Petrophysical Characteristics of Naturally Deformed Rocks

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Crystallography and Physical Chemistry of Minerals & Nanominerals".

Deadline for manuscript submissions: closed (18 December 2021) | Viewed by 4265

Special Issue Editors

Department of Biological, Geological and Environmental Sciences (BIOMLG), University of Catania, 95129 Catania, Italy
Interests: microtectonics; rock rheology; petrophysics
Special Issues, Collections and Topics in MDPI journals
Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland
Interests: rock magnetism; magnetic fabrics; anisotropy
Department of Biological, Geological and Environmental Sciences (BIOMLG), University of Catania, 95129 Catania, Italy
Interests: petrophysics; anisotropy; petrofabric
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Petrophysical properties of rocks and their anisotropy are fundamental aspects when a comprehensive framework of rock properties is needed.

Naturally deformed rocks commonly show macroscopic fabrics characterized by typical features (e.g., CPO and SPO, microfractures, banding) that allow determining characteristics of the dominant stress field. Deformed rocks therefore represent an interesting opportunity to study tectonic processes or fluid migration.

The deformation behavior of mono- and poly- mineralic rocks is influenced by their mineralogy and modal composition, in particular the rheology contrast between weak and strong constituent minerals and their connectivity. Deformation results in mineral fabrics in rocks as it causes both shape as well as crystallographic preferred orientation of minerals. In turn, the mineral alignment in deformed rocks provides information on the conditions under which they deformed and also leads to anisotropy pore space, which affects flow properties.

Linking fabric to bulk rock properties is the aim of many studies. A fast and efficient way to assess microfabrics is via the anisotropy of physical properties (e.g., seismic velocities, magnetic susceptibility, thermal diffusivity, electrical conductivity, permeability). Anisotropy-based interpretation of deformation and flow processes requires a detailed, thorough, and quantitative understanding of the sources of the anisotropy. Based on this understanding, robust and reliable interpretations of natural rock deformation are possible. This allows a better understanding of the tectonic processes active on Earth and possibly also infers the evolution of other planets, showing traces of past deformation-related structures.

Seismic anisotropy significantly influences geophysical models of earthquake-prone areas, contributing to improve mitigation of seismic waves on buildings.

This Special Issue welcomes articles on the following main categories:

- Understanding/modeling the relationships between rock fabric and measured anisotropy and method development;
- Application of anisotropy measures to interpret geodynamics/tectonics/fluid migration;
- Correlations between different types of anisotropy.

Dr. Eugenio Fazio
Prof. Dr. Andrea R. Biedermann
Prof. Dr. Rosalda Punturo
Guest Editors

Manuscript Submission Information

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Keywords

  • Magnetic fabrics
  • Seismic anisotropy
  • Crystallographic preferred orientation (CPO)
  • Shape preferred orientation (SPO)
  • Mineral rheology
  • Phase interconnectivity
  • Fluid migration
  • Stylolites
  • Reservoir characterization
  • Pores
  • Permeability
  • Microfractures
  • Shear bands
  • Synchrotron-based micro-CT imaging

Published Papers (2 papers)

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Research

17 pages, 21672 KiB  
Article
Magnetic Fabrics and Petrography of Rocksalts Reveal Preferred Orientation of Anhydrites within a Halite Matrix
Minerals 2022, 12(2), 192; https://doi.org/10.3390/min12020192 - 31 Jan 2022
Cited by 1 | Viewed by 1879
Abstract
We investigate the magnetic fabrics and microstructures of diamagnetic rocksalt samples from the Sedom salt wall (diapir), Dead Sea Basin, as possible strain markers. A comprehensive study of anisotropy of magnetic susceptibility (AMS), combined with magnetic, microtextural, geochemical and mineralogical analyses allows us [...] Read more.
We investigate the magnetic fabrics and microstructures of diamagnetic rocksalt samples from the Sedom salt wall (diapir), Dead Sea Basin, as possible strain markers. A comprehensive study of anisotropy of magnetic susceptibility (AMS), combined with magnetic, microtextural, geochemical and mineralogical analyses allows us to depict the deformation mechanisms and to reveal the mineral sources of the AMS. The rocksalts are composed of halite as the major mineral phase (>80%) and anhydrite as a minor phase (5–20%), and have an average magnetic susceptibility value of −13.4 ± 0.7 × 10−6 SI. Ferromagnetic and paramagnetic minerals make a negligible contribution to the bulk magnetic properties of the samples. The AMS indicates and reveals significant anisotropy with the maximum susceptibility axis (K1) subparallel to the bedding strike, although the cubic halite crystals are isotropic. Polarizing microscope and SEM images show preferred alignment of needle-like anhydrite crystals parallel to the direction of the K1 axis. Petrographic investigation of gamma irradiated thin sections reveals the deformation recorded in the microstructures of the rocksalts and points to a dominant contribution by dislocation creep, although both dislocation creep and pressure solution were active deformation mechanisms. We infer that during dislocation creep, the thin bands of anhydrite crystals deform along with the surrounding halite grains. We suggest that although the shape preferred orientation of halite grains is not indicative of finite strain because of resetting by grain boundary migration, the preferred orientation of the anhydrite crystals may be. These results suggest that the AMS of the rocksalts provides a textural proxy that reflects deformation processes of the rocksalts, despite their very low magnetic susceptibility. Full article
(This article belongs to the Special Issue Petrophysical Characteristics of Naturally Deformed Rocks)
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24 pages, 5861 KiB  
Article
Size Effect of the Number of Parallel Joints on Uniaxial Compressive Strength and Characteristic Strength
Minerals 2022, 12(1), 62; https://doi.org/10.3390/min12010062 - 03 Jan 2022
Cited by 4 | Viewed by 1289
Abstract
The number of parallel joints has an impact on the size effect of the uniaxial compressive strength and characteristic strength of a rock; however, the relationships between them are yet to be derived. We studied the influence of the number of joints and [...] Read more.
The number of parallel joints has an impact on the size effect of the uniaxial compressive strength and characteristic strength of a rock; however, the relationships between them are yet to be derived. We studied the influence of the number of joints and rock size on the uniaxial compressive strength of the rock. This study established ten numerical simulation programs using numerical simulations and the RFPA software. Stress–strain curves of different numbers of parallel joints and sizes of rocks were analyzed. Relationships between the uniaxial compressive strength and number of parallel joints and rock size were proposed, and their special functions were obtained. Mathematical models between rock characteristic size, rock characteristic strength and the number of parallel joints were established. Simulations of the verification program confirmed that these relationships are still applicable after the angle of parallel joints changes. Full article
(This article belongs to the Special Issue Petrophysical Characteristics of Naturally Deformed Rocks)
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