IOCAS-IR
西太平洋卡罗琳洋脊CM4海山铁锰结壳矿物学和地球化学特征
侯晓帆
Subtype硕士
Thesis Advisor王珍岩
2020-05-20
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Degree Name地质工程
Degree Discipline工程硕士
Keyword铁锰结壳,地球化学,矿物学,成因,卡罗琳洋脊
Abstract

20178月,中国科学院海洋研究所科学号考察船在西太平洋低纬度海区卡罗琳洋脊CM4海山开展了多学科综合调查,发现该海山山体表面分布着大量的铁锰结壳。

研究区铁锰结壳样品类型均一,基本呈单层薄状,厚度在1 mm以内。铁锰结壳附着基岩为碳酸盐岩,大多为坚硬的石灰岩和白云岩,少部分为孔隙较多的造礁珊瑚。

本文对该海山9个铁锰结壳及碳酸盐岩基岩样品进行了矿物学和地球化学研究,利用X射线衍射、电感耦合等离子光谱、电感耦合等离子质谱等测试技术,分析了铁锰结壳的矿物组成、主量元素和微量元素含量,碳酸盐岩基岩的主量元素和微量元素含量,并利用电子探针对铁锰结壳及碳酸盐岩基岩样品进行了微区分析,进一步讨论了铁锰结壳的成因机制,初步评价了卡罗琳洋脊CM4海山铁锰结壳的资源潜力。

矿物学分析表明,铁锰介壳主要由Mn-氧化物和Fe-氢氧化物组成。锰矿物相主要为水羟锰矿,部分样品含有钡镁锰矿和水钠锰矿。铁矿物相大都以隐晶质形式存在,能够识别的铁矿物主要有针铁矿和纤铁矿。此外,还含有石英、方解石等其它矿物。

根据铁锰结壳层厚度,该海山样品分为两类:铁锰结壳层厚度< 0.5 mm铁锰结壳层厚度1 mm左右。相对于第类样品,第类铁锰结壳层较厚的样品碳酸盐岩基岩中CaMgMnFe等大部分元素含量较高,SrUB元素含量相对较低。

全元素分析表明,该海山铁锰结壳的MnFeCoNi含量与全球各大洋海山区铁锰结壳的元素丰度相当,平均值分别为24.24 %15.14 %0.16 %0.34 %。该海山铁锰结壳样品Cu含量很低,平均值仅为0.01 %,可能与该海区水体中溶解态Cu含量较低或Cu大部分以有机形式存在有关。

与全球各大洋的铁锰结壳对比,该海山样品的稀土元素含量偏低。总稀土含量范围在925~1511 μg/g之间,轻稀土含量范围为826~1314 μg/g,总体为轻稀土富集。经北美页岩标准化后,稀土配分模式整体呈相对平坦的特征,呈明显的Ce正异常、轻微的Y负异常和Ho正异常。

电子探针微区分析表明,一方面,铁锰结壳碳酸盐岩基岩中成矿金属元素含量很低;另一方面,铁锰结壳层从表层到底层(靠近碳酸盐岩基岩部分)MnFeCoNi等元素含量依次降低,并未出现靠近基岩部分金属元素含量较高的情况。因此,碳酸盐岩基岩未直接向铁锰结壳的生长提供成矿金属元素。

该海山铁锰结壳的矿物组成、元素比值和元素组合等表明该海山铁锰结壳属于水成成因类型。铁锰结壳及碳酸盐岩基岩的全元素分析和电子探针分析表明,该海山碳酸盐岩基岩并未直接向铁锰结壳的生长提供成矿金属元素,上覆海水是铁锰结壳金属元素的直接来源。在CM4海山附近,并未发现热液活动,因此,铁锰结壳中成矿元素的主要来源是河流、风沙输入的陆源和海山内部水岩反应产生的元素。

与全球各大洋海山区铁锰结壳样品相比,该海山铁锰结壳中成矿元素含量与其相当,但铁锰结壳层厚度普遍较薄。目前,由于该海山未开展钻探勘察且采集的铁锰结壳样品较少,因此,现阶段尚不足以定量评价整个海山的矿产资源潜力。

Other Abstract

 

In August 2017, the Institute of Oceanology of the Chinese Academy of Sciences conducted a multidisciplinary comprehensive survey of the Caroline ridge CM4 guyot in the low latitude of the Western Pacific, founding that a large number of ferromanganese crusts are distributed on the mountain surface.

In the study area, types of ferromanganese crusts are single, which are basically in the shape of single-thin layer with the thickness of less than 1 mm. The substrate attached by ferromanganese crusts is carbonatite, most of which is hard limestone and dolomite, a little of which is hermatypic coral.

Nine ferromanganese crusts collected from Caroline ridge CM4 guyot have been studied for Mineralogy and geochemistry. By using XRD, ICP-OES, ICP-MS and EPMA, mineral composition and contents of major elements and trace elements of samples were analyzed, and the geochemical characteristics and genesis were preliminarily discussed. Based on macro and micro analyses, the resources potential of Caroline ridge CM4  guyot ferromanganese crusts was evaluated.

