| 其他摘要 | The Asikaerte Be-Mo deposit is located in the southeast of the Halong-Qinghe metallogenic belt, Altai metallogenic province, Central Asian metallogenic domain. The deposit is a medium-sized Be-Mo deposit which is rich in beryl. The deposit is a typical representative of granite type Be deposits and has important theoretical significance in economic geology. Predecessors has carried out some research on the deposit, such as the geological features, the formation mechanism, and its cause. But there is no high-precision mineralization chronology data, which is constraining the understanding of the genesis of the mineral deposit. Based on the zicon U-Pb dating of granite and pegmatite, geochemical analysis, and molybdenite Re-Os dating, We have studied the formation age, source characteristics, tectonic setting, and genesis of the deposit, providing important information for the comprehensive understanding of the tectonic evolution of the Altai orogen. Main conclusions are as follows: (1) Zircon LA-ICP-MS U-Pb dating results show that the formation age of Granodiorite is 386.8?2.6 Ma, the formation age of biotite granite is 385.4?4.4 Ma, the formation age of medium-fine granular muscovite granite is 247.5?2.2 Ma, the formation age of fine-grained albitization muscovie granite is 231.4?2.0 Ma, the formation age of banded pegmatite is 220.6?1.6 Ma. Thus, granodiorite, biotite granite, two-mica granite were formed in the Middle Devonian, while medium-fine granular muscovite granite, fine-grained albitization muscovie granite, and banded pegmatite were formed in the Indosinian. (2) Granodiorite and biotite granite of the Middle Devonian are calc-alkaline to high-K calc-alkaline I-type granites. The contents of Sr, Yb and Nb/Ta ratio characteristics indicate that continental crust formed Granodiorite and biotite granite by partial melting of dehydration at low pressure and high temperature conditions. Combining with regional geological setting, we inferred that I-type granite of the Asikaerte Be-Mo deposit is concerned with the ridge subduction of the Altai orogen and the upwelling asthenosphere. The source rocks of Triassic granite are mainly continental crust and may have a small amount of mantle, and the Triassic granite is a product of the environment within the board. (3) An isochron age of Re-Os isotope ages is 228.7±7.1 Ma, and a weighted mean age of Re-Os isotope ages is 229.0±3.0 Ma, which indicates that mineralization occurs in the Triassic. The Re contents in seven molybdenite samples range from 38.26×10-6 to 56.45×10-6, suggesting that the ore-forming metals were crust-mantle mixed source. (4) Sr-Ba and Sr-Rb relations display that Triassic granitic magma mainly underwent fractional crystallization of K-feldspar. Zr/Hf, Y/Ho, Nb/Ta and Sr/Eu ratio appear apparent differentiation in the late evolution, indicating a strong melt-fluid interaction in the late evolution. The muscovite-quartz-albite zone at the top of fine-grained albitization muscovie granite is the macro evidence of melt-fluid interactions. (5)Late magma high rich in Be is difficult to explain with the normal fractional crystallization or magmatic fluid exsolution, the Asikaerte Be deposit is likely to be the product of the interactions of late magma and external Be-rich fluid. |
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