Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy

L. Pioli, R. Lanza, Michael H Ort, M. Rosi

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.

Original languageEnglish (US)
Pages (from-to)1123-1137
Number of pages15
JournalBulletin of Volcanology
Volume70
Issue number9
DOIs
StatePublished - 2008

Fingerprint

magnetic fabric
welding
tuff
magnetic anisotropy
Welding
Textures
texture
ignimbrite
Magnetic susceptibility
Anisotropy
Ferrosoferric Oxide
Magnetization
magnetite
crystal
petrofabric
natural remanent magnetization
remanent magnetization
vesicle
magnetization
Crystals

Keywords

  • High-grade tuff
  • Laminar flow
  • Magnetic anisotropy
  • Rheomorphism
  • Sardinia
  • Welding

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy. / Pioli, L.; Lanza, R.; Ort, Michael H; Rosi, M.

In: Bulletin of Volcanology, Vol. 70, No. 9, 2008, p. 1123-1137.

Research output: Contribution to journalArticle

@article{13867c0dc4374bfdb396f70e49976bec,
title = "Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy",
abstract = "Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.",
keywords = "High-grade tuff, Laminar flow, Magnetic anisotropy, Rheomorphism, Sardinia, Welding",
author = "L. Pioli and R. Lanza and Ort, {Michael H} and M. Rosi",
year = "2008",
doi = "10.1007/s00445-008-0194-1",
language = "English (US)",
volume = "70",
pages = "1123--1137",
journal = "Bulletin of Volcanology",
issn = "0258-8900",
publisher = "Springer Verlag",
number = "9",

}

TY - JOUR

T1 - Magnetic fabric, welding texture and strain fabric in the Nuraxi Tuff, Sardinia, Italy

AU - Pioli, L.

AU - Lanza, R.

AU - Ort, Michael H

AU - Rosi, M.

PY - 2008

Y1 - 2008

N2 - Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.

AB - Anisotropy of magnetic susceptibility (AMS) has been used to interpret flow directions in ignimbrites, but no study has demonstrated that the AMS fabric corresponds to the flow fabric. In this paper, we show that the AMS and strain fabric coincide in a high-grade ignimbrite, the Nuraxi Tuff, a Miocene rhyolitic ignimbrite displaying a wide variability of rheomorphic features and a well-defined magnetic fabric. Natural remanent magnetization (NRM) data indicate that the magnetization of the tuff is homogeneous and was acquired at high temperatures by Ti-magnetite crystals. Comparison between the magnetic fabric and the deformation features along a representative section shows that AMS and anisotropy of isothermal remanent magnetization (AIRM) fabric are coaxial with and reproduce the shape of the strain ellipsoid. Magnetic tests and scanning electron microscopy observations indicate that the fabric is due to trails of micrometer-size, pseudo-single domain, magnetically interacting magnetite crystals. Microlites formed along discontinuities such as shard rims and vesicle walls mimicking the petrofabric of the tuff. The fabric was thus acquired after deposition, before late rheomorphic processes, and accurately mimics homogeneous deformation features of the shards during welding processes and mass flow.

KW - High-grade tuff

KW - Laminar flow

KW - Magnetic anisotropy

KW - Rheomorphism

KW - Sardinia

KW - Welding

UR - http://www.scopus.com/inward/record.url?scp=50249185883&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=50249185883&partnerID=8YFLogxK

U2 - 10.1007/s00445-008-0194-1

DO - 10.1007/s00445-008-0194-1

M3 - Article

AN - SCOPUS:50249185883

VL - 70

SP - 1123

EP - 1137

JO - Bulletin of Volcanology

JF - Bulletin of Volcanology

SN - 0258-8900

IS - 9

ER -