Paleo-stress fields in the Harz Mountains and surrounding areas between the Variscan convergent period and the Upper Cretaceous

这个拟议的项目是基于对申请者进行的大量调查，这些申请者在次海西盆地和弗兰科尼线之间的地区对断层运动学和古应力场进行了调查(见H.J.Franzke出版物清单)。最近的调查是在DFG资助的一个项目中进行的，该项目涉及亚海西盆地的沉降史和Harz区块的同步隆起(申请人：R.Gaupp和H.J.Franzke，2004年最后报告Fr 874/4，见附录5)。该项目的目的是在不同地层单位和几种构造环境下的同步活动断层群的野外研究的基础上，确定哈尔茨山脉及其周围地区的古应力场。在哈尔茨山脉，一堆连续的古生代沉积岩暴露得很好，周围环绕着两公里厚的二叠纪至上白垩纪岩石。同时，获得了大量的沉积发育、广泛分布的华力西晚期侵入/火山岩和无数与断层有关的热液脉状构造的放射性和古生物年龄数据。因此，从石炭纪的华力西会聚阶段到中、新生代的几个脆性断裂期之间约200 Ma的长时间内，可以对断裂活动进行详细的时间控制。这些课题的结果已经由不同的作者发表，包括申请者(见参考文献)，但到目前为止，还没有使用现代构造地质学方法对更大范围的概括性调查。为了评价哈尔茨山及其前缘地区的区域古应力分布，利用断层滑动资料进行了主应力方向的计算。滑移条纹记录的断层面上的位移矢量被认为与剪应力张量的方向和意义相对应。基于这一假设，利用计算机辅助的定量反演方法计算了偏应力张量。结果是由(1)三个主应力的取向En，(1，(2和(3))主应力差之比，((2((3和(2)主应力差之比，((2)(1(/(1(3(/with 1()组成。在多期构造的情况下，推导了连续事件的年代学，并将每个地点的总断层群定性地划分为不同的子集，每个子集与一个特定的时间应力机制相一致。由于该地区的地层学和演化是众所周知的，古应力方向的时间和空间关联是可能的。与每个构造事件相关的局部确定网络将允许在时间上重建区域古应力模式。最后，将就它们对哈兹布莱克及其前海的结构演变施加的控制进行评估。我们的研究可能会完成中生代断裂系统的项目(批准Sehe 674/1-1)，也可以用于另外两个拟议的古应力演化研究项目(Bayer和Littke；Urai和Tanner)。这意味着，制定的目标与SPP1135的其他项目相关：波动应力场下的沉积盆地动力学。

This proposed project is based on numerous investigations of the applicants conveming fault kinematics and paleo-stress fields in the area between the Subhercynian Basin and the Franconian Line (see list of publications H.J. Franzke). Most recent investigations have been conducted in a DFG-granted project about the subsidence history of the Subhercynian Basin and the synchronous uplift of the Harz block (Applicants: R. Gaupp & H. J. Franzke, final report Fr 874/4, in 2004, see appendix 5). The objective of this project is to determine the paleo-stress fields in the Harz Mountains and surrounding areas based on field studies of synchronously activated fault populations in different stratigraphic units and under several tectonic environments. In the Harz Mountains a continuous pile of Paleozoic sedimentary rocks is well exposed, surrounded by more than two kilometres thick Permian to Upper Cretaceous rocks. Meanwhile lots of radiometric and paleontological age data on the sedimentary development, the widespread Late Variscan intrusive/volcanic rocks and the countless fault-bound hydrothermal vein structures are available. Therefore a detailed time-control of fault activities can be checked over a long period of about 200 Ma between the Variscan convergent phase in the Carboniferous and several brittle faulting periods in Mesozoic and Cenozoic time. Results to these topics have already been published by different authors, including the applicants (see references), but up to now a summarising investigation over a larger area, using modern methods of structural geology, is missing. To evaluate the distribution of the regional paleo-stress pattern in the Harz Mountain area and its forelands the orientation of the principal stress directions is calculated by fault-slip data inversion. The displacement vector on fault planes recorded by slickenside striae is considered to correspond to the direction and sense of the shear-stress tensor. Based on this assumption, the deviatoric stress tensor is calculated using quantitative computeraided inversion methods. The results are obtained in terms of a reduced stress tensor, consisting of (1) orientations of the three principal stresses en, (1, (2 and (3 as with ((1 ((2 ((3 and (2) the ratio of principal stress differences,((((2((3(/((1((3(/ with 1((((. In the case of polyphase tectonics, the chronology of successive events is deduced and the total fault population from each site is qualitatively divided into different sub-sets, each being consistent with one specific temporal stress regime. Since stratigraphy and evolution of the proposed area are well known, temporal and spatial correlations of paleo-stress orientations are possible. A network of local determinations related to each tectonic event will allow to reconstruct the regional paleo-stress patterns in time. Finally they will be evaluated with respect to the control they exerted on the structural evolution of the Harz black and its forelands. Our proposed study may complete the project Mesozoic fault systems (grant Sehe 674/1- 1) and can be also useful for the other two proposed projects investigating the paleo-stress evolution (Bayer and Littke; Urai and Tanner). That means, the formulated aims are relevant to other projects of the SPP 1135: Sedimentary basin dynamics under fluctuating stress fields .