Analysis To The Structure Features And Dynamics Of Songpan-Aba And Longmen Mountain Area

Songpan-Aba and Longmen mountain belong to plate Yangtze in tectonic setting, the degree of study to geology and exploration is very low. There aren't clear cognation to the structure styles, tectonic dynamics and structural evolvement progress. So in this paper, guided by tectonic geology, the structure styles, metamorphism and tectonic dynamics had been studied in deep by integrating outcrop, volcanic testing data, analysis for stereographic projection of folds and cleavage and seismic data. The structural evolvement progress had been come back through all the studying had been made and the developing character of main faults, then built the structural evolvement pattern of Longmen mountain.Based on regional geological survey, I emphatically discussed the structural styles of Longmen mountain, deep-seated structure characteristics, dynamic setting and structural evolvement of Songpan-Aba and Longmen mountain. The extending direction of folds in Longmen mountain is northeast, and it is more distinct that the echelon fold, thrust fault and cleavage. There are many pulling and clipping fault, which are vertical or oblique faul. There are many thrust-nappe, imbricated clipping fault and décollement structure in the zone. Because there are many tectonic movement, the tectonic style is not involved on only on factor, but it is the result of many tectonic movements. For example, the clipping was formed by thrust nappe and slip.After analyzing the metamorphism and volcanic testing data, we found that the main metamorphism was deform and crushing, at the same time appeared with metamorphic differentiation, Recrystallization and metasomatism. After Sinian Period, the magmatic activities are frequent, and the magmatic rocks are different, the magma which is active in Sinian Period was felsic, the magma which is active in Pz and T1+2 was mafic, the magma which is active after T3 was felsic again. The stress of the zone is different at different period, the stress in Yinzhi period was extruding from south to north, in Yanshan period was pulling from south to north, and in Himalaya period was extruding from west to east. After the analysis for stereographic projection of folds and cleavage in the zone, we found that cleavage was formed by the stress from south to north in Yinzhi period, and the folds were formed by the stress form south to north in Yinzhi and the stress from east to west in Himalaya period.The evolvement processes were divided four phases which are uniform Yangtze continent on Jinning period, uniform Yangtze disaggregation on Jialidong period, stable evolvement on Haixi period and complete cracking through the Dongwu movement, mountain forming from Yinzhi to Himalaya period. The unique orogenic processes of Longmen mountain began on this tectonic setting.Songpan-Aba is a new exploration area. The degree of diagenetic evolution is high and there aren't valuable petroleum resources found. I think lower Paleozoic as source rocks, upper Paleozoic as reservoir and Triassic as cap according to the existed data. The structural characteristics revealed by the data of well Hongcan-1 made clear that the middle-upper formation had been folded and the Triassic was one of the main structural detachment layers. Songpan-Ganzi folded belt has been uplifted during Yinzhi period, and the strata incrassated. It is very difficult to explore the petroleum because of the many tectonic movements.