The central Taupo Volcanic Zone (TVZ) in New Zealand, the most productive of silicic volcanic centres, is flanked by younger andesitic stratovolcanoes to the south. Small basaltic scoria cones occur along the length of the TVZ, the most primitive of which contain abundant xenocrysts, giving insight into the mantle feeding the TVZ.

Here, we present major and minor element compositions of olivine from eleven mafic eruptions spanning the length of the central and south TVZ. Olivine compositions can be divided into three major groups, based on their texture, major and minor element composition, and zoning. Group 1 olivines are Fo₈₈ in the most primitive cores, with minor element concentrations consistent with magmatic origin. Group 2 olivine compositions range from Fo_72–88 but are homogeneous within individual crystals. CaO contents are consistently lower for a given forsterite content compared to group 1 olivines and are most consistent with a plutonic crystal mush origin. Group 3 olivines have core compositions of Fo_93–90, and NiO and CaO (0.36–0.56 wt%, <0.15 wt%, respectively) concentrations consistent with a primary magma or mantle-derived origin. Compositional variation within group 3 olivine allows for further characterisation of the mantle lithologies from which the crystals were sourced. Group 3 olivines from the central TVZ are lherzolite-derived, whereas group 3 olivines from the south TVZ are harzburgite-derived. However, recent whole-rock and melt inclusion data suggests that the most fertile mantle underlies the south TVZ, and the least fertile mantle underlies the inter-caldera regions of the central TVZ where caldera-forming volcanism has ceased. This is inconsistent with interpretations drawn from the olivine data. We therefore suggest that harzburgitic xenocrysts originate from old depleted sub-continental lithospheric mantle (SCLM), which is present at depths of ~30 km in the south TVZ. By contrast, rifting and crustal thinning in the central TVZ has removed the SCLM, explaining why only xenocrysts of lherzolitic origin are found. The presence of depleted SCLM may act as a boundary layer inhibiting ascent of melt from the mantle, providing an explanation for lower erupted volumes in the south TVZ. Dissolution of the orthopyroxene component in harzburgite in the presence of hydrous melt satisfies major element constraints on south TVZ basalt (high SiO₂, high MgO, low CaO/Al₂O₃). Taken together, this is the first mineralogical evidence for a tectonic and lithospheric control on the shift from andesitic to rhyolitic activity in the TVZ, implying a direct link between rifting, magma composition and volcanic productivity.

新西兰中央的陶波火山区（TVZ）是硅质火山中心，生产力最高，南部是年轻的安第斯山脉平流层火山。沿TVZ的长度分布着小的玄武岩锥，其中最原始的锥内含有大量的异晶，可以深入了解TVZ的地幔。

在这里，我们介绍了横跨中部和南部TVZ长度的11个黑手性火山喷发的橄榄石的主要和次要元素组成。根据橄榄的质地，主要和次要元素组成以及分区，可以将其分为三大类。第一组橄榄石在最原始的岩心中是Fo ₈₈，其微量元素浓度与岩浆成因一致。第2组橄榄石的成分范围为Fo _72–88，但在单个晶体中均质。与第1组橄榄石相比，对于给定的镁橄榄石含量，CaO含量始终较低，并且与深成岩结晶糊状成因最一致。第3组橄榄石的核心成分为Fo _93–90，NiO和CaO（分别为0.36-0.56 wt％，<0.15 wt％）的浓度与原生岩浆或地幔来源一致。第3组橄榄石中的成分变化可以进一步表征来源晶体的地幔岩性。来自中部TVZ的第3组橄榄石是钙铝榴石衍生的，而来自南部TVZ的第3组橄榄石则是钙锌矿衍生的。但是，最近的全岩和熔岩夹杂物数据表明，南部TVZ下方是最肥沃的地幔，而中部TVZ的破火山口间地区却是最不肥沃的地幔，在该地区火山口形成的火山作用已经停止。这与从橄榄石数据中得出的解释不一致。因此，我们建议，成年畸形异形体起源于旧的枯竭的亚大陆岩石圈地幔（SCLM），它位于南部TVZ的约30 km处。相比之下，中部TVZ的裂谷和地壳变薄已去除了SCLM，这解释了为什么仅发现来源为异沸石的异晶。耗尽的SCLM的存在可能充当边界层，抑制了来自地幔的熔体上升，为南部TVZ的喷发量较低提供了解释。含水熔体存在下邻位rox烯组分在水溶沸石中的溶解满足南TVZ玄武岩的主要元素约束（高SiO 提供了有关南部TVZ喷发量较低的解释。含水熔体存在下邻位rox烯组分在水溶沸石中的溶解满足南TVZ玄武岩的主要元素约束（高SiO 提供了有关南部TVZ喷发量较低的解释。含水熔体存在下邻位rox烯组分在水溶沸石中的溶解满足南TVZ玄武岩的主要元素约束（高SiO₂，高MgO，低CaO / Al ₂ O ₃）。综上所述，这是构造和岩石圈控制TVZ中安山岩向流纹岩活动转变的第一个矿物学证据，这暗示了裂谷，岩浆成分和火山生产力之间的直接联系。