Crazy Mountains, Montana
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Description
This trip examines a variety of mid-Eocene alkalic (feldspathoidal) stocks, laccoliths, sills, and dikes emplaced into Cretaceous and Paleozoic sedimentary strata. These rocks include mafic and felsic varieties, and are both texturally and compositionally variable. Most of the mafic alkalic rocks are unique in the Montana Alkalic Province in having Na2O > K2O. They are unusual even among feldspathoidal rocks because they are stongly enriched in incompatible elements, and have Sr, Nd, and Pb isotopic compositions which reflect an ancient source having low Rb/Sr, Sm/Nd, and U/Pb. Less
Learning Registry Activity
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Topics and Grades
Topics: Earth's Resources, Chemistry, Agriculture & Natural Resources, Earth & Space Science, Elements & the Periodic Table, Geology & the Dynamic Earth
Resource Pedagogy
Resource Type/Classification:
- Source Materials
- Teacher Materials
- Interactives
Tool for: Teachers