The geochemistry of fluids from an active shallow submarine hydrothermal system: Milos island, Hellenic Volcanic Arc

Valsami-Jones, E; Baltatzis, E; Bailey, EH; Boyce, AJ; Alexander, JL; Magganas, A; Anderson, L; Waldron, S; Ragnarsdottir, KV

dc.contributor.author	Valsami-Jones, E	en
dc.contributor.author	Baltatzis, E	en
dc.contributor.author	Bailey, EH	en
dc.contributor.author	Boyce, AJ	en
dc.contributor.author	Alexander, JL	en
dc.contributor.author	Magganas, A	en
dc.contributor.author	Anderson, L	en
dc.contributor.author	Waldron, S	en
dc.contributor.author	Ragnarsdottir, KV	en
dc.date.accessioned	2014-03-01T01:54:47Z
dc.date.available	2014-03-01T01:54:47Z
dc.date.issued	2005	en
dc.identifier.issn	0377-0273	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/27468
dc.subject	hydrothermal fluids	en
dc.subject	geothermal	en
dc.subject	submarine	en
dc.subject	water rock interaction	en
dc.subject	Hellenic Volcanic Arc	en
dc.subject	Milos	en
dc.subject.classification	Geosciences, Multidisciplinary	en
dc.subject.other	EAST PACIFIC RISE	en
dc.subject.other	BLACK SMOKER	en
dc.subject.other	GEOTHERMAL SYSTEMS	en
dc.subject.other	PHASE-SEPARATION	en
dc.subject.other	THERMAL SPRINGS	en
dc.subject.other	VENT FLUIDS	en
dc.subject.other	CHEMISTRY	en
dc.subject.other	RIDGE	en
dc.subject.other	GREECE	en
dc.subject.other	BRINE	en
dc.title	The geochemistry of fluids from an active shallow submarine hydrothermal system: Milos island, Hellenic Volcanic Arc	en
heal.type	journalArticle	en
heal.language	English	en
heal.publicationDate	2005	en
heal.abstract	Geothermal activity in the Aegean island of Milos (Greece), associated with island-arc volcanism, is abundant both on-and off-shore. Hydrothermal fluids venting from several sites, mainly shallow submarine (up to 10 m), but also just above seawater level in one locality, were sampled over four summer field seasons. Some of the discharging fluids are associated with the formation of hydrothermal edifices. Overall, the main characteristics of the hydrothermal fluids are low pH and variable chlorinity. The lowest recorded pH was 1.7, and chlorinity ranged from 0.1 to 2.5 times that of seawater. The highest fluid temperatures recorded on site were 115 degrees C. Two main types of fluids were identified: low-chlorinity fluids containing low concentrations of alkalis (potassium, lithium, sodium) and calcium, and high concentrations of silica and sulphate; and high-chlorinity fluids containing high concentrations of alkalis and calcium, and lower concentrations of silica and sulphate. The type locality of the high-chlorinity fluids is shallow submarine in Palaeochori, near the cast end of the south coast of the island, whereas the type locality of the low-chlorinity fluids is a cave to the west of Palaeochori. The two fluid types are therefore often referred to as "submarine" and "cave" fluids respectively. Both fluid types had low magnesium and high metal concentrations but were otherwise consistently different from each other. The low-chlorinity fluids had the highest cobalt, nickel, aluminium, iron and chromium (up to 1.6 mu M, 3.6 mu M, 1586 mu M, 936 mu M and 3.0 mu M, respectively) and the high-chlorinity fluids had the highest zinc, cadmium, manganese and lead (up to 4.1 mu M, 1.0 mu M, 230 mu M and 32 mu M, respectively). Geochemical modelling suggests that metals in the former are likely to have been transported as sulphate species or free ions and in the latter as chloride species or free ions. Isotopic values for both water types range between delta D -12 to 33 parts per thousand and delta(18)O 1.2 to 4.6 parts per thousand. The range of fluid compositions and isotopic contents indicates a complex history of evolution for the system. Both types of fluids appear to be derived from seawater and thus are likely to represent end members of a single fluid phase that underwent phase separation at depth. Crown Copyright (c) 2005 Published by Elsevier B.V. All rights reserved.	en
heal.publisher	ELSEVIER SCIENCE BV	en
heal.journalName	JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH	en
dc.identifier.isi	ISI:000233951500010	en
dc.identifier.volume	148	en
dc.identifier.issue	1-2	en
dc.identifier.spage	130	en
dc.identifier.epage	151	en