渭北隆起构造—热演化与晚期差异隆升过程研究

发布时间：2018-02-22 23:44

  本文关键词： 渭北隆起 裂变径迹 中-新生代 构造-热演化 差异隆升　出处：《西北大学》2017年硕士论文　论文类型：学位论文

【摘要】：渭北隆起与秦岭造山带隔渭河断陷相邻,其构造热演化尤其是晚中生代以来的差异隆升过程一直是鄂尔多斯盆地南缘“盆-山”关系研究和油气勘探关注的热点问题。本文主要采用野外地质构造剖面勘察、地震剖面解释与构造热年代学分析相结合的研究方法,综合分析了渭北隆起区加里东晚期与燕山中期挤压冲断变形的叠加复合关系、构造分区特征和晚中生代的构造热事件及其后期差异抬升冷却过程-剥蚀改造状况,探讨阐释了渭北隆起后期差异隆升过程与相邻构造带活动的关系。主要取得如下成果认识:(1)野外露头剖面勘察与地震剖面解释相结合的构造分析结果表明,渭北隆起区至少经历了受控于北秦岭加里东晚期和燕山中期两次不同性质造山事件的挤压冲断变形,加里东晚期韧-脆性褶断变形层系主要残存于圣人桥-潼关断裂以南,燕山中期脆性褶断变形层系可向北扩展至灵台-黄陵断裂;后期的差异抬升和渭河断陷的叠加改造作用最终铸成了渭北隆起区东、西分段和南、北分带的构造单元分区特征。(2)镜质体反射率数据分析与井剖面沉降埋藏-热演化史模拟的研究结果表明,渭北隆起区经历了早白垩世(140～120Ma)与盆地区域近乎同步的燕山中期构造热事件,相应的地温梯度达到40～50℃/km,明显大于现今地温梯度(29.4℃/km);研究区前新生代沉积埋藏条件与构造热事件的共同作用,不仅造成该区上古生界烃源岩层系普遍达到了高或过成熟热演化阶段(Ro1.8～2.4%),同时表现出“中北部高、东南缘低和西段局部构造-岩浆活动热异常”的热演化程度差异分区特征。(3)裂变径迹年龄统计分布及其差异分区特征的研究结果表明,渭北隆起区晚中生代以来至少经历了三期构造抬升冷却事件,主要发生在早中侏罗世174～168Ma的燕山早期、早白垩世晚期116～100Ma的燕山中晚期和始新世-渐新世39～27Ma以来的喜山中晚期;晚中生代以来的构造抬升冷却过程总体表现出西南部较早(155～65Ma)、东北部较晚(66～32Ma)的时-空差异分区特点。(4)磷灰石裂变径迹热史模拟与差异抬升速率分析结果表明,渭北隆起燕山中晚期以来的构造抬升过程总体呈现出早期(120～65Ma)较快(56～61m/Ma)、中期(65～30Ma)缓慢(5～10m/Ma)和晚期(30～5Ma以来)最快(67～85m/Ma)的差异抬升特点。其中,渭北隆起内带的早期(120～110Ma)、中期(110～40Ma)和晚期(40～17Ma以来)的抬升速率分别接近56m/Ma、5m/Ma和67m/Ma;渭北隆起外带的早期(120～65Ma)、中期(65～30Ma)和晚期(30Ma～5以来)的抬升速率分别接近61m/Ma、10m/Ma和85m/Ma。
[Abstract]:The Weibei uplift is adjacent to the Qinling orogenic belt across the Weihe fault depression. The tectonic thermal evolution, especially the differential uplift process since the late Mesozoic, has always been a hot issue in the study of the "basin-mountain" relationship in the southern margin of the Ordos basin and in oil and gas exploration. By combining seismic section interpretation with tectonic thermochronology analysis, the superimposed composite relationship between late Caledonian and mid-Yanshanian extrusion and thrust deformation in Weibei uplift region is comprehensively analyzed. The characteristics of tectonic zoning and the late Mesozoic tectonic thermal events and their late differential uplift and cooling process-denudation and transformation, The relationship between the differential uplift process in the late Weibei uplift and the activity of adjacent tectonic zones is discussed. The Weibei uplift area experienced at least two extrusion and thrust deformation controlled by two different orogenic events of late Caledonian and mid-Yanshanian orogenic events in the North Qinling Mountains. The late Caledonian ductile-brittle fold deformation strata mainly remained south of the Saint-Qiao-Tongguan fault. In the middle Yanshan period, the deformed series of brittle fold faults can extend northward to Lingtai-Huangling fault, and the late differential uplift and the superposition transformation of Weihe fault depression finally cast the east, west and south of Weibei uplift area. The analysis of vitrinite reflectance data and the simulation of the subsidence and burial history of well sections show that, The Weibei uplift area experienced an early Cretaceous tectonic heat event in the middle Yanshanian period, which was nearly synchronized with the basin area. The corresponding geothermal gradient is 40 ~ 50 鈩，

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