Fluid flow and water–rock interaction across the active Nankai Trough subduction zone forearc revealed by boron isotope geochemistry
Fluid flow and water–rock interaction across the active Nankai Trough subduction zone forearc revealed by boron isotope geochemistry
复制标题
硼同位素地球化学揭示的活跃南海海槽俯冲带弧前的流体流动和水岩相互作用
DOI：
10.1016/j.gca.2016.08.014
复制
发表时间：
2016
影响因子：
5
通讯作者：
Shinjo
中科院分区：
文献类型：
--
作者：
Hüpers;Kasemann;Meixner;Shinjo
俯冲带沉积物的成分变化、脱水反应和流体流动影响着俯冲带的地震成因和弧岩浆作用。为了确定南海海槽西部俯冲带（日本西南部）的流体流动和水-岩相互作用过程，我们分析了四次综合大洋钻探计划（IODP）考察期间在俯冲带弧前从海底以下10922 m深处取样的孔隙流体的硼浓度和硼同位素组成（δ 11 B）。通过取心取样的主要构造体制包括：（1）沉积输入，（2）前缘冲断带，（3）巨型活动断裂带，（4）弧前盆地。从质量平衡考虑，我们发现，通过灰分蚀变和有机质降解介导的B从固相解吸的硼（B）消耗，导致B浓度随着深度下降到120 μM而净减少，δ 11 B值在120 ‰ +20‰和+49‰之间变化。由于温度升高和大洋地壳的蚀变，可交换的B从固相中更有效地活化，从而影响了进入大洋板块的沉积物中的间隙水，而大洋地壳是10 B的汇。在巨型活动断裂带的尖端，高B浓度和B同位素组成表明，俯冲粗粒斜坡沉积物提供了一个通道，流体的上部（<2公里）增生棱镜。下行板块俯冲带的粉砂层有利于流体从相当于60-150 °C温度范围的深度向海方向逃逸。在这两个位置，δ 11 B特征在上倾迁移过程中通过再吸附而演变。质量平衡的考虑表明，较浅的流体源深度相比，孔隙流体采样以前附近的滑脱带沿着南开边缘的中部。
Compositional changes, dehydration reactions and fluid flow in subducted sediments influence seismogenesis and arc magmatism in subduction zones. To identify fluid flow and water–rock interaction processes in the western Nankai Trough subduction zone (SW Japan) we analyzed boron concentration and boron isotope composition (δ11B) of pore fluids sampled across the subduction zone forearc from depths of up to ∼922 m below seafloor during four Integrated Ocean Drilling Program (IODP) Expeditions. The major structural regimes that were sampled by coring include: (1) sedimentary inputs, (2) the frontal thrust zone, (3) the megasplay fault zone, and (4) the forearc basin. From mass balance consideration we find that consumption of boron (B) by ash alteration and desorption of B from the solid phase, mediated by organic matter degradation, produces a net decrease in B concentrations with depth down to ∼120 μM and variable δ11B values in the range of ∼+20‰ and +49‰. Interstitial water in sediments on the incoming oceanic plate are influenced by more efficient mobilization of exchangeable B from the solid phase due to higher temperatures and alteration of the oceanic crust that acts as a sink for10B. At the tip of the megasplay fault zone, elevated B concentration and B isotopic composition suggest that underthrust coarse-grained slope sediments provide a pathway for fluids out of the upper (<2 km) accretionary prism. Silt and sand layers in the underthrust section of the downgoing plate favor fluid escape in seaward direction from depths equivalent to the temperature range of 60–150 °C. At both locations the δ11B signature evolves during updip migration through re-adsorption. Mass balance considerations suggest a shallower fluid source depth compared to pore fluids sampled previously near the décollement zone along the central portion of the Nankai margin.
登录
查看更多内容
海洋钻探计划会议记录，131 份初步报告
影响因子：
2.9
作者：
A. Taira;I. Hill;J. Firth
通讯作者：
J. Firth
影响因子：
3.5
作者：
Huepers, A.;Kopf, A. J.
通讯作者：
Kopf, A. J.
影响因子：
5.2
作者：
A. Spivack;M. Kastner;B. Ransom
通讯作者：
A. Spivack;M. Kastner;B. Ransom
希腊萨摩斯岛卡洛瓦西盆地富硼地下水的地球化学
影响因子：
--
作者：
M. Stamatakis;E. Tziritis;N. Evelpidou
通讯作者：
N. Evelpidou
影响因子：
3.7
作者：
G. Moore;A. Taira;A. Klaus;L. Becker;B. Boeckel;B. Cragg;A. Dean;C. Fergusson;P. Henry;S. Hirano;T. Hisamitsu;S. Hunze;M. Kastner;A. Maltman;J. Morgan;Y. Murakami;D. Saffer;M. Sánchez-Gómez;E. Screaton;David C. Smith;A. Spivack;J. Steurer;H. Tobin;K. Ujiie;M. Underwood;M. Wilson
通讯作者：
G. Moore;A. Taira;A. Klaus;L. Becker;B. Boeckel;B. Cragg;A. Dean;C. Fergusson;P. Henry;S. Hirano;T. Hisamitsu;S. Hunze;M. Kastner;A. Maltman;J. Morgan;Y. Murakami;D. Saffer;M. Sánchez-Gómez;E. Screaton;David C. Smith;A. Spivack;J. Steurer;H. Tobin;K. Ujiie;M. Underwood;M. Wilson