In Central Asia, the Altaids (Suess 1901, Sengör et al. 1993) also called Central Asian Orogenic Belt represents a large orogenic complexe that extend over more than 4000 km from the Uralides in the west to the Pacific cost in the east and that is bounded by the Arctic cost and the Siberian craton in the north and the Tarim-Sino/Korean cratons in the south. The Altaid Tectonic Collage is an accretionary orogen characterized by alternating belts formed by subduction-accretion complexes of island arcs, accretionary prisms, ophiolites and slivers of Precambrian microcontinents. Beside the fact that the origin and tectonic evolution of the Altaid Collage is still an issue of debate, it provides a good example of continental crustal growth during the Phanerozoic and appears as a place of choice to study the mechanism and processes of such crustal generation.
Located in the central part the Altaid Collage, southern Mongolia records a significant part of the development of this accretionary orogen from Cambrian to early Permian time. More specifically, the western Gobi Desert is characterized by individual ranges trending WNW-ESE separate by large intramontane valleys. The different ranges are mainly composed of Late Cambrian/Late Carboniferous metavolcanic and metasedimentary sequences intruded by Late Palaeozoic/Early Mesozoic undeformed K-rich granitoids and Late Carboniferous/Early Permian undeformed volcanic sequences.
In this area, seven localities were investigated to constrain the time of emplacement of these volcanic sequences, to characterize the genesis of these rocks and their tectonic settings in order to explore the development and the evolution of this part of the Altaid Collage. For these purposes the project include field work, U-Pb dating on zircon by Isotope Dilution or SHRIMP (Sensitive High-Resolution Ion MicroProbe) methods, whole rock analyses for major and trace elements (XRF, ICP-MS) and whole rock Nd-Sr isotopic measurements.
Sengör AMC, Natal'in BA, Burtman VS, 1993. Evolution of the Altaid tectonic collage and Palaeozoic crustal growth in Eurasia. Nature, 364, 299-307.
Suess E., 1901. Das Antlitz der Erde. Vienna/Prague: Tempsky; Leipzig: Freytag. Vol. III/1, IV. 508 pp.
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