鄂尔多斯盆地东缘奥陶纪构造特征及其对成钾凹陷的控制

At present domestic potash resources is in short supply, especially marine solid potash needs to break through. In recent years, 1.2 meters thin potash ore bed and 64.7 meters thick potash high mineralization period have been found in the sixth sub-member of the fifth member of Majiagou Group of Ordovician in Eastern Ordos Basin which shows potassium prospect is good, and there is hope for breakthrough of marine solid potash. For potash exploration in Ordovician in Ordos basin, we must find the Ordovician potash structural forming sag. At present, the structure study in eastern margin of Ordos Basin is less, and no structure study based on the seismic reflection profile, so it is necessary to elaborately analyze the structure of the Ordos east edge. This application will study tectonic activity of Lishi Fault in Ordovician by using basin seismic data combining the surface geological profile through balancing profile restore, and establish tectonic geometry model of eastern margin of Ordos basin by using the principle of the fault-related-fold, and at last reveals the ordovician tectonic activity’s control on potassium sag in eastern margin of Ordos.

目前国内钾盐资源十分短缺，尤其是海相固体钾盐亟需突破。近年来，在鄂尔多斯盆地中东部奥陶系马家沟组马五6亚段陆续发现1.2米薄钾石盐矿层和64.7米厚层钾石盐矿化段，成钾前景好，有希望获得海相固体钾盐突破。在鄂尔多斯盆地奥陶系找钾必须找到奥陶纪构造成钾凹陷，但是目前鄂尔多斯盆地东缘奥陶纪构造研究较少，且尚未有基于地震反射剖面的构造研究，东缘边界断层-离石断层奥陶纪的构造性质尚不清楚，因此有必要对鄂尔多斯东缘的奥陶纪构造进行精细解剖。本申请拟通过盆内地震资料与地表地质剖面相结合，通过平衡剖面恢复方法，研究离石断层奥陶纪构造活动，运用断层相关褶皱几何学原理，建立鄂尔多斯盆地东缘构造几何学模型，最终揭示盆地东缘奥陶纪构造活动对成钾凹陷的控制作用。

鄂尔多斯盆地陕北盐盆奥陶系马家沟组具有很好的成钾潜力，但目前仅发现薄钾石盐矿层和厚层钾石盐矿化段，尚未发现成规模的钾盐矿。通过对鄂尔多斯盆地东缘的地震剖面进行构造分析，认为盆地东缘晋西挠褶带西部马五6亚段沉积期可能存在古正断层，在该断层作用下，形成东断西倾的活动同沉积凹陷，大量富钾卤水汇聚于此凹陷，在持续干旱的强蒸发环境下，卤水持续浓缩，成钾窗口出现，钾石盐大规模析出，从而形成整装海相优质固体钾石盐矿床。侏罗纪末期，挤压应力致使成钾凹陷发生抬升，形成古凹今隆的格局，钾盐层抬升至较浅部位，便于水溶法经济开采。