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RESEARCH PRODUCT

Tectono-Magmatic Evolution, Age and Emplacement of the Agardagh Tes-Chem Ophiolite in Tuva, Central Asia: Crustal Growth by Island arc Accretion

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Publisher Summary The Agardagh Tes–Chem ophiolite in Tuva, Central Asia, is part of the Central Asian Mobile Belt which formed during subduction–accretion processes lasting from the early Neoproterozoic to the late Palaeozoic. The Agardagh Tes–Chem ophiolite marks the northwestern border of the Tuva–Mongolian Massif (TMM), which comprises several intrusive and metamorphic complexes. These complexes consist of metatonalites, gneisses, migmatites, amphibolites, marbles, quartzites, low-grade metasedimentary rocks and minor ultramafic lenses, and radiometric ages range between 536 and 464 Ma. Field observations suggest that the southwestern part of the Tes–Chem unit represents the lower to intermediate part of a sheeted dyke complex. This is evident from the widespread occurrence of microgabbroic and doleritic dykes and the overall absence of chilled margins, typically found only in higher levels of a sheeted dyke complex. Due to the boninitic nature of the parentalmelts of the ultramafic cumulates and gabbros, their formation requires an already depleted, sub-arc mantle wedge as well as sufficient heat to permit remelting of refractory harzburgite.