【作者】 郑冰；

【导师】 尹观；

【作者基本信息】 成都理工大学 ， 地球化学， 2008， 博士

【摘要】 本项目通过对中扬子区海相中古生界盆地的原型与构造演化史的研究,着重论述了江汉盆地印支—早燕山运动期在大别造山带与江南—雪峰基底拆离体偏力偶双向挤压作用下的改造变形特征,认为:中扬子区中古生界盆地自晚元古代雪峰运动（8亿年）以来,经历了晚震旦—奥陶纪克拉通内凹陷—克拉通周边拗陷盆地,志留纪前陆盆地,泥盆纪—中三叠世克拉通内凹陷盆地,晚三叠世—侏罗纪前陆盆地和白垩—第三纪中扬子区挤出与走滑拉张盆地,形成现今的叠合盆地。根据“盆地为体、改造划界”的构造区划原则,对江汉盆地进行“印支—早燕山运动挤压期盆地构造单元区划”和“喜山运动挤出与走滑拉张期构造单元区划”。将江汉中古生界瓮地划分为5个Ⅱ级构造单元,10个Ⅲ级构造单元,16个凹陷与凸起。根据江汉盆地演化与构造单元区划结果,将江汉盆地的埋藏史划分为当阳地区古生代浅埋—中生代深埋型、荆州—沔阳地区古生代浅埋—新生代深埋型、乐乡关—天门地区古生代浅埋—中新生代长期剥蚀型、咸宁—大冶地区古生代浅埋—中新生代长期浅埋型、宜昌斜坡地区古生代浅埋—中新生代深埋型等五种类型。运用粘土矿物混层比和伊利石结晶度计算了盆地演化过程中各阶段的地温梯度,喜山期（K—E）的地温梯度为3.7℃/100m;印支—燕山期（T₃—J₃）地温梯度为2.7℃—2.2℃/100m;海西期（D—P—T₂）地温梯度为3.1℃/100m;加里东期（Z—S）地温梯度为3.1℃/100m。通过采集11块岩样进行磷灰石裂变径迹分析,探讨江汉盆地热构造史。在江汉盆地南部,磷灰石裂变径迹年龄在24.8—28.3Ma之间,表明在渐新世与中新世之间的喜山运动,其抬升幅度约为2500m左右。在当阳地区,热史表明,下第三系与上白垩统热史为升温—降温—升温型,即:白垩—下第三系地层沉积时进入升温退火带;渐新世与中新世之间江汉运动隆升期温度降低（剥蚀幅度＜500m）,但未退出退火带,之后在中新统地层叠加下又略升温。并且采用TSM盆地模拟技术计算了海相中古生界地层的剥蚀量,恢复了盆地的埋藏史和热史。中扬子区古生界三套烃源岩（∈₁,O₃—S₁,P₁）的生烃模拟表明,不同层系生烃演化差异形成了江汉盆地不同时期生烃量的差异。泥盆纪—中三叠世时期古生界烃源岩总生烃量为24.797万亿m³,占总量的31.31%;晚三叠—侏罗纪时期生烃量为39.939万亿m³,占总量的50.43%;白垩—老第三纪渐新世时期生烃量为12.567万亿m³,占总量的15.87%,新第三纪以来很少。到现今为止,江汉盆地古生界烃源岩累计生烃总量为78.239万亿m³。在区块分布上,沔阳凹陷和江陵凹陷累计生烃总量最大,分别为31.82万亿m³和22.208万亿m³,其他区块均普遍小于10万亿m³。通过对江汉盆地北缘、西缘和盆地内钻井海相中古生界地层地化剖面的实验测试,着重分析了作为多源、多期成藏物质基础的∈₁、O₃—S₁、P₁三大套烃源岩的有机地化特征与热演化程度。并通过中扬子区南山坪古油藏沥青/源岩对比研究、建南气田的气/源对比研究、苗市、北门岔、雁门口二叠系油苗研究及沔31井白垩系油藏的油源对比研究,揭示多源、多期成藏史。在对中扬子区江汉盆地原型与构造演化史、埋藏史、地热史,以及海相中古生界三大套主要烃源岩地化分析的基础上,同时采用TSM盆地模拟技术对江汉盆地海相中古生界烃源岩进行了生烃史模拟研究,计算了烃源岩热演化史和各演化阶段的生烃强度与生烃量。该计算结果为江汉盆地海相油气勘探的区带综合评价提供依据。对于中扬子区江汉盆地海相中古生界圈闭的评价按照“近油源,保存好,原地体,弱变形,逆冲断层下盘”的评价标准进行了圈闭评价。Ⅰ类区:海相中古生界烃源岩保存较好,晚期（二次）生烃强势区的Ⅰ类区为沔阳逆冲—褶皱带（沔阳凹陷、小板凹陷、通海口低凸起、岳口低凸起）及江陵凹陷。Ⅱ类区:海相中古生界烃源岩受到部份剥蚀,保存一般;晚期（二次）生烃中等强势区;如荆州逆冲—褶皱带（潜江凹陷、丫新低凸起）;宜昌斜坡区（枝江凹陷）、当阳复向斜带（河溶凹陷）。Ⅲ类区:海相中古生界烃源岩受到较多剥蚀,保存较差;晚期（二次）生烃弱势区;如大冶逆冲—褶皱带,天门—乐乡关复背斜带（荆门凹陷、汉水凹陷、永隆河、乐乡关凸起）、洪湖—通山冲断带、巴洪冲断带。结合中扬子区中古生界圈闭条件的分析,进行了勘探选区的综合评价和勘探目标的对比优选。为进一步的勘探提出了部署建议。更多还原

【Abstract】 Based on the study of the prototypes and tectonic evolution of the marine Mesozoic basins in the Middle Yangzi area,the deformation of the Jianghan Basin was studied, which underwent bi-directional compression of the DaNe orogenic belt and the Jiangnan - Xuefeng basement detachment during the Indosinian - Early Yanshanian movement.It indicated that the Paleozoic and Mesozoic basins in the Yangzi area had undergone the Late Sinian - Ordovician inner cratonic depression - peripheral cratonic basin,the Silurian foreland basin,the Devonian - Middle Triassic inner cratonic depression,the Late Triassic - Jurassic foreland basin and the CretaceousTertiary extensional strike-slip basin since the Late Proterozoic Xuefeng movement （800Ma）,resulted in recent superimposed basin.According to the principle of " basin as the pattern and modification as the boundary",the Jianghan basin was divided into "structural units of the IndosinianEarly Yanshanian compressional basin" and "structural elements of the Himalayan sqeezing and strike slip basin".The Paleozoic and Mesozoic Jianghan basin was divided into 5 classⅡstructural units,10 classⅢstructural units,and 16 depressions and uplifts.On basis of evolution and division of structural units of the Jianghan Basin,the burial history of the basin was divided into shallow buried Paleozoic - deep buried Mesozoic in Danyang and Jinzhou - Gaiyang area,shallow buried Paleozoic and long erosion in the Mesozoic and Cenozoic in Lexianguan - Tianmen area,shallow buried Paleozoic to Cenozoic in Xianning - Daye area,and shallow buried Paleozoic and deep buried Mesozoic and Cenozoic in Yichang slope area.Geothermal gradient in every stages of basinal evolution was calculated with ratio of mixed layer clay minerals and crastallinity of illite.Geothermal gradient was 3.7℃/100m in Himalayan period（K-E）,2.7 - 2.2℃/100m in IndosinianYanshanian period（T3-J3）,3.1℃/100m in Hercynian period（D-P-T2）and 3.1℃/100m in Caledonian period（Z-S）.In order to study of thermal - structural history,11 samples were carried out apatite fission - track analysis.Fission-track age of apatite was 24.8 - 28.3 Ma in the southern part of the Jianghan basin,indicating 2500m of uplift during the Himalayan movement in the Oligocene and Miocene.In Danyang area,the geo-temperature showed rising - falling - rising during the Paleogene and Late Cretaceous,i.e.it was in temperature rising annealing zone during sedimentation of the CretaceousPaleogene sequences;temperature was fall during uplift（erosion level less than 500m） due to Jianghan movement between the Oligocene and the Miocene,but not retreated from the annealing zone;then the temperature was slightly rose as a result of superimposition of the Miocene sequence.The denudation amount of the marine Paleozoic and Mesozoic strata was calculated by TSM basin modeling method,and the burial history and thermal history of the basin was restored.Result of hydrocarbon generation simulation of 3 sets of Paleozoic source rocks（C1,O3-S1,P1）in the Middle Yangzi area showed that different hydrocarbon generation of different sequences resulted in the difference of hydrocarbon generating amount in different periods in the Jianghan Basin.The total hydrocarbon generating amount of the Paleozoic source rocks in the DevonianMiddle Triassic was 24.797^*10¹²m³,accounting for 31.31%;39.939^*10¹²m³ in the Late Triassic-Jurassic,accounting for 50.43%;12.567^* 10¹²m³ in the CretaceousPaleogene, accounting for 15.87%;with small amount since the Eocene.Till recent, total hydrocarbon generating amount of the Paleozoic source rocks in the Jianghan Basin was 78.239^* 10¹²m³.In terms of its distribution,the Gaiyang and