Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Evidence for limited zonation in silicic magma systems, Taupo volcanic zone, New Zealand

Nelia W. Dunbar, Philip R. Kyle and Colin J. N. Wilson
Evidence for limited zonation in silicic magma systems, Taupo volcanic zone, New Zealand
Geology (Boulder) (March 1989) 17 (3): 234-236

Abstract

Smith (1979) suggested that all pyroclastic eruptions that exceed 1 km (super 3) will show pronounced systematic compositional zonation. Since then, chemical and thermal zonation in large silicic magma bodies has become the expected condition in rhyolitic magma bodies. However, trace-element chemistry and Fe-Ti oxide geothermometry of Quaternary rhyolitic Plinian tephras from two volcanic centers in the Taupo Volcanic Zone, New Zealand, suggest that no strong systematic chemical or thermal zonation was present in either magma system. Of the Plinian tephra units erupted over the past 50 ka from the Taupo and Okataina volcanoes, 28 were sampled, and most were analyzed for Th, Pb, Rb, Sr, Y, Zr, and Nb, as well as Fe-Ti oxide composition. Taupo volcano tephras erupted over the past 10 ka have uniform compositions for all elements except Sr, and all these samples fall on the same T/f (sub O2) buffer trend. However, pre-22 ka Taupo tephras are mineralogically and chemically distinct from the younger group and fall on a different T/f (sub O2) buffer trend. This may be a result of the large eruption (>155 km (super 3) of magma) from the Taupo volcano at 22.5 ka, and subsequent reequilibration of the magmatic system. The Okataina volcano tephras erupted over the past 31 ka show slight systematic and considerable nonsystematic trace-element variation, but all fall on a single T/f (sub O2) buffer trend. This may indicate slight preeruptive alteration of a single Okataina magma body.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 17
Serial Issue: 3
Title: Evidence for limited zonation in silicic magma systems, Taupo volcanic zone, New Zealand
Affiliation: N.M. Inst. Min. and Technol., Dep. Geosci., Socorro, NM, United States
Pages: 234-236
Published: 198903
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1989-031410
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
S39°00'00" - S38°00'00", E175°00'00" - E178°00'00"
Secondary Affiliation: Univ. Cambridge, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 1989
Close Modal

or Create an Account

Close Modal
Close Modal