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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Geochemical and isotopic development of the Coromandel Volcanic Zone, northern New Zealand, since 18 Ma
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Geochemical and isotopic development of the Coromandel Volcanic Zone, northern New Zealand, since 18 Ma

机译：自18 Ma以来新西兰北部科罗曼德火山区的地球化学和同位素发育

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摘要

Cenozoic subduction-related volcanism in northern New Zealand developed from mainly basaltic and andes-itic volcanisms in the Early Miocene to mainly silicic volcanism in the present Taupo Volcanic Zone. The first explosive silicic eruptions occurred at 12 Ma and large silicic calderas formed from 8 Ma. This transition is recorded by the 18-1.9 Ma Coromandel Volcanic Zone (CVZ) succession, which provides an outstanding opportunity to investigate the origins of the modern North Island volcanism. New major and trace element data on a rock suite representing CVZ andesites, rhyolites and basalts indicate a consistent subduction-related origin for the entire succession. The CVZ andesites generally define a consistent medium-potassic differentiation trend, however, distinct andesites with relatively sodic compositions occur at the bases of two consecutive eruptive series at -18 and -10 Ma. The distinct andesites are geochemically similar to basalts that erupted sporadically near the oceanic margin of the CVZ. CVZ rhyolites are medium- to high-potassic, peraluminous rocks with initial ~(87)Sr/~(86) Sr values comparable to or somewhat more radiogenic than coeval andesites (≥0.7049). Their bulk rock composition suggests derivation from sources comparable to least-differentiated andesites or basalts. We interpret the consecutive andesitic successions to represent stages in CVZ development during which distinct arc segments developed consecutively. The early stage in each segment yielded mainly intermediate volcanism whereas in the later stage volcanism locally proceeded rapidly (within ～1 Myr of initial andesitic activity) to silicic activity. Taken together, the succession records the rapid development and migration of arc system in a dynamic plate boundary setting.
机译：新西兰北部与新生代俯冲有关的火山活动从中新世早期的主要玄武岩和安第斯山脉的火山活动发展到目前的陶波火山带的主要的硅质火山活动。第一次爆炸性硅质爆发发生在12 Ma，大型硅质火山口由8 Ma形成。 18-1.9 Ma Coromandel火山带（CVZ）的演替记录了这一转变，这为调查现代北岛火山活动的起源提供了绝佳的机会。代表CVZ安山岩，流纹岩和玄武岩的岩石套件中的新主要和微量元素数据表明整个演替过程中一致的俯冲相关成因。 CVZ安山岩通常定义了一致的中钾分化趋势，但是，具有相对钠盐成分的独特安山岩出现在两个连续的喷发序列的底部，分别为-18 Ma和-10 Ma。独特的安山岩在地球化学上类似于在CVZ海洋边缘附近零星喷发的玄武岩。 CVZ流纹岩是中等至高钾质，钙铝质岩石，其初始〜（87）Sr /〜（86）Sr值可比同年龄安山岩（≥0.7049）或更具有放射成因。它们的大块岩石成分表明其来源与可分辨的最小安山岩或玄武岩相当。我们解释连续的安山岩序以代表CVZ发展的阶段，在此阶段不同的弧段连续发展。每个阶段的早期主要产生中层火山活动，而在后期阶段，局部火山活动迅速发展（在初始安山岩活动的〜1 Myr之内）发展为硅质活动。综上所述，连续过程记录了弧形系统在动态板边界设置中的快速发展和迁移。

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