A TEACHING EXERCISE IN VIRTUAL MAPPING INTEGRATING “MAGMATIC MAPPING” THROUGH PETROGENESIS

The Springerville Volcanic Field (SVF) is a well mapped intraplate volcanic field in east-central Arizona, one of six, with distributed characteristics rimming the southern margin of the Colorado Plateau, (Condit et al., 1999, Mnich and Condit, 2018). Its extensive dataset, compiled into a Dynamic Digital Map (DDM-SVF), Condit 1995, 2020, brings an in-depth look at real field geology and relationships to a virtual format, including detailed maps, photographs and videos. We recommend this program and the associated dataset for use as an exercise to integrate field data and volcanic petrogenesis as an experiential project for a petrology or field geology course to augment or be used in lieu of traditional field work.

The first step in this exercise is creating a photogeologic map of the area. Such maps are utilized prior to traditional field work to serve as the framework for mapping and provide an opportunity to become familiar with the area. Google Earth and field photographs for the northeastern part of the SVF provide the basis for this introduction to the field. Using the DDM, this first step in “magmatic mapping” (Mnich and Condit, 2018) can then be compared to existing geologic maps of lithology and geochemistry. Aided by overlying/underlying relationships, paleomagnetic data and radiometric dates, ages can be constrained in directed graphs (Mnich and Condit, 2018), serving as an integral piece of the petrogenetic story. An extensive geochemical dataset, formatted for use, including major, trace, mineral and isotopic data, provides ample opportunity to turn the data into a petrogenetic exercise demonstrating mass-balance principles. Using major element chemistry, field and chemical observations can be used to select lavas which may have a parent-daughter relationship. To establish these potential petrogenetic relationships, the program IgPet (Carr and Gazel, 2017), can be used to create Harker diagrams for "mineral extract diagrams" and mix models to assess fractionating minerals between the pairs.

The DDM and robust dataset provide a unique opportunity to bring field mapping into virtual space and give students real world examples of translating field data into a deeper petrogenetic understanding.