This work is dedicated to comparative study of the best known compartmentalization schemes and of definitions of formation of Devonian and Early Carboniferous terrigene-volcanogenic series of Ore Altai published during the period from 1998 to 2017 by various researchers. Compartmentalization of these series is based on distinguishing of volcanogenic and volcanogenic-sedimentary cycles, which are attributable for Devonian tectogenesis of the region. However, there’s no universal compartmentalization scheme for these series of Ore Altai megatrough worked out yet. That’s because of some inconsistencies in single schemes. It is concluded that most of these inconsistencies are related to time-related lateral zonality of volcanic and tectonic processes, specificity caused by appearing within different blocks and different cycles of geological history of the megatrough and not taking the peculiarities of regional volcanic and tectonic structures formation into account. There are a number of works, which contain evidences of presence of certain volcano-tectonic morphostructures of the Ore Altai megatrough. However, there was no complete distinguishing and systematization of such structures yet. Also the principle of synchronous lagoon-continental series distinguishing was not applied for Ore Altai megatrough study, while this method is basic and successfully used one for the series of Altai-Sayan region. Considering the disadvantages of schemes developed before by various researchers, a method of distinguishing of regressiontransgression cycles within Devonian series was developed and applied in Zmeinogorsky ore district study. Also, main types of morphostructures were distinguished in these cycles paleotopography study and petro-geochemical characteristics of the volcanites, which make up these morphostructures, were given. This work contains the results obtained by use of this method for Zmeinogorsky district Early Devonian/Early Eifelian series study. Main conclusions are given below. There are Rudnichnaya caldera-ring (Zmeinogorskaya) and Karamyshevskaya dome-ring central type morphostructures defined within the central part of the ore district. Significant part of ore deposits in general and all of gold-silver barite-polymetallic formation deposits belong to this structures. Studied central type morphostructures had formed during two subsequent subcycles: 1) late (Emsian) subcycle of Early Devonian; 2) early (Eifelian) subcycle of Middle Devonian. Appliance of the method to middle-upper Devonian rocks study allowed to find out that there was certain paleotopography for each of regression-transgression cycles. Certain ore formations are related to these certain paleotopography features. Such relations show new possibilities of targeting and prospecting of ore deposits within the bounds of Ore Altai megatrough. Petro-geochemical study of Early and Middle Devonian volcanic rocks of Zmeinogorsky district showed that they belong to discretic basalt-andesite-dacite-rhyolite assemblage with significant subalkaline (predominant one) and tholeitic trends of differentiation. Alkalinity of the rocks varies significantly: basalts mostly contain Na, partially K-Na, andesite–dacites are of K-Na type and rhyolites mostly contain К. Geochemical features of the rocks indicate that they are more similar to island arc basalts (IAB) than to OIB or N-MORB. But still they differ significantly from IAB because of increased content of mobile large ion lithophile elements and decreased content of stable and inert high field strength elements and rare earth elements. According to the study volcanites of studied morphostructures and linear outcrops of melnichnaya suite rocks, which connect morphostructures to each other, formed in deep-laid regional fault zone, which bounds south-east flank of Zmeinogorsky-Bystrushinsky trough. Tectonics and volcanism within zones of this one and other such faults caused interaction between regional structures of forming fold belt (paleoocean) of Hercynides of Ob-Zaysan region, Ore Altai megatrough and adjacent consolidated structures of Altai Mountains, which have undergone synchronous riftogenic-continental destruction. Discriminant geochemical diagrams features are caused by similarity between studied basalts and IAB, and also between studied rocks and continental formations. Plume material with less N-MORB (E-MORB) content was the predominant source.
Петрология магматических и метаморфических комплексов : материалы IX Всероссийской конференции с международным участием, 28 ноября - 2 декабря 2017 года. Томск, 2017. Вып. 9. С. 118-127
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Геолого-географический факультет
Морфоструктуры и вещественный состав эмс-раннеэйфельских вулканитов Змеиногорского рудного района (Рудный Алтай)