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Three-dimensional textural and quantitative analyses of orogenic gold at the nanoscale

M. Sayab, J. P. Suuronen, F. Molnar, J. Villanova, A. Kallonen, H. O'Brien, R. Lahtinen and M. Lehtonen
Three-dimensional textural and quantitative analyses of orogenic gold at the nanoscale
Geology (Boulder) (September 2016) 44 (9): 739-742

Abstract

Ore textures provide direct clues for tracking ore-forming processes. In this regard, most of our knowledge is generally based on two-dimensional (2-D) image analyses, leaving a considerable gap in comprehending three-dimensional (3-D) in-situ textural settings. Recent advances in lab-based and synchrotron radiation-based X-ray computed microtomography and nanotomography have made it possible to visualize and quantify rock volumes in a 3-D space. In this study, we first analyzed microscale textures in oriented drill cores from the world-class Suurikuusikko orogenic gold deposit of northern Finland using lab-based X-ray computed microtomography. The technique revealed a kinematic history and a number of in-situ 3-D quantitative aspects including size, shape, spatial distribution, and geometrical orientation of arsenopyrite and pyrite in a highly altered host-rock matrix. For 3-D nanotomography, the experimental procedure known as holotomography was adopted. Individual arsenopyrite crystals were separated and scanned with voxel sizes ranging from 50 nm to 150 nm using the X-ray nanoprobe beamline (ID16B) at the European Synchrotron Radiation Facility, France. This ultrahigh-resolution technique illustrated the 3-D distribution of micron- to nanoscale gold inclusions, mostly associated with primary rutile or along secondary microfractures inside arsenopyrite. The workflow, from micro- to nanotomography, outlined in this study offers an indispensable new technique in quantifying and characterizing 3-D textural settings of ores, which is otherwise impossible with conventional 2-D imaging devices. The method can also be highly useful in evaluating the amenability of ores to treatment with different processing options.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 44
Serial Issue: 9
Title: Three-dimensional textural and quantitative analyses of orogenic gold at the nanoscale
Affiliation: Geological Survey of Finland, Espoo, Finland
Pages: 739-742
Published: 201609
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 15
Accession Number: 2016-083471
Categories: Economic geology, geology of ore depositsStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2016241
Illustration Description: illus.
N67°55'00" - N67°55'00", E25°23'60" - E25°23'60"
Secondary Affiliation: European Synchrotron Radiation Facility, FRA, FranceUniversity of Helsinki, FIN, Finland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201640
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