Late Palaeozoic to Late Triassic northward accretion and incorporation of seamounts along the northern South Pamir: Insights from the anatomy of the Pshart accretionary complex

Abstract

Late Palaeozoic-Mesozoic volcano-sedimentary rocks within the Rushan-Pshart Suture zone in the Pamir contain critical information on the subduction-accretion history of the Rushan-Pshart Ocean (Meso-Tethys) prior to the Central-South Pamir collision. In this article, we report new field, petrographic, geochronological, and geochemical data of the Permian to Triassic basic volcanic and sedimentary rocks from the Pshart area. Our field study unravels block-in-matrix components within some sedimentary mélanges, which, together with some previously defined ophiolitic mélanges, enables us to define the Pshart accretionary complex (AC), and thus for the first time to discuss the subduction-accretion history of the Rushan-Pshart Ocean and the growth of the Pshart AC. The youngest detrital U-Pb zircons suggest that deposition of sediments was in the Late Triassic (212 Ma). Detritus of Triassic age was primarily derived from the Triassic Karakul-Mazar Arc-AC (Northern Pamir) and the Bashgumbaz Magmatic Arc, which developed along the northern margin of South Pamir. The evidence of north-directed thrusts along the Kara Djilga-2 and Ken Djilga transverses confirms previous interpretations of southward subduction of the Rushan-Pshart oceanic lithosphere beneath the South Pamir. Geochemical OIB-type data of the Pshart alkaline basaltic rocks suggest formation in seamounts incorporated into the Pshart AC during the southward subduction of the Rushan-Pshart Ocean. The youngest Late Triassic deposition age is consistent with the coeval time of closure of the Palaeo-Tethys and Meso-Tethys oceans in the Pamir. The Pshart AC formed by subduction-accretion processes during the southward subduction of the Meso-Tethys Ocean along the northern South Pamir and the final docking of the Central and South Pamir (Cimmerian Blocks) may have occurred after the Late Triassic.

Geochemistry of Thermal and Cold Mineral Water and Gases of the Tien Shan and the Pamir

“…The Pamir orogen consists of several allochthonous micro-continents (Northern, Central, and South Pamir). The Rushan-Pshart Suture zone separates the South Pamir to the south from the Central Pamir to the north (Figure 1), contains remnants of the consumed Meso-Tethys Rushan-Pshart Ocean, and records the evolution of the Rushan-Pshart Ocean from its birth to southward travel, subduction, and subsequent collision between the Central and Southern Pamirs [34]. Seismicity in the south-western Pamir features frequent intermediatedepth earthquakes, reaching hypocentral depths of 300 km, which is rare for regions not obviously related to active subduction of the oceanic lithosphere.…”

“…Within the mountain uplifts, the thermal N 2 -rich waters are typically associated with Paleozoic-Mesozoic granites, granodiorites, or their extrusive equivalents (#1, 16,10,17,32,33,34,39,40,42,49). These waters are widespread within the mountain ranges of North and South Tien Shan, and on the territory of Chinese Tien Shan [17].…”

Skarn-Borosilicate Giant Deposits: Derivates of the Fluid-Hydrothermal Reworking of Atoll Fragments in a Subduction Melange of Mesozoic Orogenic Belts of Asia

“…Рудоносная площадь является частью Rushan-Pshart сутуры, на границе микроконтинентальных блоков Центрального и Южного Памира. Формирование сутуры сопряжено с триасовой субдукцией океанической плиты Палео-Тетиса под блок Южного Памира [27]. Рудовмещающий складчатый комплекс представлен породами позднетриасовой аккреционной призмы, перекрытой с несогласием в северной части территории терригенными породами средней юры.…”

“…Современный анализ условий локализации боросиликатных руд месторождения Ак-Архар на основе новейших обобщений геологии Памира определенно указывает на аналогичную сопряженность этого месторождения с позднетриасовым меланжем в составе аккреционно-складчатого комплекса Памирского орогена [27]. При этом сходство месторождений подчеркивается однотипной минералогией, спецификой микроэлементного состава руд и рудообразующих флюидов.…”

Nature of the Skarn–Borosilicate Deposit Giants of the Sikhote-Alin and Pamir Mountains

“…The Ak-Arkhar field is located in the eastern part of the Bazar-Darinskii ridge (Pamir). The ore-bearing area is part of the Rushan-Pshart suture associated with Triassic subduction of the Paleo-Tethys oceanic basin plate beneath the South Pamir block [13]. The ore-bearing folded complex is composed of rocks of the Late Triassic accretionary prism, overlapped with unconformity by Middle Jurassic sediments.…”