马里亚纳海沟挑战者深渊南坡JL7KBC03短柱样硅质软泥沉积的物源、沉积环境和碳储库效应

Provenances,sedimentary environment of diatom ooze from core JL7KBC03,southern Challenger Deep,Mariana Trench,and its implication for carbon cycle and burial

海斗深渊是影响地球系统演化的关键一环,但由于超深水深导致的样品匮乏,对其沉积过程的精细研究仅见零星报道。本研究基于马里亚纳海沟挑战者深渊南坡JL7KBC03插管柱样系统的微体古生物、沉积学、矿物学研究,对该区沉积档案的物源、沉积环境记录进行解读。结果显示:(1)沉积物以第四纪硅藻软泥为主,其中大筛盘藻(Ethmodiscus rex)含量达99%以上。大筛盘藻的激发,可能为晚更新世冰期时段南极中层水入侵西北太平洋期间,南极“硅溢漏”效应对低纬水体溶解硅的补充,以及冰期风尘铁元素的激发所致。(2)沉积柱样中夹杂的数层暗色薄层,指示了研究区频繁的火山、热液活动。沉积物矿物、元素地球化学物源分析结果表明:研究区非生物组分物质与九州-帕劳海脊和马里亚纳海槽物质相近,陆源风尘和太平洋热液物质的贡献则相对较小。(3)海斗深渊独特的地形特征与水动力条件,利于有机质的快速沉降与埋藏,以硅藻软泥等形式将大量有机碳封存在深渊底部,动态调节着海洋碳储库与岩石圈碳储库之间的相互转化,是研究全球碳循环和碳封存的重要组成部分。

The Hadal Trench plays a major role in driving the evolution of Earths system.However,research on sedimentary processes in the Hadal Trench remains limited due to the challenges posed by its extreme depth.In this study,we present the sedimentary environment and provenances of the southern Mariana Trench,Challenger Deep,based on the systematic analysis of micropaleontology,sedimentology,and mineralogy.The results show that:①The sediment lithology is diatom ooze,dominated by large quantities of Ethmodiscus rex fragments.Silicic acid leakage from the Southern Ocean may have a significant impact on the blooming of E.rex,which enhanced silica content and reduced diatom dissolution,as well as supplementing silica in subsurface waters.The stimulation of Fe from eolian dust may also promote the blooming of E.rex.②Several dark laminations indicate frequent volcanic and hydrothermal activity.Provenance analysis,based on mineralogy and elemental geochemistry,suggests that abiogenic components were mainly contributed from the Kyushu-Palau Ridge and the Mariana Trench rather than from aeolian dust and hydrothermal materials sourced from the Pacific Ocean.③The unique funnel-like topography and localized current dynamics of the Hadal Trench have been proven to contribute to the rapid precipitation and burial of organic matter.Plenty of organic matter was buried in the Hadal Trench seabed as diatom ooze,which plays an important role in balancing carbon storage between the lithosphere and the ocean.This process may represent a significant component of the global carbon cycle and burial.