We consider the thermal state of the lithosphere in the poorly studied region, including the NE flank of the Baikal rift zone and its adjacent areas (110°–122° E, 50°–63° N). For this purpose, spectral analysis of the EMAG2v3 lithospheric geomagnetic field model using the centroid method is performed, average temperature–depth geotherms are calculated from surface heat flow measurements, and the depth to the bottom of the seismogenic layer is estimated from the data on hypocentral depths of regional earthquakes which occurred in 2000–2018. The distribution of the bottom depths of the lithospheric magnetic sources, regarded as the Curie point depths (CPDs) in this study, which are obtained, demonstrates a southward decrease of the CPD values. The shallowest (22.5 km) and deepest (48.5 km) depths are observed in Transbaikalia and at the Siberian Platform, respectively, while the NE flank of the Baikal rift zone is characterized by intermediate CPDs varying from 32 to 44 km. This tendency is clearly seen in the average CPD estimates which are 33, 37, and 40 km in Transbaikalia, Baikal rift, and Siberian Platform, respectively. In Transbaikalia, the average CPDs, estimated from geomagnetic and geothermal data, are close to each other in contrast to the other structures, where the obtained inconsistency could result from a small number and uneven distribution of surface heat flow measurements, their distortion by permafrost and convection, or assumptions about the radiogenic heat production near the surface. The centroid of the magnetic sources is approximately equal or slightly shallower than the seismicity cutoff depth at the NE flank of the Baikal rift. For the major part of the considered territory, the same relation between the CPD and Moho depths is observed, except for two areas at the Siberian Platform and the Vitim volcanic field, where the uppermost mantle is magnetic. Intermediate relative to the Siberian Platform and Transbaikalia, values of the CPD, obtained at the NE flank of the Baikal rift, indicate no significant heating of the lithosphere; they do not agree with a hypothesis of active rifting but provide evidence for its passive character.

Article Highlights

• The thermal state of the lithosphere under the NE flank of the Baikal rift is studied using a variety of data and methods.

• Southward lithospheric heating is revealed from geomagnetic and geothermal data.

• The obtained results provide evidence for the passive character of the lithospheric extension in the Baikal rift.

我们考虑了研究不足的地区岩石圈的热状态，包括贝加尔湖裂谷带的 NE 侧翼及其相邻区域（东经 110°–122°，北纬 50°–63°）。为此，使用质心法对 EMAG2v3 岩石圈地磁场模型进行频谱分析，根据地表热流测量值计算平均温度 - 深度地温，并根据震源数据估计到发震层底部的深度。 2000-2018 年发生的区域性地震深度。获得的岩石圈磁源底部深度分布，在本研究中被视为居里点深度（CPD），表明 CPD 值向南减小。最浅（22.5 公里）和最深（48. 5 公里）的深度分别在外贝加尔湖和西伯利亚地台观察到，而贝加尔湖裂谷带的 NE 侧翼的特征是中间的 CPD，从 32 到 44 公里不等。这种趋势在外贝加尔、贝加尔裂谷和西伯利亚地台的平均 CPD 估计中清楚地看到，分别为 33、37 和 40 公里。在 Transbaikalia，根据地磁和地热数据估计的平均 CPD 彼此接近，与其他结构形成对比，其中获得的不一致可能是由于地表热流测量的数量少且分布不均匀、永久冻土造成的变形和对流，或关于地表附近辐射热产生的假设。磁源的质心与贝加尔湖裂谷东北侧的地震活动截止深度大致相等或略浅。对于所考虑领土的主要部分，观察到 CPD 和莫霍面深度之间的相同关系，除了西伯利亚地台和维蒂姆火山场的两个区域，其中最上层地幔是磁性的。相对于西伯利亚地台和外贝加尔湖，在贝加尔湖裂谷东北侧获得的 CPD 值表明岩石圈没有显着加热；他们不同意主动裂谷的假设，但为其被动性质提供了证据。除了西伯利亚地台和维蒂姆火山场的两个区域，它们的最上层地幔是磁性的。相对于西伯利亚地台和外贝加尔湖，在贝加尔湖裂谷东北侧获得的 CPD 值表明岩石圈没有显着加热；他们不同意主动裂谷的假设，但为其被动性质提供了证据。除了西伯利亚地台和维蒂姆火山场的两个区域，它们的最上层地幔是磁性的。相对于西伯利亚地台和外贝加尔湖，在贝加尔湖裂谷东北侧获得的 CPD 值表明岩石圈没有显着加热；他们不同意主动裂谷的假设，但为其被动性质提供了证据。

文章亮点

• 使用各种数据和方法研究了贝加尔湖裂谷东北侧岩石圈的热状态。

• 地磁和地热数据揭示了向南的岩石圈加热。

• 所得结果为贝加尔湖裂谷岩石圈伸展的被动特征提供了证据。