Geological characteristics and models of fault-foldfracture body in deep tight sandstone of the second member of Upper Triassic Xujiahe Formation in Xinchang structural belt of Sichuan Basin,SW China

In the second member of the Upper Triassic Xujiahe Formation(T_(3)x_(2))in the Xinchang area,western Sichuan Basin,only a low percent of reserves has been recovered,and the geological model of gas reservoir sweet spot remains unclear.Based on a large number of core,field outcrop,test and logging-seismic data,the T_(3)x_(2) gas reservoir in the Xinchang area is examined.The concept of fault-fold-fracture body(FFFB)is proposed,and its types are recognized.The main factors controlling fracture development are identified,and the geological models of FFFB are established.FFFB refers to faults,folds and associated fractures reservoirs.According to the characteristics and genesis,FFFBs can be divided into three types:fault-fracture body,fold-fracture body,and fault-fold body.In the hanging wall of the fault,the closer to the fault,the more developed the effective fractures;the greater the fold amplitude and the closer to the fold hinge plane,the more developed the effective fractures.Two types of geological models of FFFB are established:fault-fold fracture,and matrix storage and permeability.The former can be divided into two subtypes:network fracture,and single structural fracture,and the later can be divided into three subtypes:bedding fracture,low permeability pore,and extremely low permeability pore.The process for evaluating favorable FFFB zones was formed to define favorable development targets and support the well deployment for purpose of high production.The study results provide a reference for the exploration and development of deep tight sandstone oil and gas reservoirs in China.

The Impact of the“Belt and Road”Initiative on Industrial Structure Upgrading Along the Corridor

The“Belt and Road”initiative functions as a novel impetus for China’s external economic development within the framework of the new normal of economic growth.By leveraging panel data from 30 provinces and regions across China for the period of 2010 to 2020,this research assesses the influence of the“Belt and Road”initiative on the enhancement of the industrial structure along its trajectory.The findings indicate that:the most notable influence on the rationalization and progress of the industrial structure is observed in the eastern region,with the central region following suit,whereas the western region has yet to exhibit a significant transformation.The analysis delves into the role of technological innovation,concluding that the initiative primarily catalyzes optimization and upgrading through the effect of technological advancement.The study advances several pertinent policy recommendations to support and enhance these developments.

Structural Variation between the Western and Eastern Kuqa Fold-and-thrust Belt,China:Insights from Seismic Interpretation and Analog Modeling

The Kuqa fold-and-thrust belt exhibits apparent structural variation in the western and eastern zone.Two salt layer act as effective decollements and influence the varied deformation.In this study,detailed seismic interpretations and analog modeling are presented to construct the suprasalt and subsalt structures in the transfer zone of the middle Kuqa and investigate the influence of the two salt layers.The results reveal that the relationship of the two salt layers changes from separated to connected,and then overlapped toward the foreland in the transfer zone.Different structural models are formed in the suprasalt and subsalt units due to the interaction of the two salt layers.The imbricate thrust faults form two broom-like fault systems in the subsalt units.The suprasalt units develop detached folds terminating toward the east in the region near the orogenic belt.Whereas,two offset anticlines with different trends develop at the frontal edge of the lower salt layer and the trailing edge of the upper salt layer,respectively.According to exploration results in this region,the relationship between suprasalt and subsalt structures has an influence on hydrocarbon accumulation.We believe that the connected deformation contains high-risk plays while the decoupled deformation contains well-preserved plays.

Fouimba and Goma Mounts Greenstone Belts Litho-Structural Analysis Related to Côte D’Ivoire Birimian Geodynamic Setting and Implying in West-Africa Craton Gold Deposits

Mount Fouimba and Mount Goma (Seguela) greenstone belts petro-structural studies combine remote sensing, geophysics, petrography and structural analysis. In view of establishing mapping details of paleoproterozoic geological formations, geological setting rocks observed are essentially magmatic formations, such as two-mica granite, granodiorites, and porphyritic basalts;and a few metamorphics which are metatonalite, amphibolites and amphibo-lopyroxenites. Remote sensing, such as Landsat 8 OLI satellite imagery and geophysical data, has been combined to show regional NNE-SW shear zone. Tectonic structures and microstructures have enabled to identify two main deformation phases: D1 phase corresponding to compression, and D2 is a transpression phase. Mechanisms responsible for deformations are respectively flattening and transpression. Geological formations derived from mantle origin but contain crustal components, and their tectonic setting occurred during subduction.

