| The study area is located in the Akesu River area,Qiemo County in Xinjiang.the geotectonic position is located in the west of the East Kunlun fault zone belt,the border of the Kunbei（Qimantag）Back-arc basin and Kunnan accretionary wedge complexes.This paper studied the petrology,geochronology and Geochemical characteristics of the Akesu River based on the research project about the Paleozoic tectonic degeneration features and dynamic mechanism,and discussed its tectonic significance:1.Systematically and comprehensively drafted the lithologic and spatial distribution of granites in Akesu River through researching of field geology and petrography.It showed that the rock of the Akesu River from south to North is the mylonitized fine-grained tonalite,mylonitic fine-grained granodiorite,granodiorite porphyry,medium grain with monzonitic granite and granitell,and medium grain with muscovite monzonitic granite.2.The Akesu River rock formed at the late Devonian-Early Carboniferous period based on the emplacement relation and U-Pb annual data results.From the old to the new in order is the mylonitized fine-grained tonalite（355±5Ma）,fine-grained granodiorite（354±4.3Ma）,granodiorite porphyry（362±2.3Ma）,medium grain with monzonitic granite and granitell（339.7± 3.9Ma）and medium grain with muscovite monzonitic granite（331±5Ma）.3.We can learn from the the geochemical characteristics of Akesu river rocks that it is the strongly peraluminous,high K-C alkaline S granite: rich in aluminum,silicon and alkali（SiO2:69.2%-77.77%;Al2O3:12.00-14.78;total alkali content,relative enrichment of the Na2O and K2O were: 4.27-7.98;2.95-4.39;1.70-4.23）,little iron（0.73-3.78）,magnesium（0.11-1.37）calcium,（0.87-1.16）,titanium（0.03-0.51）,phosphorus（0.02-0.16）,high K-C alkaline stronglyperaluminous（ASI:1.02-1.30）,a relatively high degree of differentiation（DI:74.49-95.64）,CaO,Al2O3,TFeO,MgO,P2O5,TiO2 were negatively correlated with SiO2;the total amount of the rare earths(∑REE:77.78-161.68×10-6).The fractionation of the light and heavy earth is obvious,and the light rare earth is relative enrichment（LREE/HREE:2.71-11.19）,the weight of the europium is significant（δEu:0.05-0.75）;The Rb、Th、U、Zr、Hf are relatively enriched and the P、Ti、Ta、Nb are relatively low;The saturation temperature of zircon（TZr:705-835℃）,the Ti temperature of zircon（T:524-756℃）with low pressure;The Nb/Ta、CaO/Na2O、Zr/Hf and the discrimination diagrams in the source region all have the features of continental crust.With the changes of the lithology,age,silicon content,europium depletion and other factors,the magmatic showed a good trend of the differentiation and evolution.4.This paper argues that the study area in the Early Carboniferous was the active continental margin arc-plate collision stage. |
