Brittle deformation events at the western border of the Bohemian Massif (Germany)
Brittle deformation events at the western border of the Bohemian Massif (Germany)
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波希米亚地块西部边界的脆性变形事件（德国）
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
G. Zulauf
中科院分区：
文献类型：
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作者：
G. Zulauf
对巴伐利亚奥贝普法兹结晶岩中存在的脆性变形结构的研究揭示了一个复杂的晚期到后华力西时期的地壳演化。上石炭统(主要是威斯特伐利亚)花岗岩分别侵位于埃尔本多夫-沃亨斯特拉乌带(ZEV)和埃尔本多夫绿片岩单元(EGZ)的半脆-脆性岩石中。从花岗岩的走向和与花岗岩有关的拉伸槽的方向来看，岩浆活动期间必须假定为东北-东北-西南-西南伸展。除花岗岩侵入外，地壳快速抬升(约1.5公里/米)导致地温梯度从华力西前花岗岩晚期的30℃/公里增加到华力西后花岗岩晚期的40℃/公里。由于晚石炭世(可能是斯蒂芬期)的东西向挤压和东北-西南向挤压，地温梯度的增加在随后的反向断裂过程中持续存在。尽管在所研究的地区没有直接证据，但走滑断层似乎在华力西晚期地壳演化中发挥了重要作用，特别是在二叠纪早期。走滑事件表明，在南北挤压作用下，地壳进一步缩短和压痕。白垩纪也存在类似的压痕。在早白垩世由南北挤压形成的逆断层活动的弱阶段之后，在北西-西南-东南和南北挤压下形成了走滑断裂。所有这些断裂，特别是走滑断裂，似乎与阿尔卑斯山/喀尔巴山造山带的白垩纪和最低第三纪的会聚有关。地壳伸展的晚期阶段，以径向应力张量(σ2=σ3)为特征，通过高角度正断层指示，可能是在邻近的新近纪埃格尔地块下沉期间形成的。
Investigations of brittle deformation structures, present within the crystalline rocks of the Bavarian Oberpfalz, reveal a complex late to post-Variscan crustal evolution. Upper Carboniferous (mainly Westphalian) granites were emplaced into semibrittle to brittle rocks of the ZEV (zone of Erbendorf-Vohenstrauß) and the EGZ (Erbendorf greenschist unit), respectively. From both the alignment of the granites and the direction of granite-related tension gashes a north-east-south-west extension must be assumed for the period of magmatic activities. Apart from the granite intrusions, rapid crustal uplift (about 1.5 km/my) led to an increase in the geothermal gradient from < 30 °C/km (late Variscan pre-granitic) to > 40 °C/km (late Variscan post-granitic). The increased geothermal gradient persisted during the succeeding reverse faulting which results from late Carboniferous (probably Stephanian) east-west and northeast-south-west compression. Although not evidenced directly in the area considered, strike-slip faults seem to have played an important part during the late Variscan crustal evolution, particularly in the Early Permian. The strike-slip events indicate further crustal shortening and indentation under north-south compression.A similar indentation was present in Cretaceous time. After a weak phase of Early Cretaceous reverse faulting, which results from north-south compression, strike-slip faults formed under north-west-south-east and north-south compression. All these faults, in particular the strike-slip faults, seem to be related to the Cretaceous and lowermost Tertiary convergence of the Alpine/Carpathian orogeny.A late stage of crustal extension, characterized by a radial stress tensor (σ2 = σ3), is indicated through high angle normal faults which probably formed during the subsidence of the adjacent Neogene Eger Graben.