Zircon U-Pb geochronological framework of Qitianling granite batholith, middle part of Nanling Range, South China

摘要: The Qitianling granite batholith (QGB) is located in the southern Hunan Province, middle part of Nanling Range, South China. Its total exposure area about 520 km2. Based on our 25 single grain zircon U-Pb age data and 7 published as well geological, petrological, space distribution characteristics, we conclude that QGB an Early Yanshanian (Jurassic) multi-staged composite pluton. formation process can be subdivided into three major stages. first stage, emplaced at 163-160 Ma with a peak 161 Ma, mainly composed hornblende-biotite monzonitic granites locally biotite granites, distributed eastern, northern, western peripheral parts second 157-153 157-156 containing hornblende, southeastern third 150-146 149 fine-grained (locally porphyritic) middle-southern Each stage further disintegrated several bodies. two intrusive stages comprise phase QGB, comprises additional phase. Many bosses dykes intruded host clear chilling margin-baking phenomena their contacts. They were open fracture earlier consolidated rocks. Their isotopic ages are mostly 2–6 younger than hosts. Conceivably, time interval from magma emplacement, through cooling, crystallization, solidification, up to fracturing cannot exceed Ma. During Middle-Late Jurassic neighboring coeval granitic basic-intermediate magmatic activities widely developed. It indicates period was culmination this region. Range under post-orogenic, intracontinental geotectonic environment obvious lithospheric extension thinning. crust-mantle interaction played important role rocks