Scholarlink

<p>Subduction-driven water (H<sub>2</sub>O) cycling plays a fundamental role in Earth’s geodynamics. However, the migration of H<sub>2</sub>O during continental slab exhumation is poorly constrained. This study investigates Triassic ultrahigh-pressure (UHP) garnet pyroxenites from the Dabie Orogen, China, to quantify H<sub>2</sub>O loss during hot exhumation (&gt;900 °C). By integrating petrology, Fourier transform infrared spectroscopy (FTIR), and phase equilibrium modeling, we reconstructed the pressure-temperature (<i>P-T</i>) evolution of UHP garnet pyroxenites. This reveals a clockwise trajectory from UHP eclogite-facies conditions (3.2–3.6 GPa, 960–1 040 °C) to retrograde high-pressure (HP) granulite-facies overprinting (1.7–2.0 GPa, 1 040–1 120 °C). The FTIR analyses reveal that primary H<sub>2</sub>O concentrations in mineral domains remain unaffected by later fluid influx or diffusion. Clinopyroxene cores (407 ppm–2 114 ppm; average of 1 135 ppm) and garnet inclusions (1 648 ppm–2 138 ppm; average of 1 893 ppm) retain UHP signatures, while clinopyroxene rims (65 ppm–928 ppm; average of 475 ppm) record HP signatures. Using a clinopyroxene-garnet partition coefficient (0.6) calibrated under UHP conditions, HP garnet H<sub>2</sub>O content is estimated at 108 ppm–1 546 ppm (average of 792 ppm). Phase equilibrium calculations indicate that both UHP eclogite-facies and HP granulite-facies mineral assemblages primarily consist of garnet and clinopyroxene and lack hydrous minerals. Thus, the total H<sub>2</sub>O loss from these phases during hot exhumation approximates that of the whole rock in this process. Data analysis reveals a considerable H<sub>2</sub>O loss during the initial stage of decompressional exhumation. The spatio-temporal distribution of the selected samples indicates that UHP metamorphic fluids likely flowed during early hot exhumation, with 1 m<sup>3</sup> of UHP eclogite potentially releasing ∼3.11 kg of H<sub>2</sub>O. Petrographic evidence (omphacite-hosted melt pseudomorphs: quartz + plagioclase ± albite) links H<sub>2</sub>O release to partial melting, which may enhance mechanical decoupling during exhumation. Our results reveal the migration of H<sub>2</sub>O during hot exhumation and advance the understanding of crust-mantle interactions in continental collisional orogens.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Water Migration during Deep Continental Crust Exhumation: Ultrahigh-Pressure Garnet Pyroxenite Constraints from the Dabie Orogen, China

  • 期刊论文

  • 发表日期：

    2026年3月13日

查看全文
  • Ling Wang,
  • Fujun Zhong,
  • Liangpeng Deng,
  • Hengcong Lei,
  • Xiao-Ying Gao

摘要

Subduction-driven water (H2O) cycling plays a fundamental role in Earth’s geodynamics. However, the migration of H2O during continental slab exhumation is poorly constrained. This study investigates Triassic ultrahigh-pressure (UHP) garnet pyroxenites from the Dabie Orogen, China, to quantify H2O loss during hot exhumation (>900 °C). By integrating petrology, Fourier transform infrared spectroscopy (FTIR), and phase equilibrium modeling, we reconstructed the pressure-temperature (P-T) evolution of UHP garnet pyroxenites. This reveals a clockwise trajectory from UHP eclogite-facies conditions (3.2–3.6 GPa, 960–1 040 °C) to retrograde high-pressure (HP) granulite-facies overprinting (1.7–2.0 GPa, 1 040–1 120 °C). The FTIR analyses reveal that primary H2O concentrations in mineral domains remain unaffected by later fluid influx or diffusion. Clinopyroxene cores (407 ppm–2 114 ppm; average of 1 135 ppm) and garnet inclusions (1 648 ppm–2 138 ppm; average of 1 893 ppm) retain UHP signatures, while clinopyroxene rims (65 ppm–928 ppm; average of 475 ppm) record HP signatures. Using a clinopyroxene-garnet partition coefficient (0.6) calibrated under UHP conditions, HP garnet H2O content is estimated at 108 ppm–1 546 ppm (average of 792 ppm). Phase equilibrium calculations indicate that both UHP eclogite-facies and HP granulite-facies mineral assemblages primarily consist of garnet and clinopyroxene and lack hydrous minerals. Thus, the total H2O loss from these phases during hot exhumation approximates that of the whole rock in this process. Data analysis reveals a considerable H2O loss during the initial stage of decompressional exhumation. The spatio-temporal distribution of the selected samples indicates that UHP metamorphic fluids likely flowed during early hot exhumation, with 1 m3 of UHP eclogite potentially releasing ∼3.11 kg of H2O. Petrographic evidence (omphacite-hosted melt pseudomorphs: quartz + plagioclase ± albite) links H2O release to partial melting, which may enhance mechanical decoupling during exhumation. Our results reveal the migration of H2O during hot exhumation and advance the understanding of crust-mantle interactions in continental collisional orogens.