Mineralogical analysis shows that ferromanganese crusts are mainly composed of manganese mineral phase, iron mineral phase, detrital mineral phase and biogenic mineral phase. Manganese minerals are dominated by vernadite with a small amount of todorokite and birnessite. The crystallinity of iron minerals is low, and some minerals are difficult to be recognized. The iron minerals that can be identified are goethite and lepidocrocite. Other minerals include quartz and calcite.

According to the thickness of the ferromanganese crusts, samples are divided into two categories: thickness < 0.5 mm; thickness about 1 mm. Compared with samples with the thin thickness, contents of elements, such as Ca, Mg, Mn, Fe and other elements in the carbonatite with the large thickness are relatively higher, while contents of Sr, U and B are relatively lower.

Element analysis shows that the average concentration of Mn, Fe, Co, Ni of the samples is 24.24 %, 15.14 %, 0.16 %, 0.34 %, respectively. Compared with these of ferromanganese crusts in Pacific, Atlantic and Indian Ocean, Cu contents of this seamount samples are very low, with the average value is only 0.01 %, which may be related to the low dissolved Cu contents or the majority of Cu in organic form in the seawater of the area.

Compared with these around the world, ∑REE contents of CM4 guyot samples are relatively lower. ΣREE contents range from 925 to 1511 μg/g. ΣLREE contents range from 826 to 1314 μg/g. LREE is generally enriched. According to the north American shale–normalized, CM4 guyot samples show a relatively flat REE distribution model, with obvious positive Ce anomalies, negative Y anomalies and positive Ho anomalies.

Electron probe microanalysis shows that metal elements contents in the carbonatite are very low. On the other hand, Mn, Fe, Co, Ni contents of ferromanganese crusts reduce from the surface to the bottom. Therefore, carbonatite substrate does not directly provide ore-forming elements for ferromanganese crusts.

Mineral composition, element ratios and element groups indicate that samples are hydrogenetic, without obvious diagenesis. The element analysis and electron probe analysis of ferromanganese crusts and substrate indicate that carbonatite does not directly provide ore-forming elements for ferromanganese crusts. The overlying seawater is the direct source of contents of ferromanganese crusts. Hydrothermal activity is not found near the CM4 guyot. Therefore, the main sources of ore-forming elements of ferromanganese crusts are the continental sources of river, wind-sand input or elements produced by water-rock reactions in the seamounts.

The ore-forming elements contents of CM4 guyot samples are equivalent to these of ferromanganese crusts in the global oceans, but the thickness of ferromanganese crusts is smaller. Due to the small number of stations and the lack of drilling data for seamounts, the resources potential cannot be estimated for the time being.

MOST Discipline Catalogue工学:地质资源与地质工程
Pages62
Language中文
Table of Contents

1 绪论... 1

1.1 研究背景及意义... 1

1.1.1 研究背景... 1

1.1.2 研究意义... 1

1.2 铁锰结壳研究概况... 3

1.2.1 铁锰结壳调查历史... 3

1.2.2 铁锰结壳研究现状... 4

1.3 研究工作... 10

1.3.1 研究目的... 10

1.3.2 研究思路... 11

1.3.3 完成工作量... 11

2 研究区区域地质概况... 12

2.1 区域地质背景... 12

2.2 海山特征... 14

2.2.1 地形地貌特征... 14

2.2.2 水文环境特征... 14

3 材料与方法... 15

3.1 样品概况... 15

3.1.1 样品采集... 15

3.1.2 样品特征... 17

3.1.3 样品处理... 17

3.2 分析方法... 18

3.2.1 矿物相分析... 18

3.2.2 元素分析... 19

3.2.3 微区分析... 19

4 铁锰结壳矿物组成... 21

4.1 矿物学特征... 21

5 铁锰结壳地球化学特征... 23

5.1 铁锰结壳碳酸盐岩基岩化学成分... 23

5.2 铁锰结壳主量元素和微量元素特征... 23

5.3 铁锰结壳稀土元素特征... 25

5.4 铁锰结壳及碳酸盐岩基岩微区分析... 27

6 铁锰结壳成因机制及物质来源... 30

6.1 铁锰结壳成因类型... 30

6.2 铁锰结壳物质来源... 31

7 铁锰结壳资源潜力... 37

7.1 铁锰结壳资源情况... 37

7.2 铁锰结壳开采技术... 38

8 结论与展望... 39

8.1 结论... 39

8.2 展望... 40

参考文献... 42

... 51

作者简历及攻读学位期间发表的学术论文与研究成果... 52

Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/164649
Collection中国科学院海洋研究所
海洋地质与环境重点实验室
Recommended Citation
GB/T 7714
侯晓帆. 西太平洋卡罗琳洋脊CM4海山铁锰结壳矿物学和地球化学特征[D]. 中国科学院海洋研究所. 中国科学院大学,2020.
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