Late Paleozoic and Early Mesozoic rare-metal magmatism of Central Asia: Stages, provinces, and formation settings

Abstract

The paper presents the first tectonophysical reconstruction of initial divisibility of the protolithosphere as a result of convection in the cooling primitive mantle. Initial division of the protolithosphere into separate masses, i.e. prototypes of the blocks, and their size are predetermined by the emerging Rayleigh-Benard convection cells. In studies of geology and geodynamics, the Rayleigh-Benard convection cells were first referred to as a factor to explain the formation of initial continental cores. Considering the Rayleigh-Benard cells and their structural relics can help clarify initial divisibility of the protolithosphere and the origin of the major lithospheric plates, i.e. prototypes of continents. In our opinion, the initial mega-scale block structure of the protolithosphere and the emerging lithosphere were predetermined by the Rayleigh-Benard cells as they were preserved in the emerging lithosphere and their lower boundaries corresponded to the core-mantle boundary, i.e. one of the major discontinuities of the planet. Our theoretical estimations are in good agreement with the number and sizes of the Earth's theorized first supercontinents, Vaalbara and Ur. In our tectonophysical discussion of the formation of the lithospheric block structure, we analyze in detail the map of modern lithospheric plates [Bird, 2003] in combination with the materials from [Sherman et al., 2000]. In the hierarchy of the blocks comprising the contemporary lithosphere, which sizes are widely variable, two groups of blocks are clearly distinguished. The first group includes megablocks with the average geometric size above 6500 km. Their formation is related to convection in the Earth mantle at the present stage of the geodynamic evolution of the Earth, as well as at all the previous stages, including the earliest one, when the protolithosphere emerged. The second group includes medium-sized blocks with the average geometric size of less than 4500 km and those with minimum sizes, such as rock lumps. They reflect primarily the degradation of megablocks as a result of their destruction due to high stresses in excess of the tensile strength of the medium. This group may also include blocks which formation is related to convection in the upper mantle layer, asthenosphere. There are grounds to assume that through the vast intermediate interval of geologic time, including supercycles of Kenorlend, Rodin, and and partically Pangea, the formation of the large lithospheric blocks was controlled by convection, and later on, they were 'fragmented' under the physical laws of destruction of solid bodies. However, it is difficult to clearly distinguish between the processes that predetermine the hierarchy of formation of the block structures of various origins-sizes of ancient lithospheric blocks cannot be estimated unambiguously. Thus, mantle convection is a genetic endogenous source of initial divisibility of the cooling upper cover of the Earth and megablock divisibility of the lithosphere in the subsequent and recent geodynamic develop...

The Precambrian history of the origin and evolution of the Solar System and Earth. Part 1

“…Все это позволяет сделать обзор процессов ранних этапов как становления Солнечной системы, так и начала становления Земли как планеты. С другой стороны, рассмотрение этих проблем позволяет провести оценку формирования поверхностных и глубинных оболочек Земли, изучить работу мантии Земли в более поздние геологические эпохи и ее воздействие на формирование поверхностных структур, магматических пород и руд [Yarmolyuk, Kuzmin, 2012]. Рассмотрению этих проблем посвящена настоящая статья, которая во многом представляет собой обзор последних данных о ранних этапах развития нашей планеты.…”

Leading genetic types of base metal deposits of Rudny Altai

“…According to pyritechalcopyrite geothermometer data, the temperatures of various ore types formation were determined as 180-450 °C for copperpyrite stockworks, 133-195 °C for tabular pyritepolymetallic ores, 120-165 °C for densely impregnated copperzinc ores, 100-170 ˚С for polymetallic ores, 155-285 ˚С for baritepoly metallic ores. The isotopic composition of sulfur in sulfides is close to meteoric composition, it varies within a narrow range of values (δ 34 S from -4.2 to +5.2 ‰, from 2.2 to +2.0 ‰ on average) [14,15].…”

Composition, Age and Geodynamic Position of Alkaline Rocks in the Borgoy and Botsy Massifs (Dzhida Alkaline Province)

“…Стоит отметить, что в этот период в пределах Сибирского кратона образовались крупные Хангайская и Сибирская изверженные провинции. При этом с учетом новых возрастных данных по щелочным породам и пространственному положению Джидинский сегмент принадлежит к Хангайской магматической провинции (возраст ее оценивается в интервале 269-243 млн лет [Yarmolyuk, Kuzmin, 2012]), которая характеризуется редкометалльной минерализацией (Zr, Nb, РЗЭ) и связывается с деятельностью Хангайского мантийного плюма [Kuzmin, Yarmolyuk, 2014].…”