Multistage CO2 sequestration in the subduction zone: Insights from exhumed carbonated serpentinites, SW Tianshan UHP belt, China
Multistage CO2 sequestration in the subduction zone: Insights from exhumed carbonated serpentinites, SW Tianshan UHP belt, China
复制标题
俯冲带多阶段二氧化碳封存：来自中国西南天山超高压带挖掘出的碳化蛇纹岩的见解
DOI：
10.1016/j.gca.2019.11.025
复制
发表时间：
2020-02
影响因子：
5
通讯作者：
Han Hu
中科院分区：
文献类型：
--
作者：
Peng Weigang;Lifei Zhang;Manuel D. Menzel;Alberto Vitale Brovarone;Simone Tumiati;Tingting Shen;Han Hu
气候受到碳酸盐-硅酸盐循环的调节，其中碳板脱气到深层流体中和火山将二氧化碳脱气到大气中是重要部分。然而，俯冲带中碳迁移的机制在很大程度上仍未得到解决。先前的研究主要集中在研究弧前地幔交代作用和部分熔融过程中板片衍生的含碳流体的向上转移。此外，与下行板块平行的含二氧化碳流体的渗透可能会驱动俯冲岩石的碳化，从而影响对收敛边缘碳通量的全球估计。然而，人们对流体-岩石相互作用导致俯冲带岩性碳化的地质条件和过程仍然知之甚少。在这里，我们展示了来自中国西南天山高压-超高压变质带的碳化蛇纹岩——高压（HP）蛇纹岩和低压（LP）闪镁岩和利斯特韦岩——的新野外、岩石学和同位素结果。这些岩石记录了折返过程中俯冲带蛇纹岩在高压和低压条件下的碳化作用，反映了含碳流体沿板块边界的多阶段转移和渗透。 HP 蛇纹石的特征是碳酸盐（白云石、文石和镁方解石）的生长，以牺牲主体蛇纹岩中的硅酸盐为代价。综合Sr-C-O同位素数据和热力学模型表明，源自含碳酸盐变镁岩（例如榴辉岩）的碳酸盐流体（含有CO2，水浓度高达1.9摩尔）可能有助于在约15-25kbar和550-600°C下蛇纹岩的高压碳化。蛇绿岩和碳化变沉积岩在野外的密切接触以及它们在锶同位素组成上的相似性表明后者也可能是可能的碳源。或者，两种岩性可能是通过沿着蛇纹岩和变沉积岩之间的岩性界面耦合高压碳酸化而形成的。随后在相对较浅的地壳水平上的流体-岩石相互作用导致蛇纹岩碳化的第二阶段，形成LP蛇镁岩和listvenite，在此期间，交代的含CO2流体可能源自变沉积岩。俯冲带蛇纹岩中的多阶段CO2封存意味着俯冲板片中的水合超镁铁质岩石是在各种P-T条件下捕获和储存板片释放的C的高效反应物，有可能显着控制浅层和深层储层之间的C分布，从而调节俯冲带中的C通量。
Climate is regulated by the carbonate–silicate cycle in which slab outgassing of C into deep fluids and volcanic degassing of CO2into the atmosphere are an important part. However, the mechanisms of C mobility in subduction zones remain largely unresolved. Previous research has focused mainly on investigating the upward transfer of slab-derived carbonic fluids for the forearc mantle metasomatism and partial melting. Furthermore, percolation of CO2-bearing fluids parallel to the downgoing plates can potentially drive carbonation of subducted rocks, which influences the global estimates of C fluxes at convergent margins. Nevertheless, the geological conditions and processes leading to the carbonation of subduction-zone lithologies by fluid–rock interactions are still poorly understood. Here, we present new field, petrological, and isotopic results of carbonated serpentinites—high-pressure (HP) ophidolomites and low-pressure (LP) ophimagnesites and listvenites—from the Chinese southwestern Tianshan HP–UHP metamorphic belt. These rocks recorded the carbonation of subduction-zone serpentinites at HP and LP conditions during exhumation, reflecting the multistage transfer and infiltration of carbonic fluids along the plate boundary. The HP ophidolomites are characterized by the growth of carbonates (dolomite, aragonite, and Mg-calcite) at the expense of silicates in the host serpentinites. Integrated Sr–C–O isotopic data and thermodynamic modelling suggest that carbonic fluids (containing a CO2,aqconcentration of up to 1.9 molal) emanating from carbonate-bearing metamafic rocks (e.g., eclogites) likely contributed to HP carbonation of serpentinites at about 15–25 kbar and 550–600 °C. The close contact of ophidolomites and carbonated metasedimentary rocks in the field as well as their similarities in Sr isotope compositions suggests that the latter could also have acted as the possible C source. Alternatively, both lithologies may have formed by coupled HP carbonation along the lithological interface between serpentinites and metasedimentary rocks. Subsequent fluid–rock interactions at relatively shallow crustal levels resulted in a second stage of serpentinite carbonation to form LP ophimagnesites and listvenites, during which the metasomatic CO2-bearing fluids may have originated from metasedimentary rocks. The multistage CO2sequestration in subduction-zone serpentinites implies that hydrated ultramafic rocks in subducted slabs are highly effective reactants to capture and store slab-released C over a wide range ofP–Tconditions, with the potential to substantially control the C distribution between shallow and deep reservoirs and thus modulate C fluxes in subduction zones.
登录
查看更多内容
DOI：
10.1007/978-3-319-78527-1
发表时间：
1973
期刊：
Stable Isotope Geochemistry
影响因子：
--
作者：
J. Hoefs
通讯作者：
J. Hoefs
影响因子：
3.5
作者：
C. Spandler;J. Hermann;K. Faure;J. Mavrogenes;R. Arculus
通讯作者：
C. Spandler;J. Hermann;K. Faure;J. Mavrogenes;R. Arculus
Sartohay蛇绿混杂岩中的Listwaenite（中国新疆）：基于岩石学、U-Pb年代学和微量元素地球化学的成因模型
影响因子：
3.5
作者：
Qiu Tian;Zhu Yongfeng
通讯作者：
Zhu Yongfeng
影响因子：
5.3
作者：
J. Padrón-navarta;A. Tommasi;C. Garrido;V. L. Sánchez‐Vizcaíno
通讯作者：
J. Padrón-navarta;A. Tommasi;C. Garrido;V. L. Sánchez‐Vizcaíno
影响因子：
0.8
作者：
Yong‐Fei Zheng
通讯作者：
Yong‐Fei Zheng