Late Triassic Intracontinental Deformation of South Tianshan,Central Asia:Evidence from Syn-tectonic Sedimentation and Detrital Zircon Provenances of the Kuqa Depression

The Tianshan range,a Paleozoic orogenic belt in Central Asia,has undergone multiple phases of tectonic activities characterized by the N-S compression after the early Mesozoic,including the far-field effects of the Cenozoic Indian-Asian collision.However,there are limited reports on the tectonic deformation and initiation of Triassic intracontinental deformation in the Tianshan range.Understanding this structural context is crucial for interpreting the early intracontinental deformation history of the Eurasian continent during the early Mesozoic.Growth strata and syn-tectonic sediments provide a rich source of information on tectonic activities and have been extensively used in the studies of orogenic belts.Based on detail fieldwork conducted in this study,the middle-late Triassic Kelamayi Formation of the northern Kuqa Depression in the southern Tianshan fold-thrust belt has been identified as the typical syn-tectonic growth strata.The youngest detrital zircon component in two lithic sandstone samples from the bottom and top of the Kelamayi growth strata yielded U-Pb ages of 223.4±3.1 and 215.5±2.9 Ma,respectively,indicating that the maximum depositional age of the bottom and top of the Kelamayi growth strata is 226-220 and 218-212 Ma.The geochronological distribution of detrital samples from the Early-Middle Triassic and Late Triassic revealed abrupt changes,suggesting a new source supply resulting from tectonic activation in the Tianshan range.The coupling relationship between the syn-tectonic sedimentation of the Kelamayi Formation and the South Tianshan fold-thrust system provides robust evidence that the Triassic intracontinental deformation of the South Tianshan range began at approximately 226-220 Ma(during the Late Triassic)and ended at approximately 218-212 Ma.These findings provide crucial constraints for understanding the intraplate deformation in the Tianshan range during the Triassic.

Factors controlling the distribution of granite reservoirs of hydrothermal system type in South China:A case study of Huangshadong geothermal field in Yuezhong Depression,China

The granitoids widely distributed in South China are characterized by multi-stage evolution via episodic intrusions,in a complex geodynamic setting.Since granites have high radioactive heat generation and excellent thermal conductivity,a deep moderate-to high-temperature geothermal system can be formed in the presence of high-quality,fissured granite geothermal reservoirs and thermal insulation with appropriate cap rocks.The key to exploring deep geothermal resources is to identify high-quality fissured granite geothermal reservoirs of a certain scale in a thermal anomaly zone with high background heatflow values.To determine the controlling effects of the distribution and development characteristics of granite geothermal reservoirs on the generation and enrichment of deep geothermal resources,this study analyzed the characteristics of the geothermal reservoirs in the Huangshadong geothermal field in the Yuezhong Depression,Guangdong Province,and their controlling effects on the formation of geothermal resources.The results are as follows.The hydrothermal system in the Huangshadong geothermal field mainly distributed in the contact zones between magmatic plutons and surrounding rocks,is significantly controlled by faults,followed by neoid volcanic apparatus and magmatic activities.That is,the geothermal system therein is under joint control of structures and magmas.Moreover,fractured zones of neoid transtensional faults conduct the geothermal water in the hydrothermal system and control its shallow discharge.Therefore,the hydrothermal system in the study area is characterized by the control of transpressional tectonic zone and volcanic apparatus,and geothermal water conduction through fractured zones of transtensional faults.

The Relationship between Fractures and Tectonic Stress Field in the Extra Low-Permeability Sandstone Reservoir at the South of Western Sichuan Depression

The formation and distribution of fractures are controlled by paleotectonic stress field, and their preservative status and effects on development are dominated by the modern stress field. Since Triassic, it has experienced four tectonic movements and developed four sets of tectonic fractures in the extra low-permeability sandstone reservoir at the south of western Sichuan depression. The strikes of fractures are in the S-N, NE-SW, E-W, and NW-SE directions respectively. At the end of Triassic, under the horizontal compression tectonic stress field, for which the maximum principal stress direction was NW.SE, the fractures were well developed near the S-N faults and at the end of NE-SW faults, because of their stress concentration. At the end of Cretaceous, in the horizontal compression stress fields of the NE-SW direction, the stress was obviously lower near the NE-SW faults, thus, fractures mainly developed near the S-N faults. At the end of Neogene-Early Pleistocene, under the horizontal compression tectonic stress fields of E-W direction, stress concentrated near the NE-SW faults and fractures developed at these places, especially at the end of the NE-SE faults, the cross positions of NE-SW, and S-N faults. Therefore, fractures developed mostly near S-N faults and NE-SW faults. At the cross positions of the above two sets of faults, the degree of development of the fractures was the highest. Under the modern stress field of the NW-SE direction, the NW-SE fractures were mainly the seepage ones with tensional state, the best connectivity, the widest aperture, the highest permeability, and the minimum opening pressure.

