Magnetofabric and textural analysis from highly anisotropic magnetite bearing shear zones in metamorphic nappes of the Scandinavian Caledonides

斯堪的纳维亚喀里多尼亚变质推覆体中高度各向异性磁铁矿剪切带的磁织物和结构分析

基本信息

批准号：
51421436
负责人：
Privatdozentin Dr. Agnes Kontny
金额：
--
依托单位：
Abteilung Strukturgeologie und Tektonophysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2007
资助国家：
德国
起止时间：
2006-12-31 至 2011-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/51421436?language=en
关键词：
Magnetofabric textural analysis highly anisotropic

项目摘要

The first documentation of very high anisotropies (P´ > 4) of the magnetic susceptibility in metamorphic nappes from the Scandinavian Caledonides raises questions about the causative processes. Magnetite in a platy shape was identified as the main carrier of the magnetic susceptibility and the main reason for these high degrees of anisotropy. A major question is whether these extremely flattened magnetite grains are controlled by mimetic growth, ductile deformation, or both. Since ductile deformation can influence the grain shape of magnetite and thus the extrinsic susceptibility the AMS can be linked with ductile deformation processes. This is in marked contrast to paramagnetic minerals, which will attain fabric saturation at very high strain and are thus suitable for quantification of low to moderate strain. The exhumation of high-grade metamorphic rocks is commonly accompanied by ductile shearing localized in zones of various dimensions, geometries, lithologies, p-T-conditions and activity periods. Total strain is expected to be high in major shear zones within high-grade metamorphic nappes, but difficult to quantify. The study of shear zones with very high anisotropies of the magnetic susceptibility provides a chance to monitor systematic changes of rock magnetic parameters and petrofabrics – quantified by low- and high-field AMS, IRM, and AARM – and to link them with field observations, meso- to microscale structural data, textural data, magnetomineralogy (SEM, EMP), and image analysis. For the reintegration of the results into the geological realm a few 40Ar/39Ar-datings of recrystallized, synkinematic white micas are considered.

斯堪的纳维亚喀里多尼德斯变质推覆体中磁化率非常高的各向异性 (P´ > 4) 的首次记录提出了关于板状磁铁矿被确定为磁化率的主要载体和主要原因的问题。对于这些高度的各向异性，一个主要问题是这些极度扁平的磁铁矿晶粒是否受到模拟生长、延性变形或两者的控制。延性变形可以影响磁铁矿的晶粒形状，因此 AMS 的外在磁化率可以与延性变形过程联系起来，这与顺磁矿物形成鲜明对比，顺磁矿物将在非常高的应变下达到织物饱和，因此适合于低应变的量化。高品位变质岩的折返通常伴随着位于不同尺寸、几何形状、岩性的区域的韧性剪切。 p-T 条件和活动周期。预计高级变质推覆带内的主要剪切带的总应变较高，但难以量化。对磁化率非常高的各向异性的剪切带的研究提供了监测系统变化的机会。岩石磁性参数和石油结构的分析——通过低场和高场 AMS、IRM 和 AARM 进行量化——并将它们与现场观测、中观到微观结构数据、纹理数据联系起来，磁矿物学（SEM、EMP）和图像分析为了将结果重新整合到地质领域中，考虑了一些重结晶同运动白云母的 40Ar/39Ar 年代测定。