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Microtexture and Distribution of Minerals in Hydrothermal Barite‐Silica Chimney from the Franklin Seamount, SW Pacific: Constraints on Mode of Formation

Microtexture and Distribution of Minerals in Hydrothermal Barite‐Silica Chimney from the Franklin... An extinct hydrothermal barite‐silica chimney from the Franklin Seamount of the Woodlark Basin, in the southwestern Pacific Ocean, was investigated for mineral distribution and geochemical composition. Six layers on either side of the orifice of a chimney show significant disparity in color, mineral assemblage and major element composition. Electron microscope (SEM) images reveal that the peripheral wall of the chimney is composed of colloform silica, suggesting that incipient precipitation of silica‐saturated hydrothermal fluid initiated the development of the chimney wall. Intermediate layers, between the exterior wall and the inner fluid‐orifice, dominate with barite and sulfides. Low Sr‐to‐Ba ratios (SrO/BaO = 0.015–0.017) indicate restricted fluid‐seawater mixing, which causes relatively high‐temperature formation of the intermediate layers. Whereas the innermost layer bordering the chimney orifice is characterized by more silica and a higher Sr‐to‐Ba ratio (SrO/BaO = 0.023), could have formed due to a paragenetic shift from a high‐temperature active phase to a cooler waning stage of formation. A paragenetic shift is also probably responsible for the change in mineral formation mechanism that resulted in the textural variation of barite and colloform silica developed during different growth phases of this barite‐silica chimney. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Geologica Sinica (English Edition) Wiley

Microtexture and Distribution of Minerals in Hydrothermal Barite‐Silica Chimney from the Franklin Seamount, SW Pacific: Constraints on Mode of Formation

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References (43)

Publisher
Wiley
Copyright
© 2014 Geological Society of China
ISSN
1000-9515
eISSN
1755-6724
DOI
10.1111/1755-6724.12192
Publisher site
See Article on Publisher Site

Abstract

An extinct hydrothermal barite‐silica chimney from the Franklin Seamount of the Woodlark Basin, in the southwestern Pacific Ocean, was investigated for mineral distribution and geochemical composition. Six layers on either side of the orifice of a chimney show significant disparity in color, mineral assemblage and major element composition. Electron microscope (SEM) images reveal that the peripheral wall of the chimney is composed of colloform silica, suggesting that incipient precipitation of silica‐saturated hydrothermal fluid initiated the development of the chimney wall. Intermediate layers, between the exterior wall and the inner fluid‐orifice, dominate with barite and sulfides. Low Sr‐to‐Ba ratios (SrO/BaO = 0.015–0.017) indicate restricted fluid‐seawater mixing, which causes relatively high‐temperature formation of the intermediate layers. Whereas the innermost layer bordering the chimney orifice is characterized by more silica and a higher Sr‐to‐Ba ratio (SrO/BaO = 0.023), could have formed due to a paragenetic shift from a high‐temperature active phase to a cooler waning stage of formation. A paragenetic shift is also probably responsible for the change in mineral formation mechanism that resulted in the textural variation of barite and colloform silica developed during different growth phases of this barite‐silica chimney.

Journal

Acta Geologica Sinica (English Edition) – Wiley

Published: Feb 1, 2014

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