New Apatite Fission-Track Ages of the Western Kuqa Depression:Implications for the Mesozoic–Cenozoic Tectonic Evolution of South Tianshan,Xinjiang

The Mesozoic–Cenozoic uplift history of South Tianshan has been reconstructed in many ways using thermochronological analyses for the rocks from the eastern Kuqa Depression. The main difference in the reconstructions concerns the existence and importance of Early Cretaceous and Paleogene tectonic activities, but the existence of a Cenozoic differential uplift in the Kuqa Depression remains enigmatic. Here, we present new apatite fission-track ages obtained for 12 sandstone samples from the well-exposed Early Triassic to Quaternary sequence of the Kapushaliang section in the western Kuqa Depression. The results reveal that there were four pulses of tectonic exhumation, which occurred during the Early Cretaceous（peak ages of 112 and 105 Ma）, Late Cretaceous（peak age of 67 Ma）, Paleocene–Eocene（peak ages at 60, 53, and 36 Ma）, and early Oligocene to late Miocene（central ages spanning 30–11 Ma and peak ages of 23 and 14 Ma）, respectively. A review of geochronological and geological evidence from both the western and eastern Kuqa Depression is shown as follows.（1） The major exhumation of South Tians Shan during the Early Cretaceous was possibly associated with docking of the Lhasa block with the southern margin of the Eurasian plate.（2） The Late Cretaceous uplift of the range occurred diachronically due to the far-field effects of the Kohistan-Dras Arc and Lhasa block accretion.（3） The Paleogene uplift in South Tianshan initially corresponded to the far-field effects of the India–Eurasia collision.（4） The rapid exhumation in late Cenozoic was driven by the continuous far-field effects of the collision between India and Eurasia plates. The apatite fission-track ages of 14–11 Ma suggest that late Cenozoic exhumation in the western Kuqa Depression prevailed during the middle to late Miocene, markedly later than the late Oligocene to early Miocene activity in the eastern segment. It can be hypothesized that a possible differential uplift in time occurred in the Kuqa Depression during the late Cenozoic.

Upper Paleozoic Marine Shale Characteristics and Exploration Prospects in the Northwestern Guizhong Depression,South China

Multiple sets of organic-rich shales developed in the Upper Paleozoic of the northwestern Guizhong Depression in South China. However, the exploration of these shales is presently at a relatively immature stage. The Upper Paleozoic shales in the northwestern Guizhong Depression, including the Middle Devonian Luofu shale, the Nabiao shale, and the Lower Carboniferous Yanguan shale, were investigated in this study. Mineral composition analysis, organic matter analysis(including total organic carbon(TOC) content, maceral of kerogen and the vitrinite reflection(Ro)), pore characteristic analysis(including porosity and permeability, pore type identification by SEM, and pore size distribution by nitrogen sorption), methane isothermal sorption test were conducted, and the distribution and thickness of the shales were determined, Then the characteristics of the two target shales were illustrated and compared. The results show that the Upper Paleozoic shales have favorable organic matter conditions(mainly moderate to high TOC content, type Ⅰ and Ⅱ_1 kerogen and high to over maturity), good fracability potential(brittleness index(BI) > 40%), multiple pore types, stable distribution and effective thickness, and good methane sorption capacity. Therefore, the Upper Paleozoic shales in the northern Guizhong Depression have good shale gas potential and exploration prospects. Moreover, the average TOC content, average BI, thickness of the organic-rich shale(TOC > 2.0 wt%) and the shale gas resources of the Middle Devonian shales are better than those of the Lower Carboniferous shale. The Middle Devonian shales have better shale gas potential and exploration prospects than the Lower Carboniferous shales.

