期刊
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
卷 3, 期 -, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2001GC000190
关键词
Central Pacific; Line Islands; Mesozoic volcanism; geochronology; igneous petrology; trace elements; 1035 geochemistry : geochronology; 3640 mineralogy and petrology : igneous petrology; 3670 mineralogy and petrology : minor and trace element composition; 9609 information related to geologic time : mesozoic
[1] New 40Ar/39Ar ages of mineral separates and whole rock samples from nine volcanic edifices in the northern Line Islands region, between latitudes 20degreesN and 6degreesN, are incompatible with single or multiple hot spot models. Instead, two major episodes of volcanism, each lasting similar to5 Ma and separated by similar to8 Ma, occurred synchronously over long distances, not just along the main chain but also at nonaligned edifices. Volcanism during the older episode (81-86 Ma) extended over a distance of at least 1200 km along the eastern part of the complex seamount chain. Volcanism during the younger episode (68-73 Ma) was concentrated in the western part of the chain and may have extended over a distance of >4000 km. Chemical analyses of 68 samples represent a compositionally diverse suite, including tholeiitic, transitional, and alkalic basalt, strongly alkalic basanite and nephelinite, and alkalic differentiates ranging from hawaiite to trachyte. The most diverse assemblage of rocks was recovered from a cross-trending seamount chain south of Johnston Atoll. Although compositions of rocks from the two volcanic episodes overlap, compositions from the younger episode generally are more alkalic and include a larger proportion of highly differentiated compositions. None of the samples from the older episode, but many from the younger one, contain hydrous mineral phases such as amphibole and biotite. Extensive coeval volcanism along major segments of the chain is compatible with decompressional melting of heterogeneous mantle due to diffuse lithospheric extension along pre-existing zones of weakness. Episodes of volcanism are probably related to broad upwarping of the Superswell region in the eastern South Pacific, where these lavas originated.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据