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Structural controls on sulphide deposition at the dyke-lava boundary, slow-spreading ocean crust, Macquarie Island

journal contribution
posted on 2023-05-16, 16:04 authored by Davidson, GJ, Varne, R, Brown, AV, Connell, RD
Ocean Drilling Program hole 504B revealed an ocean crust hydrothermal sulphur anomaly on the dyke-lava transition, with implications for global sulphur sinks. Here we confirm the presence of the anomaly sporadically along 7.5 km of dyke-basalt contact on the Macquarie Ridge at Macquarie Island, a 39-9.7 Ma slow-spreading setting. Background contact-zone pyrite S contents average 1845 p.p.m. across ∼50 m. However, zones of small-scale brittle faulting that commonly occur on and above the dyke-basalt contact average between 5000 and 11 000 p.p.m. S (20-30 m widths). These consist of steep ridge-parallel faults and fault splays on the contact, overlain by up to 50 m of linked pyritic fault trellis. The contact zone faults are haloed by disseminated pyrite-chlorite, cross-cut by quartz-chlorite-sphalerite and epidote-cemented breccias, containing evidence of turbulent flow. The structural control on sulphur deposition is attributed to the active extensional slow spreading setting. With increasing extension, diffuse mixing across the contact was replaced by channellized flow and dynamic mixing in fault arrays. The magnitude of the dyke-lava transition sulphur sink must be reassessed to take account of this heterogeneity. © 2003 Blackwell Publishing Ltd.

History

Publication title

Terra Nova

Volume

16

Pagination

9-15

ISSN

0954-4879

Department/School

School of Natural Sciences

Publisher

Blackwell Publishing

Place of publication

London, UK

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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