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

陶波火山带 (TVZ) 的特征是残余重力负异常，该异常与自 c. 的正断层、沉降和大量硅质火山活动区相关联。2 马。陡峭的重力梯度与其东部和西部边缘的中生代变沉积基底的下断层有关，所有已知的破火山口都与显着的局部重力低点有关。展示了新的布格和残余重力异常图，显示比以前的地图改进的细节。TVZ 的西缘表现为一系列平行的东北走向边界和西北走向的跨界带。新地图还揭示了 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，这表明它们可能是更大的火山口复合体中的独立坍塌区域。在 TVZ 边缘，Hamilton、Waimiha、Galatea 和 Waiohau 的 Hauraki 地堑/裂谷和沉积盆地也具有低残余重力的特点。