Jurassic oceanic lithosphere beneath the southern Ontong Java Plateau: Evidence from xenoliths in alnoite, Malaita, Solomon Islands
Jurassic oceanic lithosphere beneath the southern Ontong Java Plateau: Evidence from xenoliths in alnoite, Malaita, Solomon Islands
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DOI：
10.1130/g21205.1
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发表时间：
2005-05-01
期刊：
影响因子：
5.8
通讯作者：
Mahoney, JJ
中科院分区：
文献类型：
--
作者：
Ishikawa, A;Nakamura, E;Mahoney, JJ
在Malaita岛Ontong爪哇高原南部的钠长花岗岩侵入地壳中，发现了少量交代的尖晶石二辉橄榄岩和辉长岩捕虏体，其Sm-Nd年龄为约1.54Ma。160 Ma和初始Nd值类似于+8。高原基底则相反。120 Ma，初始钕（Nd）在+3.7和+6.5之间。捕虏体似乎代表了正常的太平洋洋岩石圈（上地幔和下地壳），形成时间类似于4000万年。在高原之前，表明高原南部是在成熟海底上离轴侵位的。距离马莱塔最近的160 Ma海底距离北部> 1800 km，位于高原东北边缘，这意味着存在一个插入的大偏移断裂带或三联点。在高原下面存在着明显更古老的海洋岩石圈，这对高原的起源提出了限制。
The least metasomatized xenoliths of spinel lherzolite and gabbro recovered from ainoite intruding crust of the southern Ontong Java Plateau on the island of Malaita yield an Sm-Nd age of ca. 160 Ma and an initial epsilon(Nd) value of similar to+8. In contrast, the plateau basement is ca. 120 Ma with initial epsilon(Nd) between +3.7 and +6.5. The xenoliths appear to represent normal Pacific oceanic lithosphere (uppermost mantle and lower crust) formed similar to 40 m.y. before the plateau, indicating that the southern part of the plateau was emplaced off axis on mature seafloor. The closest 160 Ma seafloor to Malaita is > 1800 km to the north, off the northeastern margin of the plateau, implying the presence of either an intervening large-offset fracture zone or a triple junction. The presence of significantly older oceanic lithosphere beneath the plateau places restrictions on proposed origins for the plateau.