DOI: 10.1016/j.epsl.2018.09.009
Scopus记录号: 2-s2.0-85054425097
论文题名: Ore component mobility, transport and mineralization at mid-oceanic ridges: A stable isotopes (Zn, Cu and Fe) study of the Rainbow massif (Mid-Atlantic Ridge 36°14′N)
作者: Debret B. ; Beunon H. ; Mattielli N. ; Andreani M. ; Ribeiro da Costa I. ; Escartin J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 503 起始页码: 170
结束页码: 180
语种: 英语
英文关键词: hydrothermal deposits
; metals mobility
; serpentinized peridotites
; stable isotopes
Scopus关键词: Alumina
; Aluminum oxide
; Buildings
; Carrier mobility
; Copper
; Deposits
; Fractionation
; Iron
; Iron oxides
; Isotopes
; Magnesite
; Magnetite
; Mineralogy
; Ore deposits
; Ores
; Precipitation (chemical)
; Seawater
; Sulfur compounds
; Temperature
; Hydrothermal deposits
; Hydrothermal fluids
; Isotopic fractionations
; Isotopic variations
; Metal precipitation
; Serpentinized peridotites
; Slow-spreading ridges
; Stable isotopes
; Zinc compounds
; copper
; element mobility
; geochemistry
; hydrothermal deposit
; iron
; mid-ocean ridge
; ore deposit
; peridotite
; serpentinization
; stable isotope
; transport process
; zinc
; Atlantic Ocean
; Mid-Atlantic Ridge
英文摘要: Ultramafic hosted hydrothermal deposits are ubiquitous along slow-spreading ridges such as the Mid-Atlantic Ridge (MAR; e.g., Ashadzé Rainbow, Lost City) where they exert a major control on the cycling of economically important elements (e.g., Zn, Cu, Ni). However, the origin of metal mobility in these environments remains unclear. Here we use Zn (δ66Zn), Cu (δ65Cu) and Fe (δ56Fe) stable isotopes to explore the mobility of metals during (1) the serpentinization of the Rainbow massif basement in a seawater dominated system at low temperature (<250 °C) and (2) the subsequent high temperature (>350 °C) mineralization of serpentinites through seawater-derived fluids that interacted with gabbro prior to interacting with serpentinite near hydrothermal sites (stockworks). The Rainbow samples display among the largest range of isotopic variations ever reported for ultramafic rocks (−0.10‰ ≤ δ66Zn ≤ +0.47‰; −0.93‰ ≤ δ65Cu ≤ +0.24‰; −0.15‰ ≤ δ56Fe ≤ +0.25‰). These variations reflect a two-stage process. (1) Serpentinization of the ultramafic basement is accompanied by a decrease in Zn (26–41 ppm) and Cu (1–13 ppm) concentrations and an increase of δ66Zn (+0.30–+0.47‰) in peridotites relative to primitive mantle (Zn ∼ 55 ppm, Cu ∼ 20 ppm, δ66Zn ∼ +0.16‰). Striking correlations between δ66Zn and indices of serpentinization (LOI and Fe/3+ΣFe) show preferential leaching of isotopically light Zn by fluids during the serpentinization of the massif. This isotopic fractionation is controlled by the dissolution of both mantle sulfides and/or spinels and Zn complexation with chlorine in fluids. At this stage, Fe seems to be immobile as attested by correlations between δ56Fe and indices of peridotite fertility (e.g., Al2O3/SiO2). (2) The mineralization of serpentinites near the Rainbow stockwork is accompanied by an increase in Fe/3+ΣFe (>0.7), FeO (up to 19.8 wt%), Zn (≫50 ppm) and Cu (≫20 ppm) concentrations. The δ66Zn and δ65Cu values progressively decrease with indices of serpentinite mineralization (e.g., Zn, Cu, Fe/3+ΣFe), while several samples display abnormally high δ56Fe (up to 0.25‰) relative to primitive mantle (δ56Fe ∼ 0.025‰), suggesting a high mobility of Zn, Cu and Fe in high temperature hydrothermal fluids. These isotopic fractionations can be explained by the local oxidation of sulfur bearing fluids in contact with seawater. This process enhances metal precipitation as well as the formation of Fe3+-bearing phases, such as magnetite, beneath the stockwork, explaining the presence of magnetic anomalies below the Rainbow hydrothermal field. Our study shows that the mobility of metals in hydrothermal fluids can be enhanced by both peridotite interaction with seawater or with fluid that interacted with deeper mafic bodies and then flowed to the surface. These processes may generate hydrothermal deposits with distinct metal signatures. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109616
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Laboratoire G-Time, DGES, Université Libre de Bruxelles, ULB, CP 160/02, Brussels, 1050, Belgium; Université de Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, LGL-TPE, Villeurbanne, F-69622, France; Dept. de Geologia, Faculdade de Ciências, Universidade de Lisboa Edifício C6 – Piso 4, Campo Grande, Lisboa, 1749-016, Portugal; Institut de Physique du Globe de Paris, CNRS UMR 7154, Paris, France
Recommended Citation:
Debret B.,Beunon H.,Mattielli N.,et al. Ore component mobility, transport and mineralization at mid-oceanic ridges: A stable isotopes (Zn, Cu and Fe) study of the Rainbow massif (Mid-Atlantic Ridge 36°14′N)[J]. Earth and Planetary Science Letters,2018-01-01,503