西盘古海盆锰结核的元素地球化学特征及生长机制

杨叶飘; 韩宗珠; 来志庆; 龙时迈; 顾伟; 窦连想

doi:10.16028/j.1009-2722.2022.093

西盘古海盆锰结核的元素地球化学特征及生长机制

1.
中国海洋大学海洋地球科学学院，青岛 266100

2.
海底科学与探测技术教育部重点实验室，青岛 266100

基金项目: 国家自然科学基金（41376053）

详细信息

作者简介: 杨叶飘（1998—），硕士，主要从事海洋地质方面的研究工作. E-mail：15207121940@163.com

通讯作者: 韩宗珠（1964—），男，教授，主要从事岩石学和地球化学方面的研究工作. E-mail：hanzongzhu@ouc.edu.cn

中图分类号: P736.4

收稿日期: 2022-04-05

刊出日期: 2023-09-28

Geochemical constraints on the formation mechanisms of manganese nodules from Cipangu Basin

1.
College of Marine Geosciences, Ocean University of China, Qingdao 266100, China

2.
Key Laboratory of Submarine Geosciences and Prospecting Techniques, Qingdao 266100, China

More Information

Corresponding author: HAN Zongzhu, hanzongzhu@ouc.edu.cn

Received Date: 05 April 2022

Publish Date: 28 September 2023

摘要

摘要:
通过对西盘古海盆(Cipangu Basin)15个锰结核样品开展系统的形态结构、显微构造、矿物组成、常微量元素和稀土元素含量特征差异性研究，进而探讨该区锰结核的成因类型和生长机制。西盘古海盆锰结核外观为椭球状或连生体状，表面光滑，组成矿物主要有水羟锰矿、石英、钙长石和石盐；其稀土元素配分模式图表现出明显的Ce正异常、Y负异常和轻稀土富集特征。样品Mn/Fe比值均<2.5，与Ni、Cu正相关，且Mn与Cu、Co和Ni高度正相关，这表明因Cu²⁺、Ni²⁺、Co²⁺更易占据层板结构锰氧八面体MnO₆的空位而在锰矿物表面富集。锰结核显微构造区域可划分为Type-Ⅰ型和Type-Ⅱ型，其中Type-Ⅰ型为结构致密高反射率的层纹状、柱状、叠层状构造的显微构造区域，Type-Ⅱ型为结构疏松低反射率的掌状、混杂状、环状构造的显微构造区域；Type-Ⅰ型区域的Mn/Fe比值和Ni、Ni + Cu、Co含量均高于Type-Ⅱ型区域。构造致密的Type-Ⅰ型区域代表沉积环境变化较小，生长速率较小；构造疏松的Type-Ⅱ型区域代表沉积环境剧烈变化、结核生长速率较大。西盘古海盆锰结核具有典型的水成型成因特征，通过常微量元素测试数据估算得出西盘古海盆锰结核样品的形成时间为1.48 Ma。据微区分析数据估算得出其生长年龄为2.44 Ma。
- 锰结核 /
- 西盘古海盆 /
- 成因类型 /
- 生长机制
Abstract:
In this study, a total of 15 manganese nodule samples were collected from Cipangu Basin in North Pacific Ocean. The morphological structure, microscopic structure, mineral composition, contents of trace elements and rare earth elements, and the differences among samples from different regions were studied systematically. The genetic types and growth mechanism of the manganese nodules were discussed. The manganese nodules are elliptic and intergrowth body with smooth surface. The major minerals are vernadite, quartz, albite, and halite. The REE distribution pattern shows obvious positive Ce anomaly, negative Y anomaly, and LREE enrichment characteristics. The Mn/Fe ratios of the samples from three sites of the study areas are all less than 2.5, which are positively correlated with Ni and Cu; and Mn is highly positively correlated with Cu, Co, and Ni, indicating that Cu, Ni, and Co are more likely to occupy the δ-MnO₂ enrichment at the surface of manganese minerals. The microlayers of manganese nodules can be divided into two types, Type Ⅰ and Type Ⅱ. Type Ⅰ is laminated, columnar and laminated with dense and high reflectance structure, and Type Ⅱ is hybrid and ring with loose and low reflectance structure. The Mn/Fe, Ni, Ni + Cu, and Co in Type Ⅰ were greater than those of Type Ⅱ. The Type Ⅰ area has loose manganese nodule in structure reflecting great changes in sedimentary environment with great growth rate of nodule, while the Type Ⅱ zone has small changes in sedimentary environment with small growth rate. The manganese nodule samples are formed by metal precipitation from the ambient seawater (hydrogenetic) and the age was estimated to be 1.48 Ma based on the ordinary trace element test data. At last, according to the micro-analysis data, the growth age was 2.44 Ma by estimation.
- manganese nodules /
- Cipangu Basin /
- genetic types /
- formation mechanism

