Crustal basement terranes under the Taupō Volcanic Zone, New Zealand: Context for hydrothermal and magmatic processes

Mortimer, Nick; Charlier, B. L.; Rooyakkers, Shane M.; Turnbull, Rose; Wilson, Colin; Negrini, Marianne; Bannister, Stephen; Milicich, Sarah D.; Chambefort, Isabelle; Miller, Craig A.; Kilgour, Geoff

doi:10.1016/j.jvolgeores.2023.107855

Cited by 5 publications

(1 citation statement)

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“…However, this is shallower than the DBMS determined in this area (∼15 km) and is taken to reflect localized high temperatures caused by magma intrusion that are not resolvable in our model. The mineralogy of crustal xenoliths erupted elsewhere in the TVZ (e.g., Graham, 1987; Mortimer, Charlier, et al., 2023) suggest temperatures higher than the Curie point exist within the crust, however the depth determination of these samples is poorly constrained. We propose the DBMS in the TVZ reflects the Curie temperature isotherm, however this likely rapidly varies spatially.…”

Section: Discussionmentioning

confidence: 99%

The Thermal Structure of Central Te Riu a Māui/Zealandia Continent as Determined From the Depth to Base of Magnetic Sources

Miller,

Kirkby,

Mortimer

et al. 2023

JGR Solid Earth

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To investigate the thermal structure of central Te Riu a Māui/Zealandia continent we estimate the depth to base of magnetic sources (DBMS), using an updated compilation of magnetic data. We calculate thousands of power spectral density estimates and solve an analytic solution for the fractal distribution of magnetization using a Bayesian method constrained by a sediment thickness model. Our DBMS results are broadly similar to a global model yet show complex relationships with independent models of crust and elastic thicknesses, and depth to base of seismicity (D90). Across central Zealandia, DBMS occurs above, coincident with, and below the Moho reflecting that factors additional to temperature influence DBMS. Away from subduction zones crustal thickness likely modulates DBMS while plate margins show varying influence dependent on margin characteristics. In the Taupō Volcanic Zone we interpret DBMS to reflect Curie point temperature at an average depth of 9–11 km. Error analysis shows that the choice of prior influences the posterior standard deviation and can result in counter intuitive error versus DBMS relationships. We use the DBMS as a basal temperature isotherm in heat flow models to compare with heat flow derived from borehole temperature measurements. Using the standard Curie point temperature of 580°C we find that DBMS derived heat flow models over estimate heat flow in areas underlain by plutonic rocks. We propose this reflects a higher titanomagnetite content in these rocks, although detailed studies of the magnetic mineralogy of Zealandia's plutonic rocks are required.

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Section: Discussionmentioning

confidence: 99%