ABSTRACT

The Taupō Volcanic Zone (TVZ) is characterised by a negative residual gravity anomaly that correlates with a zone of normal faulting, subsidence and voluminous silicic volcanism from c. 2 Ma. A steep gravity gradient is associated with downfaulting of the Mesozoic metasedimentary basement at its eastern and western margins, and all known calderas are associated with prominent local gravity lows. New Bouguer and residual gravity anomaly maps are presented that show improved detail over previous maps. The western margin of the TVZ shows as a series of parallel northeast-trending boundaries and northwest-trending step-over zones. The new map also reveals the complex boundaries of the Okataina caldera, and greater detail north of Taupō where gravity lows at Reporoa and Mihi form part of a larger and more extensive, elliptical low-gravity feature, suggesting that they may be separate collapse areas within a larger caldera complex. Around the margins of the TVZ, the Hauraki graben/rift and sedimentary basins at Hamilton, Waimiha, Galatea and Waiohau are also characterised by low residual gravity.

摘要

陶波火山区（TVZ）的特征是负残留重力异常，与异常断层，下沉和c上大量硅质火山岩带相关。2妈 陡峭的重力梯度与中，西部沉积界基底在其东部和西部边缘的断层作用有关，并且所有已知的火山口与明显的局部重力低点有关。提出了新的布格和剩余重力异常图，这些图显示了比以前的图更好的细节。TVZ的西边缘显示为一系列平行的东北趋势边界和西北趋势过渡区。新地图还显示了Okataina火山口的复杂边界，以及陶波以北的更多细节，其中Reporoa和Mihi的重力低点构成了更大，更广泛的椭圆形低重力特征的一部分，这表明它们可能是较大的破火山口综合体内的单独坍塌区域。在TVZ边缘附近，汉密尔顿，怀米哈，加拉蒂亚和怀奥豪的豪拉基（Hauraki）裂谷/裂谷盆地和沉积盆地也具有低残留重力的特点。