MORB-Normalized Spider Diagram for Cascade Convergent Margin
Media
Part of Cascade Arc: Chondrite- and MORB- Normalized Spider Diagrams
- Title
- MORB-Normalized Spider Diagram for Cascade Convergent Margin
- Description
- This geochemical plot shows the compatibility of the Lanthanide series in the Cascade Volcanic Arc representative data set. Each line represents a percentile of wt% SiO2. All lines show a negative slope, suggesting increasing compatibility across the Lanthanide Contraction. As the Cascade samples were formed from a melt, the elements with the highest concentration in the resulting rock are the most incompatible, as they were the first to escape from the parent rock. Therefore, in this case, La is the most incompatible. This is consistent with Goldschmidt's Rules, as La has the highest ionic radius in the series, thus is preferentially incorporated into the liquid. Elements with smaller ionic radii, such as Lu, fit more easily into a crystal structure. These samples are depleted in Lu, which suggests that the parent rock was not fully melted (in which case, the line would have a slope of 0 at 1. The slope of this line is extremely steep as the samples were normalized to a MORB. As MORBs have already been extensively depleted, the amount of an REE in a convergent setting relative to a MORB will vary very greatly.
- Creator
- Devon Gorbey
- Source
- PetDB
- Mediator
- Tamara Carley