Research On Transformation Of Tectonic Framwork In The Northeast Sichuan Basin On Triassic And It’s Control Of Multi Minerals Deposition

The Sichuan basin experienced multiple tectonic movements from Neoproterozoic to Cenozoic.Multi-stage tectonic movement reformed the basin in different degrees.Therefore,the Sichuan basin provides favorable conditions for various energy sources such as Oil and gas,shale gas,potassium salt,lithium ore,etc..The northeast area of Sichuan is an important part of the Sichuan basin,there are Yuanba gas field,Puguang gas field,Nongle potassium salt mine,Guangwang coal field and Huayingshan coal field located here.Oil,gas and salt are enriched in the Jialingjiang Formation and LeikoupoFormation.Coal,oil and gas are enriched in the Xujiahe Formation.During Jialingjiang period,the sedimentary environments were mainly tidal flat,lagoon and salt.Salt was mainly concentrated on breccia and dolomitein the supratidal zone,while oil and gas were mainly reservoired in limestone,bioclastic limestone and oolitic limestone.During the Leikoupo period,the sedimentary environmentswere mainly tidal flat andsaline lagoon.The salt was mainly concentrated in the Suining area,while oil and gas are mainly concentrated in reef shoal and limestone.In the Xujiahe Formation,the depositional environmentsare alluvial fan,delta and lake.Coal is mainly concentrated in delta swamp,and oil and gas reservoirs are fluvial and delta sandstone.Comprehensive analysis of mineralogy,petrology and chronology shows that salt was from potassium-rich rocks such as mung bean rock.The mung bean rock mainly comes from 252 Ma magmatic rocks in the North Daba mountains.The oil and gas of Jialingjiang Formation and Leikoupo Formation are mainly derived from the Late Permian,Middle-Late Triassic hydrocarbon source rocks.Heavy minerals electron microprobe of Xujiahe Formation sandstone shows that the sources are mainly from the northern Daba mountains.The composition and characteristics of organic fluids of the basin orogenic belt indicate that oil-gas and salt are controlled by the same orogenic belt fluid.As one of the most important controlling factors of various energy sources in Sichuan basin,tectonic framwork transferred in the Leikoupo period.During the Jialingjiang Formation,tectonic setting is passive continental margins,while tectonic settingof Leikoupo Formation and Xujiahe Formation transferred to foreland basin.The paleostructural analysis shows that the ancient depression is a favorable area for salt,while the paleoprotruding may develop the beach and become a favorable area for oil and gas.The later tectonic movement developed gliding layers in the Jialingjiang Formation and Leikoupo Formation,providing conditions for the formation of various energy sources.Tectonic fluids is divided into two stages.The early stage is the main ore-forming fluid and the homogenization temperature is relatively high.The late fluid is not related to the mineralization and the homogenization temperature is relatively low.The migration time of brine,oil and gas is in late Triassic,which is consistent with the thrust nappe orogeny.Orogenic fluids as a carrier and source area are involved in the material source,migration and accumulation process in the basin.