| In this paper, Devonian of Emin Qianjin pasture area is regarded as study, measured bycross-section, the basic characteristics of each group Devonian spatial distribution, rockassociation, the basic sequence, fossils and their relationship with the macroscopic contacts,combined with geochemical characteristics of volcanic rock, making the followingunderstanding:1. According to lithology, rock assemblages, sedimentary facies and fossils characteristicEarly Devonian Mala Su will be divided into six segments:Marlasu group of the first segmentis given priority to with fine clastic sediments, and the main rock types is tuffite; Secondsegment is characterized by coarse clastic sediments, up from fine tuffaceous conglomerateinto pebbly coarse sandstone and then into thin tuffaceous sandstone, reflecting shallow water,strong hydrodynamic characteristics， and collect Leptaenopyxis Havlicek in thatsegment(Early Devonian fossils); the major rock types of third segment are tuffaceoussandstone, fine-grained clastic deposition reflecting over the second shallow water,hydrodynamic strong, and the segment formation harvesting Parsspirifer (intended Shi Yan),etc. fossils; fourth segment is characterized by a set of sedimentary conglomerate; The maincombination of fifth segment is altered tuff and conglomerate, showing rhythmic layers. Toreflect the overall fine clastics and middle accompanied by coarse clastic sediments; sixthsegment is coarse clastic sediments, which main combination of rock is gray pebbly coarsefeldspathic lithic sandstone, conglomerate clip taking up a small amount. Rock wavy beddingdevelopment reflects the relatively turbulent water, and the water becomes strong momentum.From bottom to top, water of Malasu is fades, but hydrodynamic enhances. Volcaniclasticcomponent from the first segment to the sixth overall segment display up again by a fewfewer rules, and the maximum is in the third segment. The group is a deep-shallowtransitional phase deposition.2. Rock combination of Kulumudi group, Middle Devonian, is fine sandstone-tuffinterbedded in the study area, where is swallowed by Eastern Kulumusu rock invasion, andcovered by western Quaternary.The outcrop is limited. By rock assemblages, fossils and basicsequence, Kulumudi group is thought as a product of shallow marine environment.3Tielieketi group of Late Devonian consists of volcanic breccia-lava-Tuff eruptioncycle, containing large conglomerate and a small amount of volcanic lava. Conglomerate islow maturity and volcanic breccia，with direction and weak layering，is molasse accumulationconsistof volcanic features. Based on a combination of sedimentary rock signs and adjacentareas such as biomarker analysis, that it`s sedimentary environment is coastal-marginal sea.4Malasu volcanic rocks of Early Devonian are mainly basalt, andesite and basalticandesites, belonging to calc-alkaline series. Rocks are relatively enriched in LILE (LILE), theelements of strong activity,such as Ba, K, Rb and Sr, are fluctuated obviously;rocks are lossof high field strength elements (HFSE)(eg: Nb, Ta and Ti)；Tielieketi volcanic rocks of Late Devonian are mainly Basalt, basaltic andesite, dacite and trachyandesite, belonging tocalc-alkaline series. Rocks are relatively enriched in LILE (LILE), such as Ba, and K; rocksare loss of high field strength elements (HFSE)(eg: Nb, Ta and Ti), showing a significantTNT negative anomalies. LA-ICP-MS zircon U-Pb dating of volcanic age is obtained364.4±4.2Ma, belonging to Late Devonian era. According to volcanic rock geochemistry, combinedwith a comprehensive analysis of rock assemblages that volcanic rock formed volcanic islandarc environment.5Emin Qianjin pasture area as a whole experienced a Devonian basin fill-the demise ofthe process: Early Devonian sedimentary overall for the deep-sea environment, represents amajor filling of the basin; Kulumudi groups of Middle Devonian sedimentary representes theconstruction of shallow marine clastic rocks.Affected S-N compressive stress regime, thedeposition of water fades lower; Some part area of Late Devonian has transited to thecontinental deposits, volcanic activity being strong,deposited volcanic molasse as representedby Tielieketi group. From Early to Late Devonian, when the water becomes faded deposition,sediment grain size gradually is thicker, increasing the column clastic rocks share ratio.According to regional data analysis, overall Devonian sedimentary-Uplift-fold orogenictectonic evolution of this feature is the performance of early Variscan tectonic movement.Emin County Qianjin pasture area by research of Devonian strata, identifies the areastratigraphic sequence correctly and a brief analysis of the sedimentary environment. And alsoprovides a reliable basis for the restoration and reconstruction of the Devonianpaleogeography, ancient tectonic evolution, West Junggar. |
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