Jiangling depressions accounted for the biggest hydrocarbon generating amount,with 31.82^*10¹²m³ and 22.208^* 10¹²m³ respectively,and the other areas were less than 10^*10¹²m³.The geochemical sections of the marine Paleozoic and Mesozoic sequences in northern margin,western margin and wells in the Jianghan Basin were analyzed. Especially,the geochemical feature and thermal evolution of 3 sets of source rocks of C1,O3-S1 and P1 age were studied in detail.By correlation of the bitumen/source rocks in Nanshanping ancient oil reservoir and correlation of gas/source rocks in Jiannan gas field,study of Miaoshi,Beicamen and Yanmenkou Permian oil show,and correlation of oil/source in well 631 Cretaceous oil reservoir,a multiple source rocks and multiple hydrocarbon accumulation was indicated.Based on study of basin prototype,structural evolution,burial and thermal history of the Jianghan Basin of the Middle Yangzi area,and analysis of geochemical characteristics of the marine Paleozoic and Mesozoic source rocks,combining with modeling of hydrocarbon generating history of the source rocks by TSM basin modeling method in the Jianghan Basin,the hydrocarbon generating intensity and hydrocarbon amount was calculated in different evolutional stages.The results provided some basis for assessment of marine exploration targets in the Jianghan Basin.The evaluation of traps was in the line of "near source rocks,good preservation, original block,weak deformation and in footwall of thrust" for the marine Paleozoic and Mesozoic traps of the Jianghan Basin of the Middle Yangzi area.TypeⅠarea:The marine Paleozoic and Mesozoic source rocks were well preserved. Favorable area for late（secondary）hydrocarbon generation is in Gaiyang thrustfolds belt（Gaiyang depression,Xiaoban depression,Tonghaikou low uplift and Yekou low uplift）and Jiangling depression.TypeⅡarea:The marine Paleozoic and Mesozoic source rocks were generally preserved with part denudation.It showed medium intensity of late（secondary） hydrocarbon generation,such as in Jingzhou thrust - folds belt（Qianjiang depression, Yaxin low uplift）,Yichang slope area（Zhijiang depression）and Danyang synclinorium（Herong depression）.TypeⅢarea:The marine Paleozoic and Mesozoic source rocks were denudated and were poorly preserved with small late（secondary）hydrocarbon generation.For examples,Daye thrust - folds belt,Tianmen - Lexiangguan syclinorium（Jingmen depression,Haishui depression,and Yonglonghe and Lexiangguan uplift）,HonghuTongshan thrust belt and Bahong thrust belt.In accordance with analysis of the Paleozoic and Mesozoic trap conditions in the Middle Yangzi area,comprehensive assessment of exploration areas and optimization of exploration targets was carried out.And future exploration decision was proposed.更多还原