Extensional Tectonic System of Erlian Fault Basin Groupand Its Deep Background

The Erlian fault basin group, a typical Basin and Range type fault basin group, was formed during Late Jurassic to Early Cretaceous, in which there are rich coal, oil and gas resources. In the present paper the abundant geological and petroleum information accumulated in process of industry oil and gas exploration and development of the Erlian basin group is comprehensively analyzed, the structures related to formation of basin are systematically studied, and the complete extensional tectonic system of this basin under conditions of wide rift setting and low extensional ratio is revealed by contrasting study with Basin and Range Province of the western America. Based on the above studies and achievements of the former workers, the deep background of the basin development is treated.

Structural architecture of Neoproterozoic rifting depression groups in the Tarim Basin and their formation dynamics

The Tarim Basin is the largest, oil-bearing, superimposed basin in the northwest of China. The evolution and tectonic properties of the initial Tarim Basin have been hotly disputed and remain enigmatic. The Neoproterozoic basin is covered by a vast desert and a huge-thickness of sedimentary strata, has experienced multiple tectonic movements, had a low signal to noise ratios(SNRs) of deep seismic reflection data, all of which have posed critical obstacles to research. We analysed four field outcrops, 18 wells distributed throughout the basin, 27 reprocessed seismic reflection profiles with higher SNRs across the basin and many ancillary local 2D and 3D profiles and aeromagnetic data. We found about 20 normal fault-controlled rifting depressions of the Cryogenian and Ediacaran scattered throughout the basin, which developed on the Precambrian metamorphic and crystalline basement. The structural framework is clearly different from that of the overlying Phanerozoic. The rifting depressions consist of mainly half grabens, symmetrical troughs and horst-grabens. From the northeast to southwest of the basin,they are divided into three rifting depression groups with the WNW, ENE, and NW-trends that are mainly controlled by normal faults. The maximum thicknesses of the strata are up to 4100 m. From the Cryogenian to Ediacaran, most of the main inherited faults to active and eventually ceased at the end of the Ediacaran or Early Cambrian, while subsidence centres appeared and migrated eastward along the faults. They revealed that the different parts of the Tarim continental block were in NNE-SSWoriented and NNW-SSE-oriented extensional paleo-stress fields(relative to the present) during the Neoproterozoic, and were accompanied by clockwise shearing. According to the analysis of the activities of syn-sedimentary faults, filling sediments,magmatic events, and coordination with aeromagnetic anomalies, the tectonic properties of the fault depressions are different and are primarily continental rifts or intra-continental fault-controlled basins. The rifting phases mainly occurred from 0.8–0.61 Ga.The formation of the rifting depression was associated with the initial opening of the South Altun-West Kunlun Ocean and the South Tianshan Ocean, which were located at the northern and southern margins of the Tarim Block, respectively, in response to the break-up of the Supercontinent Rodinia and the initial opening of the Proto-Tethys Ocean.

下江群沉积地质特征及其对华南新元古代构造演化的约束

华南西部新元古代裂陷纪大地构造属性和原型盆地性质是一个涉及到扬子古陆在全球构造中的定位、且争议较大的基础地质问题。新元古代下江群发育于强变形变质的盐边群和弱变形变质的板溪群之间,处于以滨浅海沉积为主的板溪群向深海沉积转化的过渡带内。下江群以浊流沉积的杂砂岩为主,沉积物扩散方向指向西。下江群清水江组砂岩骨架颗粒统计分析表明,物源来自再旋回造山带。常量元素地球化学特征显示,下江群碎屑岩系形成于活动陆缘区的弧后盆地靠大陆一侧。结合盐边群、苏雄组大地构造属性及其与下江群的空间关系,推测当时的华南西部处于汇聚型板块边缘内,总体属弧后伸展型盆地。

二连断陷盆地群伸展构造系统及其发育的深部背景

二连盆地形成于侏罗纪到早白垩世期间，是东北亚断陷盆地系内的一个典型的盆岭式断陷盆地群，其内蕴藏丰富的煤和油气资源．综合分析了二连盆地油气勘探中积累的地质资料，系统地研究了与盆地形成有关的构造，并与北美西部盆岭省进行了对比，揭示了二连盆地宽裂陷作用和低拉伸率条件下的伸展构造系统．以上述研究和前人的研究成果为基础，探讨了盆地发育的深部背景．

