关键词: 昌都盆地, 构造背景, 地球化学, 成煤, 构造控煤

Abstract: The Qamdo Basin in eastern Tibet is a tectonic basin formed from multi-stage coal-forming basins that underwent the superposition transformation of Carboniferous, Permian and Triassic. The coal-bearing strata in the Late Triassic Bagun Formation are widely distributed in the basin. During the Triassic period, the Jinsha and Lancang River ocean basins on either side of the Qamdo Terrane closed successively, resulting in the complex regional tectonic background that largely determined the paleogeographical conditions for coal forming. Different tectonic background yielded specific magma rock types and tectonic-magmatic combinations. The geochemical characteristics of Late Triassic volcanic rocks on either side of Qamdo showed that the bimodal volcanic rock development at the eastern margin of the Qamdo Basin is dominated by stretching stress, forming rift and resulting in large terrain fluctuation and subsidence and fast deposition rate which were disruptive to stable coal-forming environment. The development of intrusive rocks associated with the subduction of Lancang River ocean crust at the western margin of the Qamdo Basin led to a depression under the compressional background; and the relatively simple basement structure provided a good paleogeographical environment for the continuous and stable coal accumulation process. Under the control of later stage tectonic activity, the continuous coal seams were segmented into monoclines or folds with different angles and scales, producing industrial grade coal mining fields in the Bagun, Take Gellar and surrounding areas.

Key words: Qamdo Basin, tectonic background, geochemical, coal forming, structural controls of coal