Talc-dominated seafloor deposits reveal a new class of hydrothermal system.

Matthew R S Hodgkinson,Stephen Roberts,Rachel A Mills,Alexander P Webber,Bramley J Murton,Douglas P Connelly

doi:10.1038/ncomms10150

Matthew R S Hodgkinson, Stephen Roberts + Show 4 more

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https://doi.org/10.1038/ncomms10150

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Abstract

The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13 km west of the axial rift, within a gabbro and peridotite basement. Unlike any other active vent field, hydrothermal precipitates at the VDVF comprise 85–90% by volume of the magnesium silicate mineral, talc. Hydrothermal fluids vent from a 3-m high, 1-m diameter chimney and other orifices at up to 215 °C with low metal concentrations, intermediate pH (5.8) and high concentrations (667 mmol kg−1) of chloride relative to seawater. Here we show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. The heat flux at the VDVF is measured at 487±101 MW, comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models.

Highlights

The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13 km west of the axial rift, within a gabbro and peridotite basement
The discovery of ultramafic-hosted hydrothermal vent fields demonstrates the diversity of hydrothermal activity associated with medium-slow spreading ridges[2,3]
A new class of hydrothermal system, the Von Damm Vent Field (VDVF), was discovered in the Caribbean during cruise JC044 of the RRS James Cook in April 2010, which hosts a community of hydrothermal vent fauna similar to those at the Mid-Atlantic Ridge[6]

Summary

Introduction

The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13 km west of the axial rift, within a gabbro and peridotite basement. We show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. Hydrothermal activity at mid-ocean ridges is dominated by basalt-hosted, high-temperature, metal-rich vent systems driven by magmatic activity[1]. The discovery of ultramafic-hosted hydrothermal vent fields (for example, the high-temperature Rainbow and the low-temperature Lost City Vent Fields) demonstrates the diversity of hydrothermal activity associated with medium-slow spreading ridges[2,3]. A new class of hydrothermal system, the Von Damm Vent Field (VDVF), was discovered in the Caribbean during cruise JC044 of the RRS James Cook in April 2010, which hosts a community of hydrothermal vent fauna similar to those at the Mid-Atlantic Ridge[6]. The processes leading to the formation of the VDVF may be widespread throughout medium to ultraslow mid-ocean spreading ridges medium-ultraslow spreading mid-ocean ridges and could play a significant role in the cooling and chemical exchange between oceanic crust and seawater

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