Gejiu is one of the largest polymetallic tin ore-concentrating districts over the world,which is a granite-related magmatic-hydrothermal system.In this paper,the high-middle thermal evolutional history of granites was drew based on zircon U-Pb dating and 40Ar/39Ar geochronology.The analytical results revealed that the high-middle temperature phase thermal evolution history curves of south granite body and north granite body have the same trend,except a temporal lapse of 3-6 Ma.The Xinshan granite body in the south region of the Gejiu deposit has undergone rapid cooling with cooling rate of 58.70-62.08 ℃/Ma immediately subsequent to its formation at 85 Ma to 89 Ma,and then slowed down to temperature range of 400-250 ℃ with cooling rate of 17.39-19.32 ℃/Ma,this slow cooling process continued until 68-69 Ma;And the thermal evolution history of the Gaofengshan granite body in the north region of the Gejiu lags behind that of the south granite body.The Gaofengshan granite body formed at 83-82 Ma experienced rapid cooling with cooling rate of 295.59 ℃/Ma and 103.29 ℃/Ma,and the temperature dropped into 400-250 ℃ at 80 Ma,thereafter it fell into the extremely slow cooling process with rate of 7.14-5.69 ℃/Ma which continued into 67 Ma.The cooling mode of granite body that is rapid cooling at the beginning and then slow down and persists for a long period at middle temperature range plays a very important role in the formation of the Gejiu tin-copper polymetallic district.It provided a continuous source of heat and geodynamic drives for the regional mineralization,and this is also consistent with the temporal difference of the mineralization between the north and south parts of the Gejiu area.%云南个旧是全球最大的锡铜多金属矿床,主要成矿作用是与燕山期花岗岩密切有关的岩浆-热液体系.本文依据锆石U-Pb测年和40Ar/39Ar年代学对矿区内新山和高峰山花岗岩体进行测试分析,数据揭示矿区内南部和北部的花岗岩体的高-中温阶段热演化史曲线具有相似的演化趋势,只是冷却时间存在3～6 Ma的间隔.南部新山岩体于89～85 Ma形成,此后岩体经历了快速冷却过程,冷却速率为58.70～62.08℃/Ma.之后进入中温400～250℃的缓慢冷却过程,冷却速率为17.39～19.32℃/Ma,并持续到68～69 Ma.北部岩体的热演化史曲线明显滞后于南部岩体,北部高峰山岩体于83～82 Ma形成,之后经历快速冷却过程,冷却速率为295.59℃/Ma和103.29℃/Ma,于80 Ma进入400～250℃,此后以冷却速率为7.14～5.69 ℃/Ma,进入极其缓慢冷却过程并持续至67 Ma.矿区内花岗岩体先遭受快速冷却后进入中温阶段的缓慢长时间冷却作用过程,为锡铜主期成矿作用提供了持续的热源和流体运移动力学过程,也与矿区南、北部的成矿作用差异相吻合.
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