Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia
Temporal and geochemical evolution of the Cenozoic intraplate volcanism of Zealandia
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DOI：
10.1016/j.earscirev.2009.10.002
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发表时间：
2010
影响因子：
12.1
通讯作者：
C. Timm;K. Hoernle;R. Werner;F. Hauff;P. Bogaard;J. White;N. Mortimer;C. Garbe-Schönberg
中科院分区：
文献类型：
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作者：
C. Timm;K. Hoernle;R. Werner;F. Hauff;P. Bogaard;J. White;N. Mortimer;C. Garbe-Schönberg
为了更好地确定新西兰微大陆Zealandia上广泛分布的新生代板内火山活动的分布、时代、地球化学特征和成因，本文报道了新的40 Ar/39 Ar和地球化学特征。海洋沉积物中常量、微量元素和Sr-Nd-Hf-Pb同位素数据（查塔姆高地、坎贝尔和挑战者高原）和陆上（新西兰的北、南、奥克兰、坎贝尔、查塔姆和安提波德群岛）西兰迪亚的火山活动。样品包括霞石、响岩中的碧玄岩、粗面岩/流纹岩中的碱性玄武岩、少量拉斑玄武岩和玄武安山岩，它们都具有洋岛玄武岩（OIB）型微量元素特征，年龄范围为64.8 ~ 0.17Ma。同位素比率显示了组成的广泛变化（87Sr/86Sr=0.7027- 0.7050，143Nd/144Nd=0.5128- 0.5131，177Hf/176Hf=0.2829- 0.2831，206Pb/204Pb=18.62-20.67，207 Pb/204 Pb =15.54-15.72和208 Pb/204 Pb =38.27-40.34），样品分布在大洋中脊玄武岩（MORB）和白垩纪新西兰板内火山岩之间。西兰迪亚新生代火山作用的主要特征包括寿命长、分布不规则和缺乏板块运动方向的年龄进程，或任何系统的时间或空间地球化学变化。我们认为，这些特点可以最好地解释在岩石圈拆离的背景下，这导致上涌和熔化的软流圈地幔和部分被删除的岩石圈。我们认为，一个大规模的地震低速异常，从西南极洲下方延伸到西兰迪亚在深度> 600公里可能代表一个地球化学水库，自白垩纪以来一直存在，并已提供西兰迪亚下的上地幔与HIMU型羽状物质在整个新生代。此外，新生代板内火山作用的物质来源可能至少部分来自局部分离的西兰迪亚下部岩石圈的熔融。
In order to constrain better the distribution, age, geochemistry and origin of widespread Cenozoic intraplate volcanism on Zealandia, the New Zealand micro-continent, we report new40Ar/39Ar and geochemical (major and trace element and Sr–Nd–Hf–Pb isotope) data from offshore (Chatham Rise, Campbell and Challenger Plateaus) and onland (North, South, Auckland, Campbell, Chatham and Antipodes Islands of New Zealand) volcanism on Zealandia. The samples include nephelinite, basanite through phonolite, alkali basalt through trachyte/rhyolite, and minor tholeiite and basaltic andesite, all of which have ocean island basalt (OIB)-type trace element signatures and which range in age from 64.8 to 0.17Ma. Isotope ratios show a wide range in composition (87Sr/86Sr=0.7027–0.7050,143Nd/144Nd=0.5128–0.5131,177Hf/176Hf=0.2829–0.2831,206Pb/204Pb=18.62–20.67,207Pb/204Pb=15.54–15.72 and208Pb/204Pb=38.27–40.34) with samples plotting between mid-ocean-ridge basalts (MORB) and Cretaceous New Zealand intraplate volcanic rocks. Major characteristics of Zealandia's Cenozoic volcanism include longevity, irregular distribution and lack of age progressions in the direction of plate motion, or indeed any systematic temporal or spatial geochemical variations. We believe that these characteristics can be best explained in the context of lithospheric detachment, which causes upwelling and melting of the upper asthenospheric mantle and portions of the removed lithosphere. We propose that a large-scale seismic low-velocity anomaly, that stretches from beneath West Antarctica to Zealandia at a depth of >600km may represent a geochemical reservoir that has been in existence since the Cretaceous, and has been supplying the upper mantle beneath Zealandia with HIMU-type plume material throughout the Cenozoic. In addition, the sources of the Cenozoic intraplate volcanism may be at least partially derived through melting of locally detached Zealandia lower lithosphere.