Stable isotope compositions and water contents of boninite series volcanic rocks from Chichi-jima, Bonin Islands, Japan
Stable isotope compositions and water contents of boninite series volcanic rocks from Chichi-jima, Bonin Islands, Japan
复制标题
日本小笠原群岛父岛栉长岩系列火山岩的稳定同位素组成和含水量
DOI：
10.1016/0012-821x(87)90108-7
复制
发表时间：
1987
影响因子：
5.3
通讯作者：
J. R. O'neil
中科院分区：
文献类型：
--
作者：
P. Dobson;J. R. O'neil
对小笠原诸岛七日岛玻安岩系火山岩的稳定同位素组成和含水量的测定证实，该火山岩中含有大量（1.6- 2.4wt.%）在这些不寻常的岩浆中存在着原始水。分异过程中0.6‰的18 O富集是由亏损18 O的镁铁质相结晶作用造成的。硅质玻璃具有较高的δ 18 O值和较低的δ D值，表明它们受到低温蚀变和水化过程的改性。另一方面，自始新世以来，镁铁质玻璃的大部分保留了它们的主要同位素特征。玻安岩玻璃的原始δ D值为−53，高于MORB，表明水来自俯冲洋壳岩石圈。
Measurements of stable isotope compositions and water contents of boninite series volcanic rocks from the island of Chichi-jima, Bonin Islands, Japan, confirm that a large amount (1.6–2.4 wt.%) of primary water was present in these unusual magmas. An enrichment of 0.6‰ in18O during differentiation is explained by crystallization of18O-depleted mafic phases. Silicic glasses have elevatedδ18Ovalues and relatively lowδDvalues indicating that they were modified by low-temperature alteration and hydration processes. Mafic glasses, on the other hand, have for the most part retained their primary isotopic signatures since Eocene time. PrimaryδDvalues of −53 for boninite glasses are higher than those of MORB and suggest that the water was derived from subducted oceanic lithosphere.