Geological Society of America

T21 When Water Meets Rock: Aqueous Alteration in the Solar System

Sunday, 1 November 2015
8:00 AM - 12:00 PM
Room 344

HYPERSPECTRAL MAPPING OF A HYDROTHERMAL VUG AND ITS WEATHERING PRODUCTS AT THE HAUGHTON IMPACT STRUCTURE, CANADA

Paper number: T21-5
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM

Authors

Rebecca N. Greenberger Presenting Author
Brown University, Providence, RI
Rebecca N. Greenberger Presenting Author
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA
John F. Mustard
Brown University, Providence, RI
Gordon Osinski
University of Western Ontario, London, ON
Livio L. Tornabene
University of Western Ontario, London, ON
Alexandra Pontefract
University of Western Ontario, London, ON
Cassandra L. Marion
University of Western Ontario, London, ON
Roberta L. Flemming
University of Western Ontario, London, ON
Janette H. Wilson
Headwall Photonics, Inc, Fitchburg, MA
Edward A. Cloutis
University of Winnipeg, Winnipeg, MB

Abstract

Meteorite impacts into H₂O-bearing targets can generate hydrothermal systems, modifying impactite mineralogies. We present the results of a project that uses hyperspectral imaging in the field to map a hydrothermal calcite- and marcasite-bearing vug and the low temperature weathering products within the clast-rich impact melt rocks at the 23-km diameter Haughton impact structure, Devon Island, Canada. The goals of this work are to characterize the spectral signatures of the hydrothermal and weathering assemblages, map their spatial distributions, and understand the evolving aqueous environments and the implications for habitability using imaging spectroscopy and supporting analyses of chemistry and mineralogy in the laboratory.

We infer the following alteration sequence. Marcasite formed first at elevated temperatures and under acidic and reducing conditions. At low temperatures and under acidic and more oxidizing conditions, thin brown coatings of gypsum and jarosite formed on the marcasite through very limited interaction with water. Then, a popcorn-textured mixture of fibroferrite and copiapite precipitated on relatively flat surfaces below the marcasite from acidic and more oxidized fluids. Further interaction with water dissolved some copiapite and fibroferrite, creating acidic fluids that reacted with the calcite host rock to form dark red coatings of gypsum and ferric oxide and sulfate.

This sequence of secondary phases shows transitions from high to low temperature, acidic to more neutral, and reducing to oxidizing aqueous conditions. In addition, some changes in mineralogy reflect interaction of fluids with the calcite host rock in addition to the marcasite. The sequence of mineral assemblages resulting from water-rock interactions over a scale of meters is similar to those observed at gossans and oxidized massive sulfide deposits on a much larger scale. In addition, the boundaries between assemblages mapped here have redox gradients ideal for microbial colonization as proposed by Izawa et al. (2011). Finally, this vug is the modern, surface expression of a post-impact hydrothermal system and has abundant low temperature weathering assemblages despite the initial hydrothermal origin.