Are plutons assembled over millions of years by amalgamation from small magma chambers?

Allen F. Glazner, John M. Bartley, Drew S. Coleman, Walt Gray, Ryan Z. Taylor

Research output: Contribution to journalArticle

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Abstract

Field and geochronologic evidence indicate that large and broadly homogeneous plutons can accumulate incrementally over millions of years. This contradicts the common assumption that plutons form from large, mobile bodies of magma. Incremental assembly is consistent with seismic results from active volcanic areas which rarely locate masses that contain more than 10% melt. At such a low melt fraction, a material is incapable of bulk flow as a liquid and perhaps should not even be termed magma. Volumes with higher melt fractions may be present in these areas if they are small, and this is consistent with geologic evidence for plutons growing in small increments. The large melt volumes required for eruption of large ignimbrites are rare and ephemeral, and links between these and emplacement of most plutons are open to doubt. We suggest that plutons may commonly form incrementally without ever existing as a large magma body. If so, then many widely accepted magma ascent and emplacement processes (e.g., diapirism and stoping) may be uncommon in nature, and many aspects of the petrochemical evolution of magmatic systems (e.g., in situ crystal fractionation and magma mixing) need to be reconsidered.

LanguageEnglish (US)
Pages4-11
Number of pages8
JournalGSA Today
Volume14
Issue number4-5
DOIs
StatePublished - Apr 1 2004

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magma chamber
pluton
magma
melt
emplacement
stoping
diapirism
ignimbrite
volcanic eruption
fractionation
crystal
liquid

ASJC Scopus subject areas

  • Geology

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Are plutons assembled over millions of years by amalgamation from small magma chambers? / Glazner, Allen F.; Bartley, John M.; Coleman, Drew S.; Gray, Walt; Taylor, Ryan Z.

In: GSA Today, Vol. 14, No. 4-5, 01.04.2004, p. 4-11.

Research output: Contribution to journalArticle

Glazner, Allen F. ; Bartley, John M. ; Coleman, Drew S. ; Gray, Walt ; Taylor, Ryan Z. / Are plutons assembled over millions of years by amalgamation from small magma chambers?. In: GSA Today. 2004 ; Vol. 14, No. 4-5. pp. 4-11.
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