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Cindy Lizeth Urueña

Cindy Urueña

Doctoral student

Cindy Lizeth Urueña

The effect of metamorphism on the aggregate properties of gabbroic rocks

Author

  • Cindy Urueña
  • Charlotte Möller
  • Jenny Andersson
  • Jan Erik Lindqvist
  • Mattias Göransson

Summary, in English

Granitic rocks are durable materials sought after for the production of road and railroad aggregates. Granitic bedrock commonly, however, includes gabbroic components, which may enhance or decrease the aggregate performance. This study evaluates the variation in resistance to fragmentation (Los Angeles value, LA) and wear/abrasion (micro-Deval value, MDE) for the fraction 10/14 mm of gabbro in different metamorphic states. Samples were collected along a 150-km profile where metamorphic conditions grade from epidote–amphibolite to high-pressure granulite-facies, and the degree of metamorphic recrystallization varies with the amount of hydrous fluid. Rocks with no or incipient metamorphic recrystallization preserving their primary igneous fabric and interlocking texture meet the criteria for both asphalt base course and track ballast in railroad, with LA and MDE values below 25% and 14%, respectively. Mafic granulite and fine-grained amphibolite have LA values below 25% and can be used in unbound layers. Mafic granulites crystallize at high temperatures but commonly preserve a relict igneous texture due to limited hydration. Coarse-grained amphibolite and migmatitic amphibolite have the poorest performance. They recrystallized at hydrous conditions, leading to complete recrystallization, grain coarsening, and loss of interlocking igneous texture. This study shows that both temperature and infiltration of hydrous fluids significantly affect the technical properties. Even at high metamorphic temperatures, gabbroic rocks may yield aggregates of high technical performance. At hydrous conditions, however, recrystallization results in rock aggregates suitable for unbound layers only. The variation in metamorphic grade and hydration is easily assessed by the geologist in the field and by using standard petrographic microscopy.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2022

Language

English

Publication/Series

Bulletin of Engineering Geology and the Environment

Volume

81

Issue

5

Document type

Journal article

Publisher

Springer

Topic

  • Geochemistry

Keywords

  • Crushed rock aggregates
  • Gabbroic rocks
  • Los Angeles
  • Metamorphic recrystallization
  • Micro-Deval

Status

Published

ISBN/ISSN/Other

  • ISSN: 1435-9529