Pb and Hf isotope evidence for mantle enrichment processes and melt interactions in the lower crust and lithospheric mantle in Miocene orogenic volcanic rocks from Monte Arcuentu (Sardinia, Italy)

• Published in: Geosphere (Boulder, Colo.) Colo.), 2018-06, Vol.14 (3), p.926-950
• Main Authors: Kempton, Pamela D, Downes, Hilary, Lustrino, Michele
• Format: Article
• Language: English
• Subjects: andesites; basalts; Cenozoic; crust; enrichment; Europe; fractional crystallization; geochemistry; Geophysics; hafnium; Hf-177/Hf-176; igneous and metamorphic rocks; igneous rocks; isotope ratios; isotopes; Italy; lead; magma contamination; magmas; mantle; metals; Miocene; Monte Arcuentu; Nd-144/Nd-143; neodymium; Neogene; Pb-206/Pb-204; Pb-207/Pb-204; Pb-208/Pb-204; Petrology; plate tectonics; radioactive isotopes; rare earths; Sardinia Italy; solid Earth (tectonophysics); Southern Europe; stable isotopes; subduction; Tertiary; volcanic rocks
• ISSN: 1553-040X; 1553-040X
• DOI: 10.1130/GES01584.1

Miocene (ca. 18 Ma) subduction-related basalts and basaltic andesites from Monte Arcuentu, southern Sardinia, Italy, show a remarkable correlation between 87Sr/86Sr (from ∼0.705 to ∼0.711) over a small range of SiO2 (∼51-58 wt%) that contrasts with most other orogenic volcanic suites worldwide. New high-precision Pb and Hf isotope data help to constrain the petrogenesis of these rocks. The most primitive Monte Arcuentu rocks (MgO >8.5 wt%) were sourced from a mantle wedge metasomatized by melts derived from terrigenous sediment, likely derived from Archean terranes of northern Africa. This gave rise to magmas with high 87Sr/86Sr (0.705-0.709) and 207Pb/204Pb (15.65-15.67) with moderate εHf (-1 to +8) and εNd (-6 to +1), but it does not account for the full range of compositions observed. More evolved rocks (MgO