ABSTRACT Volcaniclastic deposits, pillow lavas, dikes and sills of the intraplate Waiareka-Deborah Volcanic Field in North Otago were emplaced into and onto the Zealandia Eocene-Early Oligocene continental shelf. The on-land extent is ∼890 km2 but offshore volcanic rocks occurring over an additional ∼3500 km2 may be related. Examination of the on-land volcaniclastic deposits indicates volcanism was dominated by short-lived clustered surtseyan-style eruptions. Pyroclast glass and sill and lava bulk rock chemistries show that the magmas were mainly sub-alkaline basalt to basaltic andesite. Minor alkaline centres are best represented by basanitic-melanephelinitic volcaniclastic deposits at Kakanui, which also contain an array of megacrysts plus mantle and crustal xenoliths. The sub-alkaline and alkaline source reservoirs had similar Sr and Nd isotope ratios (87Sr/86Sr34 Ma = 0.70346 ± 40, 143Nd/144Nd34 Ma = 0.51282 ± 4) but the sub-alkaline rocks tend to be slightly less radiogenic in 206Pb/204Pb or 208Pb/204Pb versus 207Pb/204Pb space. The dominant sub-alkaline nature and the isotopic compositions distinguish this volcanic field from the nearby Dunedin Volcanic Group and Alpine Dike Swarm. As the Waiareka-Deborah isotopic compositions are poorly represented in the Otago mantle lithosphere, the magmas may have been derived from the asthenosphere. There were multiple modes of Cenozoic intraplate volcanism in Otago.

中文翻译：

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西兰西亚始新世-早渐新世大陆架上的板内火山作用：北奥塔哥的怀亚雷卡-德博拉火山场

摘要 北奥塔哥的怀亚雷卡-德博拉火山区的火山碎屑沉积物、枕状熔岩、岩脉和岩床被安置在西兰西亚始新世-早渐新世大陆架上。陆地范围约为 890 平方公里，但在额外的约 3500 平方公里范围内发生的离岸火山岩可能与此有关。对陆上火山碎屑沉积物的检查表明，火山活动主要是由短期的成簇苏尔特塞式喷发所主导。火山碎屑玻璃和窗台和熔岩大块岩石化学表明，岩浆主要是亚碱性玄武岩到玄武安山岩。次要碱性中心最好由 Kakanui 的玄武质-黑镍质火山碎屑沉积物代表，其中还包含一系列巨晶以及地幔和地壳捕虏体。亚碱性和碱性源储层具有相似的 Sr 和 Nd 同位素比（87Sr/86Sr34 Ma = 0.70346 ± 40, 143Nd/144Nd34 Ma = 0.51282 ± 4）但亚碱性岩石在 204P/204P 中的放射成因略低或 208Pb/204Pb 对比 207Pb/204Pb 空间。主要的亚碱性性质和同位素组成将这个火山场与附近的但尼丁火山群和高山堤防群区分开来。由于 Waiareka-Deborah 同位素组成在奥塔哥地幔岩石圈中的代表性较差，岩浆可能来自软流圈。奥塔哥新生代板内火山活动有多种模式。主要的亚碱性性质和同位素组成将这个火山场与附近的但尼丁火山群和高山堤防群区分开来。由于 Waiareka-Deborah 同位素组成在奥塔哥地幔岩石圈中的代表性较差，岩浆可能来自软流圈。奥塔哥新生代板内火山活动有多种模式。主要的亚碱性性质和同位素组成将这个火山场与附近的但尼丁火山群和高山堤防群区分开来。由于 Waiareka-Deborah 同位素组成在奥塔哥地幔岩石圈中的代表性较差，岩浆可能来自软流圈。奥塔哥新生代板内火山活动有多种模式。