PILLOW BASALTS AND BLUESCHISTS ON BOL'SHOI LYAKHOVSKY ISLAND (THE NEW SIBERIAN ISLANDS) - FRAGMENTS OF THE SOUTH ANYUI OCEANIC LITHOSPHERE
A.B. Kuzmichev, E.V. Sklyarov*, and I.G. Barash*
Geological Institute of the RAS, 7 Pyzhevsky per., Moscow, 119017, Russia
* Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul. Lermontova, Irkutsk, 664033, Russia
Keywords: Arctic tectonics, oceanic basalts, blueschists, South Anyui suture, New Siberian Islands, counterclockwise PT trend of metamorphism
Pages: 1349-1363
Abstract
Low-K medium-Ti tholeiite basic rocks represented by weakly altered pillow basalts as well as by their metamorphosed counterparts (amphibolites and blueschists) are exposed on tectonic slices in the southeast of Bol'shoi Lyakhovsky Island. The rocks are depleted in light rare-earth elements and were melted out of a depleted mantle source. A different mantle source enriched in incompatible high-field strength elements, such as Th, Nb, Zr, also contributed to the rock formation. The magma sources were not affected by subduction-related fluids or melts. The basalts represent the upper portion of oceanic crust of the Jurassic South Anyui ocean. The blueschists belong to the same oceanic crust subducted beneath the more southern Anyui-Svyatoi Nos arc to a depth of 25-30 km. Pressure and temperature of metamorphism indicate a
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