Authors / CoAuthors
Bultitude, R.J. | Johnson, R.W. | Chappell, B.W.
Abstract
Chemically analysed lavas from Bagana, an active andesitic volcano on Bougainville Island, can be assigned to one of three age groups - pre-1943, 1943-53, or 1959-75. Lavas of the oldest group are chemically the most fractionated, whereas those of the 1943-53 group are the most mafic. The rocks of the youngest group, although intermediate in degree of fractionation have K2O, Rb, and Ba abundances similar to, or lower than, the rocks of the 1943-53 group. The three groups appear to represent distinct batches of magma that were successively erupted from Bagana, possibly from a high-level reservoir that was periodically emptied and refilled. The andesites are regarded as fractionates of mantle-derived mafic magmas. Most of the crystal fractionation probably took place during ascent from the mantle source region, and before entry into the reservoir beneath the volcano. An average chemical composition of the analysed Bagana andesites has major-element values close to those of the mean for more than 800 analysed late Cainozoic volcanic rocks from Papua New Guinea, and is proposed as a reference andesite composition for comparative studies.
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document
eCat Id
80971
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- GA PublicationJournal
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- PNG
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_External
Publication Date
1978-01-01T00:00:00
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geoscientificInformation
Series Information
BMR Journal of Australian Geology and Geophysics 3:4:281-295
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Unknown
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Extents
[-6.4, -6.0, 155.0, 155.25]
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