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图 1 西盘古海盆的地理及采样位置

Figure 1.

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图 2 西盘古海盆锰结核样品照片

Figure 2.

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图 3 西盘古海盆锰结核样品核心照片

Figure 3.

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图 4 西盘古海盆锰结核壳体X射线粉晶衍射特征性图谱

Figure 4.

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图 5 西盘古海盆锰结核内部显微构造的背散射图片

Figure 5.

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图 6 西盘古海盆锰结核REY的PASS标准化配分模式

Figure 6.

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图 7 锰结核中Mn/Fe-Ni、Mn/Fe-Ni+Cu、Mn/Fe-Co的EMPA分析图

Figure 7.

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图 8 锰结核Mn/Fe-Al的常量分析和EMPA分析

Figure 8.

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图 9 Fe-Mn-（Co+Ni+Cu）×10三角图^[20]

Figure 9.

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图 10 15×（Cu+Ni）-100×（Zr+Y+Ce）-（Fe + Mn）/4三角图^[3]

Figure 10.

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图 11 Ce_SN/Ce_SN*与Y_SN/Ho_SN和Nd比值图^[17]

Figure 11.

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表 1 西盘古海盆锰结核壳体常量元素和金属元素含量

Table 1. Macro element and metal element contents of manganese nodule from the Cipangu Basin

%
	Fe	Mn	Al₂O₃	CaO	K₂O	MgO	Na₂O	P₂O₅	TiO₂	Ba	Sr	Co	Ni	Cu	Mn/Fe
最小值	8.72	3.99	5.49	2.24	0.98	1.92	3.33	0.34	0.54	0.05	0.04	0.02	0.04	0.05	0.33
最大值	16.46	19.5	11.08	3.04	1.8	2.71	6.64	0.6	0.86	0.12	0.07	0.06	0.43	0.28	1.45
平均值	13.81	10.97	7.58	2.46	1.24	2.26	4.43	0.49	0.77	0.08	0.06	0.04	0.19	0.13	0.78

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表 2 西盘古海盆锰结核壳体微量元素含量

Table 2. Trace element content in the shell of manganese nodule from the Cipangu Basin

mg/kg
	Cr	V	Zn	Zr	Sc	Rb	Nb	Mo
最小值	15.01	192.68	208.22	197.1	11.9	21.09	11.37	27.89
最大值	35.43	428.18	744.25	396.2	19.29	57.02	22.58	309.01
平均值	23.18	330.32	430.47	311.64	14.1	31.48	17.6	141.05

	Cd	Cs	Hf	W	Tl	Pb	Th	U
最小值	0.98	1.73	5.11	6.19	9.99	248.4	23.76	2.46
最大值	8.57	4.71	8.14	21.04	46.77	687.7	51.72	5.16
平均值	3.91	2.59	6.83	11.08	25.66	519.27	40.9	3.77

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表 3 西盘古海盆锰结核稀土元素组成

Table 3. Rare earth elements of manganese nodules in the Cipangu Basin

mg/kg
	La	Ce	Pr	Nd	Sm	Eu	Gd	Tb	Dy	Ho
最小值	90.48	431.84	25.5	108.58	25.7	6.14	25.83	3.9	21.7	4.14
最大值	50.03	217.4	13.43	57.01	13.03	3.16	13.43	2.06	11.45	2.22
平均值	123.5	570.4	34.02	145.7	34.62	8.26	35.02	5.26	29.64	5.54

