High-Mg basaltic pillow lavas, important for an understanding of the petrogenetic evolution of the Tertiary volcanism of Sardinia, have recently been recognized in the lower part of the Early-Burdigalian volcano-sedimentary succession of the Villanovaforru (VF) area (Southern Sardinian Trough). Their textures vary from porphyritic to highly phyric types (doleritic) and the paragenesis is represented by Pl+Ol+Cpx±Opx±Opq. These basalts are sub-alkaline with a tholeiitic tendency; they display high MgO (mg-number 64-68), high Ni and Cr contents and their geochemical features are related to subduction-related magmas, with large-ion lithophile element enrichment and negative Nb, Zr and Ce spikes in mantle-normalized diagrams. The mineralogical and geochemical characteristics indicate that the VF basalts crystallized from primitive magmas within an extension-dominated tectonic setting. The presence of primitive basalts suggests crustal thinning in association with the Burdigalian extensional tectonics affecting the Sardinian Trough.
High-Mg Tertiary basalt in Southern Sardinia (Italy)
MATTIOLI, MICHELE;GUERRERA, FRANCESCO;TRAMONTANA, MARIO;RAFFAELLI, GIULIANA;D'ATRI, MARIO
2000
Abstract
High-Mg basaltic pillow lavas, important for an understanding of the petrogenetic evolution of the Tertiary volcanism of Sardinia, have recently been recognized in the lower part of the Early-Burdigalian volcano-sedimentary succession of the Villanovaforru (VF) area (Southern Sardinian Trough). Their textures vary from porphyritic to highly phyric types (doleritic) and the paragenesis is represented by Pl+Ol+Cpx±Opx±Opq. These basalts are sub-alkaline with a tholeiitic tendency; they display high MgO (mg-number 64-68), high Ni and Cr contents and their geochemical features are related to subduction-related magmas, with large-ion lithophile element enrichment and negative Nb, Zr and Ce spikes in mantle-normalized diagrams. The mineralogical and geochemical characteristics indicate that the VF basalts crystallized from primitive magmas within an extension-dominated tectonic setting. The presence of primitive basalts suggests crustal thinning in association with the Burdigalian extensional tectonics affecting the Sardinian Trough.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
