Fluid inclusions in high pressure/low temperature rocks from the Calabrian Arc (Southern Italy): the burial and exhumation history of the subduction‐related Diamante‐Terranova unit

• Published in: Journal of Metamorphic Geology
• Main Authors: INVERNIZZI, C., VITYK, M., CELLO, G., BODNAR, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1998
• Subjects: Terranova
• Online Access: http://dx.doi.org/10.1111/j.1525-1314.1998.00138.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1998.00138.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1998.00138.x

The Diamante‐Terranova Unit (DIATU), in the Calabrian Arc of southern Italy, is part of an ophiolitic sequence involved in a high pressure/low temperature event ( P =8 kbar; T =400 °C) followed by re‐equilibration at greenschist facies conditions ( P =3 kbar; T =300 °C). The rocks contain two types of quartz–calcite veins – an earlier generation of deformed, folded and faulted veins formed during or before subduction, and a later set of planar, undeformed veins formed during exhumation of the DIATU. The earlier folded quartz–calcite veins contain regularly shaped aqueous inclusions as well as inclusions with a highly irregular dendritic texture. The later planar veins contain only regularly shaped aqueous inclusions similar to those in the earlier veins. In both vein types, all inclusions are demonstrably secondary in origin. Regularly shaped inclusions from both vein types are low salinity (0–5 wt% NaCl). Most contain liquid and vapour and homogenize to the liquid (Th 135–180 °C), whereas others contain only liquid at room temperature. Both the two‐phase and monophase inclusions occur in the same fractures and are thought to record the same trapping event, with the monophase inclusions remaining metastable liquid at room temperature. No microthermometric data could be obtained from the dendritic inclusions in the earlier folded veins. Inclusions with the highly irregular dendritic texture found in the earlier veins are similar to those produced experimentally during laboratory‐induced deformation of synthetic inclusions in quartz under conditions of internal underpressure, simulating either isobaric cooling or isothermal compression. The occurrence of inclusions with the dendritic texture in the earlier folded veins, and their absence from the later planar veins, suggests that the earlier veins formed before or during subduction and were folded and faulted in a compressional environment and their contained fluid inclusions were modified to produce the dendritic texture. During later uplift of the DIATU, planar ...