The Shalap Mélange of the Salairian Alambay Ophiolite Zone (Northwestern Central Asian Orogenic Belt), Geological Structure and Compositional Features of Amphibolites and Greenstone Basalts

Abstract

The Alambay ophiolite zone (AOZ) is located in the axial part of the Early Paleozoic Salair orogen and includes the northern extension of the Alambay-Kaim zone, Salair and Altai Mountains. The Shalap area of the AOZ is predominantly composed of clastic mélange with occasional serpentine mélange. The geological and geochemical studies showed that in the Shalap mélange there are basalt blocks of the Alambay formation whose petrogeochemical features are similar to those of the oceanic island basalts (OIB). Metamorphic rocks of the Angurep complex, represented by garnet and non-garnet amphibolites, form a tectonic slab which is a part of the accretionary complex east of the Shalap mélange area. Metamorphic rocks also form blocks in the Shalap mélange. The amphibolites of the Angurep complex are similar in their petrogeochemical features to the basalts of intraoceanic island arcs. The Shalap mélange is a fragment of the Salairian Cambrian paleosubduction zone. The subduction and exhumation processes in this paleosubduction zone terminated by the 500 Ma time stage.