郯庐断裂带肥东段烟头山及桃源地区构造变形特征研究

郯庐断裂带肥东段烟头山及桃源地区，发育多条左行韧性剪切带，岩性以糜棱岩和糜棱岩化片麻岩为主，岩石变形强烈。通过详细的野外观测及室内分析发现：肥东北部烟头山及桃园地区几何学形态呈一背形构造，其枢纽走向NE-SW，轴面倾向SE，自核部向两翼岩性出露具有一定的规律性和对称性。古应力方向及运动学涡度研究表明：研究区内构造体主要受到近南北方向的挤压，涡度值W_k在0.73～0.90之间，指示区域内的韧性剪切活动以简单剪切为主。对区内变形岩石展开精细化的构造变形分析，包括石英的分形特征、变质变形温度估计、差应力和应变速率的计算等，结果显示：区内动态重结晶石英颗粒边界具有统计学上的自相似性，分维值D在1.111～1.187之间，变质变形温度集中在520 ℃～610 ℃之间，为高绿片岩相到低角闪岩相变质；韧性剪切带的差异应力Δσ介于18.493～95.266 MPa之间，应变速率ε范围在5.418×10^-15 s^-1～4.748×10^-11 s^-1之间。对比以上参数发现：韧性剪切带核部和背形转折端附近，岩石变形强烈，变质变形温度高，动态重结晶石英颗粒粒径较小，分维值较大，差异应力和应变速率也较大，远离剪切带核部和背形两翼则相反。本文从几何学、运动学特征以及显微构造变形分析等方面展开精细化研究，对进一步认识郯庐断裂带乃至大型韧性剪切带的构造样式和演化过程有着重要的意义。

Sturctural characteristic of the faults in the southern North China Basin and its relationship with petroleum exploration

There are three periods main faults in the southern North China Basin. The first period faults are thrust faults because of compressive stress in Late Triassic, with near EW trend, thrusting direction from south to north. The second period faults are strike slip faults mainly trending NNE caused by tensional-shear stress in Late Jurassic-Early Cretaceous. The third period faults are a series of normal faults mainly trending NNE related with the structural movement in Late Cretaceous and Paleogene. Thrusting and uplifting of the faults in Late Triassic resulted in serious erosion and discontinuity to Carbon-Permian source rocks. The faults in Late Jurassic-Early Cretaceous and the faults in Late Triassic cut the southern North China Basin just as chess board, and the igneous rock associated with the faults destroyed the source rocks in a certain degree. The faults in Late Cretaceous and Paleogene reinforced the discontinuity of source rocks. The faults in later two periods usually reached the land surface and destroyed the oil and gas reservoir formed before Late Jurassic. Therefore, the oil and gas exploration in the southern North China Basin should avoid the strike slip faults, normal faults and igneous body, search for the Paleozoic source rocks of good continuity, hunt for the sedimentary facies belts in favor of developing source rocks.