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Acceleration of sinter diagenesis in an active fumarole, Taupo volcanic zone, New Zealand

Bridget Y. Lynne, Kathleen A. Campbell, Randall S. Perry, P. R. L. Browne and J. N. Moore
Acceleration of sinter diagenesis in an active fumarole, Taupo volcanic zone, New Zealand
Geology (Boulder) (September 2006) 34 (9): 749-752

Abstract

Siliceous sinters form where nearly neutral pH, alkali chloride waters discharge at the surface (< or =100 degrees C). They may preserve biogenic and abiogenic material and therefore archive paleoenvironmental settings. Freshly precipitated sinters undergo diagenesis through a five-step series of silica mineral phase changes, from opal-A to opal-A/CT to opal-CT to opal-C to quartz. Transformation rates vary among sinters because postdepositional conditions can accelerate or retard diagenesis, meanwhile preserving or destroying biosignals. We monitored alteration and diagenesis of newly precipitated, filamentous microbe-rich sinter during a two-year field experiment, where sinter was suspended inside a fumarole at Orakei Korako, Taupo volcanic zone, New Zealand. Patchy and complex diagenesis resulted from changes in environmental conditions, including variations in temperature, pH, and the intermittent deposition of sulfur. Throughout the experiment, opal-A was dissolved by acidic steam condensate, and reprecipitated locally. Quartz crystals grew on the sinter surface within 21 weeks. Previous reports of transformation rates from opal to quartz are on the order of thousands of years in duration. Thus, our results show that fumarolic overprinting accelerates diagenesis. Microbial preservation was not favorable because primary filamentous fabrics were obscured by deposition of opal-A microspheres, smooth silica infill, and sulfur. If ancient hydrothermal systems were among the likely places where early life flourished, it is necessary to distinguish between depositional features and those inherited during diagenesis. This near-real time experiment enabled observations on environmental controls of diagenetic change in silica minerals and illustrated the variability of conditions that can occur in nature during this complex process.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 34
Serial Issue: 9
Title: Acceleration of sinter diagenesis in an active fumarole, Taupo volcanic zone, New Zealand
Affiliation: University of Auckland, Geology Department, Auckland, New Zealand
Pages: 749-752
Published: 200609
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 30
Accession Number: 2006-071523
Categories: Sedimentary petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2006157
Illustration Description: illus. incl. sketch map
S38°28'60" - S38°28'60", E176°09'00" - E176°09'00"
Secondary Affiliation: University of London, GBR, United KingdomUniversity of Utah, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200641

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