内蒙古黑山头花岗岩的形成时代及地质意义

通过对额尔古纳地区黑山头花岗岩体的岩石学和激光剥蚀等离子质谱法(LA-ICP-MS)锆石U-Pb年代学研究,揭示了研究区内花岗岩形成的准确时间。在研究区内共采集2个花岗岩样品,其中的锆石均呈自形—半自形晶,并显现典型的岩浆生长环带,结合其较高的Th/U比值(0.74/0.77),暗示其岩浆成因——即定年结果应代表了花岗岩体的形成时代。经测定,在黑山头南采集的两块样品。锆石U-Pb年龄分别为255.2±4.4Ma和247.8±4.1Ma,表明研究区内的花岗岩为印支期晚二叠世-早三叠世。花岗岩呈条带状分布在得尔布干大断裂东南侧,形成时期在得尔布干断裂发生之后,岩石云英岩化、孔雀石化较发育,与附近许多斑岩型矿床成矿母岩类似,具有很好的对比性,为该区内寻找铜钼矿床提供了有利条件。

THE AGE AND GEOLOGICAL SIGNIFICANCE OF HEISHANTOU GRANITE HILLS IN INNER MONGOLIA

By Petrology andLA-ICP-MS zircon U-Pb geochronology, this paper reveals the accurate formation time of the Heishantou granite in Ergun region. The zircon of two granite samples showed euhedral-subhedral, and showed a typical magmatic growth zoning, combined with the high Th/u ratios of 0.74/0.77, suggesting their magmatic origin that the data results should represent the formation time of granite. Zircon U-Pb ages of two samples collected in southern Heishantou are 255.2 ± 4.4 Ma and 247.8 ± 4.1Ma, shows that granite formed in the Indosinian. The granite is banding distributed in the southeast of the Derbugan fault, and the formation of the granite occurs after the fault activity. Greisenization and peacock petrochemical developed well in granite, which similar with many nearby porphyry deposit ore-forming parent rock, has provided favorable conditions for looking for copper molybdenum deposit in this area.