COMPOSITIONS OF GABBRO INTRUSIONS IN THE KRESTOVSKY ZONE (western Baikal region): A RECORD OF PLUME-SUPRASUBDUCTION MANTLE INTERACTION
A.V. Lavrenchuk1,2, E.V. Sklyarov3,4, A.E. Izokh1,2, A.B. Kotov5, E.B. Sal’nikova5, V.S. Fedorovsky6, A.M. Mazukabzov3
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
4Far Eastern Federal University, ul. Sukhanova 8, Vladivostok, 690950, Russia
5Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034, Russia
6Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 109017, Russia
Keywords: Mafic magmatism, isotopic age, plume-lithosphere interaction, magma source, western Baikal region
Abstract
We provide new geochemical and isotope-geochronological evidence for gabbro intrusions of the Krestovsky zone in the Olkhon composite terrane. The intrusions belong to the Birkhin (~500 Ma) and Ust’-Krestovsky (~470 Ma) complexes, which underwent several pulses of magmatism. Rock structures and textures record magma crystallization in tectonically turbulent conditions. The compositions of gabbro are similar to those of subduction-related basalts, but the Ust’-Krestovsky gabbro is richer in incompatible elements than the Birkhin rocks. A similar composition trend of gabbro is observed in other areas of the Central Asian Orogenic Belt (CAOB): southeastern Tuva, Gornaya Shoria, and western Mongolia. We suggest a model of regular composition changes in parental magmas during the interaction of a mantle plume with suprasubductional lithospheric mantle.
|