Factor Structure of the Center for Epidemiologic Studies Depression Scale in South Korea

Results of previous studies from North America reported that only 14 out of the 20 items from the Center for Epidemiologic Studies Depression Scale (CES-D) were required to assess negative affect, somatic symptoms, and anhedonia. However, it remains unclear whether this three-factor structure of the CES-D would be valid in South Korea. The purpose of this study is to examine the validity of the three-factor structure with a Korean version of the CES-D. The participants were Korean college students (N = 215), elementary school teachers (N = 234), and parents of elementary school students (N = 230). Confirmatory factor analysis was performed to examine the scale’s validity. Results indicated that the three-factor structure showed acceptable fit to data (comparative fit index = 0.95;root mean square error of approximation = 0.06). The findings indicated that the three-factor structure of the CES-D was valid in South Korea.

Suicide ideation, depression and HIV among pregnant women in rural South Africa

Background: Despite public perception to the contrary, pregnancy does not offer a protective effect for suicide ideation. In low and middle income countries (LMIC) multiple concurrent risk factors including unplanned pregnancies, testing for HIV, intimate partner violence and depression may increase suicide risk among pregnant women. We examine suicide ideation among women attending routine antenatal care in rural South Africa. Method: A consecutive series of 109 women in the second half of pregnancy were enrolled in a cross-sectional study at a large primary health care facility in a rural area of KwaZulu-Natal with high HIV prevalence. Using a mixed-methods approach, women were assessed using the Major Depression Section of the Structured Clinical Interview for Depression (SCID) for DSM-IV diagnosis;qualitative interview data were collected on women’s experiences of suicide ideation and plans. Women were assessed two weeks after routine HIV testing as part of Prevention of Mother-to-Child Transmission (PMTCT) screening. Results: Both HIV-positive (49/109) and HIV-negative (60/109) women were assessed. Depression was high (51/109, 46.7%) and equally common amongst HIV-positive and negative women. Suicide ideation was high (30/109, 27.5%) with thoughts of self harm closely linked to suicide plans. Age, previous history of depression and current depression were significantly associated with suicide ideation. Close to equal numbers of HIV-positive and negative women were suicidal. Suicide methods were frequently violent and most women cited family and partnership conflict related to an unplanned pregnancy or their newly HIV-positive status as triggers to their suicide ideation. Conclusions: Rates of suicide ideation among pregnant women testing for HIV are high. Testing HIV-positive causes considerable distress, and among HIV-negative women unplanned and unwanted pregnancies are important risk factors for suicide ideation. Pregnancy brings women into increased contact with the health services with important opportunities for prevention and intervention.

Hydrocarbon Detection Based on Phase Decomposition in Chaoshan Depression, Northern South China Sea

Located in the northern South China Sea,Chaoshan Depression is mainly a residual Mesozoic depression,with a construction of Meso-Cenozoic strata over 7000m thick and good hydrocarbon accumulation conditions.Amplitude attribute of-90°phase component derived by phase decomposition is employed to detect Hydrocarbon in the zone of interest(ZOI)in Chaoshan Depression.And it is found that there are evident amplitude anomalies occurring around ZOI.Phase decomposition is applied to forward modeling results of the ZOI,and high amplitudes occur on the-90°phase component more or less when ZOI is charged with hydrocarbon,which shows that the amplitude abnormality in ZOI is probably caused by oil and gas accumulation.

INVERSION OF TEMPERATURE FROM AMSU-A AND ITS APPLICATION ON WARM-CORE OF TROPICAL DEPRESSION OVER THE SOUTH CHINA SEA

The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure.

Closing the treatment gap for depression co-morbid with HIV in South Africa: Voices of afflicted women

This Background: In South Africa the rising comorbidity of mental disorders with other non-communicable and communicable diseases, particularly in people living with HIV/AIDS (PLWHA), has helped raise the public health priority of mental ill-health. Depression, in particular, compromises anti-retroviral treatment (ART) adherence and virological suppression, thus threatening the effectiveness of South Africa’s ART programme. Given that evidence-based treatment for depression comprises medication and/ or Western-derived psychotherapies, responding to the current interest in expanding mental health services for PLWHA demands an understanding of how best to provide culturally competent care within existing resource constraints. Aim: To explore the context and local understandings of depression in women living with HIV to inform the development of contextually appropriate mental health services that could be delivered within existing resource constraints inSouth Africa. Method: Semi-structured qualitative interviews were held with 35 women living with HIV in South Africa who met the diagnostic criteria for a major depressive disorder. Results: Being HIV-positive per se was not reported to be a major cause of depression. Instead, a number of social factors were reported. These included stigma and discrimination, poverty, and stressful life events. Symptoms of depression, especially social withdrawal, negative ruminating thoughts and excessive worry suggestive of comorbid anxiety, functioned to exacerbate and trap women in a negative depressive cycle. Social support emerged as a dominant coping strategy. Group-based interventions, which afford greater opportunities for improved social support, were mooted as the most appropriate intervention by the majority of participants. Individual counselling provided through a home visitation programme was suggested for those who were too ill or too poor to attend clinics. Task sharing was also endorsed. Conclusion: The need for multi-sector engagement in mental health promotion to address factors that trigger, maintain and exacerbate depression at a community level in PL-WHA is highlighted. The triggers, symptoms and local coping strategies employed by afflicted women in this study suggest a resonance with Western derived evidence-based psychological therapies. In relation to delivery channels, there was support for the provision of group interventions or home-based individual counselling using a task sharing model.

