松辽盆地裂后期异常热演化的多重热年代学探针

The widely used lithosphere-stretching models (McKenzie, 1978) provide a classic quantitative framework for predicting the tectonic subsidence history of a rifted basin or margin. This classic model serves as an useful approximation for subsidence and paleo-temperature in rifted basins under passive margins settings, whose post-rift thermo-tectonic evolution is rather simple by the power exponent decaying of paleo-heat flow. However, the stratigraphy of the Songliao Basin, which is the most representative Mesozoic rifting structure in Eastern Asia, shows that the post-rift evolution was punctuated by the episodic alternation of burial heating and uplift cooling events, accompanying by extraheating events and coeval anomaly geothermal area. It seems that the post-rift history in the Songliao Basin deviated from the theoretical McKenzie model. In this project, based on tectostratigraphic analysis of the post-rift sequence of the Songliao Basin, we integrated multiple thermochronology and modelling of six radioactive decay schemes, each with different temperature window for isotopic closure, apatite Lu-Hf (Ap-Lu-Hf, 675-750℃), apatite U-Pb (Ap-U-Pb, 350-550℃), apatite fission track (AFT, 110-60℃), apatite U-Th/He (AHe, 40-80℃), zircon fission track (ZFT, 170-330℃) and zircon U-Th/He (ZHe, 170-190℃) for the analyzing the continuous sediment cores from the Cretaceous Continental Scientific Drilling, SK-1 & SK-2 and other petroleum exploration core samples. The primary research objective of this project is to evaluate the post-rift thermo-tectonic evolution of the Songliao Basin by extracting the signatures of provenance-basin, crystallization- exhumation, heating- cooling. This project also investigates how, when and why the anomaly post-rift thermal event occurred and developed. Moreover, we try to establish tight tectonic linkage between basin post-rift evolution and the coeval adjacent plate reorganization event and/or crust-mantle thermo-structure. This project promotes scientific progress on understanding the evolution of rifting basin system controlled by the convergent plate tectonic settings.

基于离散板块背景形成的大西洋被动大陆边缘裂谷而建立的经典裂谷盆地演化模型，其裂后期热演化表现为简单持续的幂指数降温过程。与此不同，松辽盆地裂后期构造热演化显示出降温与升温事件交替出现的幕式演化特征，期间还可能存在异常加热升温事件。针对这一现象，本研究选择我国东部最典型的中生代裂谷盆地—松辽盆地为研究区，在盆地裂后期地层构造-沉积解析的基础上，应用多重热年代学探针技术对松科1井、2井等钻井的连续岩芯剖面开展系统的定年工作。通过热年代学信息的提取、分析和模拟，结合已发表的定年和热史资料，试图建立盆地裂后期完整的热史剖面，获得源区—盆地、结晶—剥露、加热—冷却的构造热演化曲线，确定裂后期异常高热事件发育时间、分布范围、演化规律和控制机制。总结分析周缘板块运动重组事件、岩石圈深部热动力作用对松辽盆地的控制和影响，确定盆地裂后期异常热演化的动力学背景，为汇聚板块背景下裂谷盆地裂后期演化提供典型范例。

经典裂谷盆地演化模型的裂后期热演化过程，表现为简单持续的幂指数降温过程。然而，位于东北亚地区的松辽大陆裂谷盆地，其裂后期构造热演化显示出降温与升温事件交替出现的幕式演化特征，期间还可能存在异常加热升温事件。针对这一现象，本研究选择松辽盆地为研究区，在盆地裂后期地层构造-沉积解析的基础上，应用多重热年代学探针技术对松科1井、2井等钻井的连续岩芯剖面开展系统的定年工作。通过热年代学信息的提取、分析和模拟，结合已发表的定年和热史资料，建立了盆地裂后期完整的热史剖面，并在上白垩统嫩江组沉积时期（85-80Ma）识别出一幕异常高热事件，异常高热区的分布范围主要为中央坳陷区，其中大庆长垣地区所经历的最高古地温可能高达170-220℃。总结分析周缘板块运动重组事件、岩石圈深部热动力作用对松辽盆地的控制和影响，确定盆地裂后期异常高热事件发生的地球动力学背景主要为古代太平洋板块晚白垩世期间的快速西向俯冲。