AMS record of brittle dilation, viscous-stretching and gravity-driven magma ascent in area of magma-rich crustal extension (Vosges Mts., NE France)

作者：Kratinova Zuzana^*; Schulmann Karel; Edel Jean Bernard; Tabaud Anne Sophie

来源：International Journal of Earth Sciences, 2012, 101(3): 803-817.

DOI：10.1007/s00531-011-0711-x

• Anisotropy of magnetic susceptibility
• Crustal extension
• Magmatic fabrics
• Carboniferous

Orogenic compression-related fabrics (similar to 340-335 Ma) were reworked during regional extensional deformation (similar to 328-325 Ma) in a large anatectic crustal domain of the Central Vosges (NE France). The extension was first accommodated by brittle dilation affecting vertically anisotropic high-grade rocks associated with emplacement of subvertical granitic sheets. The AMS fabric of granitoids is consistent with highly partitioned transtensional deformation marked by alternations of flat and steep foliations and development of orthogonal lineations. This deformation passes to top-to-the-southwest ductile shearing expressed in southerly migmatitic middle crust. The AMS fabric revealed moderately west-dipping foliations bearing subhorizontal NNW-SSE-trending lineations and predominantly plane strain to prolate shapes. This fabric pattern is interpreted as a viscous response of stretched partially molten crust during continuous ductile extension. Vertical ascent of voluminous granites and stoping of the upper crust occurs further south. This gravity ascent triggered by extension leads to development of south-dipping AMS foliations, south-plunging lineations and oblate fabrics in various crustal granites. Vertical shortening related to ascent of these (similar to 325 Ma) granitoids and persistent N-S stretching is responsible for reworking and remelting of originally vertical compression-related fabric in roof supracrustal granites (similar to 340 Ma) and development of highly prolate fabrics in these rocks. This work shows that the finite shape of AMS fabric ellipsoid is highly sensitive to both strain regime and superpositions of orthogonal deformation events.

• 出版日期2012-4