Factors Associated with Mental Depression among Men Who Have Sex with Men in Southern India

Background: Mental health has been a largely neglected issue among Men Who Have Sex with Men (MSM) across the world. This study examines the prevalence and correlates of depression among MSM. Data and Methods: Data for this study are used from a cross-sectional Behavioral Tracking Survey—2012 conducted among 1176 MSM from Andhra Pradesh (undivided), a southern state of India. Depression of MSM was assessed using Patient Health Questionnaire-2 scale. Descriptive statistics, bivariate and multivariate logistic regression techniques were used for analysis. Results: More than one-third of MSMs (35%) in the survey reported to have depression. The likelihood of experiencing depression was 5 times higher among MSM who were mobile for sex work outside their place of residence (55% vs 17%, AOR: 5.2, 95% CI: 3.7 - 7.3) and had experienced physical or sexual violence (82% vs 33%, AOR: 6.0, 95% CI: 2.1 - 17.4) than their respective counterparts. Rates of depression were significantly higher among MSM who had experienced Sexually Transmitted Infections symptoms;knowledge of their HIV positivity;who didn’t use condoms during anal sex with any clients/partners;those who consumed alcohol and were in financial debt at the time of survey than others. Those who were associated with any community groups have significantly less chances of reporting depression. Discussion: The study certainly highlighted that the HIV prevention efforts with MSM in India require an integrated approach on addressing the mental health issues. To support this, programs and research-based evidence will be highly needed to ensure that mental health issues are properly addressed among MSM and other high risk groups.

A comparison analysis between developed and undeveloped depressions over the South China Sea

-- In this paper, by using two sets of composite data of developed and undeveloped depressions over the South China Sea, we analyze and compare the dynamic structures, the heating fields and the vorticity budget residuals of two different types of depressions. Our conclusions are as follows:The two types of depressions are similar in thermodynamical and dynamical structures. The main differ ences are : in the high layer of developed depression there is a divergence field, with a center near the zero line of vertical wind shear, and over undeveloped depression, the divergence field is weaker and the vertical wind at its center is greater than 5 m s-1. The thermodynamical field of the former is asymmetrical and that of the latter is quasi - symmetrical. As far as the dynamics structure is concerned, the convergence in the lower layer and the difference of divergence between the upper and lower layers of developed depression is three tmies larger than that of undeveloped depression. The upward motion and heating field at the center of developed depression is also stronger than that of undeveloped one.The vorticity budget of the two types of depressions is mainly determined by the divergence term, the vorticity advection term and the vertical transport term. The residual term is also important.The principal contribution comes from the divergence term . This is more significant for developed depression than for undeveloped depression.

Characteristics and origin of continental marginal fault depressions under the background of preexisting subduction continental margin,northern South China Sea,China

Based on the new seismic and drilling data and the recent related research results,this paper systematically analyzes the diversity and complexity of evolution process of crustal lithosphere structure and basin structure in the Pearl River Mouth Basin on the northern margin of the South China Sea.Three types of detachment faults of different structural levels exist:crust-mantle detachment,inter-crust detachment and upper crust detachment.It is considered that different types of extensional detachment control different subbasin structures.Many fault depressions controlled by upper crust detachment faults have been found in the Zhu I Depression located in the proximal zone.These detachment faults are usually reformed by magma emplacement or controlled by preexisting faults.Baiyun-Liwan Sag located in the hyperextension area shows different characteristics of internal structure.The Baiyun main sag with relative weak magmatism transformation is a wide-deep fault depression,which is controlled by crust-mantle detachment system.Extensive magmatism occurred in the eastern and southwest fault steps of the Baiyun Sag after Middle Eocene,and the crust ductile extensional deformation resulted in wide-shallow fault depression controlled by the upper crust detachment fault.Based on the classical lithosphere extensional breaking and basin tectonic evolution in the Atlantic margin,it is believed that the magmatic activities and pre-existing structures in the Mesozoic subduction continental margin background are important controlling factors for the diversified continental margin faulted structures in the northern South China Sea.

