Age and geochemistry of volcanic rocks from the Hikurangi and Manihiki oceanic Plateaus
Age and geochemistry of volcanic rocks from the Hikurangi and Manihiki oceanic Plateaus
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DOI：
10.1016/j.gca.2010.09.030
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发表时间：
2010-12-15
影响因子：
5
通讯作者：
Davy, Bryan
中科院分区：
文献类型：
--
作者：
Hoernle, Kaj;Hauff, Folkmar;Davy, Bryan
本文介绍了R/V Sonne 168巡航期间获得的Hikurangi高原基底和高原及其附近海山样品的第一个放射性年龄数据和综合地球化学数据集（包括主要元素和微量元素以及Sr-Nd-Pb-Hf同位素比值），以及Manihiki高原DSDP站点317的年龄和地球化学数据。40Ar/39Ar年龄和地球化学数据表明，Hikurangi基底熔岩（118-96 Ma）与Ontong爪哇高原熔岩（约120和90 Ma）具有惊人的主微量元素和同位素特征，主要是kwaimbaita型成分，而Manihiki DSDP站点317熔岩（117 Ma）与Ontong爪哇高原Singgalo熔岩具有相似的成分。而Hikurangi高原及其邻近地区（Kiore海山）的碱性、不相容元素富熔岩（99 ~ 87 Ma和67 Ma）则来源于明显的高时间积分U/Pb （HIMU）型地幔源。海山熔岩在成分上与新西兰相似年龄的碱性火山活动相似，表明在高原形成事件后大约20 Ma开始的第二次广泛事件来自一个不同的来源。邻近东北Hikurangi高原边缘的两个Osbourn海山的拉斑岩熔岩具有极贫的不相容元素组成，但不相容元素特征与Hikurangi和Ontong爪哇高原熔岩相似，且同位素组成介于正常海中脊玄武岩（N-MORB）和高原基底之间。这些较年轻（类似于52 Ma）的海山可能是通过与高原形成相关的基性堆积岩的重熔而形成的。Hikurangi高原、Ontong爪哇高原和Manihiki高原的年龄和地球化学特征相似，表明它们起源于一个共同的地幔源。我们认为，在大安通爪哇事件期间，地球表面大约1%的面积被火山活动覆盖，这是由于热化学超级羽流/圆顶在过渡带停滞，与目前在南太平洋超级井下方成像的结构相似但更大。后来在Hikurangi高原和西兰迪亚微大陆上的碱性火山活动可能是第二次大规模火山活动的一部分，该活动也可能引发了冈瓦纳大陆的最后分裂阶段，导致西兰迪亚碎片从西南极洲分离出来。(C) 2010 Elsevier Ltd.版权所有。
Here we present the first radiometric age data and a comprehensive geochemical data set (including major and trace element and Sr-Nd-Pb-Hf isotope ratios) for samples from the Hikurangi Plateau basement and seamounts on and adjacent to the plateau obtained during the R/V Sonne 168 cruise, in addition to age and geochemical data from DSDP Site 317 on the Manihiki Plateau. The 40Ar/39Ar age and geochemical data show that the Hikurangi basement lavas (118-96 Ma) have surprisingly similar major and trace element and isotopic characteristics to the Ontong Java Plateau lavas (ca. 120 and 90 Ma), primarily the Kwaimbaita-type composition, whereas the Manihiki DSDP Site 317 lavas (117 Ma) have similar compositions to the Singgalo lavas on the Ontong Java Plateau. Alkalic, incompatible-element-enriched seamount lavas (99-87 Ma and 67 Ma) on the Hikurangi Plateau and adjacent to it (Kiore Seamount), however, were derived from a distinct high time-integrated U/Pb (HIMU)-type mantle source. The seamount lavas are similar in composition to similar-aged alkalic volcanism on New Zealand, indicating a second wide-spread event from a distinct source beginning ca. 20 Ma after the plateau-forming event. Tholeiitic lavas from two Osbourn seamounts on the abyssal plain adjacent to the northeast Hikurangi Plateau margin have extremely depleted incompatible element compositions, but incompatible element characteristics similar to the Hikurangi and Ontong Java Plateau lavas and enriched isotopic compositions intermediate between normal mid-ocean-ridge basalt (N-MORB) and the plateau basement. These younger (similar to 52 Ma) seamounts may have formed through remelting of mafic cumulate rocks associated with the plateau formation. The similarity in age and geochemistry of the Hikurangi, Ontong Java and Manihiki Plateaus suggest derivation from a common mantle source. We propose that the Greater Ontong Java Event, during which similar to 1% of the Earth's surface was covered with volcanism, resulted from a thermo-chemical superplume/dome that stalled at the transition zone, similar to but larger than the structure imaged presently beneath the South Pacific superswell. The later alkalic volcanism on the Hikurangi Plateau and the Zealandia micro-continent may have been part of a second large-scale volcanic event that may have also triggered the final breakup stage of Gondwana, which resulted in the separation of Zealandia fragments from West Antarctica. (C) 2010 Elsevier Ltd. All rights reserved.