Page 36 - Caldera Volcanism Analysis, Modelling and Response

Residence Times of Silicic Magmas Associated with Calderas 11

3. Residence Times of Magmas Associated with
Selected Calderas

The caldera complexes (Figure 1) are described from the youngest to the
oldest. Each section contains a brief introduction to the main geological and
petrological features of the system and is followed by the residence times
and process rates. The data sources are cited in the text and/or shown in Tables 3–8
and Figures 3–8.

3.1. Taupo volcanic zone

The Taupo volcanic zone (New Zealand) is 300 km long and up to 60 km wide and
lies above a subduction zone. At least 34 caldera-forming events have produced a
complex of overlapping volcanic centres over 1.6 My, with a total estimated volume
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of 15,000–20,000 km (Figure 3). Houghton et al. (1995) presented the following
eruptive history: (1) Period I from 1.68 to 1.53 Ma is the earliest ignimbrite
volcanism. Three units erupted from the Mangakino volcanic centre and a fourth
from an eastern source. (2) Period II (1.21–0.89 Ma) during which two of the
largest ignimbrites were erupted (e.g., Ongatiti). The main active centres were
Mangakino and Kapenga. (3) Period III (0.34 Ma –present) includes the
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voluminous ignimbrites (300–1,000 km ) of the Whakamaru group at ca. 330 ka,
and the Oruanui eruption at 26.5 ka (Figure 3). Pre-eruptive temperatures for
dacitic to rhyolitic compositions vary between 940 and 7301C, whereas their
liquidus obtained with the whole-rock compositions are about 1–601C higher
(Smith et al., 2005).

Figure 3 Location of TaupoVolcanic Zone (a), and of the main calderas (b), Maps modi¢ed
after Houghton et al. (1995).