Background heat flow values in the region of the Sea of Okhotsk

Particular features of tectonic structure and anomalous distribution of geothermal, geomagnetic, and gravity fields in the region of the Sea of Okhotsk are considered. On the basis of heat flow data, ages of large-scale structures in the Sea of Okhotsk are estimated at 65 Ma for the Central Okhotsk Rise and 36 Ma for the South Okhotsk Basin. Age of the South Okhotsk Basin is confirmed by data on kinematics and corresponds to 50 km thickness of the lithosphere. This is in accordance with thickness value obtained by magnetotelluric soundings. Comparative analysis of model geothermal background and measured heat flow values on the Akademii Nauk Rise is performed. Analysis points to abnormally high (~20%) measured heat flow agrees with high negative gradient of gravity anomalies. Estimates of deep heat flow and basement age of riftogenic basins in the Sea of Okhotsk were carried out in the following areas: Deryugin Basin (18 Ma, Early Miocene), TINRO Basin (12 Ma, Middle Miocene), and West Kamchatka Basin (23 Ma, Late Oligocene). Temperatures at boundaries of the main lithological complexes of the sedimentary cover are calculated and zones of oil and gas generation are defined. On the basis of geothermal, magnetic, structural, and other geological-geophysical data a kinematic model of the region of the Sea of Okhotsk for period of 36 Ma was calculated and constructed.本文探讨了鄂霍次克海区域构造结构（tectonic structure）的独有特征，以及地热场（geothermal field）、地磁场（geomagnetic field）与重力场（gravity field）的异常分布规律。基于热流（heat flow）数据，估算得到鄂霍次克海大型构造的形成年代：鄂霍次克中央海隆（Central Okhotsk Rise）为65 Ma，鄂霍次克南部盆地（South Okhotsk Basin）为36 Ma。鄂霍次克南部盆地的形成年代经运动学（kinematics）数据验证，与50 km厚度的岩石圈（lithosphere）厚度结果一致，该厚度值亦可通过大地电磁测深（magnetotelluric soundings）得到印证。针对科学院海隆（Akademii Nauk Rise），开展了模拟地热背景与实测热流值的对比分析，结果显示实测热流异常偏高（约20%），与重力异常的高负梯度特征相契合。针对鄂霍次克海裂谷盆地（riftogenic basins）的深部热流与基底年代，研究在以下区域完成了估算：德留金盆地（Deryugin Basin，18 Ma，早中新世（Early Miocene））、TINRO盆地（TINRO Basin，12 Ma，中中新世（Middle Miocene））以及西堪察加盆地（West Kamchatka Basin，23 Ma，晚渐新世（Late Oligocene））。计算了沉积盖层主要岩性复合体界面处的温度，并划定了油气生成带。综合地热、地磁、构造及其他地质地球物理数据，构建并计算得到了鄂霍次克海区域对应36 Ma时段的运动学模型（kinematic model）。