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Title: Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico

Abstract

Two distinctive ash-flow tuffs occur around the base of Volcan Las Navajas, a Pleistocene trachyte - peralkaline rhyolite center located in the northwestern segment of the Mexican Volcanic belt. The lower ash-flow unit is locally up to 65 m thick, is lithic rich and contains pumice blocks of comenditic rhyolite. The unit is not extensively exposed, and thus its areal extent and volume cannot be determined. Its chemical characteristics and stratigraphic relationship to other products erupted from Las Navajas suggest that it is related to the formation of the older of the two calderas which occur on Las Navajas. Unconformably overlying this unwelded ash-flow is a pantelleritic airfall pumice unit which is locally welded. This airfall unit is conformably overlain by a welded as-flow tuff that contains fiamme of pantelleritic composition (72 %SiO/sub 2/, 8% FeO*, 900 ppm Zr, agpaitic index of 1.7) as well as pumice blocks that show evidence of various degrees of mixing between pantellerite and trachyte. This suggests eruption from a chemically zoned magma chamber. This unit is locally up to 20 m thick, although its top has been removed by erosion. It is found on all sides of Las Navajas except on the south wheremore » it may be covered by Volcan Sanganguey, a Pleistocene to Recent calc-alkaline volcano. The welded ash-flow has been dated by K - Ar at 0.2+/-0.1 m.y. Stratigraphically and chemically this ash-flow appears to be related to the formation of younger of the two calderas.« less

Authors:
;
Publication Date:
Research Org.:
Tulane Univ., New Orleans, LA (USA)
OSTI Identifier:
6194937
Report Number(s):
CONF-8510489-
Journal ID: CODEN: GAAPB
Resource Type:
Conference
Journal Name:
Geol. Soc. Am., Abstr. Programs; (United States)
Additional Journal Information:
Journal Volume: 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; MEXICO; VOLCANIC ROCKS; CHEMICAL COMPOSITION; PETROLOGY; CALDERAS; EROSION; ERUPTION; GEOCHEMISTRY; GEOLOGIC HISTORY; LAVA; PUMICE; STRATIGRAPHY; TUFF; VOLCANISM; VOLCANOES; CHEMISTRY; DEVELOPING COUNTRIES; GEOLOGY; IGNEOUS ROCKS; LATIN AMERICA; NORTH AMERICA; ROCKS; 580300* - Mineralogy, Petrology, & Rock Mechanics- (-1989); 580400 - Geochemistry- (-1989)

Citation Formats

Nelson, S A, and Hebre, J A. Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico. United States: N. p., 1985. Web.
Nelson, S A, & Hebre, J A. Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico. United States.
Nelson, S A, and Hebre, J A. 1985. "Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico". United States.
@article{osti_6194937,
title = {Comenditic and pantelleritic ash-flow tuffs from Volcan Las Navajas, Nayarit, Mexico},
author = {Nelson, S A and Hebre, J A},
abstractNote = {Two distinctive ash-flow tuffs occur around the base of Volcan Las Navajas, a Pleistocene trachyte - peralkaline rhyolite center located in the northwestern segment of the Mexican Volcanic belt. The lower ash-flow unit is locally up to 65 m thick, is lithic rich and contains pumice blocks of comenditic rhyolite. The unit is not extensively exposed, and thus its areal extent and volume cannot be determined. Its chemical characteristics and stratigraphic relationship to other products erupted from Las Navajas suggest that it is related to the formation of the older of the two calderas which occur on Las Navajas. Unconformably overlying this unwelded ash-flow is a pantelleritic airfall pumice unit which is locally welded. This airfall unit is conformably overlain by a welded as-flow tuff that contains fiamme of pantelleritic composition (72 %SiO/sub 2/, 8% FeO*, 900 ppm Zr, agpaitic index of 1.7) as well as pumice blocks that show evidence of various degrees of mixing between pantellerite and trachyte. This suggests eruption from a chemically zoned magma chamber. This unit is locally up to 20 m thick, although its top has been removed by erosion. It is found on all sides of Las Navajas except on the south where it may be covered by Volcan Sanganguey, a Pleistocene to Recent calc-alkaline volcano. The welded ash-flow has been dated by K - Ar at 0.2+/-0.1 m.y. Stratigraphically and chemically this ash-flow appears to be related to the formation of younger of the two calderas.},
doi = {},
url = {https://www.osti.gov/biblio/6194937}, journal = {Geol. Soc. Am., Abstr. Programs; (United States)},
number = ,
volume = 17,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 1985},
month = {Tue Jan 01 00:00:00 EST 1985}
}

Conference:
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