Geophysical imaging of buried volcanic structures within a continental back-arc basin: The Central Volcanic Region, North Island, New Zealand

TY - JOUR

T1 - Geophysical imaging of buried volcanic structures within a continental back-arc basin

T2 - The Central Volcanic Region, North Island, New Zealand

AU - Stratford, Wanda Rose

AU - Stern, T.A.

PY - 2008

Y1 - 2008

N2 - Hidden beneath the ~2 km thick low-velocity volcaniclastics on the western margin of the Central Volcanic Region, North Island, New Zealand, are two structures that represent the early history of volcanic activity in a continental back-arc. These ~20×20 km structures, at Tokoroa and Mangakino, form an adjacent gravity high and low, respectively. Interpretations from seismic refraction arrivals and gravity modelling indicate the -65 mgal Mangakino residual gravity anomaly can be modelled, in part, by two low-density bodies that reach depths of ~6.5 km, whereas the Tokoroa gravity anomaly is due to a higher density rock coming, at most, to within ~650 m of the surface. The Mangakino anomaly is interpreted to be due to the remnants of magma chambers that fed large ignimbrite eruptions from about 1.2 Ma. An andesite volcano or complex volcanic structure is the preferred interpretation for the Tokoroa gravity high. The size of the putative volcanic structure is comparable to the presently active Tongariro Volcanic Complex in the centre of North Island.

AB - Hidden beneath the ~2 km thick low-velocity volcaniclastics on the western margin of the Central Volcanic Region, North Island, New Zealand, are two structures that represent the early history of volcanic activity in a continental back-arc. These ~20×20 km structures, at Tokoroa and Mangakino, form an adjacent gravity high and low, respectively. Interpretations from seismic refraction arrivals and gravity modelling indicate the -65 mgal Mangakino residual gravity anomaly can be modelled, in part, by two low-density bodies that reach depths of ~6.5 km, whereas the Tokoroa gravity anomaly is due to a higher density rock coming, at most, to within ~650 m of the surface. The Mangakino anomaly is interpreted to be due to the remnants of magma chambers that fed large ignimbrite eruptions from about 1.2 Ma. An andesite volcano or complex volcanic structure is the preferred interpretation for the Tokoroa gravity high. The size of the putative volcanic structure is comparable to the presently active Tongariro Volcanic Complex in the centre of North Island.

KW - Faculty of Science

KW - Calderas

KW - gravity anomalies

KW - andesite arc

KW - refraction seismology

KW - Central Volcanic Region

KW - New Zealand tectonics

KW - continental back-arc

U2 - 10.1016/j.jvolgeores.2008.02.011

DO - 10.1016/j.jvolgeores.2008.02.011

M3 - Journal article

SN - 0377-0273

VL - 174

SP - 257

EP - 268

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

ER -