A refined approach for quantitative kinematic vorticity number estimation using microstructures

Riccardo Graziani, Kyle P. Larson, Richard D. Law, Marc Antoine Vanier, James R. Thigpen

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

This study proposes a refined approach for quantification of the vorticity of kinematic flow in natural shear zones. This approach, here called C′-c method, is based on estimation of the angle between the flow apophyses A1 and A2 by performing two independent measurements. The tilting angle of a quartz crystallographic preferred orientation (β) and the orientation of the C′ shear bands (θ). Using these two angles it is possible to quantify the sectional vorticity number using the following formula: Wn = Cos[2(θ-β)]. Data obtained by applying the C′-c method on known shear zones well match the vorticity numbers estimated with other approaches on the same structures. In this study, we applied the C′-c method to the Abloviak Shear Zone (Torngat Orogen) and the Ben Hope Thrust (Caledonides of NW Scotland) obtaining the first vorticity data on these structures. Our data show that the C′-c method can increase the potential range of rocks in which it is possible to estimate kinematic vorticity. Our results also show that the C′-c method can be negatively affected by microscale kinematic flow partitioning, highlighting the importance of a detailed microstructure characterization of the studied rocks before any estimate of kinematic vorticity is attempted.

Original languageEnglish
Article number104459
JournalJournal of Structural Geology
Volume153
DOIs
StatePublished - Dec 2021

Bibliographical note

Funding Information:
This work was supported by a Natural Sciences and Engineering Research Council Discovery Grant and Canadian Foundation for Innovation Leaders Opportunity Fund Award to K. Larson. Additional stipend support for R. Graziani was provided by a grant through the Geo-mapping for Minerals 2 program from Natural Resources Canada . We would like to thank Prof. Carl Guilmette (Laval University) for supplying the specimens for the Abloviac shear zone. We also acknowledge Prof. Joseph White (University of New Brunswick) and Laura Nania (University of Florence) for their useful suggestions. We thank Manuel Díaz-Azpiroz (Pablo de Olavide University) and Gregory Dumond (University of Arkansas) for their constructuve comments during the revision process.

Funding Information:
This work was supported by a Natural Sciences and Engineering Research Council Discovery Grant and Canadian Foundation for Innovation Leaders Opportunity Fund Award to K. Larson. Additional stipend support for R. Graziani was provided by a grant through the Geo-mapping for Minerals 2 program from Natural Resources Canada. We would like to thank Prof. Carl Guilmette (Laval University) for supplying the specimens for the Abloviac shear zone. We also acknowledge Prof. Joseph White (University of New Brunswick) and Laura Nania (University of Florence) for their useful suggestions. We thank Manuel D?az-Azpiroz (Pablo de Olavide University) and Gregory Dumond (University of Arkansas) for their constructuve comments during the revision process.

Publisher Copyright:
© 2021 Elsevier Ltd

Keywords

  • Crystallographic preferred orientation
  • C′ shear bands
  • Kinematic vorticity
  • Scottish highlands scandian belt
  • Shear zones
  • Torngat orogen

ASJC Scopus subject areas

  • Geology

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