Geochemical and molecular characteristics of ferromanganese deposits and surrounding sediments in the Mariana Trench: An Implication for the geochemical Mn cycle in sedimentary environments of the trench zone
Geochemical and molecular characteristics of ferromanganese deposits and surrounding sediments in the Mariana Trench: An Implication for the geochemical Mn cycle in sedimentary environments of the trench zone
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马里亚纳海沟铁锰矿床及周围沉积物的地球化学和分子特征：对海沟区沉积环境中地球化学锰循环的影响
DOI：
10.1016/j.gca.2021.07.018
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发表时间：
2021
影响因子：
5
通讯作者：
Xiaotong Peng
中科院分区：
文献类型：
--
作者：
Jiwei Li;Ling Li;Shijie Bai;Shun Chen;Hengchao Xu;Kaiwen Ta;Yuangao Qu;Yuguang Wang;Huiqiang Yao;Yanhui Dong;Shamik Dasgupta;Mengran Du;Shuangquan Liu;Fanyu Lin;Xiaotong Peng
海沟系统是地球上一些最重要的地球动力学环境，对全球金属循环有重大影响。海沟环境不仅受火山灰幕式沉积的影响，还表现出连续的水岩化学交换。锰铁结核是海洋锰循环的档案，是2016年中国在马里亚纳海沟南部进行的1万米大海沟科学考察中首次发现的。然而，它们在海沟带沉积环境中的地球化学特征和形成机制仍然是个谜。本文采用地球化学和微生物学方法对锰铁结核及其周围沉积物进行了研究。总体地球化学特征表明，海沟结核具有高Mn/Fe的特征，结核结构发育速度快，Mn主要来源于火山灰蚀变和海沟海底流体排放。高分辨率现场地球化学分析将单个结核的微层划分为三种类型。I型为高Mn/Fe比（bbb20）和高生长速率（52.19-3571.73 mm/Myr）的内部部分，受该区域周围流体排出活动的影响而形成。II型为外部层状岩，具有较低的Mn/Fe比（0.01 ~ 2.50）和较低的生长速率（4.54 ~ 9.86 mm/Myr）。III型为外部纹层，具有较高的Mn/Fe比值（2.5 ~ 15.0）和较高的生长率（12.40 ~ 18.93 mm/Myr），具有成岩成因。16S rRNA基因序列分析显示，以shewanellaand colwellia为主的含瘤沉积物样品中的细菌群落结构与对照沉积物样品存在较大差异。本文首次利用地球化学和微生物数据，提出了海沟沉积环境中地球化学锰旋回和结核形成的概念模型。
Trench systems are some of the most important geodynamic settings on Earth and have a substantial influence on the global metal cycle. Trench environments are affected not only by episodic deposition of volcanic ash, but also exhibit a continuous water–rock chemical exchange. Ferromanganese nodules, which are archives for the marine Mn cycle, were first discovered in the southern Mariana Trench during China’s major 10,000-meter hadal trench scientific expedition in 2016. Nevertheless, their geochemical characteristics and formation mechanism in sedimentary environments of the trench zone remain enigmatic. In this study, these ferromanganese nodules and surrounding sediments were examined by geochemical and microbial methods. Bulk geochemistry indicated that trench nodules are characterized by high Mn/Fe ratios and nodule textures indicate a rapid growth rate, with Mn mainly from two sources: volcanic ash alteration and fluids discharge from the trench seabed. High-resolutionin situgeochemical analysis categorized microlayers of an individual nodule into three types. Type I is the interior part that has a high Mn/Fe ratio (>20) and high growth rate (52.19–3571.73 mm/Myr), and formed by the influence of fluid discharge activities around this region. Type II is laminae from the exterior part that have a hydrogenetic origin with lower Mn/Fe ratio (0.01–2.50) and lower growth rate (4.54–9.86 mm/Myr). Type III is laminae from the exterior part that have a diagenetic origin with moderately high Mn/Fe ratio (2.5–15.0) and moderately high growth rate (12.40–18.93 mm/Myr). 16S rRNA gene sequence analysis revealed that the bacterial community structures in the nodule-bearing sediment samples, dominated byShewanellaandColwellia, were substantially different from those of reference sediment samples. For the first time, we propose a conceptual model for a geochemical Mn cycle and nodule formation in trench sedimentary environments using both geochemical and microbial data.