Argon/Argon, micropaleontological and Uranium/Lead geochronological data for igneous and sedimentary rocks dredged during the VESPA scientific cruise

abstract: the 2015 vespa voyage (volcanic evolution of south pacific arcs) was a seismic and rock dredging expedition to the loyalty and three kings ridges and south fiji basin. in our paper we present 33 40ar/39ar, 22 micropaleontological, and two u/pb ages for igneous and sedimentary rocks from 33 dredge sites in this little-studied part of the southwest pacific ocean. igneous rocks include basalts, dolerites, basaltic andesites, trachyandesites, and a granite. successful ar/ar dating of altered and/or low-k basalts was achieved through careful sample selection and processing, detailed petrographic and element mapping of groundmass, and incremental heating experiments on both phenocryst and groundmass separates to interpret the complex spectra produced by samples having multiple k reservoirs. the 40ar/39ar ages of most of the sampled lavas, irrespective of composition, are latest oligocene to earliest miocene (25-22 ma); two are eocene (39-36 ma). the granite has a u/pb zircon age of 23.6±0.3 ma. 40ar/39ar lava ages are corroborated by microfossil ages from associated sedimentary rocks. the vespa lavas are part of a >3000 km long disrupted belt of eocene to miocene subduction-related volcanic rocks. the belt includes arc rocks in northland new zealand, northland plateau, three kings ridge, and loyalty ridge and, speculatively, d’entrecasteaux ridge. this belt is the product of superimposed eocene and oligocene-miocene remnant volcanic arcs that were stranded along and near the edge of zealandia while still-active arc belts migrated east with the pacific trench.plain word summary: samples of lava from the seabed between new zealand and new caledonia have been dated using atomic clocks and fossils. most lavas erupted in a big pulse of volcanic activity between 25 and 22 million years ago. they are part of a belt of now-extinct undersea volcanoes that stretches for more than 3000 km between new zealand and the solomon islands. these volcanoes were formed by subduction of the pacific plate under the australian plate.

摘要：2015年维萨普航程（南太平洋弧火山演化）是一项针对忠诚群岛、三王群岛脊和南斐济盆地的地震和岩石勘探远征。在本文中，我们展示了来自西南太平洋这一少为人知区域的33个采集点的33个40Ar/39Ar、22个微古生物学样本以及两个铀/铅年代数据，这些数据涉及岩浆岩和沉积岩。岩浆岩包括玄武岩、辉长岩、玄武岩安山岩、透长安山岩以及花岗岩。通过对改造后的低钾玄武岩进行谨慎的样本选择和处理、详细的地质学特征和元素映射分析，以及对晶质和基质分离进行逐步加热实验，成功实现了对具有多个钾储库的样本产生的复杂光谱的解读。大多数采集的岩浆的40Ar/39Ar年龄，无论成分如何，均为晚中新世至早中新世（25-22百万年前）；其中两个为古新世（39-36百万年前）。花岗岩的铀/铅锆石年龄为23.6±0.3百万年前。40Ar/39Ar岩浆年龄得到了相关沉积岩微化石年龄的证实。维萨普岩浆是长达超过3000公里的、古新世至中新世与俯冲作用相关的火山岩带的一部分。该带包括新西兰北地、北地高原、三王群岛脊和忠诚群岛的弧岩，以及推测中的邓特拉斯群岛脊。这个带是叠加在西兰地边缘的、仍在活跃的弧带随着太平洋海沟向东迁移的同时，古新世和奥利地-中新世残留火山弧形成的。概述：利用原子钟和化石对新西兰与新喀里多尼亚之间海底的岩浆样本进行了年代测定。大多数岩浆是在约2500万至2200万年前的一次大规模火山活动期间喷发的。它们是连接新西兰和所罗门群岛之间超过3000公里长的、现已灭绝的海底火山带的一部分。这些火山是由太平洋板块在澳大利亚板块下俯冲而形成的。