摘要
对于开阔大洋海山结壳的矿物组成和地球化学特征研究已经比较深入,但对边缘海海山铁锰结壳的研究却较少。以在南海东部管事海山上采集的两块铁锰结壳为研究材料,对其进行了X射线衍射、扫描电镜及电子探针微区的分析,结果显示结壳矿物以水羟锰矿为主,含有少量针铁矿,碎屑矿物主要是石英和长石。结壳的显微结构呈现条带状分布,有10~15μm长的空隙和0.5μm直径大小的孔洞。相对于大洋结壳,结壳的Mn含量较高,与马尼拉海沟附近火山喷发物质有关,但Cu、Co和Ni含量更低,可能与边缘海沉积速率高或有机络合物吸附有关。矿物组成及元素比值表明结壳主要是水成的,但未发生明显磷酸盐化作用。元素比值和相关性表明,Mn主要来源于南海扩张停止后火山喷发、玄武岩风化形成溶解Mn;Fe与Si元素均来自火山碎屑、生源物质和陆源物质,还受到管状蠕虫吸附的影响。南海管事海山结壳是在富氧环境中上升流作用下选择性吸附水体中溶解化学元素缓慢沉积而成。结壳中元素含量随时间变化趋势反映了南海的古环境变化。
Although the mineral composition and geochemistry of ferromanganese crusts in the open ocean are well understood to researchers,those on seamounts in a marginal sea remains little known.In this study,two ferromanganese crust samples are collected from the Guanshi seamount located in the eastern South China Sea(SCS).We analyzed the mineral composition,microstructures,and major elements contents of the ferromanganese crusts,by means of X-ray diffraction(XRD),scanning electron microscope(SEM)and electron microprobe,respectively.Both of the two ferromanganese crusts are dominated by vernadite with a small amount of geothite,while the detrital minerals dominated by quartz and feldspar.The two crusts are all striped in microstructure,with pores of 10-15μm and holes of 0.5μm in diameters.Compared with those from the open ocean,the crusts from Guanshi seamount is higher in Mn,due to the volcanic eruption near the Manila Trench,and lower in Cu,Co and Ni contents due to the higher deposition rate and higher adsorption of organic complex in the South China Sea.Mineral composition and element ratios indicate that the two crusts are both hydrogenetic,without obvious phosphatization.The element ratios and correlation of elements show that Mn mainly deposited from the dissolved Mn supplied by volcanic eruption and the weathering of basalt formed in the post-spreading stage of the South China Sea.Fe and Si elements are both derived from volcanic,biogenic and terrestrial materials,and also affected by the adsorption of tubular worms.Two crusts from the Guanshi seamount in the South China Sea are formed by the slow accumulation of dissolved chemical elements of seawater affected by upwelling under an oxygen enriched environment.The temporal variations of element contents in the ferromanganese crusts reflect paleoenvironmental evolution history of the South China Sea.
作者
刘兴健
唐得昊
阎贫
葛晨东
LIU Xingjian;TANG Dehao;YAN Pin;GE Chendong(CAS Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology.Guangzhou 510301,China;Evaluation and Detection Technology Laboratory of marine mineral resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266071,China;Guangzhou Marine Geological Survey,Guangzhou 510760,China;Key Laboratory of Coast and Island Development,MOE,Nanjing University,Nanjing 210023,China)
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2019年第3期94-103,共10页
Marine Geology & Quaternary Geology
基金
青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室开放基金“南海东部海山铁锰结壳的成因及其古环境意义”(KC201706)
中国科学院海洋地质与环境重点实验室开放基金“南海东北部浦元海山的地球物理研究”(MGE2018KG14)
国家自然科学基金“东沙海区反射/折射联合成像与南海裂谷发生机制研究”(91328205),“基于生态能质理论的大型底栖生物碳与有机碎屑碳间量化关系研究——以南海北部近岸海域为例”(41806130)
关键词
铁锰结壳
地球化学
矿物组成
水成成因
南海管事海山
ferromanganese crust
geochemistry
mineral composition
hydrogenesis
Guanshi seamount from South China Sea
