Zn isotopes in hydrothermal sulfides and their oxidation products along the south mid-Atlantic ridge: evidence of hydrothermal fluid deposition

被引：9

作者：

Li, Xiaohu ^{[1
]}

Wang, Jianqiang ^{[1
]}

Chu, Fengyou ^{[1
]}

Lei, Jijiang ^{[1
]}

Wang, Hao ^{[1
]}

Li, Zhenggang ^{[1
]}

机构：

[1] State Ocean Adm, Inst Oceanog 2, Key Lab Submarine Geosci, Hangzhou 310012, Zhejiang, Peoples R China

来源：

GEO-MARINE LETTERS | 2018年 / 38卷 / 02期

基金：

中国国家自然科学基金;

关键词：

OCEANIC MASS-BALANCE; STABLE-ISOTOPES; DISSOLVED IRON; TRACE-ELEMENT; VENT FLUIDS; ZINC; COPPER; FRACTIONATION; CONSTRAINTS; SULFUR;

D O I：

10.1007/s00367-017-0519-1

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

Significant Zn isotope fractionation occurs during seafloor hydrothermal activities. Therefore, exploring variations in Zn isotope composition affected by hydrothermal fluids and oxidative processes would help to better understand hydrothermal fluid cycling and sulfide deposition on mid-ocean ridges. In this paper, the Zn isotope compositions of different types of sulfides and their oxidation products obtained from hydrothermal fields on the South Mid-Atlantic Ridge (13-15A degrees S) were analyzed using a Neptune plus MC-ICP-MS. The delta Zn-66 ratios range from -0.14aEuro degrees to +0.38aEuro degrees, and the average delta Zn-66 ratio is +0.12 +/- 0.06aEuro degrees (n=21, 2 SD) for all the studied sulfides and oxidation products. The Cu-rich sulfides have a slightly heavier Zn isotope composition (average delta Zn-66=+0.19 +/- 0.07aEuro degrees, n=6) than the Zn-rich sulfides (average delta Zn-66=-0.02 +/- 0.06aEuro degrees, n=5). The Zn isotope compositions of the oxidation products are similar to those of the Cu-rich sulfides, with an average delta Zn-66 ratio of 0.14 +/- 0.06aEuro degrees (n=10, 2 SD). The Zn isotope compositions of all the samples are generally within the ranges of sulfides from hydrothermal fields on other mid-ocean ridges, such as the East Pacific Rise (9A degrees N, 21A degrees N) and the Trans-Atlantic Geotraverse. However, the average Zn isotope composition indicates the presence of significantly lighter Zn isotopes relative to those reported in the literature (average delta Zn-66=+0.39aEuro degrees). The significant enrichment of the Zn-rich sulfides with light Zn isotopes reveals that kinetic fractionation likely occurs during mineral deposition. Furthermore, the Zn isotope compositions of the sulfides and their oxidation products (average delta Zn-66=+0.12aEuro degrees) are significantly lighter than the average Zn isotope composition of the ocean (delta Zn-66=+0.5aEuro degrees), which could further constrain the modern Zn isotope cycle in the ocean by serving as a sink for light Zn isotopes.

引用

页码：131 / 138

页数：8

共 45 条

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