Caledonian high-pressure metamorphism in the Strona-Ceneri Zone (Southern Alps of southern Switzerland and northern Italy)

摘要: The Strona-Ceneri Zone comprises a succession of polymetamorphic, pre-Alpidic basement rocks including ortho- and paragneisses, metasedimentary schists, amphibolites, eclogites. rock pile represents Late Proterozoic or Palaeozoic subduction accretion complex that was intruded by Ordovician granitoids. Eclogites, which occur as lenses within the ortho-paragneiss xenoliths granitoids record related high-pressure event (D1) with peak metamorphic conditions 710 ± 30 °C at 21.0 2.5 kbar. After isothermal uplift, eclogites experienced Barrowtype (D2) tectonometamorphic overprint under amphibolite facies (570-630 °C, 7-9 kbar). U-Pb dating on zircon gives age 457 5 Ma, syn-eclogite rutile 206Pb/238U 443 19 Ma classifying Caledonian event. These data show main evolution most probably took place in convergent margin scenario, accretion, eclogitization MOR-basalt, polyphase (D1 D2) deformation, anatexis magmatism all occurred during Ordovician. metamorphism, subsequent Barrow-type metamorphism are believed to be collision northern Gondwana.