| In this article, through field geological survey, combined with indoor and comprehensive analysis, regional stratigraphic framework was established in Tarbagatay and adjacent areas of the Devonian. On this basis, to Tarbagatay and adjacent areas of Devonian sedimentary phase were divided with the provenance analysis of heavy minerals, clastic rock geochemistry, detrital zircon geochronology and paleocurrent analysis method. According to the above contents of tarbagatay and adjacent areas of Devonian Tectonic evolution are discussed, the main understanding:(1) Tarbagatay and adjacent areas in Early Devonian Hebukesaier Formation is a set of grey calcareous fine, silty sandstone, yellow gray sandy limestone and bioclastic limestone combination; Middle Devonian Sawuershan Formation mainly gray green, dark purple mountain crystal tuff and breccia lava, volcanic breccia, Ann porphyrite uniform cross layer, siliceous rocks, siltstone and carbonate rock body; Late Devonian-Early Carboniferous Tarbagatay Formation is mainly feldspathic lithic sandstone, limestone, siltstone and fine sandy slate, tuff, andesite and basalt.(2)On the basis of the study of Devonian stratigraphic frame in Tarbagatay and adjacent areas and combined with rock and tectonic features, tarbagatay and adjacent area development delta depositional system, bin coastal depositional system shelf depositional system and platform sedimentary system, and further in the delta depositional system identified as delta front and prodelta two Subfacies and in the Littoral depositional system were identified after bin, foreshore and nearshore 3 Subfacies, in the continental shelf system identified inner shelf Subfacies, in the platform system recognition Shoal facies. Tarbagatay and adjacent area of Devonian bottom overall performance coarse fine regression sequence. Early Devonian tarbagatay and adjacent areas from the platform shoal phase gradually to the coastal phase evolution, gradually entered a stable period, middle Late Devonian- Early Carboniferous Sedimentary are mainly shallow marine facies, littoral facies and delta.(3) The Devonian sediment source rock types are intermediate-acidic volcanic rocks, metamorphic and sedimentary rocks, parent rocks in the source region of the depleted mantle, Majority lithology is andesite. Middle Devonian sediments from the south-southeast and north-northeast, south-southeast possible material from the Tacheng micro continental block, north-northeast may come from the Middle Ordovician Brook group. Late Devonian sediments from the south west side, probably from the Tacheng micro continental block.(4) The zircon U-Pb dating of Sawuershan Formation clastic rocks records for at least 4 tectonic thermal events, respectively is 364~369Ma, 380~400Ma, 417~493Ma, 511~565Ma. The main value of 453 Ma, in combination with CL image shows that this area has large-scale magmatic activity in Tacheng city in 453 Ma. Samples obtained a Mesoproterozoic zircon age, indicating Tacheng area may have 1.5ga since ancient continental block, and experienced multi stage of continental crust formation and evolution. The effective age of the clastic rock U-Pb in Tarbagatay Formation records for at least 2 tectonic thermal events, 323~350Ma and 453 Ma respectively. The peak value of 344 Ma, combined with CL images, study area with large scale magmatic activity in 344 Ma.(5) Cambrian-Early Ordovician Junggar evolved for mature ocean, ocean basin tectonic attribute back arc basin; Middle Ordovician-Silurian study area presents the coarse fine similar to back arc foreland flysch rock basin nature of the sedimentary characteristics; Middle Devonian-Early Carboniferous, subduction accretion began, the subduction accretionary complex rock and back arc basin, paleo Asian Ocean at the end of the Early Carboniferous extinction; Late Carboniferous- Permian in the study area into fault depression basin development stage and along evolution stage. |
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