Dynamic damage evolution of bank slopes with serrated structural planes considering the deteriorated rock mass and frequent reservoirinduced earthquakes

To investigate the dynamic damage evolution characteristics of bank slopes with serrated structural planes,the shaking table model test and the numerical simulation were utilized.The main findings indicate that under continuous seismic loads,the deformation of the bank slope increased,particularly around the hydro-fluctuation belt,accompanying by the pore water pressure rising.The soil pressure increased and then decreased showed dynamic variation characteristics.As the undulation angle of the serrated structural planes increased(30°, 45°, and 60°),the failure modes were climbing,climbinggnawing,and gnawing respectively.The first-order natural frequency was used to calculate the damage degree(Dd)of the bank slope.During microseisms and small earthquakes,it was discovered that the evolution of Dd followed the“S”shape,which was fitted by a logic function.Additionally,the quadratic function was used to fit the Dd during moderately strong earthquakes.Through the numerical simulation,the variation characteristics of safety factors(Sf)for slopes with serrated structural planes and slopes with straight structural planes were compared.Under continuous seismic loads,the Sf of slopes with straight structural planes reduce stalely,whereas the Sf for slopes with serrated structural planes was greater than the former and the reduction rate was increasing.

Formation and destruction processes of upper Sinian oil-gas pools in the Dingshan-Lintanchang structural belt, southeast Sichuan Basin, China

The lower Cambrian Niutitang Formation hydrocarbon source rocks at the Dingshan- Lintanchang structure in the southeast Sichuan Basin were of medium-good quality with two excellent hydrocarbon-generating centers developed in the periphery areas, with a possibility of forming a medium to large-sized oil-gas field. Good reservoir rocks were the upper Sinian （Dengying Formation） dolomites. The mudstone in the lower Cambrian Niutitang Formation with a good sealing capacity was the cap rock. The widely occurring bitumen in the Dengying Formation indicates that a paleo oil pool was once formed in the study area. The first stage of paleo oil pool formation was maturation of the lower Cambrian source rocks during the late Ordovician. Hydrocarbon generation from the lower Cambrian source rocks stopped due to the Devonian-Carboniferous uplifting. The lower Cambrian source rocks then restarted generation of large quantities of hydrocarbons after deposition of the middle Permian sediments. This was the second stage of the paleo oil pool formation. The oil in the paleo oil pool began to crack during the late Triassic and a paleo gas pool was formed. This paleo gas pool was destroyed during the Yanshan-Himalayan folding, uplifting and denudation. Bitumen can be widely seen in the Dengying Formation in wells and outcrops in the Sichuan Basin and its periphery areas. This provides strong evidence that the Dengying Formation in the Sichuan Basin and its periphery areas was once an ultra-large structural-lithologic oil-gas field, which was damaged during the Yanshan-Himalayan period.

Intra-continental deformation and tectonic evolution of the West Junggar Orogenic Belt,Central Asia:Evidence from remote sensing and structural geological analyses

