西藏那曲南部早白垩世闪长玢岩LA-ICP-MS锆石U-Pb年龄

摘要

北冈底斯带东部那曲地区存在中三叠世、中-晚侏罗世和晚白垩世岩浆活动,却鲜有早白垩世岩浆活动的报道.对北冈底斯带东部那曲地区的罗马区闪长玢岩进行了系统的采样研究,并对其中2件样品进行了LA-ICP-MS锆石U-Pb定年,结果分别为116.1Ma+0.4Ma和115.9Ma±0.5Ma,在误差范围内几乎一致,应该代表了其形成的时代.表明北冈底斯带东部地区亦存在早白垩世晚期岩浆活动,这对探讨北冈底斯带早白垩世的地质演化具有重要意义.%In northern Gangdise belt, Middle Triassic, Middle-Late Jurassic and Late Cretaceous magmatic activities exist, but Early Cretaceous magmatic activity was rarely reported. The authors sampled and analyzed systematically andesite porphyrite from Luoma area of Nagqu, Tibet. Two of the samples were dated by LA-ICP-MS zircon U-Pb dating, and their ages are 116.1 ±0.4Ma and 115.9±0.5Ma respectively. These ages are almost consistent with each other within the acceptable error range, thus representing the formation age. The authors hold that the Early Cretaceous magmatic activity did exist in northern Gangdise belt, which is of great significance in the study of the Early Cretaceous geological evolution.