内蒙古宝音图-霍各乞地区宝音图岩群的时代约束及构造属性

宝音图隆起的构造归属仍然存在争议，有学者认为是兴蒙造山带中的微陆块，也有观点认为是华北克拉通的一部分.作为宝音图隆起的重要组成部分，探究宝音图岩群的形成时代、构造归属是解决这一问题的重要途径.通过对宝音图岩群3件石英岩样品进行锆石U-Pb同位素测试，在一岩组（石英岩和石英片岩岩组）、二岩组（石英岩岩组）、三岩组（片岩岩组）中分别获得较可靠的碎屑锆石最小谐和年龄为1 284 Ma、1 319 Ma、1 395 Ma，代表各岩组的沉积上限.结合侵入宝音图岩群中的变质基性脉岩的锆石U-Pb年龄为895.5±6.8 Ma，将研究区宝音图岩群一-三岩组的沉积时代大致限定在895.5~1 284.0 Ma之间，位于中元古代晚期至新元古代早期；可以和相邻区域大致形成于同一时期的阿拉善地区阿拉善群、白云鄂博地区白云鄂博群上亚群、化德-康保地区化德群上亚群对比.斜长角闪岩地球化学特征反映其形成于大陆边缘裂谷环境，可能为Rodinia超大陆裂解在本区的响应.宝音图岩群与邻区同时代沉积建造的碎屑锆石年龄谱较为相似，其主要峰值反映的地质事件与华北克拉通所经历的主要构造-热事件可以较好对应，说明宝音图岩群的物源来自于华北克拉通，为华北克拉通边缘的沉积.宝音图隆起应当为华北的一部分. 

Geochronological Constraint on the Baoyintu Group and Its Tectonic Significance in Baoyintu-Huogeqi Area,Inner Mongolia

The tectonic affinity of the Baoyintu uplift is still controversial. Some researchers believe that the Baoyintu uplift is a microblock in CAOB, but others suggested that it's a part of the North China Craton (NCC). The formation age and tectonic affinity of the Baoyintu Group is important to solve this problem. LA-MC-ICP-MS zircon U-Pb ages of three quartzite samples in the Baoyintu Group are analyzed in this study. The minimum age of the zircons in the first, second and third formation, respectively, is 1 284 Ma, 1 319 Ma, and 1 395 Ma, representing the upper limit of the sedimentary.The zircon U-Pb age of the metamorphic mafic sill is 895.5±6.8 Ma, so the sedimentary age of the first to third formation of Baoyintu Group in the study area is limited to 895.5-1 284.0 Ma. It can be compared with the upper Alashan Group, the upper Bayan Obo and upper Huade Group. Geochemical characteristics of amphibolite from the Baoyintu Group infer that it is located in the rift of continental margin, and might be associated with the breackup of Rodinia. The age spectra of the detrital zircons in these sedimentary are similar, and the geological events defined by the main peaks correspond to those of the NCC, indicating that detrital of the Baoyintu Group is from NCC. And the Baoyintu Group is the sediment on north margin of the NCC, the Baoyintu uplift should be a part of NCC.