Unravelling a Devonian–Triassic seamount chain in the South Tianshan high‐pressure/ultrahigh‐pressure accretionary complex in the Atbashi area (Kyrgyzstan)

Abstract

Seamounts are common occurrences on the extant oceanic floors of the earth, and accreted single seamounts are also widely distributed on the modern active margins, but recognition of single seamounts is an uneasy job in the ancient orogens, and the detection of a chain of accreted seamounts is even harder, therefore understanding the multiple accretion of ancient seamounts is nearly negligible. A combined analysis of geochronology and geochemistry was conducted on the basic eclogitic rocks from the Atbashi Accretionary Complex in the Kyrgyz South Tianshan, in a bid to unravel the accretion process of a chain of seamounts in the Paleo‐Asian Ocean in the southern Altaids. A set of reliable U–Pb zircon ages of 397.6 ± 8 Ma age for a basaltic andesite, 353 ± 8 Ma for a gabbro, and 317.1 ± 9 Ma for a diorite were obtained in this study. Both unmetamorphosed basic rocks and eclogites carry geochemical signatures of plume‐derived seamounts that were influenced by their respective mantle source. Taken together with previously published age data, the spatial and temporal features of these Atbashi rocks indicate the timing and sequence of formation, subduction, and extrusion of the South Tianshan oceanic remnants in the Early/Middle Devonian to Late Triassic. The integrated data indicate the existence of a seamount chain composed of Early/Middle Devonian–Late Triassic seamounts in the Atbashi Complex. The paleogeographic pattern and analysis of these fragments derived from the ocean‐type seamounts enable the reconstruction of tectonic models of that portray, magmatism, mantle‐derived plumes, subduction and exhumation of this Devonian–Triassic ocean floor.