Geological evolution of the Dongsha Uplift and its surrounding depressions in the South China Sea

-The tectonic types of the Zhujiang (Pearl) River Mouth Basin in the South China Sea are epicontinental rift-depression basins. Prior to Early Cretaceous time, the Dongsha Uplift arid its surrounding depressions had been combined with the Eurasia Plate in a single unit. Many ENE-trending narrow rifted basins were formed in the third episode of Yanshan orogeny (Late Laramide). The rifted basins in the Paleocene and Eocene were stretched and extended, forming Zhu 1, Zhu 2 and Zhu 3 depressions. The Dongsha Uplift is located between Zhu 1 and Zhu 2 depressions . covering an area of 28 000 Km2. Its geologic evolution can be divided into four stages:(1) Late Cretaceous - Paleocene block-faulting stage.(2) Eocene -Oligocene uplifting and eroding stage.(3) Late Oligocene - Early Miocene sustained subsiding stage.(4) Middle Miocene -Recent noncompensated subsiding stage.The Dongsha Uplift is a structural zone favourable for oil-gas accumulation.

Generalized Anxiety and Major Depressive Symptoms of General Public in South Korea during the Early COVID-19 Pandemic

The extent of viral spread and strategies in dealing with the COVID-19 pandemic have been different in each country.There are overall increased mental health concerns in many countries but it is unclear what the general public individuals who do not have heighten vulnerability to stressors for existing mental diseases or significant physical illnesses were experiencing during the pandemic.We evaluated the stressors and mental health of general public in South Korea that has a relatively low confirmed cases and deaths.Responses on the on-line survey questions were used to assess the mental and physical symptoms in association with individuals’reported stressors.Individuals with the symptoms of the generalized anxiety disorder(GAD)were reported in 58.9%,and major depression(MD)in 23.2%,mostly in minimal to mild degrees,cut-off scores of 5 and 10,respectively by the validated screening tools,GAD-7 and PHQ-9.Both GAD and MD symptoms were in 21.5%of the respondents.The total number of stress had significant association with the scores of GAD-7,PHQ-9,physical symptoms,sleep difficulties and resilience(p<0.01).GAD scores were also associated with sleep difficulties(p<0.01)and raising young children(p<0.05).MD scores were associated with sleep difficulties,job-dissatisfaction,and educational level(p<0.05).The limitations of the study include small sample size,usage of smartphone or email,potential under-reporting by stigma in the socio-cultural context and evolving nature of pandemic.We conclude that keeping careful watch for mental symptoms,stressors,sleep difficulties and other physical symptoms are important even for the individuals without previous mental illnesses during the pandemic era.

深反射地震成像揭示的班公湖-怒江缝合带中段Moho断阶及其大地构造意义

揭示班公湖-怒江(班怒)缝合带Moho(莫霍面)结构对于认识中特提斯洋壳俯冲和南羌塘坳陷成因具有重要地球动力学意义。基于横跨班怒缝合带的深反射地震数据(88°30′E),本文采用了中长波长静校正、噪声压制、优化叠加和叠前深度偏移(PSDM)等地震处理技术,获得了深度域地震反射偏移剖面、层速度场和高分辨率Moho结构。由深度域剖面显示,班怒缝合带Moho位于地表以下65~80 km,呈不连续北向抬升趋势,指示在拉萨地块与南羌塘地块之间存在岩石圈上地幔断阶,最大阶步可达15 km。综合分析缝合带两侧的Moho形态认为,这些断阶受南侧拉萨地体的岩石圈上地幔以19.5°北倾俯冲与北侧南羌塘地块的上地壳抬升驱动,可能与深部存在局部熔融相关。班怒缝合带下的Moho结构表明,随着晚侏罗世—早白垩世中特提斯洋闭合,南羌塘地体由边缘海沉积向前陆盆地转换,形成南羌塘坳陷。

