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Structural elements of the Svecokarelide pericratonic zone in the Karelian Massif (SE Fennoscandia) were identified and described. They were formed after the major events of the Svecofennian tectogenesis. The age ranges of the orogenic stage and the post-orogenic extension collapse were dated, and the depth levels of the corresponding structures were determined. The differentiated exhumation process of deep complexes of the post-Proterozoic Savo–Ladoga movable zone was visualized. The approximate exhumation velocities of the deep material were estimated at certain stages of Precambrian evolution in the zone under consideration. [ABSTRACT FROM AUTHOR]

Metamorphic timescales harbor crucial information for quantifying lithospheric processes and identifying tectonic regimes. The Orosirian Period is known for global orogenesis during 2.1‒1.8 Ga that possibly signifies the emergence of global-scale plate tectonics. While the metamorphic pressure–temperature (P–T) paths and T/P ratios have been extensively used to characterize 2.1–1.8 Ga orogens, their detailed metamorphic timescales remain underutilized. In this study, we use garnet diffusion modeling to explicitly explore the metamorphic timescales of dominant pelitic granulites in the Jiaobei terrane, the southwest part of the Jiao-Liao-Ji orogenic belt (JLJB), North China Craton. The pelitic granulites record high-pressure granulite-facies metamorphism of 13–14 kbar and 860–870 °C, followed by fast decompression (4‒21 mm yr−1) with some degree of heating to medium-pressure granulite-facies retrogression of 7‒8 kbar and 865‒950 °C at c. 1.85 Ga. The subsequent cooling is nearly isobaric, but likely nonlinear with initially faster and later slower cooling (17‒32 °C Myr−1, 950/865–700 °C; 5–7 °C Myr−1, 700–600 °C, respectively). The determined clockwise P–T–t path provides evidence for convergent plate boundary processes and the fast exhumation is likely related to an extensional setting. The relatively fast exhumation and cooling rates at high temperatures, as obtained via diffusion chronometry, represent the fastest rates yet reported from 2.1 to 1.8 Ga orogens and are several times to one order of magnitude slower than those observed in modern orogens. In the light of recent numerical modeling, we suggest that these slower metamorphic rates of the c. 2.1‒1.8 Ga JLJB orogenic rocks are consistent with the features of orogenesis occurring at higher mantle temperatures, such as hotter orogenic thermal structures, less over-thickened orogenic crusts, and distributed strain patterns. Therefore, the timescale information from the JLJB indicates that Paleoproterozoic plate tectonics under higher temperatures might have caused subduction and collisional orogenesis to be distinct from their modern style. Notably, the detailed ancient metamorphic timescales achieved by diffusion modeling cannot be resolved geochronologically, highlighting the necessity of applying diffusion chronometry to quantify ancient tectonic processes. [ABSTRACT FROM AUTHOR]

The results of 40Ar/39Ar dating of pseudotachylytes, first identified in the Paleoproterozoic zonally metamorphosed (greenschist to granulite facies) Ladoga complex of svecofennides, are presented. A wide age range of the formation of pseudotachylytes in the Riphean (1.59–1.31 Ga), presumably caused by the exhumation of deep rocks during the Svecofennian tectonogenesis and the subsequent orogenesis and riftogenesis in southeastern Fennoscandia, has been established. [ABSTRACT FROM AUTHOR]

The geological framework and tectonics of the East Black Sea region is characterized through balancing a geological cross-section and paleoreconstruction during the Paleogene-Neogene period. The studied area includes the Kerch-Taman trough, the Anapa Swell (a continuation of the immersed part of the Greater Caucasus Orogen), the Tuapse trough, and the Shatsky Swell. This paper is mainly focused on the Russian shelf zone of the Black Sea. The results are important for understanding the trap formation time and the preservation of hydrocarbon deposits in the Russian sector of the Black Sea shelf. [ABSTRACT FROM AUTHOR]

Foliation Intersection/Inflection Axes within porphyroblasts (FIAs) provide a quantitative approach to microstructural and metamorphic analysis that can be used to integrate multiple deformation and metamorphic events and develop lengthy PT path histories during orogenesis. This paper reviews applications of FIAs for determining (1) porphyroblast rotation vs. nonrotation; (2) inclusion trail orientations and orogenic processes involving changes in the direction of bulk horizontal shortening; (3) in situ age determinations for multiple deformation episodes; (4) P-T-t-d paths of poly-metamorphism in an orogenic belt; and (5) constraining relative plate movement paths within ancient orogens. Quantitative structural and metamorphic data correlated directly to relative plate motions, are currently allowing the tectonic reconstruction of multiply deformed and metamorphosed terrains in orogens around the world. [ABSTRACT FROM AUTHOR]

We present a tectonic map of the Tauern Window and surrounding units (Eastern Alps, Austria), combined with a series of crustal-scale cross-sections parallel and perpendicular to the Alpine orogen. This compilation, largely based on literature data and completed by own investigations, reveals that the present-day structure of the Tauern Window is primarily characterized by a crustal-scale duplex, the Venediger Duplex (Venediger Nappe system), formed during the Oligocene, and overprinted by doming and lateral extrusion during the Miocene. This severe Miocene overprint was most probably triggered by the indentation of the Southalpine Units east of the Giudicarie Belt, initiating at 23-21 Ma and linked to a lithosphere-scale reorganization of the geometry of mantle slabs. A kinematic reconstruction shows that accretion of European lithosphere and oceanic domains to the Adriatic (Austroalpine) upper plate, accompanied by high-pressure overprint of some of the units of the Tauern Window, has a long history, starting in Turonian time (around 90 Ma) and culminating in Lutetian to Bartonian time (45-37 Ma). [ABSTRACT FROM AUTHOR]

The analysis of 3D relief models of the lower Amur region and several adjacent areas suggested that the structure of the region is related to the horizontal tectonic layering of the upper part of the Amur plate. When it was dislocated to the northwest at the terminal Cretaceous, some fragments of the upper layers were displaced not strictly synchronously but with some lag relative to the whole plate. This scenario was responsible for the formation of the main morphostructural elements of the region: river valleys, mountain ranges, and graben series. These inferences are supported by field observations and some geological data. The proposed hypothesis can also be applied for several other regions. [ABSTRACT FROM AUTHOR]

A research on the Mesozoic fill-sequences of Hefei basin, located at the north foot of Dabie Mountains, shows two-phase evolution. The first phase, early- to mid-/late-Jurassic, is characterized by terrestrial clastic deposits, with four times of reverse-grading units at least, and forms greatly thick molass reconstruction in the mid-/late-phase, which reflects gradually strong thrusting-orogenesis in the north Dabie and flexural depression in the north foreland of Dabie Mountains. The second phase, late-Jurassic to Cretaceous, includes two-episode rifting processes. The first episode (J3) shows calc-alkalic and alkali volcanic rocks interstratified pyroclastic rocks, which may reflect upwelling igneous magma from mantle-source due to the Yangtze continent slab breakoff induced by deep subduction process. A suite of lacustrine, fluvial and piemount facies, about 3000 –3500 m in thickness, develops in the second episode (J3-K1), which reflects regional extensional setting and intense elevator diversity of mountain-basin in the study area. This research renews and deepens cognition for the Mesozoic Dabie orogenesis [ABSTRACT FROM AUTHOR]