	Er	Tm	Yb	Lu	Y	ΣREY	ΣCe/ΣY	δCe	δEu	Y/Ho
最小值	10.78	1.45	9.13	1.35	66.57	833.09	6.42	2.07	1.12	16.27
最大值	5.96	0.83	5.24	0.77	39.28	435.31	5.53	1.92	1.09	15.26
平均值	14	1.87	11.95	1.8	85.5	1107.07	7.33	2.37	1.15	17.73

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表 4 西盘古海盆锰结核元素相关系数矩阵

Table 4. The Pearson correlation coefficient matrix for major and valuable metal elements of manganese nodule shell from the Cipangu Basin

	TFe	TMn	Al₂O₃	CaO	MgO	K₂O	Na₂O	Ti₂	P₂O₅	Ba	Co	Cu	Ni	Sr	REY
TFe	1
TMn	0.499	1
Al₂O₃	−0.687	-0.919	1
CaO	−0.2	−0.475	0.531	1
MgO	−0.421	−0.633	0.763	0.542	1
K₂O	−0.822	−0.853	0.958	0.343	0.686	1
Na₂O	−0.727	−0.868	0.81	0.292	0.556	0.848	1
Ti₂ O	0.864	0.335	−0.397	0.016	−0.081	−0.583	−0.646	1
P₂O₅	0.957	0.553	−0.771	−0.232	−0.601	−0.888	−0.715	0.738	1
Ba	0.555	0.978	−0.91	−0.463	−0.692	−0.856	−0.91	0.395	0.61	1
Co	0.779	0.899	−0.954	−0.491	−0.734	−0.954	−0.893	0.577	0.834	0.932	1
Cu	0.444	0.977	−0.858	−0.404	−0.567	−0.791	−0.856	0.322	0.49	0.974	0.869	1
Ni	0.48	0.977	−0.873	−0.451	−0.609	−0.807	−0.866	0.357	0.531	0.982	0.898	0.993	1
Sr	0.815	0.875	−0.962	−0.425	−0.72	−0.979	−0.87	0.593	0.87	0.902	0.982	0.828	0.852	1
REY	0.862	0.825	−0.937	−0.463	−0.729	−0.964	−0.862	0.651	0.908	0.864	0.982	0.774	0.811	0.988	1

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表 5 常量分析生长速率计算

Table 5. Calculations of growth rate from constant analysis

编号	NWPB1	NWPB2	NWPB3	NWPB4	NWPB5	NWPB6	NWPB7	NWPB8	NWPB9
R/（mm/Ma）	0.93	0.98	1.4	0.9	1.36	1.46	1.39	0.98	0.89

编号	NWPB10	NWPB11	NWPB12	NWPB13	NWPB14	NWPB15	最小值	最大值	平均值
R/（mm/Ma）	1.94	2.12	1.12	2.17	1.1	1.46	0.89	2.17	1.35

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表 6 基于全岩常量元素含量的生长年龄计算

Table 6. Calculations of growth age based on major elements of whole rocks

		R/（mm/Ma）	厚度/mm	年龄/Ma
西盘古海盆	最小值	0.89	2.00	2.25
	最大值	2.17	2.00	0.92
	平均值	1.35	2.00	1.48

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表 7 基于EPMA分析数据的生长速率计算

Table 7. Calculations of growth rate based on EPMA data

样品区域	结构类型		Fe/%	Mn/%	R/（mm/Ma）
西盘古海盆	总平均	最小值	4.56	0.06	0.46
		最大值	28.04	21.29	1.29
		平均值	15.22	8.7	0.82
	Type-Ⅰ型	最小值	18.75	10.5	0.7
		最大值	26.15	21.29	1.29
		平均值	22.03	16.22	1.02
	Type-Ⅱ型	最小值	4.56	0.06	0.46
		最大值	28.04	17.52	1.13
		平均值	10.67	3.69	0.69

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