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GUAN Yao,SUN Xiaoming,JIANG Xiaodong,SA Rina,ZHOU Li,HUANG Yi,LIU Yating,LI Xiaojie,LU Rongfei,WANG Chi. 2017. The effect of Fe-Mn minerals and seawater interface and enrichment mechanism of ore-forming elements of polymetallic crusts and nodules from the South China Sea. Acta Oceanologica Sinica, 36(6):34－46

The effect of Fe-Mn minerals and seawater interface and enrichment mechanism of ore-forming elements of polymetallic crusts and nodules from the South China Sea

南海多金属结壳(核)铁锰矿物/海水界面效应与成矿元素的富集

Received:February 16, 2016 Revised:April 18, 2016

DOI：10.1007/s13131-017-1004-4

Key words:polymetallic crust and nodule mineralogy characteristic interface effect element enrichment surface complexation

中文关键词: 多金属结壳和结核矿物学特征界面效应元素富集表面络合

基金项目:The National Natural Science Foundation of China under contract Nos 40473024 and 40343019; the research fund from State Key Laboratory for Mineral Deposits Research in Nanjing University under contract No. 20-15-07; the Investigation and Development of Marine Resources during the 12th Five Year Plan Project under contract No. DY125-13-R-05; the Doctoral Program of Higher Education Research Fund under contract Nos 20040558049 and 20120171130005; the Project of High Level Talents in Colleges of Guangdong Province (2011) and the Fundamental Research Funds for Central Universities under contract Nos 16lgjc11, 12lgjc05 and 09lgpy09.

Author Name	Affiliation	E-mail
GUAN Yao	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
SUN Xiaoming	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China School of Earth Sciences and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210046, China	eessxm@mail.sysu.edu.cn
JIANG Xiaodong	School of Earth Sciences and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China
SA Rina	School of Earth Sciences and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China
ZHOU Li	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
HUANG Yi	School of Earth Sciences and Geological Engineering, Sun Yat-sen University, Guangzhou 510275, China
LIU Yating	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
LI Xiaojie	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
LU Rongfei	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China
WANG Chi	School of Marine Sciences, Sun Yat-sen University, Guangzhou 510006, China Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou 510006, China

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Abstract:

Ferromanganese crusts and nodules are important submarine mineral resources that contain various metal elements with significant economic value. In this study, polymetallic crusts and nodules obtained from the South China Sea (SCS) were determined by using X-ray power diffraction (XRD), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to systematically investigate and analyze the mineralogical and spectral characteristics of the Fe-Mn minerals. XRD measurements revealed that the SCS polymetallic crusts and nodules were composed of vernadite, quartz, and plagioclase. The nodules also contained todorokite. The Fe-phase minerals of the SCS crusts and nodules were composed of amorphous Fe oxide/hydroxide, and the Mn-and Fe-phases minerals exhibited relatively poor degrees of crystallization. FTIR results showed that the Fe-Mn minerals in the crusts and nodules included a large number of surface hydroxyl groups. These surface hydroxyl groups contained protons that could provide reactive sites for complexation of ore-forming elements in seawater. XPS results indicated that the surfaces of the Fe-Mn minerals mainly contained Fe, Mn, and O. Fe was present in the trivalent oxidation state, while Mn, which may contain several bivalent oxidation state, was present in the tetravalent and trivalent oxidation states. The SCS polymetallic crusts and nodules were compared with Pacific seamount crusts, and results showed that the surface hydroxyl (-OH) groups of the SCS crusts and nodules numbered more than the lattice oxygen (O^2-). But the lattice oxygen of Pacific seamount crusts numbered more than the surface hydroxyl groups. This characteristic indicated that the degree of crystallization of Fe-Mn minerals from the Pacific Ocean was higher than that of minerals from the South China Sea. Comprehensive studies showed that ore-forming elements in the interface between seawater and the Fe-Mn minerals in the submarine ferromanganese crusts and nodules employed the following enrichment mechanisms:(1) the metal ion complexed with the surface hydroxyl of Fe-Mn minerals to form hydroxyl complexes, which were connected by coordination bonds or stable inner-sphere complexes that exchanged protons on the mineral surfaces; (2) the charged surfaces of the minerals and metal cations formed outer-sphere complexes, which made up the electrostatic double layer, through electrostatic adsorption; and (3) the metal cations isomorphously exchanged the Mn and Fe ions of the mineral lattice structure.

中文摘要:

海底铁锰结壳和结核是重要的海底矿产资源，蕴含着丰富的金属元素并且具有巨大的经济价值。本文主要以南海多金属结壳（核）为研究对象，采用X射线粉晶衍射（XRD）、激光拉曼光谱、红外光谱分析（FTIR）以及X射线光电子能谱对铁锰矿物的矿物学和谱学特征进行了系统的分析和研究。粉晶衍射和拉曼光谱分析结果表明，南海多金属结壳的矿物组成为水羟锰矿、石英和长石，结核的矿物组成为钡镁锰矿、水羟锰矿、石英和长石，铁相矿物均为无定形铁氧化物/氢氧化物，并且锰相矿物和铁相矿物的结晶程度均较差。红外光谱分析结果显示多金属结核和结壳中的铁锰矿物具有大量表面羟基，这些含质子表面羟基官能团，可为海水中各成矿元素的络合提供丰富的活性位点。XPS分析表明多金属结核和结壳中铁锰矿物表面以Fe、Mn和O元素为主，其中Fe呈正三价态，Mn以正四、正三价为主，可能还含有少部分正二价态。对比南海多金属结壳（核）与太平海山结壳，南海多金属结壳（核）具有更为显著的表面羟基氧（-OH）含量，而太平洋海山结壳则以晶格氧（O^2-）为主，表明太平洋海山结壳铁锰矿物结晶程度较南海多金属结壳（核）高。综合研究表明，在海底铁锰结壳和结核中（氢）氧化锰/铁矿物与海水之间界面效应对金属离子的富集机理主要有：（1）金属离子与矿物表面羟基进行络合反应，形成以配位键相连的羟基络合物，或与表面的质子交换生成稳定的内层络合物；（2）矿物的带电表面与金属离子通过静电作用形成双电层，生成外层络合物；（3）金属离子与矿物结构中的Mn、Fe离子同晶置换而成为结构阳离子。

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