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Are the granitic rocks of the Salinian block trondhjemitic?

March 1, 1973

Trondhjemitic rocks are relatively abundant in the granitic terranes of the western Sierra Nevada and the Klamath Mountains but have not been found in the granitic plutons of the Salinian block, which lies westward, across the San Andreas fault. A ternary plot of modal quartz : K-feldspar : plagioclase from more than 200 granitic samples from the Salinian block has an elongate, nearly horizontal, quartz-rich trend that appears trondhjemitic to some observers. However, petrographic and chemical comparison of these rocks with trondhjemite from the type area in Norway and with rocks called trondhjemite in the Western United States shows that the granitic rocks of the Salinian block are not trondhjemitic. The absence of trondhjemite in the Salinian block further supports the contention that this terrane is not merely a westward continuation of Sierran basement but is a displaced basement block.

Publication Year 1973
Title Are the granitic rocks of the Salinian block trondhjemitic?
Authors Donald C. Ross
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Research of the U.S. Geological Survey
Index ID 70160735
Record Source USGS Publications Warehouse
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