Tectonics of the Basement of the Kara-Bogaz Arch (Turan Plate)

Abstract

The Kara-Bogaz geoblock is interpreted by many researchers as a structure underlain by the Precambrian sialic crust, incorporated in the young (epi-Hercynian) Turan Plate. The paper presents the results of a detailed study of the material composition of igneous and metamorphic rocks making up the basement of the Kara-Bogaz Arch and recovered by deep boreholes. To subdivide and correlate the sections, we employed data of geophysical borehole surveys, including all types of logging. Microscopic examination of rocks was also performed to determine their composition, genesis, and degree of postsedimentation alterations. Data on absolute ages of rocks and paleontological data were also employed. The results of the work of our predecessors have been studied and critically analyzed. It is established that there are no direct indications of the continental crust older than Paleozoic in the basement of the Near-Kara-Bogaz region. The metamorphic units of the Kara-Bogaz Arch are represented by primary sedimentary and volcanosedimentary deposits that were altered at the stage of regional greenschist metamorphism. These rocks are intruded by granitoid bodies corresponding to the final stages of Hercynian tectogenesis. In parts spatially close to intrusions, the degree of secondary alterations in metamorphic rocks increases due to the thermal effect. Amphibolites of the Kara-Bogaz Arch are metamorphosed igneous rocks, which are closely associated with primary terrigenous deposits and have undergone subsequent metamorphosis (greenschist facies regional metamorphism). Gneisses of the discussed region refer to the marginal facies of granitoid plutons that formed as a result of metasomatic reworking of the host strata (protomagmatic gneissic banding). We think that the Kara-Bogaz Arch is a Hercynian megaanticlinorium of the young platform, and this does not exclude the possibility of fragments of more ancient crust in the structure of this arch. The sedimentary–metamorphic and volcanosedimentary rocks making it up and intruded by multiple granitoid bodies are units of the active margin.

Reservoir Characterization of the Pliocene Red Series, Lam Field and Surrounding Areas, Offshore Western Turkmenistan

“…Igneous rock fragments were not observed in the latter, and no igneous rocks outcrop in the Bolshoi Balkhan, but Palaeozoic intrusive and extrusive igneous rocks do outcrop in the Kubadag ridge, which is essentially a WNW-ward continuation of the Bolshoi Balkhan close to the Caspian coastline. The Karabogaz Arch farther north also includes granites but these are overlain by Cretaceous and younger sediments (Popkov and Popkov, 2022) so they could not have been the source of this igneous material, but the area may still have been a source of sediments transported into the South Caspian.…”

To the problem of origin volcanoplutonic processes

“…Their centers are associated with the decompressed upper mantle substances, where catastrophic increase in the volume of mantle substance occurs. The formation of volcanic-plutonic processes and earthquakes are associated with these phenomena [40][41][42][43][44][45]. As a result of physicochemical phase transformations, a huge number of gas products are released, which have a special property to penetrate the solid zone of the lithosphere, to introduce magmatic melts in the upper zones of the Earth's crust and its surface.…”