南海北部深水区古近系沉积物源演变及古地理意义

南海北部深水区古近纪经历了由陆到海的环境转换过程,沉积物源也随时间发生明显改变。由于水深的限制,目前对深水区的沉积物来源及古地理背景存在争议。通过碎屑锆石U-Pb年龄谱系源汇对比方法,对南海北部珠二坳陷古近系沉积物来源进行系统研究。结果发现,在早中始新世,珠二坳陷沉积物以近源输入为特征,沉积物主要来自坳陷周缘的局部隆起区;晚始新世,源自坳陷西侧的昆莺琼古河为盆地提供大量沉积物,坳陷北侧的珠江沉积物对珠二坳陷影响较小;渐新世,珠江沉积物从北向南越过番禺低隆起进入珠二坳陷,与昆莺琼古河沉积物在白云凹陷北部和中西部混合沉积,形成大型河流三角洲体系。南海北部深水区古近系物源演变过程明显受中生代末区域构造古地理控制,查明该时期物源演变对恢复区域古地理格局具有重要意义。

渤海湾盆地辽西凹陷南洼原油的生物标志化合物特征及运聚模式

辽西低凸起是渤海湾盆地重要的含油气构造,南部油气环绕辽西凹陷南洼呈带状分布,辽西凹陷南洼对油气的贡献以及贡献多寡的问题一直存在争议,制约了该地区勘探进程。本研究通过分析围绕辽西凹陷南洼分布的油气生物标志化合物组成和地球化学特征,厘清原油与辽西凹陷南洼和辽中凹陷中洼烃源岩的关系。结果表明:①辽西低凸起南部油气带分布在辽西大断层两侧,环绕辽西凹陷南洼东北侧的油藏有LD5N、SZ36、LD5和LD4油藏,其中LD4油藏和LD5东二下段油藏具有高甲藻甾烷、低C_(30)4-甲基甾烷的低成熟特征,来源于辽西凹陷南洼沙三段和沙一段烃源岩;LD5东二上段油藏和SZ36S油藏分布在断层两侧,发育甲藻甾烷、C_(30)4-甲基甾烷和伽马蜡烷,原油处于成熟阶段,属于辽西凹陷南洼和辽中凹陷中洼混合来源;LD5N油藏和SZ36油藏具有高C_(30)4-甲基甾烷、低伽马蜡烷的特征,均为成熟原油,由辽中凹陷中洼烃源岩生成;②辽西凹陷南洼以低熟油为主,沿断层向LD5、LD4构造带深部运移充注,形成LD4和LD5东二下段油藏;LD5、LD4东二下段充满后,辽西凹陷南洼低熟油沿断层继续向浅部运移,与辽中凹陷中洼成熟油在LD5东二上段、SZ36S汇合,形成LD5东二上段、SZ36S混合类油藏,辽中凹陷中洼成熟油向SZ36油藏东北侧运移,跨过辽西大断层后在浅部形成LD5N油藏。

涠西南凹陷南部斜坡带油气运移地球化学与成藏特征

涠西南凹陷南部斜坡带是重要的油气聚集区,在角尾组、涠洲组、流沙港组和石炭系地层中均发现了油气显示。通过原油地球化学特征分析,本区原油主要为凹陷中央流沙港组二段下部烃源岩生成的成熟原油,原油以轻质油为主,为咸水湖相环境形成原油。油源精细对比揭示,涠西南凹陷流沙港组二段、三段、角尾组和石炭系地层均属于同一类原油,通过全烃谱图中正构烷烃分布特征建立适合本区的运移分馏指数FI=(nC8~nC12)/(nC25~nC32),并结合饱和烃、芳烃比值和油气运移分馏指数关系分析,WB到WC流沙港组二段和流沙港组三段原油样品均呈现出运移分馏指数增加,饱芳比增加的趋势,指示WB构造流沙港组二段和流沙港组三段原油为侧向运移至WC构造。同时通过WA构造含氮化合物含量与深度关系分析,揭示浅部含氮化合物屏蔽型异构体相对富集,暴露型异构体相对减少,指示垂向上具有明显的沿断裂带从深部向浅部运移的特征。综合考虑本地区输导体系的空间叠置关系,认为南部斜坡带是洼陷中央烃源生成油气经由断层、砂体等输导体系运聚到浅部和斜坡带成藏,此次研究对本区带下步油气勘探具有重要意义。