吕梁山脉中北段元古代花岗岩体隆升演化的裂变径迹证据

Fission Track Evidence of Tectonic Evolution of the Paleoproterozoic Granitic Pluton in the North-Central Part of Lüliang Mountain

研究区位处华北克拉通中部造山带,在中-新生代经历了多次构造体制与区域构造属性的重大转变。对吕梁山脉中北段古元古代花岗岩体隆升剥露的定量化研究,可以更加整体、直观的认识中部构造带内基底岩石隆升剥露作用,有助于了解华北克拉通演化过程。同时能为周围能源型盆地的形成演化提供佐证,深化对盆地资源赋存条件的认识,从而为资源的开发提供基础证据。通过对研究区古元古代花岗岩体系统的裂变径迹热年代学采样分析,揭示了基底岩石初始隆升剥露作用发生在晚白垩世至新生代早期,主要有两个阶段:白垩世晚期约88~77Ma和新生代早期约65~53Ma。之后,样品处在磷灰石退火带之上,虽有短暂的再次埋藏,但总体一直处在抬升剥露作用下。磷灰石裂变径迹数据和热史模拟表明,不同岩体抬升剥蚀在时空上具有非均衡性,晚白垩世早期,中部关帝山岩体呈穹隆状隆升剥蚀。北部芦芽山岩体和云中山岩体晚白垩世遭受挤压,发生隆褶变形。新生代以来,岩体加速隆升,早期(65~53Ma)是岩体抬升-剥露速率出现转折的关键时期,与东西两侧相邻断陷的发育具成因上的耦合联系,在华北地块中部地区具有区域响应,并可能奠定了现今吕梁山脉中北段的地势发展格局。

The study area,located in the central orogenic belt of the North China Craton,experienced the significant changes of several tectonic regimes and regional tectonic features during the Mesozoic-Cenozoic era.The quantitative study of Paleoproterozoic granitic pluton in the north-central part of Lüliang Mountain can directly and intuitively reveal the uplift and exhumation history of basement rocks.This will not only benefit understanding the evolution of the North China Craton but also provide evidence for the formation and evolution of energy-type basins in neighboring areas.All the knowledge will deepen our understanding of resource preservation conditions in basins and thus provide basic evidence for resources development.Fission track thermochronology analysis of Paleoproterzoic granitic pluton reveals that initial uplift and denudation of Lüliang Mountain occurred in Late Cretaceous（88-77 Ma）to Early Cenozoic（65-53 Ma）.Our study also shows that apatite was on the annealing zone,indicating that this area was in a short bury period but generally in uplift and denudation state.Fission track dating and thermal-simulation results indicate that since the Late Cretaceous,the uplift and cooling/exhumation history recorded by bedrocks in the north-middle part of the Lüliang Mountain is spatiotemporally characterized by imbalance,with the central dome Guandishan granite intrusive pluton in uplift and exhumation in early Late Cretaceous.During Late Cretaceous,Yunzhongshan and Luyashan granite plutons in the north underwent tectonic uplifting and deformation due to compression.Since Early Cenozoic,fast uplifting（65-53 Ma）of the plutons was the key change period between uplift and exhumation,which has some genetic link to the development of faulting on both eastern and western neighboring areas.Therefore,regional response in the central part of North China block may establish the development pattern of modern terrain for the north-middle part of Lüliang Mountain.