Geochemistry, Geochronology And Metallogenic Significance Of Granitic Intrusion In The Suyunhe Molybdenite Deposit Of Xinjiang

The Suyunhe molybdenite deposit, located in the western part of Barluk mountain of West Junggar, is a large porphyry molybdenum deposit discovered in recent years. Based on the previous work, the ? and ? granitic body in the deposit were studied in this thesis through petrography, geochemistry, zircon U-Pb and isotopic analysis etc. Combined with the research result of ? granitic body, the petrogenesis, mineralization significance and others were discussed. Some advances were obtained as following:The granitic bodies in Suyunhe area can be classified into two categories: one is represented by the ? and ? granitic bodies, which are mainly composed of monzonite granite-porphyry, granodiorite, diorite porphyry and so on, and molybdenum mineralization is mainly developed near the body; the other is represented by the ? granitic body, which is mainly composed of monzonite granite-porphyry and porphyritic monzogranite, and besides the development of molybdenum mineralization, the body is also accompanied by relatively strong copper mineralization.The geochemical analysis results show that the ? granitic body is of highly silicon content ?SiO₂=77.95%?80.92%?, medium rich in aluminum ?Al₂O₃=10.01%?12.38%? highly alkali content ?Na₂O+K₂O=7.27%?8.74%?, relatively rich in potassium ?Na₂O/K₂O=0.52?0.95?, and A/CNK=0.98-1.06, A/NK=1.05?1.12, ?=1.39?2.18. All the parameters indicate that the ? granitic body belongs to the high potassium calc alkaline and weakly peraluminous granite series, and the body has got a strong differentiation and evolution process. The ? granitic body can be defined as highly fractionated I-type granite. The ? granitic body has relatively lower silicon content than the ? granitic body ?SiO₂=68.76%?72.32%?, and features as rich in aluminum ?A12O3=14.64%?15.33%?, medium alkali content ?Na₂O+K₂O=6.59%?7.25%?, relatively rich in Na ?Na₂O/K₂O=1.17?1.53?, and A/CNK=0.98-1.48, A/NK= 1.49?1.63, ?=1.48?1.90. The ? granitic body belongs to the calc alkaline-high K calc alkaline ?strong? peraluminous granites, and shows both the characteristics of I-type granites and S-type granites. The ? granitic body is similar to the I granitic body, and has a lower degree of differentiation and evolution.The ? granitic body shows low REE concentrations (?REE=21.67×10^-6?57.62×10^-6) and weak differentiation between LREE and HREE ?LaN/YbN=0.87-3.24? with obvious Eu negative anomalies ??Eu=0.15?0.34?. And the rocks in it are relatively enriched in elements such as Rb?Th?U?K etc, and relatively strong depleted in Ba, Sr, P, Ti etc. The REE concentrations in the ? granitic body are obviously higher than that in the ? granitic body (?REE=75.59×10^-6?106.15×10^-6). And the ? granitic body shows obvious differentiation between LREE and HREE ?LaN/YbN=8.00?9.43?, coupling with weakly Eu negative anomalies ?8Eu=0.15?0.34?. The elements such as Rb?Th?U?K etc are enriched and Nb? Ta?Ba?Sr?P?Ti etc are relatively depleted in the ? granitic body.Zircon U-Pb dating results show that, the ? granitic body got the diagenetic age of 308±1.4Ma, the ? granitic body got the diagenetic age of 308.3±4.1Ma, and both of them are similar to the diagenetic age of the ? granitic body ?308.8±4.1Ma?. The diagenetic ages indicate that these granite bodies are formed in Late Carboniferous. Zircon Hf isotope and Sr-Nd isotope analysis show that the three granite bodies have a same ?similar? magma source region, and they all mainly origin from partial melting of the Neoproterozoic newborn mafic lower crust. The three granite bodies should have developed in the same tectonic setting, and all of them had been formed in the Late Carboniferous subduction related arc environment.The granite bodies in Suyunhe area appears unequal degree of differentiation and evolution, affected by fractional crystallization and different magma channels, which may lead to the combination of different ore-forming elements. The ? and ? granite bodies show relatively low level of differentiation and evolution, and the granite bodies that similar to them may mainly develop molybdenum mineralization; The ? granite body has a higher degree of differentiation and evolution, which makes the body be more helpful to migration and accumulation of the mineral materials, and those highly fractionated ?-type granite bodies similar to it may be more conducive to the copper mineralization. The Suyunhe deposit and its surrounding areas also have the potential of copper mineralization, attentions should be paid to the high-k calc alkaline granite porphyry that similar to the ? granite body in the prospecting and mineral exploration.