鄂尔多斯盆地渭北隆起抬升期次及过程的裂变径迹分析

Fission-track analysis of uplift times and processes of the Weibei Uplift in the Ordos Basin

渭北隆起处于活动带（秦岭造山带）与稳定地块（鄂尔多斯地块）的过渡地带，构造位置独特重要，该带抬升期次及过程的确定对盆山作用、盆地动力学演化及油气成藏研究具有重要意义．本文运用磷灰石、锆石裂变径迹分析方法及热史模拟方法对渭北隆起进行了低温热年代学研究，研究表明渭北隆起抬升冷却在南北方向上具有明显的差异性，具有南早北晚的特点．南部奥陶系一下二叠统抬升早，主要为早白垩世晚期102～107Ma以来，北部自新生代65Ma以来抬升，主要抬升时期为晚始新世40Ma以来．渭北隆起主要有早白垩世晚期（102～107Ma）及40Ma以来两期快速隆升，40Mal）以来为渭北隆起的主要快速隆升时期．热演化史模拟曲线表明渭北隆起在约125～100Ma快速抬升，在100～40Ma为缓慢抬升，自古近纪晚始新世约40Ma以来，特别是5Ma以来发生快速抬升冷却．渭北隆起新生代40Mal；以来的整体快速隆升与秦岭造山带北缘的隆升具有同时性，与渭河盆地的新生代以来快速沉降具有很好的祸合关系．

The Weibei Uplift which is located in the transition zone between an active belt （the Qinling Orogenic Belt） and a stable block （the Ordos Block）, is in a unique and important structural position. Understanding of the timing and processes of uplift of the belt is of great significance for research on basin-mountain relationships, basin dynamic evolution, and hydrocarbon accumulation. In this study, apatite fission-track analysis, zircon fission-track, and geothermal simulation were used to study the low-temperature thermochronology of the Weibei Uplift. The results show that the processes of uplift and cooling were markedly different. The cooling event took place much earlier in the south than in the north. The uplift of the Ordovician to lower Permian sequence in the south of the area during the late Early Cretaceous （102-107 Ma）, much earlier than in the northern part of the area in which uplift occurred during the Cenozoic （65 Ma）, especially during the late Eocene （40 Ma）. The Weibei Uplift experienced two episodes of rapid uplift, which began in the late Early Cretaceous （102-107 Ma） and during the late Eocene （40 Ma）, the main period of rapid uplift took place at 40 Ma. The results of the thermal evolution simulation indicate that the Weibei Uplift experienced rapid uplift during the period from 125 to 100 Ma, slow uplift between 100 and 40 Ma, and further rapid uplift and cooling after the late Eocene （40 Ma）, particularly from 5 Ma until the present. The timing of the rapid uplift since 40 Ma in the Weibei Uplift and the timing of uplift of the Qinling Orogenic Belt are consistent, The overall rapid uplift in the Weibei Uplift since 40 Ma shows good correlation with the rapid subsidence of the Weihe basin during the Cenozoic.