准噶尔盆地南缘新生代构造特征及其与砂岩型铀矿成矿作用初析

准噶尔盆地南缘盆山结合部中新生界沉积巨厚,新生代变形强烈,是研究新盆山耦合的理想场所,也是我国砂岩型铀矿找矿的远景区段。本文在综合前人资料和野外观测分析基础上,根据新生代构造活动特征,将准噶尔盆地南缘划分为博格达山前和西部断褶带两个构造分区,博格达山前以强烈的逆冲推覆为特征,发育多条活动的逆冲推覆断裂; 乌鲁木齐以西至乌苏南的西部断褶带则发育三-四排的褶皱-逆冲断裂构造带。对采自博格达山前逆冲推覆断裂带内的方解石和断层泥,利用电子自旋共振测年手段,推测博格达山前的富康-吉木萨尔断裂带和北三台断裂带分别在0.7~1Ma和0.25Ma期间,经历了一期重要的逆冲推覆作用。结合盆地南缘砂岩型铀矿的展布规律及其成矿条件的分析,探讨了新生代构造运动对砂岩型铀矿成矿的控制作用,认为西部断褶带的第一排构造带具有较好的成矿前景,而博格达山前由于新生代构造活动强烈而相对成矿不利,为此提出了准噶尔盆地南缘砂岩型铀矿成矿“构造优先权”的构造控矿模式,进而指出了区域找矿的优选区段。

Characteristics of Cenozoic structural movements in southern margin of Junggar basin and its' relationship to the mineralization of sandstone-type uranium deposits

Huge-thick Mesozoic-Cenozoic sediment deposited in the coupling areas of the southern margin of Junggar basin with north of Tianshan mountains, where Cenozoic deformations widely spread and was regard as a natural laboratory to study the dynamics of relationship between basin and range, and also was one of favorable ore-prospecting areas for sandstone-type uranium deposits. Prior data and our own field observation indicated that the area can be divided into two parts according to the characteristics of Cenozoic tectonic movements. Intense Cenozoic thrust motion took placed in north areas of Bogeda mountains, where several present active thrust faults developed. Three or four pattern fold-thrust fault belts developed in west of Urumuqi, and east of the south Wusu City in northern edge of Tianshan mountains. Calcite and gouge were collected from thrust faults in north Bogeda mountain and were dated using the ESR (Electronic Spin Resonance) method, which revealed 0.7~1.0Ma and 0.25Ma in age as an important active time of the Fukang-Jimusaer fault and the north Santai fault, respectively. The controlling of the Cenozoic deformation to the mineralization of sandstone-type uranium deposits was also discussed in this paper based on the analysis of distribution law and metallogenic elements of sandstone-type uranium deposits. It was suggest that the first-pattern structural zone in western fold-fault belts is one of the best ore-forming regions for sandstone-type uranium deposits, while north areas of Bogeda mountains are not favorable for mineralization because of the intense Cenozoic deformation. Therefore, a new model named as tectonic-prefer controlling ore-formation model was proposed and favorable ore-prospecting areas were predicted in southern margin of Junggar basin.