松辽盆地中央坳陷区中-新生代岩石圈厚度演化

Mesozoic‑Cenozoic lithospheric thickness evolution in the central depression of Songliao Basin

岩石圈厚度演化为揭示深部动力学过程提供依据和重要信息。本文通过恢复松辽盆地中央凹陷区典型单井的热历史,利用实测的热物性参数和前人所确定的地壳分层结构,基于地热学相关理论计算了松辽盆地中-新生代主要地质时期的“热”岩石圈厚度。研究表明,松辽盆地中央凹陷区热流演化有两个阶段:1)晚白垩世逐渐升温阶段,此期间热流逐渐增加,最终在白垩纪末期达到最大热流值;2)新生代以来的热流衰退阶段,此阶段构造活动相对稳定,大地热流在此期间逐渐减少,现今热流平均为78.2 mW/m^(2)。松辽盆地岩石圈厚度在早白垩世为42 km左右,白垩世末期降低至36 km左右,现今岩石圈厚度增加至55 km。这主要是由于在侏罗纪-白垩纪时期,中国东部大陆岩石圈整体处于东西拉张的环境中,地壳和岩石圈伸展减薄,导致白垩纪末期岩石圈减薄,此后盆地整体处于拗陷构造发育期,岩石圈再次增厚至现今的55 km。本文的研究成果初步揭示了松辽盆地中-新生代岩石圈演化的过程,为松辽盆地深部动力学过程提供依据,并具有重要的科学意义。

The lithospheric thickness evolution provides the basis and important information for revealing the deep dynamic processes.In this paper,by restoring the thermal history of typical single wells in the central depression of Songliao Basin,the“thermal”lithosphere thickness of the main geological periods of the Mesozoic‑Cenozoic in Songliao Basin is calculated based on the measured thermal physical parameters and the crust stratified structure.The results indicate that two stages of thermal evolution exist in the central depression of Songliao Basin:1)the gradual heating stage during the Late Cretaceous,the heat flow gradually increases during this period and reaches a maximum heat flow value at the end of the Cretaceous;2)the decline stage since Neogene,the tectonic activity is relatively stable and the geothermal heat flow is gradually reduced,and the current average heat flow is 78.2 mW/m^(2).The thickness of the lithosphere was 42 km in Early Cretaceous,decreased to 36 km at the end of Cretaceous,and increased to 55 km at present.This is mainly due to the fact that during the Jurassic‑Cretaceous period of the Songliao Basin,the continental lithosphere of eastern China was in an east‑west extension environment,and the crustal and lithosphere were extended,leading to the lithosphere thinning at the end of Cretaceous.After that,the basin as a whole was in the development stage of depression structure,and the lithosphere thickened again to the present 55 km.The research results of this paper reveal the evolution process of Mesozoic and Cenozoic lithosphere in Songliao Basin,and provide the basis for the deep dynamic process of Songliao Basin,which has important scientific significance.