LITHOSPHERIC THERMAL-RHEOLOGICAL STRUCTURE AND DEEP GEODYNAMICS IN THE YANGTZE RIVER ECONOMIC BELT
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摘要: 通过Crust 2.0模型构建有限元三维数值模型，以地表观测温度、深部反演温度和地表热流作为约束，计算了长江经济带地区岩石圈温度结构；在温度结构的基础上，通过GPS观测数据得到的地表应变率和选取代表性岩石物性，计算了长江经济带岩石圈流变强度和等效粘滞性系数。结果表明：长江经济带地区岩石圈表现出明显的横向不均匀性，其中四川盆地表现为低温、高强度和高粘滞性的特征，相同深度，四川盆地核心区比周围地块的温度低100~300℃，强度和粘滞性分别比周缘高1~2个数量级；在温度、强度和粘滞性的过渡地带构造活动性比较强烈。结合深部地球物理观测综合分析认为，长江经济带东、西部分别受到太平洋板块深俯冲和印度-欧亚大陆板块碰撞的影响，其深部影响范围分别达到四川盆地的东、西边界，深部动力学过程可能导致了岩石圈的横向不均匀性。Abstract: Constructing the finite three-dimensional numerical model through Crust 2.0, under constraints of the surface temperature, deep inversion temperature and surface heat flow, we have calculated the thermal structure of the continental lithosphere beneath Yangtze River Economic Belt and adjacent regions. On the basis of 3D thermal structure, deriving surface strain rates from GPS observation, and selecting representative rock physical properties, we have calculated the strength and effective viscosity of the continental lithosphere. The results show that there is obvious lateral heterogeneity in the Yangtze River Economic Belt. The Sichuan basin has low temperature, high strength and high viscosity. In the same depth, temperature beneath the Sichuan basin is lower than ambient region for 100~300℃. Strength and viscosity is lower for 1~2 orders of magnitude. The transition zone of temperature, strength and viscosity has strong active tectonics. Combining with deep geophysical observation, the study proposed that the Pacific Plate subduction and India-Eurasia Plate collision played important roles in the deep dynamic process respectively in the eastern and western parts of the Yangtze River Economic Belt. The effective sphere reach the eastern and western boundaries of Sichuan basin, deep dynamic process may lead to the horizontal heterpgeneity of the lithosphere.
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图 2 长江经济带地区岩石圈不同深度温度场
Figure 2. Temperature distribution at different depths of the lithosphere in the Yangtze River Economic Belt
图 3 长江经济带地区各个剖面岩石圈温度、强度和等效粘滞性系数分布(剖面位置见图 1)
Figure 3. Distributions of temperature, strength and viscosity of the lithosphere at different profiles in the Yangtze River Economic Belt
图 4 长江经济带地区岩石圈不同深度的强度分布
Figure 4. Lithospheric strength distribution at different depths in the Yangtze River Economic Belt
图 5 长江经济带地区岩石圈不同深度的等效粘滞性系数分布
Figure 5. Viscosity distribution at different lithospheric depths in the Yangtze River Economic Belt
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