Fluid-rock interactions at shallow depths in subduction zone: Insights from trace elements and B isotopic composition of metabasites from the Mariana forearc
Fluid-rock interactions at shallow depths in subduction zone: Insights from trace elements and B isotopic composition of metabasites from the Mariana forearc
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俯冲带浅层流体-岩石相互作用：马里亚纳弧前变碱岩微量元素和 B 同位素组成的见解
DOI：
10.1016/j.lithos.2022.106730
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发表时间：
2022-08
期刊：
影响因子：
3.5
通讯作者：
Jianghong Deng
中科院分区：
文献类型：
--
作者：
Haiyang Liu;Ying-Yu Xue;Tinggen Yang;Xin Jin;Chen-Feng You;Chiou-Ting Lin;Wei-Dong Sun;Jianghong Deng
为了揭示板状流体的空间变化和追踪浅俯冲带的原位脱水，我们研究了从Fantangisna和Asphalt Tesoru蛇纹岩泥火山中回收的、起源于马里亚纳俯冲带前弧浅俯冲通道的变基性岩的岩相学、矿物化学和全岩B同位素。变质基性岩中的蚀变矿物组合表明，分别在Fantangisna海山和Asphalt Tesoru海山下发生了沸石-叶蜡石-绿柱石相变质作用和硬硅钙石蓝片岩相变质作用。流体移动的元件（例如，B、As、Sb、Pb）赋存于浅变质层状硅酸盐矿物中（如，.因此，在浅俯冲过程中（<18 km），确定了俯冲洋壳中B的浓度。所研究的变基性岩的B浓度（16.7 ~ 43.9 μg/g）和δ 11 B值（− 5.0 ~+3.2‰）均显著高于新鲜的正常洋中脊玄武岩（N-MOR B）和洋岛玄武岩（OIB），一般与最上部的蚀变大洋板片相当。值得注意的是，从马里亚纳前弧中发现的变基性岩的δ 11 B值随着从凡唐吉斯纳海沟（62公里）经阿斯维特特索鲁（72公里）到南查莫罗（78公里）海山到海沟的距离增加而呈下降趋势。这一趋势与Rayleigh脱水模型相结合，表明在俯冲变质脱水过程中，俯冲板片释放了富含11B的水溶液。估计的B同位素组成。在弧岩浆成因深度释放的板状流体一般可比的马里亚纳弧熔岩。然而，在浅深度的俯冲沉积物脱水释放的流体的特点是较低的δ 11 B值比流体从板片释放的岩浆成因的深度下的岛屿。弧。因此，水化弧前地幔的再循环是解释马里亚纳弧熔岩高δ11B值的必要条件。而马里亚纳弧熔岩B同位素组成的变化则受沉积物/AOC比值的不同控制
To reveal the spatial variations of slab-derived fluids and to trace the in-situ dehydration in the shallow subduction zone, we investigated the petrography, mineral chemistry, and whole-rock B isotopes of metabasites that.were recovered from the Fantangisna ˜ and Asùt Tesoru serpentinite mud volcanoes and originated from the.shallow subduction channel at the forearc of the Mariana subduction zone. The alteration mineral assemblages in.the investigated metabasites suggest zeolite- to prehnite-pumpellyite-facies metamorphism and lawsoniteblueschist facies metamorphism beneath Fantangisna ˜ and Asùt Tesoru seamounts, respectively. The fluid mobile elements (e.g., B, As, Sb, Pb) are preserved in the low grade metamorphic phyllosilicate minerals (e.g.,.glauconite, pumpellyite, celadonite), thus fixing the B concentrations of the subducted oceanic crust during.shallow subduction (<18 km). Both B concentrations (16.7 to 43.9 μg/g) and δ11B values (− 5.0 to +3.2‰) of the.investigated metabasites are significantly higher than fresh normal mid-ocean ridge basalts (N-MORB) and ocean.island basalts (OIB), and are generally comparable to the uppermost altered oceanic slab. Notably, the recovered.metabasites from the Mariana forearc exhibit a decreasing trend in δ11B values with increasing distance to the.trench from Fantangisna ˜ (62 km) through Asùt Tesoru (72 km) to South Chamorro (78 km) Seamounts. This.trend together with Rayleigh dehydration modeling indicate that the 11B-enriched aqueous fluids were released.from the subducting slab during prograde metamorphic dehydration. The estimated B isotopic compositions of.the slab-derived fluids released at arc magma genesis depths are generally comparable to that of the Mariana arc.lavas. However, the fluids released by dehydration of subducted sediments at shallow depths should be characterized by lower δ11B values than fluids released from the slab at depths of magma genesis beneath the island.arc. Then, the recycling of the hydrated forearc mantle is necessary to explain the high δ11B values of the Mariana.arc lavas. While, the variable B isotope compositions of Mariana arc lavas should be controlled by the different.ratios of sediment/AOC ratios
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影响因子：
3.7
作者：
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