阿拉善地区新元古代晋宁期变形花岗岩的发现及其地质意义

在内蒙古阿拉善地区原划分的阿拉善岩群中识别并划分出了新元古代（晋宁期）的变形花岗岩。该期变形花岗岩主要为眼还需状片麻岩，以高SiO2、碱（NaO2 K2O）、REE，低MgO、TFeO、CaO且K2O大于Na2O，具强烈负Eu异常为特点。两相样品的锆石逐层蒸发法年龄分别为971Ma和845Ma，表明它们是晋宁期岩浆事件的产物。地球化学特征和含有电气石、白云母的矿物组合特点表明，阿拉善地区晋宁期的变形花岗岩形成于同碰撞构造环境。该区晋宁期变形花岗岩的发现意味着新元古代早期的岩浆活动一直影响到华北地台的西北缘。

The discovery of Neoproterozoic Jinningian deformed granites in Alax area and its significance

Neoproterozoic Jinningian deformed granites were recognized from the formerly_defined Alax Group. The ages of zircons from two deformed granite samples determined by step_evaporation technique are 971 Ma and 845 Ma, respectively, implying that they were formed by Jinningian magmatic event. The deformed granites are mainly augen gneisses, characterized by high content of SiO 2, alkali(Na 2O+K 2O) and REE, low content of MgO, TFeO and CaO, K 2O>Na 2O, and intense negative Eu anomaly. Geochemical characteristics and tourmaline_ and muscovite_bearing rock associations suggest that Jinningian deformed granites in Alax area were formed in the syn_collisional setting. The discovery of Jinningia deformed granites demonstrates that magmatic activity of early Neoproterozoic affected the northwest margin of North China platform.