| Abstract |
Residual gravity anomalies near the field were split into two components. A first-order component (up to -370 associated with variations in the depth of basement as a result of vertical movements on the Kaingaroa Fault: and a order component (up to associated mainly with lateral variations in the distribution of near surface 1 depth) rhyolites. Simple 3-D geophysical models suggest that rhyolites occur at depth over a wide area (including the field) which extends between Lake Rotokawa, Mt Kaimanawa, and Mt Whakapapataringa. The thickness of rhyolite predicted by the models is in good agreement with that found in drillholes 4, and 5; but much greater than found in but the reason for the discrepancy is not known. The results show that near-surface rhyolites make a significant contribution to the gravity anomaly pattern in parts of the Central Volcanic Region and these anomalies cannot be interpreted solely in terms of variations of basement depth. |