Crystalline rocks of the Lake Superior region, United States. Part 1
This report is a compendium of the available information on exposed crystalline rocks in the Lake Superior region (Wisconsin, Minnesota, and the Upper Peninsula of Michigan). The report provides background information to assist in evaluating the suitability of these crystalline rock bodies for isolating high-level radioactive waste. For each crystalline rock body or complex greater than approximately 78 km/sup 2/ (30 mi/sup 2/) in area, information is presented on size, shape, location, relative and absolute age, origin, petrography, rock structure, and geophysics. Precambrian crystalline rocks of the Lake Superior region are predominantly tonalite to granite in composition in the Archean; granodiorite and granite, with subordinate tonalite, in the early Proterozoic; and alkalic syenite, rapakivi granite, and layered gabbro-troctolite-anorthosite in the Middle Proterozoic. Vertical and horizontal movements, regional and thermal metamorphism, deformation, and intrusion are evident in the region. Based on radiometric ages, three major episodes of orogenic/igneous activity are recognized: Algoman (approx. 2650 My), Penokean (approx. 1850 My), and Keweenawan (900 to 1200 My). Anorogenic magmatism approximately 1500 My ago also played an important role, particularly in Wisconsin. References, 66 figures, 10 tables.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 6742361
- Report Number(s):
- ANL/ES-135-Pt.1; ON: DE84014801
- Resource Relation:
- Other Information: Portions are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
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