کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5785987 | 1640328 | 2017 | 16 صفحه PDF | دانلود رایگان |
- Four periods of Phanerozoic magmatic events took place in the EM-XMOB.
- Three genetic types of endogenetic metallogenesis formed in the EM-XMOB.
- Tungsten and gold deposits are related to oceanic subduction and continent-continent collision.
- Gold-copper deposits formed under extensional setting related to oceanic subduction.
The eastern margin of the Xing'an-Mongolian Orogenic Belt is characterised by widespread Phanerozoic granitic magmatism, some of which is closely related to significant ore mineralisation. This paper presents new geochronological, petrogenetic, and tectonic data for selected intrusions. Zircon U-Pb geochronology for five granitoid plutons indicates they were emplaced during the middle-late Permian (264-255Â Ma) and Cretaceous (106-94Â Ma), and thus granitic magmatism occurred throughout the Phanerozoic, Permian (268-252Â Ma), Early-Middle Triassic (248-240Â Ma), Early Jurassic (183Â Ma), and Cretaceous (112-94Â Ma). The Permian granitoids consist of monzogranite, granodiorite, tonalite, and quartz diorite, characterised by enrichment in Na2O (3.60-4.72Â wt.%), depletion in K2O (0.97-2.66Â wt.%), and a negative correlation between P2O5 and SiO2. Together with the presence of hornblende, these geochemical features are indicative of an I-type affinity. The Permian granitic magmatism is associated with quartz-vein-type tungsten deposits (252Â Ma; unpublished Sm-Nd isochron age), which formed in an active continental margin setting related to subduction of the Palaeo-Asian Ocean. The Cretaceous quartz diorites have an adakitic affinity, having relatively high Sr (374-502Â ppm), low Yb (0.51-0.67Â ppm) and Y (8.7-10.7Â ppm), and high Sr/Y (39.4-46.8) and (La/Yb)N values (16.2-34.7), suggesting that they were related to the partial melting of subducted oceanic crust. In addition, they are associated with porphyry Au-Cu deposits. We conclude that the Cretaceous granitic rocks and associated porphyry Au-Cu mineralisation occurred in an extensional tectonic setting related to the subduction of the Palaeo-Pacific Plate beneath the Eurasian Plate. In addition, the large-scale Early-Middle Triassic syn-collisional granite belt at the eastern margin of the Xing'an-Mongolian Orogenic Belt extends from the middle of Jilin Province to the Wangqing-Hunchun region, constraining the timing of the final collision between the North China Craton and the Jiamusi-Khanka Massif, and suggesting that the Xra Moron River-Changchun Suture likely extends eastward into the eastern Hunchun region. This collision caused the Middle Triassic mesothermal lode gold mineralisation.
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Journal: Journal of Asian Earth Sciences - Volume 144, 15 August 2017, Pages 368-383