Petrological Characteristics And Element Geochemical Response Of The Carboniferous Volcanic Rocks In Wulungu Area

Taking Wulungu in the north of Junggar basin as the study area and the Carboniferous volcanic rocks as the the target, and combining with the logging curve and seismic parameters, this paper studied the petrological and geochemical characteristics, tectonic environment, volcanic cycles division and favorable reservoir distribution from the view of volcanic petrology and geochemistry.On the basis of systematic carboniferous outcrop observation, core, debris logging and Sample collection. Observaing the rock ingredients, structure and the development of the pore fracture from rock slices under the microscope. Then test the content of major and trace elements, rare earths from carboniferous rock samples by XRF and ICP-MS. The results show that both lava and pyroclastic rocks were distributed in the study area. Most lavas were andesite and a little dacite. The majority of pyroclastic rocks were tufa lava, tufa, tuffite and tuffaceous sandstone- mudstone. The most common was tuff. In the TAS classification, most extrusive rock was andesite, a little dacite, trachytic dacite seen only, and the most part belongs to the sub alkaline volcanic rock; the study area was an island arc of volcanoes from ORG normalized trace element spider diagrams.Dealing Geochemical data with wavelet analysis, divided into the lower carboniferous stratigraphic 4 volcanic cycles, 18 volcanic periods The lower carboniferous stratigraphic was divided into 1 volcanic cycles, 4 volcanic periods as it’s revealed incomplete. Most of the divided lower carboniferous stratigraphic was volcanic clastic rocks and volcanic- sedimentary clastic rocks. It was equivalent to Jiangbasitao Fm. And the upper carboniferous stratigraphic in the study area was divided into 3 volcanic cycles, 14 volcanic periods. 6 volcanic periods developed on the bottom of the upper carboniferous volcanic sequence, most were interbedded tuff of the hot pyroclastic flow subfacies and andesite of the overflow facies, reflected the volcanic eruptions strongly. 3 volcanic periods developed on the central of the upper carboniferous volcanic sequencec, the majority were tuff of volcanic sedimentary facies, refleced the volcanic eruptions stoped. 5 volcanic periods developed on the top of the upper carboniferous volcanic sequencec, mainly included andesite of the overflow facies and volcano clastic rocks of eruption facies, reflected the volcanic eruptions strongly.