Petrological Characteristics And Environment Analysis Of Carboniferous Igneous Rocks In Hongshanzui Area Of Junggar Basin

With large prospecting potential but relatively low exploration degree,the exploration step of Carboniferous system in Hongshanzui area has been directly restricted.This thesis studys the Carboniferous volcanic rocks in Hongshanzui area and the Jinlong 10 well area through careful observation and description of the core and systematic collection of samples and by using modern analytical testing methods such as polarized light microscopy,scanning electron microscopy and elemental geochemistry,which combing with logging and seismic data.It aims to conduct a comprehensive research on lithologic facies,stratigraphic framework and tectonic setting.The study shows that Carboniferous system in Hongshanzui area and Jinlong 10 well area have developed six major types of igneous rocks,including five categories of volcanic rocks and one type of intrusive rocks.There are five major types of volcanic rocks developed in the study area: sub-volcanic rocks,volcanic lava,pyroclastic lava,pyroclastic rocks,and sedimentary pyroclastic rocks.The lithofacies is classified into subvolcanic,explosive,overflow,effluent and volcanic sedimentary facies.Based on lithology,texture and structure,the igneous facies is divided into seven subfacies.Identification method of igneous facies in the study area is based on different facies logging curves and seismic reflection characteristics.Based on volcanic eruption cycle theory and lithologic facies characteristics of volcanic rocks,a three-level sub-stratigraphic division scheme of “eruption cycle-eruption period-eruption rhythm”was established to determine an identifiable volcanic cycle of the Carboniferous system in study area.The igneous rocks are formed at Amass type edge of the plate;thelithology from east to west orderly transitions from volcanic lava,locally developed intrusive rocks to pyroclastic rocks and sedimentary rocks,and a small amount of sedimentary pyroclastic rocks in the north;most of the overflow and effluent facies are visible in the eastern area.Explosive facies is mainly developed in the middle area and the western area is dominated by alluvial fan facies.