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GEOREF RECORD

Diagenetic to incipient metamorphic zones of the Benton Uplift, Ouachita Orogen, Arkansas, USA

Harold E. Johnson, David V. Wiltschko and John P. Harris
Diagenetic to incipient metamorphic zones of the Benton Uplift, Ouachita Orogen, Arkansas, USA
Geological Society of America Bulletin (September 2019) 132 (5-6): 977-986

Abstract

Vitrinite reflectance analysis and the mean diameter of metamorphosed quartz, suggest that the eastern Ouachita region, Arkansas, USA reached the lower greenschist facies, regardless of burial depth. An increase in "crystallinity" may explain that the maturation is from the exhumation of the rocks from a greater depth. Shale and sandstone samples collected from outcrops along the crest of the Benton Uplift exhibit illite and chlorite crystallinities that yield higher indices compared to younger rocks adjacent to this crustal-scale anticlinal structure. Illite crystallinity d(001) of air-dried, fine (<0.2 mu m) authigenic clays (Delta degrees 2Theta (CuKalpha )=0.417 degrees to 0.875 degrees ) yield a range of conditions from diagenetic temperature to lower anchizone temperatures up to approximately 200 degrees C. Air-dried, fine authigenic chlorite clays (Delta degrees 2Theta (CuKalpha )=0.259 degrees to 1.570 degrees ) yield a wide range of diagenetic to metamorphic conditions that span the diagenetic zone through epizone, which indicate a maximum temperature slightly above approximately 300 degrees C. These results are in contrast to prior thermal maturation data. No additional heat sources, such as from pluton emplacement, were identified by major areas of anomalous high maturation based on crystallinity. Regionally, the illite and chlorite crystallinity increases toward the central axis of the Benton Uplift. Exhumation of the rocks from greater depth is all that is required to explain the illite and chlorite crystallinity data.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 132
Serial Issue: 5-6
Title: Diagenetic to incipient metamorphic zones of the Benton Uplift, Ouachita Orogen, Arkansas, USA
Affiliation: Texas A&M University, Department of Geology and Geophysics, College Station, TX, United States
Pages: 977-986
Published: 20190919
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 48
Accession Number: 2019-095121
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019322
Illustration Description: illus. incl. strat. col., 1 table, geol. sketch maps
N34°00'00" - N34°40'00", W96°00'00" - W94°30'00"
Secondary Affiliation: Sam Houston State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201950
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