A geochemical study of magmatism across a major terrane boundary: Sr and Nd isotopes in Proterozoic granitoids of the southern Laramie range, Wyoming

Journal Article · Mon May 01 04:00:00 EDT 1989 · Journal of Geology; (USA)

DOI:https://doi.org/10.1086/629306· OSTI ID:7244124

Geist, D J ^[1]; Frost, C D; Frost, B R ^[2]; Kolker, A ^[3]

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1. Hamilton College, Clinton, NY (USA)
2. Univ. of Wyoming, Laramie, (USA)
3. Department of Earth and Space Sciences, Stony Brook, NY (USA)

Proterozoic granitoids in the Laramie Range of southeastern Wyoming crop out on both sides of an inferred suture between the Archean Wyoming craton and Proterozoic terranes to the south. These rocks offer an unusual opportunity to test the various hypotheses for the geometry of the suture. No difference in major or trace element composition is observed across the suture, nor is there a large difference in isotopic composition. Nd and Sr isotopic data indicate that only a small proportion of Archean material has contributed to this granitoid suite, even in two samples that intrude Archean gnesis. The isotopic data therefore require a dominantly Proterozoic lower crust both beneath the Proterozoic rocks and beneath the margin of the Archean block. This observation is inconsistent with models in which the suture between the Archean and Proterozoic blocks dips to the south. This inconsistency can be reconciled by magmatic underplating or mechanical underthrusting of Proterozoic crust beneath the Archean block during terrane accretion or post-accretion strike-slip faulting.

• OSTI ID: 7244124
• Journal Information: Journal of Geology; (USA), Journal Name: Journal of Geology; (USA) Vol. 97:3; ISSN JGEOA; ISSN 0022-1376
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
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EVEN-EVEN NUCLEI
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GRANITES
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STRONTIUM 86
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