Variations in the illite-muscovite transition related to metamorphic conditions and detrital muscovite content: Insight from the Paleozoic passive margin of the Southwestern United States

Verdel, Charles, Niemi, Nathan and van der Pluijm, Ben A. (2011) Variations in the illite-muscovite transition related to metamorphic conditions and detrital muscovite content: Insight from the Paleozoic passive margin of the Southwestern United States. Journal of Geology, 119 4: 419-437. doi:10.1086/660086

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Author Verdel, Charles
Niemi, Nathan
van der Pluijm, Ben A.
Title Variations in the illite-muscovite transition related to metamorphic conditions and detrital muscovite content: Insight from the Paleozoic passive margin of the Southwestern United States
Journal name Journal of Geology   Check publisher's open access policy
ISSN 0022-1376
Publication date 2011-07
Sub-type Article (original research)
DOI 10.1086/660086
Open Access Status File (Publisher version)
Volume 119
Issue 4
Start page 419
End page 437
Total pages 19
Place of publication United States
Publisher University of Chicago Press
Collection year 2012
Language eng
Abstract X-ray diffraction (XRD) analysis of the illite to muscovite transition in pelitic rocks has been widely used in regional studies of low-grade metamorphism. Variations in detrital muscovite content of sediments are also measurable with XRD and may, in fact, be difficult to distinguish from metamorphic gradients. We utilize field transects to isolate detrital muscovite versus metamorphic reaction components of illite-muscovite variations in Paleozoic rocks of the western United States. One transect focuses on a single stratigraphic interval (Middle Cambrian pelites) and extends from Death Valley in the west to the Grand Canyon in the east. Detrital muscovite content is roughly constant along this 500-km-long transect, so illite-muscovite variations are ascribed to differences in low-grade metamorphism. In terms of both illite crystallinity and polytype composition, there is an overall increase in metamorphic grade to the west along the transect, from the diagenetic metapelitic zone at the Grand Canyon to epizone-low anchizone conditions near Death Valley. Most of the regional variation in illite parameters occurs between Frenchman Mountain and the southern Nopah Range, corresponding to the transition from cratonic to miogeoclinal facies and also to the leading edge of the Sevier thrust belt. In contrast to this "horizontal" transect that highlights metamorphic reactions, a vertical transect through the Paleozoic stratigraphy of the Grand Canyon targets temporal variations in the flux of detrital muscovite. In the Grand Canyon, illite crystallinity reaches a maximum at the base of the Pennsylvanian Supai Group before decreasing upsection. Deposition of the Supai Group was coeval with formation of basementcored uplifts during the Ancestral Rocky Mountains orogeny, and we suggest that the upsection change in illite composition at the Grand Canyon reflects input of detrital muscovite eroded from these uplifts
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
Non HERDC
 
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Created: Wed, 12 Oct 2011, 16:53:02 EST by Charles Verdel on behalf of School of Earth Sciences