Origin and geochemical evolution of the Madeira-Tore Rise (eastern North Atlantic)
Origin and geochemical evolution of the Madeira-Tore Rise (eastern North Atlantic)
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马德拉-托雷海隆（北大西洋东部）的起源和地球化学演化
DOI：
10.1029/2005jb003931
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发表时间：
2006
影响因子：
--
通讯作者：
B. Berning
中科院分区：
文献类型：
--
作者：
J. Geldmacher;K. Hoernle;A. Klügel;P. Bogaard;F. Wombacher;B. Berning
马德拉-托尔海隆位于非洲西北海岸外约700公里处，是东大西洋的一个突出海岭。其起源和年龄是有争议的。本文介绍了沿着隆升不同地点采集的火山岩的主量元素、微量元素、Sr、Nd、Pb、Hf同位素和40 Ar/39 Ar年龄测定结果。此外，还介绍了大西洋中部大流星海山岩石样品的同位素组成。新的放射性和古生物学约束年龄确定了两个主要的火山活动时期：第一个是上升的底部（大约80至>95 Ma），第二个是上升的海山（0.5至16 Ma）。中白垩世加那利热点与中大西洋扩张中心的相互作用形成了大西洋扩张中心以西的Madeira-Tore海隆和J-Anomaly海岭的深部基底。年龄和地球化学数据和板块构造重建表明，然而，恢复晚白垩世火山岩代表晚期火山活动的时候，马德拉-托尔隆起仍然接近加那利热点。在远离加那利热点的影响很久之后，马德拉-托雷隆起被晚新生代火山活动所覆盖。中新世至更新世火山活动在上升的北方端可以最好地解释为减压地幔融化下的亚速尔-直布罗陀断裂带（非洲-欧亚板块边界）的伸展部分。这些火山岩的地球化学成分表明，岩浆内的富集物质或来自熔融富集的物质底板在岩石圈的底部，可能来自白垩纪加那利羽的富集物质的污染。另外，这些晚新生代火山岩可能来自上地幔中富集的辉石岩/榴辉岩物质的减压熔融。马德拉-托尔隆起南端的同位素耗尽的上新世至更新世火山活动可能与附近的马德拉热点有关。
The Madeira-Tore Rise, located ∼700 km off the NW African coast, forms a prominent ridge in the east Atlantic. The age and origin of the rise are controversial. This study presents major and trace element, Sr, Nd, Pb, Hf isotope and 40Ar/39Ar age determinations from volcanic rocks dredged from different sites along the rise. In addition, isotopic compositions of rock samples from Great Meteor Seamount in the central Atlantic are presented. The new radiometric and paleontologically constrained ages identify two major episodes of volcanism: The first is the base of the rise (circa 80 to >95 Ma) and the second is seamounts on the rise (0.5–16 Ma). It is proposed that interaction of the Canary hot spot with the Mid-Atlantic spreading center formed the deep basement of the Madeira-Tore Rise and the J-Anomaly Ridge west of the Atlantic spreading center in the Mid-Cretaceous. Age and geochemical data and plate tectonic reconstructions suggest, however, that the recovered Late Cretaceous volcanic rocks represent late stage volcanism from the time when the Madeira-Tore Rise was still close to the Canary hot spot. Long after moving away from the influence of the Canary hot spot, the Madeira-Tore Rise was overprinted by late Cenozoic volcanism. Miocene to Pleistocene volcanism at the northern end of the rise can be best explained by decompression mantle melting beneath extensional sectors of the Azores-Gibraltar Fracture Zone (African-Eurasian plate boundary). The geochemical compositions of these volcanic rocks suggest that the magmas were variably contaminated by enriched material within or derived by melting of enriched material underplated at the base of the lithosphere, possibly originating from the Cretaceous Canary plume. Alternatively, these late Cenozoic volcanic rocks may have derived from decompression melting of enriched pyroxenitic/eclogitic material in the upper mantle. Isotopically more depleted Pliocene to Pleistocene volcanism at the southern end of the Madeira-Tore Rise may be related to the nearby Madeira hot spot.