Structural and anisotropy of magnetic susceptibility records of granitoid sheets emplacement during growth of a continental gneiss dome (Central Sudetes, European Variscan Belt)
Structural and anisotropy of magnetic susceptibility records of granitoid sheets emplacement during growth of a continental gneiss dome (Central Sudetes, European Variscan Belt)
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DOI：
10.1002/tect.20028
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发表时间：
2013-06
期刊：
影响因子：
4.2
通讯作者：
J. Lehmann;K. Schulmann;J. Edel;J. Jezek;F. Hrouda;Ondrej Lexa;F. Chopin
中科院分区：
文献类型：
--
作者：
J. Lehmann;K. Schulmann;J. Edel;J. Jezek;F. Hrouda;Ondrej Lexa;F. Chopin
通过构造地质学、石英和磁化率各向异性（AMS）组构研究，对Orlica‐ Penniejnik地幔片麻岩穹丘（苏台德中部，欧洲华力西带）生长期间同构造侵位的花岗岩类岩浆岩片进行了研究。岩浆侵位沿着高变质核的东海侵边缘，位于环绕穹隆南缘的低级拆离地幔之下。在第一个区域，岩浆席平行于各向异性前造山块体的扩张的近水平面理侵位。由此产生的熔体-寄主岩石多层局限于沿着的大部分岩浆侵位的水侵带。AMS研究表明，跨走向组构分带的基础是上盘的强烈平移固态变形、下盘的岩浆近水平组构和侵入体中心的过渡组构。相反，沿着南穹隆边缘，岩浆席沿着弱变质地幔岩的陡峭叶理侵入，并受到平卧褶皱和近水平剪切的影响。大部分岩席呈现浅倾岩浆叶理和沿着走向岩浆线理。石英组构和磁组构的变化是由于叠加纯剪切为主的韧性减薄，随后简单的剪切为主的剥离到原来的陡峭的组构。AMS建模证实了在渐进变形过程中侵入前各向异性的取向变化对所产生的组构图案的作用，并有助于解释观察到的组构取向和对称性的变化。这项研究突出了在不断增长的地壳规模的地幔片麻岩圆顶的不同部分同构造侵位岩浆的对比力学行为。
Granitoid magmatic sheets emplaced syntectonically during growth of the Orlica‐Śnieżnik mantled gneiss dome (Central Sudetes, European Variscan belt) were examined by means of structural geology, quartz, and anisotropy of magnetic susceptibility (AMS) fabric studies. Magmatic emplacement was localized along the eastern transpressive margin of the high metamorphic core and below the low‐grade detached mantle rimming the southern margin of the dome. In the first area, the magmatic sheets were emplaced parallel to the dilated subhorizontal foliation of an anisotropic pre‐orogenic block. The resulting melt‐host rock multilayer localized the transpressive zone along which the bulk of magma was emplaced. The AMS study shows an across‐strike fabric zonation underlying a strongly transpressive solid‐state deformation in the hanging‐wall, magmatic subhorizontal fabric in the foot‐wall and a transitional fabric in the center of the intrusion. In contrast, along the southern dome margin, magmatic sheets intruded along steep foliations of weakly metamorphic mantle rocks, and are affected by recumbent folding and subhorizontal shearing. The bulk of the sheets present a shallow‐dipping magmatic foliation and an along‐strike magmatic lineation. The variations of the quartz and magnetic fabrics are attributed to superimposition of pure shear‐dominated ductile thinning followed by simple shear‐dominated detachment onto the original steep fabric. AMS modeling confirms the role of variation of orientation of pre‐intrusive anisotropy during progressive deformation on the resulting fabric pattern and helps explaining observed variations in fabric orientations and symmetries. This study highlights contrasting mechanical behavior of syntectonically emplaced magmas in different parts of a growing crustal‐scale mantled gneiss dome.