Banks, DA orcid.org/0000-0001-9118-5298, Bozkaya, G and Bozkaya, O (2019) Direct Observation and Measurement of Au and Ag in Epithermal Mineralizing Fluids. Ore Geology Reviews, 111. 102955. ISSN 0169-1368
Abstract
Colloidal gold particles have been observed in c. 300 °C low salinity fluids from the Arapucandere intermediate sulphidation epithermal base-metal-Au deposit in NW Turkey. This is the first time colloidal gold has been recorded in an ancient mineralizing fluid. Growth, in veins, of large euhedral quartz crystals, after the deposition of sulphides, occurred in a number of stages from the introduction of fresh pulses of fluid. The quartz overgrowths have a fibrous texture which facilitated trapping of large elongate fluid inclusions between the quartz fibres which grew perpendicular to the crystal faces of the pre-existing quartz. Episodic periods of intense trapping of fluid inclusions occurred throughout the growth of quartz. Trapped within primary fluid inclusions are numerous particles of gold, the largest observed is c. 1 μm but most are smaller. BSE element mapping shows these to contain Au, Ag, Cu ± Hg. LA-ICP-MS profiles of the fluid inclusions confirm Au and Ag is not present in solution, being present as numerous particles. We have quantified the concentration of gold in fluid inclusions which are orders of magnitude greater than has been previously measured or thought likely in crustal fluids. The average Ag concentration is c. 32 ppm and Au is c. 41 ppm but the maximum concentrations of both may reach several 100’s to 1000 ppm. Calcite forms a coating on the inner surface of the inclusions and barite, pyrite, galena, sphalerite and unidentified minerals are also present with the Au-Ag particles. It is clear that the Au-Ag particles could not have precipitated in the fluid inclusions, therefore they must have precipitated elsewhere and been carried with the hydrothermal fluid. The high concentrations and their colloidal nature have implications for the enrichment of gold in mineral deposits.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2019 Elsevier B.V. All rights reserved. This is an author produced version of an article published in Ore Geology Reviews. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Fluid inclusions; Colloidal gold; LA-ICP-MS; Epithermal; Turkey |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 05 Jun 2019 11:02 |
Last Modified: | 04 Jun 2020 00:38 |
Status: | Published |
Publisher: | Elsevier BV |
Identification Number: | 10.1016/j.oregeorev.2019.102955 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:146943 |