Fluid-mobile elements in serpentinites: Constraints on serpentinisation environments and element cycling in subduction zones

Peters, Daniel; Bretscher, Annette; John, Timm; Scambelluri, Marco; Pettke, Thomas (2017). Fluid-mobile elements in serpentinites: Constraints on serpentinisation environments and element cycling in subduction zones. Chemical geology, 466, pp. 654-666. Elsevier 10.1016/j.chemgeo.2017.07.017

[img] Text
fluid-mobile.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (1MB) | Request a copy

Fluid-mobile element (FME) systematics in serpentinites are key to unravel the environments of mantle rock hydration, dehydration, and element recycling in subduction zones. Here we compile serpentinite geochemical data and, for the first time, report discriminative FME enrichment trends for mid ocean ridge vs. forearc serpentinisation by applying alkali element-U ratios. Characteristic element fractionations are thereby governed by redox-dependent differential U mobility at mid ocean ridges and in forearcs, and by high Cs input in forearcs due to fluids equilibrated with sediments. Simple modelling reproduces the observed enrichment trends in serpentinites that range over several orders of magnitude. From these systematics, first constraints on potentially discriminative fractionation trends for unconventional fluid tracers such as B, As, and Sb can be deduced. Prominent W enrichments that correlate with FMEs suggest significant W mobility in low-temperature serpentinising environments. Application of the alkali element-U systematics to the subducted metaperidotites of Erro Tobbio (recording initial brucite +antigorite breakdown during subduction) and Almirez (recording final antigorite breakdown) reveal that pre-subduction FME enrichment signatures are retained in progressively subducted hydrous mantle rocks to beyond subarc levels. Associated dehydration veins and fluid inclusions reveal subordinate alkali element- U fractionation trends during dehydration. Subducted hydrous mantle rocks therefore may introduce characteristic element signatures and thus contribute towards mantle geochemical heterogeneities.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Rock-Water Interaction

UniBE Contributor:

Peters, Daniel; Bretscher, Annette and Pettke, Thomas

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0009-2541

Publisher:

Elsevier

Language:

English

Submitter:

Thomas Pettke

Date Deposited:

18 Apr 2018 09:35

Last Modified:

12 May 2020 08:15

Publisher DOI:

10.1016/j.chemgeo.2017.07.017

BORIS DOI:

10.7892/boris.111233

URI:

https://boris.unibe.ch/id/eprint/111233

Actions (login required)

Edit item Edit item
Provide Feedback