裂陷盆地断块群类型——以东濮凹陷为例

断块是重要的油气储集单元,断块群则是断块的有序组合,是油气藏组合体。断块油气藏的勘探迫切需要一个合理的断块群分类方案。文中从几何学—运动学方面出发,讨论了裂陷盆地断块群分类方案,然后结合裂陷盆地结构,讨论了不同构造部位可能出现的断块群类型,也从这个角度初步讨论了断块群的成因。最后,结合东濮凹陷实际,讨论了不同构造部位发育的不同类型断块群的构造特点和含油气性。

大兴安岭以西弧形断陷盆地群油气地质特点与含油气性

大兴安岭以西分布一系列断陷盆地,已经发现数十个油田。从断陷盆地群的构造演化与受控机制出发分析各断陷的分布特点和类型,在分析成藏要素及其组合类型基础上研究油气成藏模式和分布特点。研究结果表明:大兴安岭以西断陷盆地群在平面上展现为3个带状弧形,断陷有单断、双断和组合式3种样式;大多数断陷具有中等—好烃源岩,储集层以岩屑长石砂岩、岩屑砂岩为主,另发育变质岩、火山岩等储层,除了常见的构造、岩性油气藏外,断陷中还发育变质岩、火山岩油藏;断陷成藏期在晚白垩世及古近纪,富烃洼槽控制油气时空分布,特殊储层具有形成大油田的有利条件,存在多个小而肥的凹槽,且稠油具有一定的勘探潜力。具相似含油气系统的断陷是今后的勘探目标。

银根-额济纳裂谷盆地群凹陷结构样式及对成藏的控制

通过对银根-额济纳裂谷盆地群各类典型凹陷结构样式的研究,指出研究区发育单断型和双断型凹陷,单断型可进一步划分为单断断阶式、单断断槽式和单断断超式,双断型主要为双断地堑式。通过对白垩系和中下侏罗统2套构造层关系的研究,指出单断型凹陷可划分为单断叠置型和单断迁移型2种。认为不同结构样式凹陷烃源岩的展布和保存条件不同,烃源岩的发育主要受沉积中心的次级“洼槽”控制;继承性发育的凹陷烃源岩条件最好,可与缓坡带多级断阶带的局部构造圈闭、缓坡带的超覆砂体形成良好配置;迁移型凹陷的烃源岩常遭受一定程度的剥蚀,中下侏罗统烃源岩与地层不整合圈闭可形成较好配置;单断型凹陷缓坡超覆带是形成地层油气藏的最有利带,缓坡多级断阶带是构造油气藏的最有利带。

中国二叠—三叠纪两大型弧后扩张盆地及其相关问题

金沙江-红河断裂带并非始于元古代,泥盆-石炭纪方开始出现,为板内大陆裂谷。断裂带南北段在二叠-三叠纪拉开,形成弧后海盆,同时在其两侧出现一系列裂谷带。南北段属于同一断裂带,晚第四纪时右旋平移,渐新世以前曾左旋平移。二叠-三叠纪两弧后扩张盆地的盆地层,即所说的印支地槽,主要造山运动发生在中晚始新世及其以后,印支期主要为造陆运动,褶皱作用较弱。中国古生代以来各陆块间缝合线,可相对地分为同源块体缝合线和异源块体缝合线。

新疆博格达中段木垒地区七角井组火山岩岩石地球化学特征及构造意义

博格达构造带木垒地区早石炭世七角井组内发育大量双峰式火山岩,火山岩的SiO 2含量在48%~65%之间出现明显的间断,具有Daly成分间断。其玄武岩具有贫K富Na、富Ti、富Al和Mg的特征,K 2O/TiO 2、K 2O/P 2O 5值高且变化范围较大,总体显示玄武质岩浆后期存在轻度地壳混染作用;英安岩具有贫K富Na、低Ti和P,和共生玄武岩的特征不同。玄武岩轻稀土中度富集,轻、重稀土元素之间存在中等分异;英安岩相对于玄武岩,稀土元素总量高于2~3倍,轻重稀土分异明显,显示为右倾且斜率较大的配分模式,具有较强的负Eu异常(δEu=0.89~0.93)。玄武质岩浆可能为亏损地幔的部分熔融作用形成,英安质岩浆可能为地壳物质重熔形成。综合分析认为博格达早石炭世处于弧后裂陷盆地环境。