Nd/144Nd. In addition, a modal estimate of the minerals of interest is necessary, and a second mineral, such as monazite, may be considered. The program evaluates the path of the host rock on a plot of time versus 143Nd/144Nd as it deviates as a result of the growth of one or two minerals. This effect can produce severe errors in estimates of the initiation and duration of porphyroblast growth especially when the volume fraction of the primary mineral of interest is large, and when other minerals, rich in the elements of interest (e.g., Nd and Sm), sequesters a large fraction of these elements and thus, in effect, changes the bulk chemistry. A text file used by the program can be easily modified by the user and contains all of the parameters needed in the calculations. A batch file to install the program on the user's hard drive is included, or the program may be run directly from diskette.
- Rare earth elements
- Sm-Nd geochronometry