Clay-mineral compositions of sediments in the Gaoping River-Sea system: Implications for weathering, sedimentary routing and carbon cycling
Clay-mineral compositions of sediments in the Gaoping River-Sea system: Implications for weathering, sedimentary routing and carbon cycling
复制标题
高平河海系统沉积物的粘土矿物成分：对风化、沉积路径和碳循环的影响
DOI：
10.1016/j.chemgeo.2016.10.024
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发表时间：
2016-12-30
期刊：
影响因子：
3.9
通讯作者：
Chang, Yuanpin
中科院分区：
文献类型：
--
作者：
Wang, Yangyang;Fan, Daidu;Chang, Yuanpin
山地小河流（SMRs）通过将巨大的颗粒和溶解负荷快速转移到海洋中，在全球沉积物和碳循环中起着至关重要的作用。高平河海水系是大洋洲小颗粒沉积物的典型代表，具有极高的剥蚀速率(15,000 t km（-2) yr(-1)）和高平海底峡谷（GPSC）陆源颗粒有机碳（POC）的埋藏效率。然而，在这样一个高活动性造山带中，硅酸盐风化作用和POC埋藏在长期碳循环中究竟起着更重要的作用，目前还存在争议。河流沉积物的粘土矿物不仅是POC的重要载体，而且还编码了陆地风化机制和海洋扩散路径的宝贵信息。为了揭示这些信息，系统地收集了高平河海系表层和岩心沉积物，进行了粘土矿物分析。为了更好地了解大洋洲岛屿和东南亚大陆的风化过程和产物，在新的结果和大量已发表的数据的基础上进行了比较研究。研究发现，高平河和台湾其他河流的黏土矿物组成是高寒河段物源岩的遗产，其特征是以伊利石和绿泥石为主，整个河道的组成变化有限。这与下游东南亚大型河流中高岭石和蒙脱石含量的增加和化学风化强度的增加形成了鲜明的矛盾。在GPSC的内部和外部也观察到高一致性的粘土矿物组成。仔细检查表明，近海累积的伊利石和绿泥石含量略有下降，同时海洋环流输入的外来粘土矿物略有增加。结合前人报道的三角洲C-13（org）和三角洲C-14（org）值的海上变化资料，认为河流主导的高平大陆边缘以成岩POC为主，与粘土矿物紧密结合，保存效率高。此外，在大洋洲和全球河流测量数据中，化学风化通量对高物理侵蚀率的缓慢反应得到了显著检验。因此，我们认为在构造活跃的高海拔岛屿及其邻近大陆边缘，陆地POC的快速转移和高埋藏效率在长期碳循环中比硅酸盐风化作用更重要。(C) 2016 Elsevier B.V.版权所有
Small mountainous rivers (SMRs) play a crucial role in the global sediment and carbon cycle by rapid transfer of huge particulate and dissolved loads into the sea. Gaoping river-sea system is a good representative of SMRs in Oceania, having an extreme high denudation rate (15,000 t km(-2) yr(-1)) and a high burial efficiency of terrestrial particulate organic carbon (POC) in the Gaoping submarine canyon (GPSC). However, it is contentious whether silicate weathering or POC burial plays more important role in long-term carbon cycling in such a high active orogen. Clay minerals of fluvial sediments not only act as an important carrier of POC, but also encode valuable information of weathering regimes on land and dispersal routes in the seas. To uncover these informations, surface and core sediments are systematically collected from the Gaoping river-sea system for clay-mineral analysis. Comparative studies are carried out on the basis of new results and vast published data to better understand weathering processes and products in Oceanian islands and Southeast Asian continent. We find that clay-mineral compositions in the Gaoping River (GPR) and other Taiwan rivers are a legacy from provenance rocks in the alpine reach, characterized by predominant illite and chlorite and limited compositional change throughout the river courses. These sharply contradict the downstream increase in compositional complexity (rich in kaolinite and smectite) and chemical weathering intensity in Southeast Asian large rivers because of strong hydrolysis and active sediment recycling at the lowland reach with extensive floodplains. High consistency of clay-mineral compositions is also observed in the interior and exterior of GPSC. Careful examination shows that a slight offshore decrease in cumulative illite and chlorite content is accompanied by a slight increase in exotic clay-mineral inputs by ocean circulations. The combination of this finding with previously reported data on the offshore change in delta C-13(org) and Delta C-14(org) values suggests that petrogenic POC predominates in the river-dominated Gaoping continental margin with high preservation efficiency due to its tight bandage with clay minerals. Moreover, a tardy response of chemical weathering fluxes to high elevated physical erosion rates is remarkably examined in the Oceanian and global river gauging data. We therefore postulate that rapid transfer and high burial efficiency of terrestrial POC in the tectonically active high-standing islands and their adjacent continental margins play much more important role in the long-term carbon cycle than silicate weathering. (C) 2016 Elsevier B.V. All rights reserved.