Depleted mantle wedge and sediment fingerprint in unusual basalts from the Manihiki Plateau, central Pacific Ocean
Depleted mantle wedge and sediment fingerprint in unusual basalts from the Manihiki Plateau, central Pacific Ocean
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DOI：
10.1130/g23741a.1
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发表时间：
2007-07-01
期刊：
影响因子：
5.8
通讯作者：
Nakanishi, Masao
中科院分区：
文献类型：
--
作者：
Ingle, Stephanie;Mahoney, John J.;Nakanishi, Masao
早白垩世期间，太平洋上形成了许多大型火成岩省，但人们对它们的起源和关系知之甚少。我们提出了新的地质年代学和地球化学数据的岩石从Manihiki高原和比较这些结果与其他白垩纪太平洋高原。一个疏浚Manihiki玄武岩的40 Ar-39 Ar年龄为117.9 +/- 3.5 Ma（2 sigma），基本上是同时代的Ontong爪哇高原类似的2500公里以西，和可能相关的Hikurangi高原类似的3000公里以南。钻探的Manihiki熔岩是具有不相容微量元素丰度的拉铁陨石，与Ontong Java玄武岩相似。这些熔岩可能是在高原形成的主要喷发阶段高度部分熔融的结果。有两种类型的疏浚熔岩从危险群岛槽，平分高原。第一种是碱性熔岩，富含轻稀土和亲石元素;这些熔岩可能代表晚期活动，因为一个样品产生的40 Ar-39 Ar年龄为99.5 +/- 0.7 Ma。第二类由拉斑玄武岩与U形不相容的微量元素模式和异常低丰度的几个元素，这些玄武岩记录了地幔成分没有以前观察到的Manihiki，Ontong Java，或Hikurangi熔岩。它们的微量元素特征可能是由于与少量火山碎屑沉积物混合的亏损地幔楔物质的广泛熔融造成的。我们不知道其他地方有类似的玄武岩。
Numerous large igneous provinces formed in the Pacific Ocean during Early Cretaceous time, but their origins and relations are poorly understood. We present new geochronological and geochemical data on rocks from the Manihiki Plateau and compare these results to those for other Cretaceous Pacific plateaus. A dredged Manihiki basalt gives an 40Ar-39Ar age of 117.9 +/- 3.5 Ma (2 sigma), essentially contemporaneous with the Ontong Java Plateau similar to 2500 km to the west, and the possibly related Hikurangi Plateau similar to 3000 km to the south. Drilled Manihiki lavas are tholefitic with incompatible trace element abundances similar to those of Ontong Java basalts. These lavas may result from high degrees of partial melting during the main eruptive phase of plateau formation. There are two categories of dredged lavas from the Danger Islands Troughs, which bisect the plateau. The first is alkalic lavas having strong enrichments in light rare earth and largeion lithophile elements; these lavas may represent late-stage activity, as one sample yields an 40Ar-39Ar age of 99.5 +/- 0.7 Ma. The second category consists of tholefitic basalts with U-shaped incompatible trace element patterns and unusually low abundances of several elements; these basalts record a mantle component not previously observed in Manihiki, Ontong Java, or Hikurangi lavas. Their trace element characteristics may result from extensive melting of depleted mantle wedge material mixed with small amounts of volcaniclastic sediment. We are unaware of comparable basalts elsewhere.