Tajik Academy of Sciences

About: Tajik Academy of Sciences is a education organization based out in Dushanbe, Tajikistan. It is known for research contribution in the topics: Meteoroid & Alloy. The organization has 791 authors who have published 836 publications receiving 7842 citations.

Assembly of the Pamirs: Age and origin of magmatic belts from the southern Tien Shan to the southern Pamirs and their relation to Tibet

Abstract: [1] Magmatic rocks and depositional setting of associated volcaniclastic strata along a north-south traverse spanning the southern Tien Shan and eastern Pamirs of Kyrgyzstan and Tajikistan constrain the tectonics of the Pamirs and Tibet The northern Pamirs and northwestern Tibet contain the north facing Kunlun suture, the south facing Jinsha suture, and the intervening Carboniferous to Triassic Karakul–Mazar subduction accretion system; the latter is correlated with the Songpan-Garze–Hoh Xi system of Tibet The Kunlun arc is a composite early Paleozoic to late Paleozoic-Triassic arc Arc formation in the Pamirs is characterized by ∼370–320 Ma volcanism that probably continued until the Triassic The cryptic Tanymas suture of the southern northern Pamirs is part of the Jinsha suture A massive ∼≤227 Ma batholith stitches the Karakul–Mazar complex in the Pamirs There are striking similarities between the Qiangtang block in the Pamirs and Tibet Like Tibet, the regional structure of the Pamirs is an anticlinorium that includes the Muskol and Sares domes Like Tibet, the metamorphic rocks in these domes are equivalents to the Karakul–Mazar–Songpan-Garze system Granitoids intruding the Qiangtang block yield ∼200–230 Ma ages in the Pamirs and in central Tibet The stratigraphy of the eastern Pshart area in the Pamirs is similar to the Bangong-Nujiang suture zone in the Amdo region of eastern central Tibet, but a Triassic ocean basin sequence is preserved in the Pamirs Arc-type granitoids that intruded into the eastern Pshart oceanic-basin–arc sequence (∼190–160 Ma) and granitoids that cut the southern Qiangtang block (∼170–160 Ma) constitute the Rushan-Pshart arc Cretaceous plutons that intruded the central and southern Pamirs record a long-lasting magmatic history Their zircons and those from late Miocene xenoliths show that the most distinct magmatic events were Cambro-Ordovician (∼410–575 Ma), Triassic (∼210–250 Ma; likely due to subduction along the Jinsha suture), Middle Jurassic (∼147–195 Ma; subduction along Rushan-Pshart suture), and mainly Cretaceous Middle and Late Cretaceous magmatism may reflect arc activity in Asia prior to the accretion of the Karakoram block and flat-slab subduction along the Shyok suture north of the Kohistan-Ladakh arc, respectively Before India and Asia collided, the Pamir region from the Indus-Yarlung to the Jinsha suture was an Andean-style plate margin Our analysis suggests a relatively simple crustal structure for the Pamirs and Tibet From the Kunlun arc in the north to the southern Qiangtang block in the south the Pamirs and Tibet likely have a dominantly sedimentary crust, characterized by Karakul–Mazar–Songpan-Garze accretionary wedge rocks The crust south of the southern Qiangtang block is likely of granodioritic composition, reflecting long-lived subduction, arc formation, and Cretaceous-Cenozoic underthrusting

Near-Ultrahigh Pressure Processing of Continental Crust: Miocene Crustal Xenoliths from the Pamir

Abstract: Xenoliths of subducted crustal origin hosted by Miocene ultrapotassic igneous rocks in the southern Pamir provide important new information regarding the geological processes accompanying tectonism during the Indo-Eurasian collision Four types have been studied: sanidine eclogites (omphacite, garnet, sanidine, quartz, biotite, kyanite), felsic granulites (garnet, quartz, sanidine and kyanite), basaltic eclogites (omphacite and garnet), and a glimmerite (biotite, clinopyroxene and sanidine) Apatite, rutile and carbonate are the most abundant minor phases Hydrous phases (biotite and phengite in felsic granulites and basaltic eclogites, amphiboles in mafic and sanidine eclogites) and plagioclase form minor inclusions in garnet or kyanite Solid-phase thermobarometry reveals recrystallization at mainly ultrahigh temperatures of 1000–1100 C and nearultrahigh pressures of 2 5–2 8GPa Textures, parageneses and mineral compositions suggest derivation of the xenoliths from subducted basaltic, tonalitic and pelitic crust that experienced highpressure dehydration melting, K-rich metasomatism, and solid-state re-equilibration The timing of these processes is constrained by zircon ages from the xenoliths and Ar/Ar ages of the host volcanic rocks to 57–11Ma These xenoliths reveal that deeply subducted crust may undergo extensive dehydration-driven partial melting, density-driven differentiation and disaggregation, and sequestration within the mantle These processes may also contribute to the alkaline volcanism observed in continent-collision zones

Geometry of the Pamir-Hindu Kush intermediate-depth earthquake zone from local seismic data

Abstract: [1] We present new seismicity images based on a two-year seismic deployment in the Pamir and SW Tien Shan. A total of 9532 earthquakes were detected, located, and rigorously assessed in a multistage automatic procedure utilizing state-of-the-art picking algorithms, waveform cross-correlation, and multi-event relocation. The obtained catalog provides new information on crustal seismicity and reveals the geometry and internal structure of the Pamir-Hindu Kush intermediate-depth seismic zone with improved detail and resolution. The relocated seismicity clearly defines at least two distinct planes: one beneath the Pamir and the other beneath the Hindu Kush, separated by a gap across which strike and dip directions change abruptly. The Pamir seismic zone forms a thin (approximately 10 km width), curviplanar arc that strikes east-west and dips south at its eastern end and then progressively turns by 90° to reach a north-south strike and a due eastward dip at its southwestern termination. Pamir deep seismicity outlines several streaks at depths between 70 and 240 km, with the deepest events occurring at its southwestern end. Intermediate-depth earthquakes are clearly separated from shallow crustal seismicity, which is confined to the uppermost 20–25 km. The Hindu Kush seismic zone extends from 40 to 250 km depth and generally strikes east-west, yet bends northeast, toward the Pamir, at its eastern end. It may be divided vertically into upper and lower parts separated by a gap at approximately 150 km depth. In the upper part, events form a plane that is 15–25 km thick in cross section and dips sub-vertically north to northwest. Seismic activity is more virile in the lower part, where several distinct clusters form a complex pattern of sub-parallel planes. The observed geometry could be reconciled either with a model of two-sided subduction of Eurasian and previously underthrusted Indian continental lithosphere or by a purely Eurasian origin of both Pamir and Hindu Kush seismic zones, which necessitates a contortion and oversteepening of the latter.