The Reporoa Caldera, Taupo Volcanic Zone: source of the Kaingaroa Ignimbrites
The Reporoa Caldera, Taupo Volcanic Zone: source of the Kaingaroa Ignimbrites
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陶波火山带的雷波罗阿火山口：Kaingaroa Ignimbrites 的来源
DOI：
10.1007/bf00302833
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发表时间：
1994
影响因子：
3.5
通讯作者：
R. A. Bailey
中科院分区：
文献类型：
--
作者：
I. Nairn;C. Wood;R. A. Bailey
Reporoa火山口位于Reporoa凹陷的北方末端，以前被描述为构造断角凹陷。早期确认地形盆地为破火山口，由于缺乏足够大体积的相关年轻火山碎屑流存款，导致破火山口坍塌而受阻。Reporoa盆地东部边缘的新出露显示，厚的岩屑滞后角砾岩（>30 m）夹在0.24 Ma Kaingaroa凝灰岩中。这些熔结凝灰岩以前被认为是邻近的Okataina火山中心。滞后角砾岩的厚度和最大碎屑的大小迅速减少向外的破火山口边缘，和离散角砾岩是不存在的熔结凝灰岩部分超过3公里的边缘。岩屑滞后角砾岩，连同结构和地球物理证据，确认Reporoa火山口的来源c。100 km3的Kaingaroa火山灰岩，在陶波火山区先前确认的七个流纹岩火山中心之外又增加了一个主要的流纹岩火山中心。其他更古老的破火山口也可能出现在雷波罗阿洼地。
The Reporoa Caldera occupies the northern end of the Reporoa Depression, previously described as a tectonic fault-angle depression. Earlier confirmation of the topographic basin as a caldera had been hindered by the lack of an associated young pyroclastic flow deposit of large enough volume to have caused caldera collapse. New exposures on the eastern margin of the Reporoa basin reveal thick lithic lag breccias (>30 m) interbedded within the 0.24 Ma Kaingaroa Ignimbrites. These ignimbrites were previously attributed to the adjacent Okataina Volcanic Centre. Lag breccia thicknesses and maximum clast sizes decrease rapidly outward from the caldera rim, and discrete breccias are absent from ignimbrite sections more than 3 km from the rim. The lithic lag breccias, together with structural and geophysical evidence, confirm Reporoa Caldera as the source of the c. 100 km3Kaingaroa Ignimbrites, adding another major rhyolitic volcanic centre to the seven previously recognized in the Taupo Volcanic Zone. Other, older, calderas may also be present in the Reporoa Depression.