准噶尔盆地东部构造抬升剥蚀对铀成矿的控制

Control of tectonic uplift and denudation on uranium mineralization in the eastern Junggar Basin

构造与成矿具有密切的动态耦合关系,长期研究发现目标层形成和之后的构造抬升剥蚀事件对砂岩型铀矿的形成和定位具有明显控制作用。为了详细地、较为合理地刻画不同类型、不同层位铀矿形成的机理和过程,实现理论模式向找矿模型的转化,建立一种可便于操作的远景预测新方法和新途径,以准噶尔盆地东部卡拉麦里山周缘铀矿床(点)为研究对象,采用盆地构造格架划分、埋藏与剥蚀史研究和蚀源区磷灰石裂变径迹模拟的方法,开展了系列研究工作。研究发现卡拉麦里山周缘不同类型的铀矿床(点)是其抬升剥蚀演化这同一成矿系统作用下的不同产物。盆地沉降曲线和蚀源区磷灰石裂变径迹模拟显示准噶尔盆地东部在中晚侏罗世以来经历了160~140、90~70和约20 Ma以来的3次快速隆升剥蚀阶段,这些构造事件均诱发了明显的铀成矿作用,其构造抬升剥蚀的强度控制了铀成矿的规模,其期次严格地控制了铀成矿的期次。在铀成矿过程中构造发展演化起到了主导作用,规模铀成矿主要发育在有完整成矿系统的构造斜坡带上,如喀木斯特进积式(剥蚀)多期次同向叠加和北三台退积式远源铀成矿模式往往能形成大型矿床;构造形态复杂多变的区段一般不会发育规模铀成矿,如卡拉麦里山南缘山前地区。上述区域构造抬升、铀成矿序列和控矿组合等规律的总结,为该区铀成矿远景预测提供了科学依据,可推广应用到其他盆地砂岩型铀矿找矿当中。

There is a close dynamic coupling relationship between tectonic and mineralization.Long-term research and observation have found that the formation and location of sandstone-type uranium deposits are obviously controlled by the formation of target layer and the subsequent tectonic uplift and denudation events.In order to describe the formation mechanism and process of different types and horizons of uranium deposits in detail and more reasonably,realize the transformation from theoretical model to prospecting model,and establish a new method and approach for target prediction that can be easily applied,a series of studies has been carried out on the uranium deposits(points)around the Kalamari Mountain in the eastern part of Junggar Basin.The study adopts the methods of the basin structural framework division,the research on burial and denudation history and the apatite fission track simulation in the source area.It is found that different types of uranium deposits (spots) in the periphery of the Kalamari Mountain are different products of the same metallogenic system, namely, uplift and denudation evolution. The basin subsidence curve and apatite fission track simulation in the source area show that the eastern Junggar basin has experienced 160−140, 90−70 Ma and about 20 Ma three rapid uplift and denudation stages since the Middle and Late Jurassic. These tectonic events have induced obvious uranium mineralization. The scale and stage of uranium mineralization are controlled strictly by the intensity and stage of tectonic uplift and denudation. In the process of uranium mineralization, tectonic development and evolution play a lead-ing role. Large-scale uranium mineralization is mainly developed in the structural slope zone with a complete mineraliza-tion system. For example, the Kamusite progradation (denudation) multi-period same-direction superposition and the Beis-antai retrogradation far source uranium mineralization model can often form some large-scale deposits. In general, a large- scale uranium mineralization will not develop in the sections with complex and variable structural forms, such as the pied-mont area at the southern edge of the Kalamari Mountain. The summary of the above regional tectonic uplift, uranium mineralization sequence and ore-control combination provide a scientific basis for the prediction of uranium mineraliza-tion prospect in this area, and can be applied to the prospecting of sandstone-type uranium deposits in other basins.