Scholarlink

<p>Phase equilibrium modeling using internally consistent thermodynamic dataset and associated activity-composition (<i>a-x</i>) models are very helpful for quantifying <i>P</i>-<i>T</i> evolution for eclogite, which is the basis for deciphering the geodynamic processes in subduction zones. In this study, we apply different versions of datasets (ds55 and ds62) and associated <i>a</i>-<i>x</i> relations to a well-established LT-HP eclogite at Huwan in the classic western Dabie orogen to constrain its <i>P</i>-<i>T</i> evolution. The eclogite comprises garnet + omphacite + amphibole + white mica + epidote + quartz + chlorite + rutile/ilmenite/sphene. Garnet porphyroblasts show mono-variation in the end members (spessartine from 17 mol% to 0, pyrope from 2 mol% to 18 mol%, almandine from 47 mol% to 64 mol% and grossular from 35 mol% to 18 mol%) from core to rim. Phase diagrams combined with compositional isopleth thermobarometry show that dataset ds62 and associated <i>a</i>-<i>x</i> relations yield <i>P</i><sub>max</sub> of ∼33 kbar at ∼560 °C, conflicting with our petrological observations and previous studies. On the other hand, phase equilibrium modeling using dataset ds62 and a revised symmetric garnet <i>a</i>-<i>x</i> model irrespective of Fe<sup>3+</sup> (O) gives <i>P</i><sub>max</sub> of ∼27 kbar at ∼560 °C, consistent with the results using dataset ds55 and associated <i>a</i>-<i>x</i> relations. Therefore, we recommend a symmetric model for garnet involving py, alm, gr and spss, without Fe<sup>3+</sup> components, instead of the asymmetric garnet <i>a</i>-<i>x</i> relations involving py, alm, gr, spss and kho by White et al. (2014), for calculating phase diagrams for LT-(U)HP eclogite when using dataset ds62. In this study, the defined <i>P</i>-<i>T</i> path is characterized by a segment of the prograde evolution showing a first moderate slope, followed by gentle then steep slopes, representing the thermal structure evolution recorded by slab surface during continental subduction. Our work combined with previous studies conclude that in western Dabie, the Huwan HP eclogite belt to the north and the Hong’an HP eclogite belt to the south belong to the same HP slice overlying the Xinxian UHP slice.</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

Petrology of Eclogite at Huwan, Western Dabie and Implications for Phase Equilibrium Modeling on LT-HP/UHP Eclogite

  • 期刊论文

  • 发表日期：

    2025年6月17日

查看全文
  • Bin Xia,
  • Ying Cui,
  • Yunfeng Shang,
  • Jingtao Shi

摘要

Phase equilibrium modeling using internally consistent thermodynamic dataset and associated activity-composition (a-x) models are very helpful for quantifying P-T evolution for eclogite, which is the basis for deciphering the geodynamic processes in subduction zones. In this study, we apply different versions of datasets (ds55 and ds62) and associated a-x relations to a well-established LT-HP eclogite at Huwan in the classic western Dabie orogen to constrain its P-T evolution. The eclogite comprises garnet + omphacite + amphibole + white mica + epidote + quartz + chlorite + rutile/ilmenite/sphene. Garnet porphyroblasts show mono-variation in the end members (spessartine from 17 mol% to 0, pyrope from 2 mol% to 18 mol%, almandine from 47 mol% to 64 mol% and grossular from 35 mol% to 18 mol%) from core to rim. Phase diagrams combined with compositional isopleth thermobarometry show that dataset ds62 and associated a-x relations yield Pmax of ∼33 kbar at ∼560 °C, conflicting with our petrological observations and previous studies. On the other hand, phase equilibrium modeling using dataset ds62 and a revised symmetric garnet a-x model irrespective of Fe3+ (O) gives Pmax of ∼27 kbar at ∼560 °C, consistent with the results using dataset ds55 and associated a-x relations. Therefore, we recommend a symmetric model for garnet involving py, alm, gr and spss, without Fe3+ components, instead of the asymmetric garnet a-x relations involving py, alm, gr, spss and kho by White et al. (2014), for calculating phase diagrams for LT-(U)HP eclogite when using dataset ds62. In this study, the defined P-T path is characterized by a segment of the prograde evolution showing a first moderate slope, followed by gentle then steep slopes, representing the thermal structure evolution recorded by slab surface during continental subduction. Our work combined with previous studies conclude that in western Dabie, the Huwan HP eclogite belt to the north and the Hong’an HP eclogite belt to the south belong to the same HP slice overlying the Xinxian UHP slice.