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Chronology and Tectonic Settings of Igneous Rocks and Origin of Volcanic Reservoirs in Ludong Area, Eastern Junggar Basin
详细信息   
摘要
Characteristics of igneous petrology and lithofacies as well as the origin,chronology and tectonic evolution settings of Carboniferous igneous reservoirs in the eastern Junggar Basin were investigated,based upon the observation and description of drilled igneous cores,the identification and quantitative statistics of normal and cast thin sections for minerals under microscope,the measurement of porosity and permeability of reservoir rocks,the determination of homogeneous temperatures and chemical compositions of diagenetic liquid inclusions from volcanic rocks,the analysis of major and trace elements of whole rocks,and the in-situ U-Pb dating of zircons from igneous rocks with LA-ICPMS technique,finally a igneous lithofacies model was established.The research result showed that the volcanic eruption activity in the study area occurred in an active continental margin island arc under an extrusion tectonic setting related to oceanic plate subduction in Early Carboniferous(321 Ma~369 Ma).The extensive intrusion of diabase occurred in Early Permian(283 Ma ±),implying that the eastern Junggar block had then been in a tectonic evolution phase of the inner-plate extension continental rift.igneous rocks were once subject to reworking by thermal events during Jurassic(190 Ma~149 Ma).The formation of volcanic reservoirs and the improvement of their quality were closely related to weathering,leaching and denudation of the top Carboniferous erosion zone.Thus,they mainly belong to a weathering-typed volcanic gas pool.The volcanic eruption in the study area was dominantly characterized by central eruption with fissure eruption in the second place.Five igneous lithfacies,including volcanic eruption,volcanic effusion,volcanic conduit,volcanic deposit and shallow intrusion along with nine sub-lithofacies,could be recognized in the study area.

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