On the significance of CO2 inclusions in plagioclase microphenocrysts in tholeiite from Moeraki,New Zealand |
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| Authors: | Douglas S Coombs Edwin Roedder |
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| Institution: | (1) Geology Department, University of Otago, Dunedin, New Zealand, NZ;(2) Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138, USA, US |
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| Abstract: | Liquid plus vapour inclusions of CO2 are widespread in plagioclase microphenocrysts in small tholeiitic intrusions and tephra of the Moeraki and adjacent areas
of northeast Otago, New Zealand. They imply the presence of immiscible CO2 droplets in the magma at depths of about 7–14 km. Their presence within 5 μm of the edges of microphenocrysts as little as
35 μm thick and 118 μm long indicates minimal feldspar crystal growth during the final ascent and quenching of the magma.
Delicate branching clusters of lath-like microphenocrysts escaped disruption during this ascent. Such CO2 inclusions are a potential source of ‘excess argon’ perturbing K-Ar age determinations.
Received March 24, 1993/Accepted September 10, 1993 |
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| Keywords: | : carbon dioxide – fluid inclusions – plagioclase – tholeiite magma – Moeraki (NZ) |
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