| Abstract: | Evidence for an extensive Archean crustal history in the Wind River Range is preserved in the Medina Mountain area in the west-central part of the range. The oldest rocks in the area are metasedimentary, mafic, and ultramafic blocks in a migmatite host. The supracrustal rocks of the Medina Mountain area (MMS) are folded into the migmatites, and include semi-pelitic and pelitic gneisses, and mafic rocks of probable volcanic origin. Mafic dikes intrude the older migmatites but not the MMS, suggesting that the MMS are distinctly younger than the supracrustal rocks in the migmatites. The migmatites and the MMS were engulfed by the late Archean granite of the Bridger, Louis Lake, and Bears Ears batholiths, which constitutes the dominant rock of the Wind River Range. Isotopic data available for the area include Nd crustal residence ages from the MMS which indicate that continental crust existed in the area at or before 3.4 Ga, but the age of the older supracrustal sequence is not yet known. The upper age of the MMS is limited by a 2.7 Ga RbSr age of the Bridger batholith, which was emplaced during the waning stages of the last regional metamorphism. The post-tectonic Louis Lake and Bears Ears batholiths have ages of 2.6 and 2.5 Ga, respectively (Stuckless et al., 1985). At least three metamorphic events are recorded in the area: (1) an early regional granulite event (M1) that affected only the older inclusions within the migmatites, (2) a second regional amphibolite event (M2) that locally reached granulite facies conditions, and (3) a restricted, contact granulite facies event (M3) caused by the intrusion of charnockitic melts associated with the late Archean plutons. Results from cation exchange geobarometers and geothermometers yield unreasonablu low pressures and temperatures, suggesting resetting during the long late Archean thermal evenn. ?? 1987. |
| Genre: | Article |
| ProdID: | 70014157 |
| Citation Author: | Koesterer, M. E.; Frost, C. D.; Frost, B. R.; Hulsebosch, T. P.; Bridgwater, D.; Worl, R. G. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 304 |
| Citation Issue: | 4 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Precambrian Research |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 18 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Development of the archean crust in the medina mountain area, wind river range, wyoming (U.S.A.); 1987; Article; Journal; Precambrian Research; Koesterer, M. E.; Frost, C. D.; Frost, B. R.; Hulsebosch, T. P.; Bridgwater, D.; Worl, R. G. |
| Citation Start Page: | 287 |
| Citation Volume: | 37 |
| Citation Year: | 1987 |
| Type: | citation/reference |
| Text: | Development of the archean crust in the medina mountain area, wind river range, wyoming (U.S.A.); 1987; Article; Journal; Precambrian Research; Koesterer, M. E.; Frost, C. D.; Frost, B. R.; Hulsebosch, T. P.; Bridgwater, D.; Worl, R. G. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1987 00:00 -0600 |
| Publisher: | |
