Secchi, Francesco and Cincotti, Francesco and Cherchi, Gian Piero and Sarria, Edoardo (2001) Geological and petrographycal aspects of late-Hercynian intrusive sequences from southern Ogliastra area (SE Sardinia, Italy). Periodico di mineralogia, Vol. 70 (3), p. 303-332. ISSN 0369-8963. Article.
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The granitoids of southern Ogliastra (central-eastern Sardinia, Italy) were emplaced at shallow levels in a nappe edifice (the so-called "thrust zone") at the end of the Hercynian orogenesis. Field relationships and textural characters indicate at least three pulses of hornblende-biotite granodioritic magmas (GD1, GD2, GD3), preceded by smaller amounts of tonalitic magma (TO). The leucogranitic magma of Monte Arista is late in the sequence. The granodiorite is crosscut by N-S-trending lamprophyre and mainly NW-SE-trending felsic dikes. Geological and petrographical observations indicate that most of the acidic dikes were injected before leucogranite was emplaced. The Altot-in hornblende barometer indicates pressure values of crystallization in the range from 1 to 3.5 Kb, in agreement with the common occurrence of andalusite-cordierite in the associated hornfels. Temperature estimates by the plagioclase/hornblende thermometer on tonalitic and granodioritic rocks gives Tmax of 1000°C. Petrographical and petrochemical data do not exclude a possible genetic link between TO tonalite and GD3 granodiorite. Instead, fluorite-bearing leucogranite should be considered genetically independent of the rest of the rock sequence.
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