East Junggar Naomao Lake Area Late Paleozoic Granite Genesisand Geological Implication

Abundant metal mineralization related to Early-Middle Paleozoic arc magmatism developed in Naomao Lake area, especially porphyry Cu & Au deposits. Although most of the deposits haved been found have relationship with Early-Middle Paleozoic arc magmatism( Chen et al., 1995; Liu et al., 2005; Guo et al., 2009; Qu et al., 2009), whether the mineralization related to subduction had extended to Late Paleozoic is still under research. This research aimed to get approach to release the genesis and the formation environment of the deposit by means of high precision U-Pb dating, Hf isotope analysis and regional comparison.This research carried out field work focused on the problems above, and take petrology, mineralogy, U-Pb dating, geochemistry and Hf isotope analysis. We get following conclusions:1.Zircons from Huigou intrusion yield a 337± 2Ma U-Pb concordia age, not a Permian magmatism as former study. Zircons from Luotuoshitougou intrusion yield a 337± 2Ma U-Pb concordia age, not a Permian magmatism as former study.Zircons from Baoxi intrusion yield a 340± 1Ma U-Pb concordia age, not a Permian magmatism as former study.2.Huigou intrusion is monzogranite, shows calc-alkaline-high K calc-alkaline and metaluminous to weak peraluminous affinities. The intrusion deplete in HFSE(Nb、Ta、P、Ti) and enriched LILE(Rb、Ba、K、Sr) relatively. It belongs to high Ba-Sr I-type granite classification. It also yield positive εHf(t)(+15.8~+16.4) and juvenile TDM2(Hf)= 311~355Ma. The magmatism should be a product of partial melting basaltic continental lower crust with fractional crystallization in an environment from subduction to collision/post-collision.Luotuoshitougou intrusion is monzogranite, shows calc-alkaline-high K calc-alkaline and metaluminous to weak peraluminous affinities. The intrusion deplete in HFSE(Nb、Ta、P、Ti) and enriched LILE(Rb、Ba、K、Sr) relatively. It belongs to high Ba-Sr I-type granite classification. It also yield positive εHf(t)(+13.4~+16.4) and juvenile TDM2(Hf)= 289~490Ma. The magmatism should be a product of partial melting basaltic continental lower crust with fractional crystallization in an environment from subduction to collision/post-collision.Baoxi intrusion is monzogranite, shows high K calc-alkaline and metaluminous to weak peraluminous affinities. The intrusion depletes in HFSE(Nb、Ta、Ti) and enriched LILE(Rb、Ba、K、Sr) relatively. It belongs to high Ba-Sr I-type granite classification. It also yields positive ε Hf(t)( +12.0~+15.1). result of fractional crystallization of the primary maga that derived by partial melts of mafic lower crust mixing with upwelling mantle materials in an environment from subduction to collision/post-collision.