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Mineralogy, sulphur isotope geochemistry and the development of sulphide structures at the Broken Spur hydrothermal vent site, 29 10'N, Mid-Atlantic Ridge

Mineralogy, sulphur isotope geochemistry and the development of sulphide structures at the Broken Spur hydrothermal vent site, 29 10'N, Mid-Atlantic Ridge
Mineralogy, sulphur isotope geochemistry and the development of sulphide structures at the Broken Spur hydrothermal vent site, 29 10'N, Mid-Atlantic Ridge
A large collection of hydrothermal sulphides from the Broken Spur hydrothermal vent site, including representative samples of mound sulphide materials, has been characterized using optical mineralogy and sulphur isotope analysis. Young mound sulphides from Broken Spur have a pyrrhotite-dominated mineralogy unusual for bare ridge vent systems. However, pyrrhotite is metastable and is ultimately converted to iron disulphides. Mature sulphides are indurated, recrystallized and contain abundant quartz. Sulphide mound materials are developed by three major processes: (i) coalescing of chimney structures; (ii) accumulation of talus from mass wasting and (iii) precipitation and growth in response to hydrothermal flow. Progressive maturation of mound materials is by modification of primary textures, development of mineralogical zoning and replacement of metastable phases. Sulphur isotope analysis of 35 mineral separates returned ?34S values of – 0.5 to +3.2‰. These values are similar to those previously measured for Broken Spur and Snakepit, but are distinctly 32S enriched compared to the TAG active mound and some Pacific sites. Seawater entrainment and sulphate reduction within the subsurface feeder zone below Broken Spur mounds do not appear to be important processes at Broken Spur, in contrast to the TAG active mound.
Mid-Atlantic Ridge, sulphides, sulphur, isotopes, hydrothermal vents
0016-7649
773-785
Butler, I.B.
9a1c2b72-9bcc-4ed2-9e5a-a2805caeca5e
Fallick, A.E.
5b1b907f-57fc-43cc-9a9f-5b9fa80c313b
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Butler, I.B.
9a1c2b72-9bcc-4ed2-9e5a-a2805caeca5e
Fallick, A.E.
5b1b907f-57fc-43cc-9a9f-5b9fa80c313b
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4

Butler, I.B., Fallick, A.E. and Nesbitt, R.W. (1998) Mineralogy, sulphur isotope geochemistry and the development of sulphide structures at the Broken Spur hydrothermal vent site, 29 10'N, Mid-Atlantic Ridge Journal of the Geological Society, 155, (5), pp. 773-785. (doi:10.1144/gsjgs.155.5.0773).

Record type: Article

Abstract

A large collection of hydrothermal sulphides from the Broken Spur hydrothermal vent site, including representative samples of mound sulphide materials, has been characterized using optical mineralogy and sulphur isotope analysis. Young mound sulphides from Broken Spur have a pyrrhotite-dominated mineralogy unusual for bare ridge vent systems. However, pyrrhotite is metastable and is ultimately converted to iron disulphides. Mature sulphides are indurated, recrystallized and contain abundant quartz. Sulphide mound materials are developed by three major processes: (i) coalescing of chimney structures; (ii) accumulation of talus from mass wasting and (iii) precipitation and growth in response to hydrothermal flow. Progressive maturation of mound materials is by modification of primary textures, development of mineralogical zoning and replacement of metastable phases. Sulphur isotope analysis of 35 mineral separates returned ?34S values of – 0.5 to +3.2‰. These values are similar to those previously measured for Broken Spur and Snakepit, but are distinctly 32S enriched compared to the TAG active mound and some Pacific sites. Seawater entrainment and sulphate reduction within the subsurface feeder zone below Broken Spur mounds do not appear to be important processes at Broken Spur, in contrast to the TAG active mound.

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Published date: 1998
Keywords: Mid-Atlantic Ridge, sulphides, sulphur, isotopes, hydrothermal vents
Organisations: Geochemistry

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Local EPrints ID: 361634
URI: http://eprints.soton.ac.uk/id/eprint/361634
ISSN: 0016-7649
PURE UUID: 6bf077a4-5789-4de6-9e68-aa39afed9642

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Date deposited: 28 Jan 2014 13:09
Last modified: 18 Jul 2017 02:59

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Author: I.B. Butler
Author: A.E. Fallick
Author: R.W. Nesbitt

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