The Cause Of Formation And Characters Of The L Tectonites In Jiefangyingzi, Chifeng

The cause of L tectonites is special due to the satisfaction ofσ1>σ2≈σ3 stress condition. The L tectonites can be formed only when the stress condition is been satisfied. The S and LS is founded more often outdoor, but there are lots of L tectonites in the Jiefangyingzi, Chifeng. Based on my tutor's Nature Science Foundation, I find out the distribution of L tectonites and collect the specimens. I research the microscopic structure, grain size and the mineral pairs of the specimens, and get a conceptual model for L tectonites formation by combining the geotectonic of Jiefangyingzi, Chifeng.1. The geological summary of Jiefangyingzi, ChifengResearchd area is located in the northern part of the North China Plate, parts of the The Trans-Asian Tectonic Mega-Belt (Chen Bingwei, 2007). The Trans-Asian Tectonic Mega-Belt (TATMB) is formed by collided microplate when the Siberia Plate is moving toward to the North China Plate. Meantime parts of the TATMB splited and formed new ocean basin, trench, island arc and back-arc basin, but the specific location and time of the rupture need to be determined by further studies. Jiefangyingzi belongs to Wenduermiao Fold Belt which is in extended environment during Late Neoproterozoic to the middle of Early Paleozoic, developed active continental margin sedimentary assemblage. It changed to compressive environment and the ocean basin closed. The L tectonites of Jiefangyingzi are formed under the Early Palaeozoic stretching deformation.2. The distribution and features of the L tectonitesThe L tectonites of Jiefangyingzi distribute within Silurian strata and intrusive bodies. The L tectonites which is formed by the Silurian clasolite and volcanic rocks formed by plastic deformation in stretching environment. But the L tectonites which is formed by intrusive bodies that freeze while crystallize during the stretching environment. The difference between them is that the lineations which are formed by extended quartz or crystallized Light and Dark mineral. They all have the micro structure characters of plastic deformation, difference is the degree. If we count the occurrence of L tectonites'lineation which are measured on field, we'll find that the attitude of most lineation's occurrence is northeast-southwest. Parts of the lineation's dips are large. Conjecturing that because of the Hercynian compressive deformation, the strata of Jiefangyingzi fold and make parts lineations'dips increased. I conjecture that the stretching deformation of this area dip northeast-southwest because that most lineations'attitude are northeast-southwest.3. The environment and the model of the L tectonitesI count the grain sizes and attitudes of the L tectonites specimens which are formed by diorite intrusive bodies, and analyze the stress of the L tectonites on this account. I found the micro grains also have preferred orientation, but i can't get the macro preferred orientation without oriented specimens. I also analyze the oxide mass percent of the 05-02-11 specimen's Muscovite-Chlorite mineral pair by electron probe, work out the forming temperature is 400 degrees. Based upon a serial of this analyses, combine the tectonic of Jiefangyingzi, i set up the model of L tectonites. When the magma rising up from deep, with the northern Siberia Plate and southern North China Plate beside,σ1 is vertical,σ2 is horizontal and attitude north-south which is roughly approximated the static stress of the country rock. The original Silurian rocks form L tectonites by monosymmetrical stretching deformation in above conditions.