Mesozoic To Palaeozoic Tectonic Characteristics And Evolution Of Yuxi Area

Yuxi area is located in the western Henan Province, that is, the west of Beijing-Guangzhou railway line, south of the Yellow River, and the north of Funiu Mountain area.The geotectonic position is the intersection point of North West nearly East West Qinling-Dabie orogenic belt along the northern margin of the Piedmont belt and North East to the uplift zone of Lvliang-Taihang.It developed many small sedimentary basin of Mesozoic and Cenozoic,mainly Luoyang,Yichuan,Yiyang,Linru and so.Because of the special tectonic position of Yuxi basin which determines the tectonic evolution in the area controlled not only by the main influence of more WE trending overthrust on the south side of the Qinling orogenic belt, but also by the Lvliang-Taihang uplift and Pacific tectonic subduction to the Asian continent caused by strike-slip effect and extension,forming a multi-phase structure superimposed tectonic framework.For the reconstruction of the Mesozoic and Cenozoic tectonic framework in the west of Henan Province and the establishment of the prototype basin tectonic evolution mechanism, the evaluation of favorable exploration zones and the favorable target zones was maked clear on the basis of tectonic evolution.This study is based on the the regional tectonic environment and transformation of tectonic system. According to the basin structure and restoration of tectonic sedimentary evolution and structural geology,we analysis the oil and gas basin structure.We use seismic data interpretation by man-machine continuous cropping,balanced cross-section recovery technology and paleostructure restoration,combining the investigation of field geology and indoor research,to analyze the regional geophysical characteristics of each period.Fault-fold and differences deformation characteristics of different stage tectonic units are combined.The main results as the following recognition:(1)According to the difference of tectonic deformation and the characteristics of north-south zoned and west-east segmented in the west of Henan Province, it divided into five first-order tectonic units and ten two-grade tectonic units in the study area.Five first-order tectonic units are southern margin overthrust-extensional tectonic belt,Mianchi-Yichuan-Ruzhou thrust-extensional tectonic belt,Songshan North Slope-rift zone,the northern margin fault block and Songshan-Jishan uplift area.The southern margin overthrust-extensional tectonic belt can be divided into Yiyang-Luoning overthrust-rift zone and southern Yichuan overthrust-rift zone; Mianchi-Yichuan-Ruzhou thrust-stretch tectonic belt is divided into Mianchi-Xin’an thrust-block,western Luoyang thrust-rift zone,Yichuan thrust-rift zone,western Ruzhou thrust-block area and eastern Ruzhou thrust-faulted zone.Songshan-Jishan uplift can be divided into Songshan mountain uplift,Dengfeng block area and Jishan uplift.(2)The study area can be divided into three structural layers:basin base, basin cap layer and overlying layer.The basin cap layer can be divided into six sub tectonic layer. Caledonian sub-structural layer, Hercynian sub-structural layer, Indosinian sub-structural layer,early and middle Yanshan sub-structural layer, late Yanshan-early Himalayan sub-structural layer,late Himalayan sub-structural layer.The overlying layer is the Quaternary sediments.(3)Deformation of shrinkage in the study area is mainly affected by extrusion effect from the south to the north in the southern margin of the Qinling-Dabie orogenic belt.The non linear distribution of orogenic belt makes the difference of the local stress at different sections.(4)Since the Indosinian reconstructing of timing sequence and characteristics of tectonic evolution in western Henan, it is considered that Yuxi area go through the late Indosinian, early and middle Yanshanian,late Yanshanian-early Himalayan and late Himalayan tectonic movement.The study area in late Indosinian to middle Yanshanian is northward overthrusting of piggy-back thrust sequence, late Yanshanian to early Himalaya is the fault and fault block, and the late Himalaya is depression.With "basin and Mountain" of Qinling-Dabie orogenic sustained coupling in late Indosinian-middle Yanshanian,it prompted to be fault-fold in Late Indosinian-middle Yanshanian in western Henan, the property of the basin is the foreland basin, and decoupling happened in late Yanshan-early Himalayan, but Qinling-Dabie orogenic belt is still providing the material source for western Henan province. Songshan Mountain is the uplift and the western Henan is basin.There are not exist massive overthrust.lt plays only the role of blocking and providing the material source.So does Zhongtiaoshan.(5) The controlling effect of tectonic evolution on hydrocarbon accumulation of each period in western Henan is obvious,tectonic evolution control the distribution of source rocks, mainly in the hydrocarbon accumulation history of substance,transform and damage.Residual hydrocarbon fluid source is located in Yichuan thrust-faulted area,west of Luoyang thrust-rift zone,mianchi-Xin’an thrust-block,secondary hydrocarbon distributed in west Luoyang thrust-faulted area,secondary hydrocarbon fluid source is mainly distributed in footwall of Yichuan thrust-nappe rift zone. The main means of destruction to reservoir is uplifting and fault transformation.The main controlling factors of the reservoirs and accumulation model in western Henan are established. Main controlling factors of hydrocarbon accumulation of residual hydrocarbon fluid source area is preservation, secondary hydrocarbon generation zone is the carrier system,and hydrocarbon fluid source area is reservoir. The accumulation model of Residual hydrocarbon fluid source area is early accumulation, long-term transformation, late residual, secondary hydrocarbon generation area is secondary hydrocarbon generation, generation below and storage above, hydrocarbon fluid source area is the blind thrust control, multi phase transformation, late accumulation.(6)To conduct a comprehensive evaluation and optimization in the tectonic deformation zone,exploration potential of each tectonic deformation zone at the study area is divided into five levels:the most favorable tectonic deformation zone,favorable tectonic deformation zone,the less favorable tectonic deformation zone,oil and gas prospects,non-hydrocarbon prospects.Yichuan thrust fault depression zone is the most favourable tectonic deformation zones, especially the footwall of thrust nappe fault, and that the zone of nappe footwall is the most favorable exploration target.