Mineralogy, Geochemistry, and Geochronology of the Yehe-Shigna Ophiolitic Massif, Tuva-Mongolian Microcontinent, Southern Siberia: Evidence for a Back-Arc Origin and Geodynamic Implications

Abstract

The new results have been represented of mineralogical–geochemical and geochronological studies of rocks of the Yehe-Shigna ophiolite massif located in the Tuva-Mongolian microcontinent in the northern part of the Central Asian orogenic belt (Eastern Sayan, Southern Siberia). The Yehe-Shigna ophiolite massif is part of the Belsk-Dugda ophiolite belt. The structural position, age, and geochemical characteristics of the belt indicate its formation in the setting of the back-arc basin of the Shishkhid intraoceanic island arc, developing in the period of 810–750 million years. It is assumed that together with the same-age formations of the Oka accretion wedge and the Sarkhoi active margin, it formed on the convergent margin of the Gondwana supercontinent. Its basement is represented by the Archean-Early Precambrian crystalline rocks and carbonate cover (“Gargan Glyba”). The gold-bearing Neoproterozoic deposits with dominant gold-telluride assemblages are localization in large ophiolites thrust zones along with the frame of the “Gargan Glyba”. They are allochthonous with respect to the Late Neoproterozoic-Cambrian Tuva-Mongolian island arc of the Siberian continent. A similar type of gold deposit is probably worth looking for ophiolites thrust zones in other Precambrian Gondwana-derived microcontinents.

Vladimirskoe Deposit (Eastern Sayan): Age of Dyke Complexes and Localization Features of Gold Mineralization

“…В интервале 830-800 млн лет в пределах краевого океанического бассейна возникает спрединговая зона и формируется Ехэ-Шигна-Шишхидская зона субдукции [Zhmodik et al, 2022], которая приводит к формированию Шишхидгольской энсиматической островной дуги (800±2.6 млн лет, U-Pb метод по циркону) [Kuzmichev, Larionov, 2011] и Окинской аккреционной призмы от 819±17 до 775±8 млн лет назад [Kuzmichev, Larionov, 2013], формирующейся в результате субдукции под Тувино-Монгольский микроконтинент (Гарганский блок). При ослаблении или замедлении процессов субдукции дополнительный перенос тепла осуществляют спрединговые струи и/или мантийные плюмы [Dobretsov, 2020].…”