| 蒙古国查干苏布尔加大型铜-钼矿床地质特征及成因 |
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| 关键词:Tsagaan Suvarga porphyry Cu-Mo deposit adakite formation age ore-forming mechanism |
| 基金项目:国家科技支撑课题(编号: 2007BAB25B02)；地质调查项目(编号: 1212010911029) |
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| The Geology and Ore-forming Mechanism of the Tsagaan Suvarga Large-size Cu-Mo Porphyry Deposit in Mongolia |
| The Tsagaan Suvarga large-size Cu-Mo porphyry deposit is located in the southern Mongolia tectonic-magmatic island arc belt between the NE-trending and EW-trending deep faults on the southern margin of the Siberian plate. The copper-molybdenum mineralization is hosted in the monzogranite porphyry and granodiorite porphyry that intruded early Devonian intermediate-mafic volcanic and volcanoclastic rocks. This paper has provided major and trace element compositions of ore-hosting monzogranite porphyry and granodiorite porphyry in the Tsagaan Suvarga large-size Cu-Mo porphyry ore district: the major compositions are SiO2 64.69?10?2~ 73.42?10?2, 67.50?10?2 on average; Al2O3 15.33?10?2~18.35?10?2, 16.88?10?2 on average; MgO 0.13?10?2~0.56? 10?2, 0.16?10?2 on average; trace element compositions are Sr 96.70?10?6~612?10?6, 382.78?10?6 on average; Y 2.21?10?6~10.20?10?6, 7.46?10?6 on average; Yb 0.30?10?6~1.48?10?6, 1.07?10?6 on average; Sr/Y 21.8-63.52, 48.12 on average; rare earth element compositions are ΣHREE 1.63-7.06 μg/g, LREE/HREE 4.96~10.74, (La/Yb)N 5.57~13.68, δEu 0.87~1.09, 0.98 on average; and Sr-Nd isotope compositions are 87Sr/86Sr initial value 0.70154~0.70397, 0.70322 on average; 143Nd/144Nd initial value 0.512290~0.512600, 0.512459 on average; εNd(t) +2.4~+8.5, +5.7 on average. These data show that the granodiorite porphyry and monzogranite porphyry has characteristics of adakitic rocks which are spatially and temporally associated with copper molybdenum minerali-zation. According to precise isotopic age studies, the Re-Os dating of molybdenite samples separated from the ore body yielded the isochron age of (370.0±5.9)Ma, and zircon SHRIMP U-Pb dating of the monzogranite porphyry yielded weighted average age of (365.7±3.6)Ma, suggesting that mineralization took place in Late Devonian, coe-val with that of the monzogranite porphyry. The Cu-Mo ore bodies are associated with the monzogranite porphyry and granodiorite porphyry in spatial distribution, and almost the whole monzogranite porphyry and granodiorite porphyry experienced mineralization and alteration in the ore district. According to the above evidence, the ada-kitic magma provided primary ore-forming materials and fluids, the ancient Mongolian oceanic plate conducted rapid low-angle subduction under the northern margin of the old Siberia plate in a high-temperature, high pressure and water-rich environment, and the adakitic magma formed from direct melting of the oceanic plate, with the si-multaneous precipitation of Cu, Mo, Au, Ag and other metallogenic elements. During the upward migration of adakitic magma, the ore-forming metallic elements were extracted from the mantle wedge, and these elements rapidly ascended to the shallow position along with the adakitic magma. With the variation of the physi-cal-chemical conditions, the metallogenic elements underwent unloading, precipitation and enrichment, and ulti-mately formed the ore deposit. |
| HOU Wan-rong,NIE Feng-jun,JIANG Si-hong,BAI Da-ming,LIU Yan,YUN Fei,LIU Yi-fei.2010.The Geology and Ore-forming Mechanism of the Tsagaan Suvarga Large-size Cu-Mo Porphyry Deposit in Mongolia[J].Acta Geoscientica Sinica,31(3):307-320. |
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