Flood Basalt from Mont Tourmente in the Central Kerguelen Archipelago: the Change from Transitional to Alkalic Basalt at ∼25 Ma
Flood Basalt from Mont Tourmente in the Central Kerguelen Archipelago: the Change from Transitional to Alkalic Basalt at ∼25 Ma
复制标题
凯尔盖朗中部群岛 Mont Tourmente 的溢流玄武岩：约 25 Ma 从过渡性玄武岩转变为碱性玄武岩
DOI：
10.1093/petrology/43.7.1367
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发表时间：
2002
影响因子：
3.9
通讯作者：
A. Giret
中科院分区：
文献类型：
--
作者：
F. Frey;K. Nicolaysen;B. Kubit;D. Weis;A. Giret
构造在南印度洋凯尔盖朗高原上的新生代凯尔盖朗群岛的表面主要是泛滥玄武岩。为了了解凯尔盖朗地幔柱的新生代历史，正在通过研究几个地点玄武岩流的地层剖面来确定这一泛滥玄武岩省的年龄和地球化学特征。对群岛西北部、中北部、东部和东南部的剖面进行了研究。在这里，我们报告的结果597米的火山熔岩从蒙特图尔门特高原中央，该地区的群岛，还没有被详细研究。Mont Tourmente熔岩的范围从约26 Ma的过渡玄武岩为主的下80%的部分到约25.3 Ma的碱性玄武岩为主的部分的上部。这种变化的时间从过渡到碱性火山作用的蒙特图尔门特部分是一致的，所定义的老的~28 - 29马过渡玄武岩在北部和~25马碱性熔岩在东部爆发。玄武岩成分的这种变化可能与群岛远离羽流的迁移或超过500万年的洪水玄武岩火山作用增加岩石圈厚度有关。碱性和过渡型图尔门特熔岩的Sr、Nd和Pb同位素比值接近均一。与东段的熔岩相比，它们具有较低的47 Sr/46 Sr和较高的112 Nd/111 Nd，这被认为是凯尔盖朗地幔柱的特征。因此，图尔门特山同位素数据可能反映了羽流内的异质性或与高87 Sr/86 Sr和低112 Nd/111 Nd羽流混合的贫化成分的恒定比例。与许多白垩纪Kerguelen高原熔岩不同，没有证据表明新生代Kerguelen群岛熔岩的微量元素丰度或Sr和Nd同位素比值受到大陆岩石圈的影响。
The surface of the Cenozoic Kerguelen Archipelago, constructed on the Kerguelen Plateau in the southern Indian Ocean, is dominantly flood basalt. With the objective of understanding the Cenozoic history of the Kerguelen mantle plume, the age and geochemical characteristics of this flood basalt province are being determined by studying stratigraphic sections of basalt flows at several locations. Sections from the NW, north central, east and SE parts of the archipelago have been studied. Here we report results for a 597 m succession of lavas from Mont Tourmente from the Plateau Central, a region of the archipelago that has not been studied in detail. Mont Tourmente lavas range from ~26 Ma dominantly transitional basalts in the lower 80% of the section to ~25.3 Ma dominantly alkalic basalts in the upper part of the section. The timing of this change from transitional to alkalic volcanism within the Mont Tourmente section is consistent with that defined by the older ~28 29 Ma transitional basalts in the north and the ~25 Ma alkalic lavas erupted in the east. This change in basalt composition may be related to migration of the archipelago away from the plume or to increasing lithosphere thickness over the ~5 Myr of flood basalt volcanism. The alkalic and transitional Tourmente lavas are nearly homogeneous in isotopic ratios of Sr, Nd and Pb. They have lower 47Sr/46Sr and higher 112Nd/111Nd compared with lavas from the eastern sections, which have been proposed to be characteristic of the Kerguelen plume. Consequently, the Mont Tourmente isotopic data may reflect heterogeneity within the plume or a constant proportion of a depleted component mixed with the high 87Sr/86Sr and low 112Nd/111Nd plume. In contrast to many of the Cretaceous Kerguelen Plateau lavas, there is no evidence in trace element abundances or Sr and Nd isotopic ratios that the Cenozoic Kerguelen Archipelago lavas were influenced by continental lithosphere.