نویسندگان
گروه زمین شناسی، دانشگاه بوعلی سینا، همدان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In the southeastern region of Hamadan, numerous pegmatitic dikes have intruded into the schists. These dikes consist of a mineralogical composition that includes albite, alkali feldspar, tourmaline, quartz, and muscovite. Based on point analyses, the tourmalines are identified as schorl, the feldspars as orthoclase, the plagioclases as albite, and the muscovites as a member of the muscovite-seladonite group. Considering the Fe# ratio against magnesium oxide, the samples are situated in domain A, and the distance of the pegmatitic veins from their fluid source is about 1 kilometer. The dikes have low to vertical dips and variable thicknesses, with a dominant trend of NW-SE. Magmatic fabrics such as mineral orientation and enclaves, banded texture within the dike, and fabrics resembling thermal lineations on the external surface of the dike have formed in interaction with the host rock. Based on field observations and microscopic studies, the dikes in the area are classified into three different types concerning their deformation: extensional dikes (tensional), active dikes, and mylonitic dikes.
Extensional dikes have formed in the fractures within the host rock (joints, faults, schistosity) and exhibit a comb texture, which indicates a low to moderate opening rate of the fractures. The second type, the active dikes, have a magmatic pressure that has resulted in a banded texture parallel to the walls. The third type, the mylonitic dikes, show evidence of solid-state deformation. These dikes have been re-deformed after cooling under the influence of shear zones, and their high-temperature deformation microstructural evidence is apparent.
کلیدواژهها [English]
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