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Geochemical comparison of alkaline volcanism in oceanic and continental settings; Clarion Island versus the eastern Trans-Pecos magmatic province

Dennis O. Nelson and Kerri L. Nelson
Geochemical comparison of alkaline volcanism in oceanic and continental settings; Clarion Island versus the eastern Trans-Pecos magmatic province (in Mantle metasomatism and alkaline magmatism, Ellen Mullen Morris (editor) and Jill Dill Pasteris (editor))
Special Paper - Geological Society of America (1987) 215: 317-333

Abstract

Clarion Island (CI) represents young (1-1.7 m.y.) fracture zone-related volcanism in the east-central Pacific ocean. The eastern Trans-Pecos magmatic province (TPMP) of west Texas represents continental volcanism that developed during waning Laramide compression, primarily 30-38 m.y. Both rock series are alkaline, with the CI rocks conforming to a trend of increased silica undersaturation, and the bulk of the TPMP rocks to a trend of increased oversaturation with respect to silica. A sodic series of alkali-basalt-hawaiite-mugearite-benmoreite-trachyte occurs in both regions. On Clarion Island, the evolved rocks tend to be phonolitic. The TPMP contains an additional potassic series, alkali-basalt-trachybasalt-tristanite-trachyte, as well as basanites. Modelling and petrography suggest that these sequences were produced by low-P crystal fractionation involving olivine, clinopyroxene, plagioclase, Ti-magnetite, amphibole and apatite. Compositional trends for CI and TPMP rocks are very similar mechanisms of evolution, possibly similar sources, and an argument for minimal crustal assimilation for the TMPM alkali basalt- trachyte sequence. In addition to these silica-enrichment trends, both regions possess a trend toward silica depletion, possibly the result of fractionation of a high-P pyroxene-dominated assemblage. The nature and thickness of the crust are regarded as important controls in the evolution of magmas in these two regions. Mafic magmas are similar in both regions. Low-P fractionation beneath Clarion Island's thin basaltic crust produced the alkali basalt-phonolite trend, whereas fractionation beneath the TPMP's thicker continental crust led to the alkali basalt-rhyolite trend.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 215
Title: Geochemical comparison of alkaline volcanism in oceanic and continental settings; Clarion Island versus the eastern Trans-Pecos magmatic province
Title: Mantle metasomatism and alkaline magmatism
Author(s): Nelson, Dennis O.Nelson, Kerri L.
Author(s): Morris, Ellen Mulleneditor
Author(s): Pasteris, Jill Dilleditor
Affiliation: Sul Ross State Univ., Dep. Geol., Alpine, TX, United States
Affiliation: Sul Ross State Univ., Dep. Geol., Alpine, TX, United States
Pages: 317-333
Published: 1987
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Meeting name: Geological Society of America, South-central Section meeting on alkalic rocks and kimberlites
Meeting location: Fayetteville, AK, USA, United States
Meeting date: 19850415Apr. 15-16, 1985
References: 68
Accession Number: 1988-001238
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch map
N29°00'00" - N32°00'00", W106°30'00" - W101°00'00"
Secondary Affiliation: Wash. Univ., USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1988
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