Regional lithofacies variation in early Proterozoic rocks of the northern Park Range, Colorado and southern Sierra Madre, Wyoming

Conference · Mon Feb 01 00:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6002431

Klipfel, P D ^[1]

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1. Mineral Resource Services, Arvada, CO (United States)

This study investigates the regional variation of 1.7 to 1.8 Ga metavolcanic, metasedimentary, and metaexhalite rocks over an area of approximately 700 km[sup 2]. Within this area, bimodal basaltic and rhyodacitic metavolcanic rocks dominate in the west but systematically decrease in proportion as gneissic rocks of interpreted metasedimentary origin increase toward the east. The proportion of metaexhalite rocks remains relatively constant despite this change. Metasedimentary rocks are primarily quartz-rich psammite and psammopelite of terrigenous origin. Both sediment and volcanic debris were deposited in a shallow basin with possible slight deepening to the east. The observed lithologic transition and interpreted basin deepening to the east is supported by systematic variation in Pb isotope ratios and by the oxidation state of Fe in garnetite which is oxidized in the west and grades to a reduced state in the east. Lithologic transition, petro-chemistry, and low P/high T metamorphism all point toward basin development by widespread ensialic crustal attenuation. This assessment is in contrast to the current island arc--back arc interpretation for this region.

• OSTI ID: 6002431
• Report Number(s): CONF-9303212-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 25:1; Conference: 27. annual Geological Society of America (GSA) South-Central Section meeting, Fort Worth, TX (United States), 15-16 Mar 1993; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COLORADO
GEOLOGIC DEPOSITS
METAMORPHIC ROCKS
PETROCHEMISTRY
PETROLOGY
WYOMING
GEOBAROMETRY
GEOGRAPHICAL VARIATIONS
GEOLOGIC HISTORY
GEOTHERMOMETRY
ISOTOPE RATIO
LEAD ISOTOPES
LITHOLOGY
METAMORPHISM
PETROGENESIS
VOLCANIC ROCKS
DEVELOPED COUNTRIES
GEOLOGY
IGNEOUS ROCKS
ISOTOPES
NORTH AMERICA
ROCKS
USA
VARIATIONS
580000* - Geosciences