Boron isotope systematics of slab fluids as inferred from a serpentine seamount, Mariana forearc
Boron isotope systematics of slab fluids as inferred from a serpentine seamount, Mariana forearc
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DOI：
10.1016/s0012-821x(01)00286-2
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发表时间：
2001-05-15
影响因子：
5.3
通讯作者：
Tera, F
中科院分区：
文献类型：
--
作者：
Benton, LD;Ryan, JG;Tera, F
蛇纹岩：从马里亚纳弧前锥形海山喷发的碎屑和泥浆，相对于地幔价值，显示出大量的B(B)和B-11(B-11增量高达+15ppm)。这些升高的B同位素特征是与上升通过海山的富含B的孔隙流体进行化学交换的结果。如果西太平洋伊祖弧和千岛弧区的岩浆套向浅层延伸(约25公里)，则它们在锥形海山与推断的板岩衍生流体的增量B-11相交(+13‰)，则B-11增量随板片深度递减。富B流体与高增量B-11和贫B地幔与低增量B-11的简单混合不足以解释组合的弧前，这是数据集。俯冲相关岩石的B同位素系统学结果表明，从下行板片演化出来的流体比板片物质更富含B-11。在深部板块上方喷发的熔岩中逐渐降低的B-11三角洲反映了从板块中逐渐消耗B-11和逐渐增加来自地幔的B的输入，这表明板块从最浅的水平向大于200公里的深度释放了富含B-11的流体。(C)2001 Elsevier Science B.V.保留所有权利。
Serpentinite: clasts and muds erupted from Conical Seamount, Mariana forearc, show substantial enrichment in boron (B) and B-11 (delta B-11 up to +15 parts per thousand) relative to mantle values. These elevated B isotope signatures result from chemical exchange with B-rich pore fluids that are upwelling through the seamount. If the trends of decreasing delta B-11 with slab depth shown by cross-are magmatic suites in the Izu and Kurile arcs of the western Pacific are extended to shallow depths (similar to 25 km), they intersect the inferred delta B-11 of the slab-derived fluids (+13 parts per thousand) at Conical Seamount. Simple mixtures of a B-rich fluid with a high delta B-11 and B-poor mantle with a low delta B-11 are insufficient to explain the combined forearc and are data sets. The B isotope systematics of subduction-related rocks thus indicate that the fluids evolved from downgoing slabs are more enriched in B-11 than the slab materials from which they originate. Progressively lower delta B-11 in are lavas erupted above deep slabs reflects both the progressive depletion of B-11 from the slab and progressively greater inputs of mantle-derived B. This suggests that the slab releases B-11-enriched fluids from the shallowest levels to depths greater than 200 km. (C) 2001 Elsevier Science B.V. All rights reserved.