Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane
A complex system of mono- and polymineralic centimeter-thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet-rich veins are margined by an amphibole layer at the interface...
Main Authors: | , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
MDPI AG
2020-08-01
|
Series: | Geosciences |
Subjects: | |
Online Access: | https://www.mdpi.com/2076-3263/10/9/344 |
id |
doaj-a35003f21e4049fb971467baf2f24f6f |
---|---|
record_format |
Article |
spelling |
doaj-a35003f21e4049fb971467baf2f24f6f2020-11-25T03:37:18ZengMDPI AGGeosciences2076-32632020-08-011034434410.3390/geosciences10090344Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite TerraneGabriele Cruciani0Marcello Franceschelli1Hans-Joachim Massonne2Giovanni Musumeci3Massimo Scodina4Dipartimento di Scienze Chimiche e Geologiche, Università di Cagliari-S.S. 554 Cittadella Universitaria, 09042 Monserrato (CA), ItalyDipartimento di Scienze Chimiche e Geologiche, Università di Cagliari-S.S. 554 Cittadella Universitaria, 09042 Monserrato (CA), ItalySchool of Earth Sciences, China University of Geosciences, Lumo Road 388, Wuhan 430074, ChinaDipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, ItalyDipartimento di Scienze Chimiche e Geologiche, Università di Cagliari-S.S. 554 Cittadella Universitaria, 09042 Monserrato (CA), ItalyA complex system of mono- and polymineralic centimeter-thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet-rich veins are margined by an amphibole layer at the interface with the host rock and/or show replacement of epidote concentrated in the vein core. Together with homogeneous matrix garnet (Grt1), millimetric, euhedral, and strongly zoned garnet porphyroblasts occur within these veins. The estimated pressure–temperature conditions (P = 1.0–1.7 GPa, T = 650–750 °C) for the formation of Grt1 match the metamorphic peak and early exhumation derived previously for the host rocks and confirm that the garnet veins also formed under high-pressure (HP) conditions. The igneous protolith of the host rocks experienced HP metamorphism in a subduction zone and underwent exhumation in an exhumation channel. The vein system in the ultrabasic amphibolites formed by cyclic hydrofracturing as rapid and transient events such as crack-seal veining. The growth of multiple vein-filling mineral assemblages indicates the formation of separate vein-producing cycles.https://www.mdpi.com/2076-3263/10/9/344ultrabasic amphibolitemetamorphic vein systemP-T evolutionVariscan Sardinia |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Gabriele Cruciani Marcello Franceschelli Hans-Joachim Massonne Giovanni Musumeci Massimo Scodina |
spellingShingle |
Gabriele Cruciani Marcello Franceschelli Hans-Joachim Massonne Giovanni Musumeci Massimo Scodina Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane Geosciences ultrabasic amphibolite metamorphic vein system P-T evolution Variscan Sardinia |
author_facet |
Gabriele Cruciani Marcello Franceschelli Hans-Joachim Massonne Giovanni Musumeci Massimo Scodina |
author_sort |
Gabriele Cruciani |
title |
Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane |
title_short |
Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane |
title_full |
Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane |
title_fullStr |
Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane |
title_full_unstemmed |
Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane |
title_sort |
garnet-rich veins in an ultrabasic amphibolite from ne sardinia, italy: an example of vein mineralogical re-equilibration during the exhumation of a granulite terrane |
publisher |
MDPI AG |
series |
Geosciences |
issn |
2076-3263 |
publishDate |
2020-08-01 |
description |
A complex system of mono- and polymineralic centimeter-thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet-rich veins are margined by an amphibole layer at the interface with the host rock and/or show replacement of epidote concentrated in the vein core. Together with homogeneous matrix garnet (Grt1), millimetric, euhedral, and strongly zoned garnet porphyroblasts occur within these veins. The estimated pressure–temperature conditions (P = 1.0–1.7 GPa, T = 650–750 °C) for the formation of Grt1 match the metamorphic peak and early exhumation derived previously for the host rocks and confirm that the garnet veins also formed under high-pressure (HP) conditions. The igneous protolith of the host rocks experienced HP metamorphism in a subduction zone and underwent exhumation in an exhumation channel. The vein system in the ultrabasic amphibolites formed by cyclic hydrofracturing as rapid and transient events such as crack-seal veining. The growth of multiple vein-filling mineral assemblages indicates the formation of separate vein-producing cycles. |
topic |
ultrabasic amphibolite metamorphic vein system P-T evolution Variscan Sardinia |
url |
https://www.mdpi.com/2076-3263/10/9/344 |
work_keys_str_mv |
AT gabrielecruciani garnetrichveinsinanultrabasicamphibolitefromnesardiniaitalyanexampleofveinmineralogicalreequilibrationduringtheexhumationofagranuliteterrane AT marcellofranceschelli garnetrichveinsinanultrabasicamphibolitefromnesardiniaitalyanexampleofveinmineralogicalreequilibrationduringtheexhumationofagranuliteterrane AT hansjoachimmassonne garnetrichveinsinanultrabasicamphibolitefromnesardiniaitalyanexampleofveinmineralogicalreequilibrationduringtheexhumationofagranuliteterrane AT giovannimusumeci garnetrichveinsinanultrabasicamphibolitefromnesardiniaitalyanexampleofveinmineralogicalreequilibrationduringtheexhumationofagranuliteterrane AT massimoscodina garnetrichveinsinanultrabasicamphibolitefromnesardiniaitalyanexampleofveinmineralogicalreequilibrationduringtheexhumationofagranuliteterrane |
_version_ |
1724545923342663680 |