The West Junggar Orogenic Belt(WJOB)in northwestern Xinjiang,China,is located in the core of the western part of the Central Asian Orogenic Belt(CAOB).It has suffered two stage tectonic evolutions in Phanerozoic,before and after the ocean–continental conversion in Late Paleozoic.The later on intracontinental deformation,characterized by the development of the NE-trending West Junggar sinistral strike-slip fault system(WJFS)since Late Carboniferous and Early Permian,and the NW-trending Chingiz-Junggar dextral strike-slip fault(CJF)in Mesozoic and Cenozoic,has an important significance for the tectonic evolution of the WJOB and the CAOB.In this paper,we conduct geometric and kinematic analyses of the WJOB,based on field geological survey and structural interpretation of remote sensing image data.Using some piercing points such as truncated plutons and anticlines,an average magnitude of^73 km for the left-lateral strike-slip is calculated for the Darabut Fault,a major fault of the WJFS.Some partial of the displacement should be accommodated by strike-slip fault-related folds developed during the strike-slip faulting.Circular and curved faults,asymmetrical folds,and irregular contribution of ultramafic bodies,implies potential opposite vertical rotation of the Miao’ergou and the Akebasitao batholiths,resulted from the sinistral strike-slipping along the Darabut Fault.Due to conjugate shearing set of the sinistral WJFS and the dextral CJF since Early Mesozoic,superimposed folds formed with N–S convergence in southwestern part of the WJOB.

Structural features and deformational ages of the northern Dabashan thrust belt

A large-scale pop-up structure occurs at the front of the northern Dabashan thrust belt （NDTB）, bound by the NNE-dipping Chengkou fault to the south, and the SSW-dipping Gaoqiao fault to the north. The pop-up structure shows different features along its strike as a direct reflection of the intensity of tectonic＂ activity. To the northwest, the structure is characterized by a two-directional thrust system forming a positive flower-like structure. In contrast, the southeastern part is composed of the vertical Chengkou fault and a series of N-directed backthrusts, showing a semi-flower-like structure. We present results from Ar-Ar dating of syntectonic microthermal metamorphic sericite which show that the Chengkou fault experienced intense deformation during the mid-Mesozoic Yanshanian epoch （about 143.3 Ma）, causing rapid uplift and thrusting of the northern Dabashan thrust belt. During the propagation of this thrust, a series of backthrusts formed because of the obstruction from the frontier of Dabashan thrust belt, leading to the development of the pop-up structure.

Structural Geochemical Study of the Yuxi Fold-Thrust Belt in the Southern North China Plate

The Yuxi （豫西） fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. The analysis of chemical compositions and new stress minerals indicates： extending from the surrounding country rocks to the center of the fracture belt, the Fe2O3 content gradually increases while the FeO content gradually decreases; regular increase, decrease or peak changes are shown for chemical compositions like SiO2, Al2O3, Fe2O3, MgO, CaO, FeO, loss on ignition, TIO：, K2O, Na2 O, etc.. New stress minerals are developed for the south branch and few for the north branch. The characteristics of chemical compositions and new stress minerals of the thrust fracture demonstrate that the fracture belt has undergone a process from a closed reducing environmental system to a relatively open. oxidizing environmental system, andcompressive fractures have resulted from compression in the late stages of evolution, and the dynamothermal metamorphism and thrusting intensities are different between the south and north branches of the belt, which is strong for the south branch but relatively weak for the north branch.

Distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression

The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried out a comprehensive analy-sis of the vast amount of data from casting thin sections, scanning electron microscope and physical data. Then we analyzed the pore types, pore evolution, distribution and genesis of secondary pores in our study area and discussed the factors controlling the distribution of secondary pores. The results show that pores in the study area are largely composed of intergranular dissolution pores and constituent dissolved pores. Three secondary pore zones were developed in the study area at depths of 2800~3400 m, 3600~4200 m and 4500~4800 m. Secondary pores have been formed mainly because carbonate cement, feldspar, clastic debris and other plastic substances were dissolved by organic acid, released during the evolution of organic matter and acid water formed by CO2. The development and distribution of secondary pores are vertically controlled by the maturity time of source rocks and hori-zontally by the distribution of acid water. As well, this distribution was affected by the sedimentary facies belt and the development of fault zones.

