Plume-lithosphere interactions in the ocean basins: constraints from the source mineralogy
Plume-lithosphere interactions in the ocean basins: constraints from the source mineralogy
复制标题
DOI：
10.1016/s0012-821x(97)00089-7
复制
发表时间：
1997-08
影响因子：
5.3
通讯作者：
C. Class;S. Goldstein
中科院分区：
文献类型：
--
作者：
C. Class;S. Goldstein
印度洋大科摩罗拉格里尔火山以及夏威夷欧胡岛檀香山火山系列的近原生碱性熔岩的微量元素关系表明，它们的来源含有角闪石和/或金云母。每种矿物的少量含量（La Grille 源头中含有 2% 角闪石，以及檀香山火山源头中含有 0.5% 金云母和一些角闪石），两个系列的部分熔融绝对程度范围为 ∼ 1% 到 ∼ 5%，与观察到的微量元素变化一致。角闪石和金云母在对流上地幔或深部地幔热羽流的温度下不稳定；然而，它们在大洋岩石圈地幔的压力-温度条件下是稳定的。因此，火山岩浆源区存在角闪石和/或金云母是岩石圈熔融的有力证据，我们得出结论，La Grille系列和檀香山系列是由大洋岩石圈地幔熔融形成的。两个系列的源区中角闪石±金云母的鉴定表明，流体或富含挥发分的熔体的交代作用发生在熔化之前。水相的存在导致岩石圈地幔的固相线温度较低，这可以通过热羽流的传导加热来达到。 La Grille 和檀香山系列的同位素比显示出有限的成分范围，并代表每个岛屿的成分最终成员。盾状熔岩中较大的同位素变化，以大科摩罗的同期卡塔拉火山和瓦胡岛较老的库劳系列为代表，反映了上升的热羽流与岩石圈地幔的相互作用，而不是深层地幔羽流来源的异质性或上升羽流中地幔物质的夹带。文献 OsSr 同位素比共变限制了地幔柱-岩石圈相互作用的过程，该相互作用是通过交代化的海洋岩石圈地幔的地幔柱熔体和低度熔体的混合而发生的。岩石圈地幔特征的表征使得深部地幔羽流成分的同位素组成得以确定，混合关系表明卡塔拉和库劳羽流端元具有几乎一致的同位素组成。根据独立论证，赫德岛和复活节岛的同位素变化已被证明是具有不同同位素组成的深部羽流源与岩石圈或浅层软流圈地幔混合的结果。这些案例研究在一定程度上代表了大洋岛屿火山活动，表明与大洋岩石圈地幔的相互作用在地幔柱岩浆形成盾构阶段喷发的熔岩成分中起着重要作用，并且深部地幔柱源的同位素组成在熔融采样的规模上几乎是均匀的。
Trace element relationships of near-primary alkalic lavas from La Grille volcano, Grande Comore, in the Indian Ocean, as well as those of the Honolulu volcanic series, Oahu, Hawaii, show that their sources contain amphibole and/or phlogopite. Small amounts of each mineral (2% amphibole in the source of La Grille and 0.5% phlogopite plus some amphibole in the source of the Honolulu volcanics) and a range of absolute degrees of partial melting from ∼ 1 to ∼ 5% for both series are consistent with the observed trace element variation. Amphibole and phlogopite are not stable at the temperatures of convecting upper mantle or upwelling thermal plumes from the deep mantle; however, they are stable at pressure-temperature conditions of the oceanic lithospheric mantle. Therefore, the presence of amphibole and/or phlogopite in the magma source region of volcanics is strong evidence for lithospheric melting, and we conclude that the La Grille and the Honolulu series formed by melting of the oceanic lithospheric mantle. The identification of amphibole ± phlogopite in the source region of both series implies that the metasomatism by fluids or volatile-rich melts occurred prior to melting. The presence of hydrous phases results in a lower solidus temperature of the lithospheric mantle, which can be reached by conductive heating by the thermal plumes. Isotope ratios of the La Grille and the Honolulu series display a restricted range in composition and represent compositional end-members for each island. Larger isotopic variations in shield lavas, represented by the contemporaneous Karthala volcano on Grande Comore and the older Koolau series on Oahu, reflect interaction of the upwelling thermal plumes with the lithospheric mantle rather than the heterogeneity of deep-seated mantle plume sources or entrainment of mantle material in the rising plume. Literature OsSr isotope ratio covariations constrain the process of plume-lithosphere interaction as occurring through mixing of plume melts and low-degree melts from the metasomatized oceanic lithospheric mantle. The characterization of the lithospheric mantle signature allows the isotopic composition of the deep mantle plume components to be identified, and mixing relationships show that the Karthala and Koolau plume end-members have nearly uniform isotopic compositions. Based on independent arguments, isotopic variations on Heard and Easter islands have been shown to be a result of mixing between deep plume sources having distinct isotopic compositions with lithosphere or shallow asthenospheric mantle. To the extent that these case studies are representative of oceanic island volcanism, they indicate that interaction with oceanic lithospheric mantle plays an important role in the compositions of lavas erupted during the shield-building stage of plume magmatism, and that isotopic compositions of deep mantle plume sources are nearly uniform on the scale that they are sampled by melting.