Rodingites from Frido Unit: evidences for metasomatic alteration.
1
Citation
0
Reference
18
Related Paper
Citation Trend
Keywords:
Metasomatism
Cite
Cite
Citations (0)
Dike
Metasomatism
Cite
Citations (0)
Abstract The metadolerite dykes from the Frido ophiolitic sequence reflect strain partitioning with textures evolving from magmatic intersertal/intergranular, blast-ophitic and incomplete metamorphic recrystallization. Amphibole and plagioclase are the main minerals in these rocks. Amphibole composition reflects both bulk compositional and P–T changes. Different Ti, IV Al values between the brown and green amphiboles clearly indicate genetic conditions of amphiboles developed in ocean-floor hydrothermal metamorphic conditions. The electron microprobe analysis showed that the assemblage developed during ocean-floor hydrothermal type metamorphism (M1) consists of two main amphibole varieties: a brown one, and green; instead during orogenic metamorphism (M2) developed a blue amphibole. The magmatic plagioclase is anorthite (PL1) and the metamorphic plagioclase are oligoclase (PL2), albite (PL3). The estimated P–T conditions are in favour of their metamorphism under ocean-floor hydrothermal type. The variety of amphibole compositions and the plagioclase found in the metadolerite dykes offers useful constraints to reconstruction of the correlated environmental conditions providing new insights on the oceanic metamorphic evolution of this orogenic sector of southern Apennines.
Amphibole
Cite
Citations (7)
Amphibole
Metasomatism
Cite
Citations (0)
1. Serpentine and Serpentinites 2. Serpentine-Group Minerals and the Processes which form Them 3. Patterns in Outcrop 4. Textures in Thin Section 5. Hydration and Serpentinization of Peridotites 6. Serpentine Recrystallization and Replacement 7. Deserpentinization 8. Rodingites, Albitites, and Other Rocks formed by Metasomatism 9. Carbonates, Sulfides, and Serpentine-related Mineralization 10. Geochemical and Geophysical Data 11. Serpentinites in their Tectonic Settings 14. Epilogue
Outcrop
Metasomatism
Recrystallization (geology)
Cite
Citations (342)
Metasomatism
Cite
Citations (0)
The Mount Avic ophiolite mainly consists of a large mass of serpentinites, which constitutes the base of a subunit of the Piemonte ophiolitic nappe. Serpentinites represent the mantle portion of the oceanic lithosphere of the Mesozoic Tethys and consist of antigorite-titanian clinohumite-diopside schists as products of oceanic metasomatism and tectono-metamorphic evolution of the Alpine orogeny, at the expense of abyssal peridotite mineral assemblage. The serpentinite mass includes metagabbro pods (without metasomatic alteration) and associated rodingitic dykes. Various rodingitic dykes can be distinguished on the basis of their mineralogical assemblages. The main assemblage consists of ugranditic garnet, chlorite ± diopside ± epidote ± vesuvianite. We observed also some other peculiar rodingites such as vesuvianite-chlorite-, diopside-epidote-chlorite-, and diopside-chlorite-bearing rodingites, as distinctive of the Mount Avic massif, as well as rodingitic reaction zones and foliated rodingites with chlorite, diopside, or epidote. These mineral assemblages are strictly related to the chemistry of the protolith (probably mafic dykes within serpentinite), as well as to the oceanic rodingitization during the serpentinization event and to the Alpine evolution that affected the Mount Avic massif.
Metasomatism
Diopside
Massif
Cite
Citations (22)
Metasomatism
Cite
Citations (0)
Accretionary wedge
Wedge (geometry)
Cite
Citations (0)
Metamorphic evolution of metabasite dykes included in tectonic slices of serpentinites in ophiolitic rocks from Frido Unit (Pollino Massif) is reported.Petrological analysis via PT pseudo-sections calculation using Theriak-Domino software have been done for the system Na2O-CaOK2O-MgO-FeO-Al2O3SiO2-H2O (NCKMFASH) and showed that the pressure and temperature conditions of blueschist metamorphism are estimated to 8-12 kbar and 300-400 °C. The minerals in the metabasite dykes are chemically homogeneous, suggesting that they are almost completely equilibrated. The retrograde metamorphic evolution of the metabasites from high- to intermediate-pressure conditions is documented by the occurrence of minerals belonging to pumpellyite facies assemblages.High-pressure metamorphism in blueschist facies condition is related to the subduction of Frido Unit in low gradient conditions. The use of pseudosections stepwise controlled by petrographic observations allowed to estimate the P-T conditions in metabasite dykes.
Blueschist
Massif
Cite
Citations (7)