Structural geology and favorable exploration prospect belts in northwestern Sichuan Basin, SW China

The northwestern Sichuan region has experienced multi-stage tectonic evolution including marine cratonic basin from the Sinian to the Middle Triassic and intra-continental basin from the Late Triassic to the Cenozoic. Several regional tectonic activities caused complicated stratigraphic distribution and structural deformations in the deep-buried layers. During the key tectonic periods, some characteristic sedimentary and deformation structures were formed, including the step-shaped marginal carbonate platform of Dengying Formation, the western paleo-high at the end of Silurian, and the passive continental margin of the Late Paleozoic–Middle Triassic. The Meso-Cenozoic intra-continental compressional tectonic processes since the Late Triassic controlled the formation of complex thrusting structures surrounding and inside the northwestern basin. The northern Longmenshan fold-thrust belt has a footwall in-situ thrust structure,which is controlled by two sets of detachments in the Lower Triassic and Lower Cambrian and presents as a multi-level deformation structure with the shallow folds, the middle thin-skin thrusts and the deeper basement-involved folds. The thrust belt in front of the Micangshan Mountain shows a double-layer deformation controlled by the Lower Triassic salt detachment, which is composed by the upper monocline and deep-buried imbricate thrust structures. The interior of the basin is characterized by several rows of large-scale basement-involved folds with NEE strike direction. From the perspective of structural geology, the favorable exploration reservoirs and belts in northwestern Sichuan have obvious zoning characteristics. The favorable exploration layers of Dengying Formation of Upper Sinian are mainly distributed in the eastern and northern areas of the northwestern Sichuan Basin, in which the Jiulongshan structural belt, Zitong syncline and Yanting slope are the most favorable. The Lower Paleozoic was transformed by Caledonian paleo-uplift and late Cenozoic folding, and the midwest area such as the Zitong syncline is a potential area for hydrocarbon exploration. The favorable part of the Upper Paleozoic is mainly distributed in the northern Longmenshan belt and its frontal area, where the deep-buried thin-skin thrust structures in the footwall are the key exploration targets.

Influence of Salt Beds on the Segmentation of Structure and Hydrocarbon Accumulation in Qiulitag Structural Belt,Tarim Basin,China

Seismic information and balanced profile technology were used to reveal the influence of the salt bed in segmentation of structure and hydrocarbon accumulation in Qiulitag structural belt in Tarim basin. From west to east, the shortening of strata above the salt beds gradually decreases, while, the shortening below the salt beds gradually increases, which shows that the segmentation of structure integrated the seismic profile. There is great difference of the deformation of strata below and above the salt beds between the west segment and the east segment. The analysis of the distribution of oil/gas fields and the hydrocarbon properties indicates the similar segmentation to the structure segmentation. The salt beds in relatively shallow layers change the stress condition from basement of Kuqa foreland basin, which leads to the segmentation of Qiulitag structural belt. Because the salt beds in the west segment came into being earlier than those in the east segment, the west segment captures hydrocarbon from two sets of source rock, while the east segment can only capture hydrocarbons from one set of source rock. So, the salt beds play an important role in the segmentation of structure and hydrocarbon accumulation.

GEOCHEMICAL CHARACTERISTICS OF GRANITES AND ITS STRUCTURAL GENETIC ENVIRONMENT IN THE NANDAN-HECHI METALLOGENETIC BELT, NORTHWEST GUANGXI

The Nandan-Hechi metallogenetic belt is the most important tin-polymetallic producing district in China, and is the location of the Dachang super-large tin deposit. Based on the detailed field investigation and isotopic data, the stages of magmatic activity in the Nandan-Hechi metallogenetic belt have been lined out in this paper. Through the study about the geochemical characteristics of different granites, and by using ω(Al2O3)-ω(SiO2), ω(TFeO)/[ω(TFeO)+ω(MgO)]-ω(SiO2), AFM, ACF and Rb-Yb+Ta, Rb-Y+Nb, Ta-Yb, Nb-Y discrimination diagrams in combination with regional geological setting analysis, the authors carried out analyses about the structural environment for the formation of the granites, and discussed the structural environment and dynamic setting for the large scale mineralization in this area. Our study indicates that the majority of the granites in Nandan-Hechi metallogenetic belt belong to the POG type, while the later stage alaskite belongs to the RRG+CEUG type. The granites were formed at the stage of structural transformation from postorogenic phase to intraplate setting. But the major structural environment is characterized by steady regional extension. The formation age for the granites coincides with the time for this transformation, and this translation environment is favored for large-scale metallogenesis.

