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•Seamounts developed in West Junggar were eventually subducted/accreted.•Seamount subduction types included accretion, underplating and collision.•Geological imprints include deformation, magmatism and tectonics.•Seamount/oceanic plateas accretion induced subduction initiation in West Junggar.

The study area in the West Junggar Basin is known to be rich in hydrothermal gold deposits and occurrences, even though there has been minimum exploration in the area. It is here hypothesised that this area could host more gold deposits if mineral exploration methods were to be reinforced. This research is aimed at identifying geochemical anomalies of Au, and determining possible factors and conditions which facilitate the formation of anomalies by referring to As and Hg as gold pathfinders. Geostatistical analyst techniques have been applied to 9,852 stream sediments and bedrock data collected on a total surface of 1,280 km2of West Junggar, Xinjiang (northwest China). The kriging interpolation and quantile-quantile plot methods, combined with statistical methods, successfully identified both Au and its pathfinders’ anomalies. In the present study, median was considered as background values (10.2 ppm for As, 9.13 ppb for Hg and 2.5 ppb for Au), whereas the 95thpercentile were threshold values (28.03 ppm for As, 16.71 ppb for Hg and 8.2 ppb for Au) and values greater than thresholds are geochemical anomalies. Moreover, the high concentrations of these three discovered elements are caused primarily by hydrothermal ore mineralisation and are found to be controlled mainly by the Hatu and Sartohay faults of a northeast-southwesterly direction as well as their related secondary faults of variable orientation, which facilitate the easy flow of hydrothermal fluids towards the surface resulting in the formation of geochemical anomalies. Most of anomalies concentration of Au are found near the mining sites, which indicates that the formation of new Au anomalies is influenced by current or previous mining sites through geological or weathering processes. In addition, the low concentration of gold and its pathfinders found far from active gold mine or faults indicates that those anomalies are formed due to primary dispersion of hosting rock.

Accretionary wedge is the typical product of subduction-zone processes at shallow depths. Determining the location, composition and mechanism of accretionary wedge has important implications for understanding the tectonism of plate subduction. The Central Asian Orogenic Belt (CAOB) is one of the world’s largest accretionary orogenic belts, and records the bulk evolution of Paleo-Asian Ocean from opening to closure, with multi-stages and multi-types of crust-mantle interaction in the Paleozoic. West Junggar (western part of Junggar Basin), located in the core area of CAOB, is characterized by a multiple intra-oceanic subduction system during the Paleozoic. In its eastern part crop out Devonian-Carboniferous marine sedimentary rocks, Darbut and Karamay ophiolitic mélanges, alkali oceanic island basalts, island arc volcanic rocks and thrusted nappe structure. Such lithotectonic associations indicate the occurrence of accretionary wedge at Karamay. In order to decipher its formation mechanism, this paper presents a synthesis of petrography, structural geology and geochemistry of volcanic rocks. In combination with oceanic subduction channel processes, it is suggested that the accretionary wedge is a composite mélange with multiple stages of formation. The application of oceanic subduction channel model to the Karamay accretionary wedge provides new insights into the accretion and orogenesis of CAOB.

•Major mechanisms of subduction initiation using natural examples.•SSZ ophiolites, forearc basalts and metamorphic soles mark subduction initiation.•Subduction initiation in northern Paleo-Asian Ocean was older than that in south.•Plume-induced subduction initiation played a dominant role in the CAOB.