A Novel Three-stage Tectonic Model for Mississippi Valleytype Zn-Pb Deposits in Orogenic Fold-and-Thrust Belts

Mississippi Valley-type(MVT) Zn-Pb deposits predominantly form within both orogenic forelands and fold-andthrust belts, yet the mineralization process within the latter tectonic setting remains inadequately understood. This study, through a comprehensive review of MVT deposits across global fold-and-thrust belts, introduces a novel model elucidating the mineralization process in the context of tectonic belt evolution. It is demonstrated that during the stage Ⅰ, regional compression is introduced by early stages of plate convergence, causing the folding and thrusting and creating structural or lithological traps such as evaporite diapirs and unconformity-related carbonate dissolution-collapse structures. Thereafter, in stage Ⅱ, hydrocarbons begin to migrate and accumulate within these traps, where reduced sulfur is generated through thermochemical or bacterial sulfate reduction concurrent with or preceding Zn-Pb mineralization. In the subsequent stage Ⅲ, as plate convergence persists, the regional stress transitions from compression to transpression or extension. Under these conditions, steeply-dipping extensional faults are generated, facilitating the ascent of metalliferous brines into early-formed structural or lithological traps. Precipitation of Zn and Pb sulfides occurs through the mixing of Zn-Pb-transporting fluids with pre-existing reduced sulfur or by interaction with hydrocarbons.

Structural features of crust-mantle assemblage in the lithosphere along the Longitudinal Seismic Belt of China and their tectonic effect

The 1°×1° distribution map of crustmantle structural ratio R for the lithosphere along the Longitudinal Seismic Belt of China has been compiled using computer based on the results of geophysical prospecting by previous researchers, and the latest results by the present authors. Based on this map, an insight into the structural features of the crustmantle assemblage along the Longitudinal Seismic Belt has been gained, while their relation to seismic activity and the distributions of geothermal flux and intracrustal high conductivitylow velocity layers, as well as their tectonic effect to seismicity have been discussed.

Silurian hydrocarbon exploration breakthrough and its implications in the Shajingzi structural belt of Tarim Basin,NW China

The Silurian hydrocarbon exploration in the northwest Tarim Basin had long been fruitless, till Well XSD1 drilled in 2018 in the Shajingzi structural belt, northwest Tarim Basin tapped industrial gas flow from the Silurian for the first time. The reservoir-forming model and resource extent need to be made clear urgently. Based on the comprehensive research of drilling,formation testing, geochemical data, and sedimentary and accumulation history, in combination with field surveys, experiments, structure interpretation and reconstruction of structure evolution, it is found that:(1) The northwest Tarim Basin had widespread tidal deltaic deposits in the Silurian period, which contain good reservoir-cap combinations;(2) the Shajingzi fault and associated faults connected the Cambrian-Ordovician source rocks in the Awati sag, and controlled the formation of Silurian structural traps, hence, the traps turned up along the structural belt in an orderly pattern and came together into contiguous tracts;(3) the Silurian petroleum in Shajingzi structural belt was dominated by gas, and the major accumulation period was the Himalayan period when the traps fixed in shape;(4) the Silurian gas resources in the Shajingzi belt were estimated at around 2.018×10^(11)m^(3), and Silurian gas resources of the northwest Tarim Basin were estimated at 2.03×10^(12)m^(3), implying huge exploration potential, so this area will become a major area for reserve and production increase from clastic strata in the basin;(5) with the Shajingzi fault of large scale and long active time connecting deep source rock layers, multiple formations in Lower Paleozoic of Shajingzi structural belt may have breakthroughs in hydrocarbon exploration.

Structural Optimization of Metal and Polymer Ore Conveyor Belt Rollers

Ore conveyor belt rollers operate in harsh environments,making them prone to premature failure.Their service lives are highly dependent on the stress field and bearing misalignment angle,for which limit values are defined in a standard.In this work,an optimization methodology using metamodels based on radial basis functions is implemented to reduce themass of twomodels of rollers.From a structural point of view,one of the rollers ismade completely of metal,while the other also has some components made of polymeric material.The objective of this study is to develop and apply a parametric structural optimization methodology to minimize the mass of the two models of rollers.To represent the mechanical behavior of the rollers,simulations were performed using the finite element method.During the numerical optimization process,the variable parameters were the dimensions of the shaft and external tube.The geometric configuration that corresponded at the same time to the lowest mass and acceptable ranges for the stress and bearingmisalignment angle was determined.With the proposed methodology,a 32.3% reduction in mass was obtained for a metal roller design and an 18.9% reduction for a polymer roller.In both cases,the constraints were not violated.For the all-metal roller,the safety factors for the maximum stress and bearingmisalignment angle were 1.44 and 1.75,respectively,while for the polymer roller the corresponding figures were 1.50 and 2.23.This work describes a low-computational-cost optimization methodology for roller designs that have been little studied in the literature.Furthermore,the methodology could be adapted for use with other types of rollers and rollers made of different materials.

Oil and gas source and accumulation of Zhongqiu 1 trap in Qiulitage structural belt, Tarim Basin, NW China

Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Zhongqiu structural belt and the reservoir formation process in Zhongqiu 1 trap remain unclear, so study on these issues may provide important basis for the next step of oil and gas exploration and deployment in Qiulitage structural belt. In this study, a systematic correlation of oil and gas source in Well Zhongqiu 1 has been carried out. The oil in Well Zhongqiu 1 is derived from Triassic lacustrine mudstone, while the gas is a typical coal-derived gas and mainly from Jurassic coal measures. The oil charging in Well Zhongqiu 1 mainly took place during the sedimentary period from Jidike Formation to Kangcun Formation in Neogene, and the oil was mainly contributed by Triassic source rock;large-scale natural gas charging occurred in the sedimentary period of Kuqa Formation in Neogene, and the coal-derived gas generated in the late Jurassic caused large-scale gas invasion to the early Triassic crude oil reservoirs. The Zhongqiu 1 trap was formed earlier than or at the same period as the hydrocarbon generation and expulsion period of Triassic-Jurassic source rocks. Active faults provided paths for hydrocarbon migration. The source rocks-faults-traps matched well in time and space. Traps in the footwall of the Zhongqiu structural fault have similar reservoir-forming conditions with the Zhongqiu 1 trap, so they are favorable targets in the next step of exploration.

Structural and Chemical Characteristic of Tourmaline, and Mineralogy of Associated Micas from Tourmaline Bearing Quartzite of KombéII (Bafia Group, Central Africa Fold Belt);Implication on the Metamorphic Conditions

Bafia Group is part of the southernmost portion of the Central African Fold Belt (CAFB) in Cameroon. The geological feature of the group is characterized by the presence of metamorphic rocks in which tourmaline had been recognized among accessory minerals. In the present study, attention is focus on the tourmaline bearing quartzite to the southeast of Kombé II. Structure refinement shows that tourmaline is a Fe-dravite with the formula X(Na0.95[]0.05)Y(Mg2.39Fe0.61)Z(Al5.10Mg0.90)(BO3)3T[Si6O18](OH)3[(O,OH)0.88F0.12]. The Fe-dravite is hosted in a Ca-poor quartzite, which is made up, in addition to quartz and tourmaline, of biotite and muscovite. The structure of the dravites shows a low vacancy at the X site, which militates for a crystallization of the tourmaline at a high temperature > 750℃. This is in agreement with previous work which shows that the metamorphic peak in the associated biotite gneiss reaches 825℃. The R1 value of 1.24% means that the crystal structure of the tourmalines is of high quality. The genetical link between gold mineralization and tourmaline should stimulate exploration interest in the study area.