羌塘盆地基底地层及大地构造性质

根据不同学者在盆地基底地层中所得出的锆石同位素测年数据进行统计分析,结合前人对羌塘地区大地构造方面的研究成果得出:羌塘盆地中央隆起带出露的变质岩基底可能经历过泛非时期构造热事件的作用,羌塘块体在演化过程中受到了南部冈瓦纳大陆的影响,这对于了解本地区的大地构造背景以及对古特提斯缝合带的研究有所帮助。     

东亚岛弧地形横剖面与板块运动

通过对东亚岛弧横剖面形态的系统分析，并结合弧前的构造应力的分析，作者认为，东亚岛弧形成于板块东移的构造环境中，横剖面形态存在两种基本类型即内缓外陡型和内陡外缓型，这两种不同的横剖面具有不同的弧前应力，前者表现弧前挤压，后者表现弧前引张，这反映地貌形态与构造应力之间的密切关系。     

A control-volume finite-element method for three-dimensional multiphase basin modeling

In this paper we describe a 3D control-volume finite-element method to solve numerically the coupled partial differential equations (PDEs) governing geological processes involved in the evolution of sedimentary basins. These processes include sediment deposition and deformation, hydrocarbon generation, multiphase fluid flow, and heat transfer in deforming porous media.     

Mantle plumes and the metamorphism of the lower crust and their influence on basin evolution

Since the stretching model appears to be not applicable to the subsidence of accretionary crust, basins located on this crust type may have an alternative origin. Examples of such basins are the West Siberia Basin and the North German Basin. Both basins showed intensive volcanism and magmatism during the initial phase of their development. Remarkably, the West Siberia Basin is closely located to the (hotspot related) Siberian flood basalts with a similar Permo-Triassic age, and the location of the North German Basin in Permian times is identical with the present day position of the Tibesti hotspot in Northern Africa. These two basins may have specific relations to hotspot heat sources of the Earth's underlying mantle. Due to these heat sources, thermal metamorphism within the lower layers of the (accretionary) crust may occur, resulting in rock density increase and subsequent shrinkage of the affected rock volumes. These shrinkage processes will lead to the development of topographic lows, their filling with sediments, and the subsequent start of an exponentially declining isostatic/metamorphic basin subsidence. In addition to the analyses of metamorphic processes, potential field anomalies, temperature fields, and histories of subsidence have been integrated into one single model that can explain the development of the North German Basin. Similarly, the East African Rift and Eifel Hotspots affected parts of the overriding continental plates. The East African Rift Hotspot can be traced back to the Afar flood basalts and the Dniepr–Donets Basin, whereas the Eifel Hotspot can be linked to the North Sea Basin. Continental drift templates, present day hotspot locations, flood basalt areas, metamorphic facies as function of temperature, and crust categories are taken as published in recent literature.     

北部湾盆地涠西南凹陷C洼烃源岩热史及成熟史模拟

北部湾盆地涠西南凹陷C洼流沙港组烃源岩热史及成熟史研究,对C洼深水油气勘探具有指导意义。在恢复涠西南凹陷C洼地史和热史的基础上,利用EASY%Ro模型计算了流沙港组烃源岩的成熟度史。研究结果表明,在涠西南凹陷发展的裂陷阶段初始期热流值较高,最大值约为77mW/m2,其后热流值逐渐减小,现今热流值约为54mW/m2;涠西南凹陷C洼流沙港组烃源岩开始生烃(Ro=0.5%)时间为51MaBP,达到生烃高峰(Ro=1%)时间为42MaBP,达到高成熟演化阶段(Ro=1.3%)时间为17MaBP;对比涠1井流沙港组烃源岩演化特征,处于C洼深水勘探区的流沙港组烃源岩成熟度较高,生烃能力较强,拥有广阔的油气勘探前景。     

Tectonic evolution of the Cape and Karoo basins of South Africa

The Cape and Karoo basins formed within the continental interior of Gondwana. Subsidence resulted from the vertical motion of rigid basement blocks and intervening crustal faults. Each basin episode records a three-stage evolution consisting of crustal uplift, fault-controlled subsidence, and long periods of regional subsidence largely unaccompanied by faulting or erosional truncation. The large-scale episodes of subsidence were probably the result of lithospheric deflection due to subduction-driven mantle flow. The early Paleozoic Cape basin records the combined effects of a north-dipping intra-crustal décollement (a late Neoproterozoic suture) and a right-stepping offset between thick Rio de la Plata craton and Namaqua basement. Following the Saldanian orogeny, a suite of small rift basins and their post-rift drape formed at this releasing stepover. Great thicknesses of quartz sandstone (Ordovician–Silurian) and mudstone (Devonian) accumulation are attributed to subsidence by rheological weakening and mantle flow. In contrast, the Karoo basin is a cratonic cover that mimics the underlying basement blocks. The Permian Ecca and lower Beaufort groups were deposited in a southward-deepening ramp syncline by extensional decoupling on the intra-crustal décollement. Reflection seismic and deep-burial diagenetic studies indicate that the Cape orogeny started in the Early Triassic. Deformation was partitioned into basement-involved strike-slip faults and thin-skinned thrusting. Uplift of the Namaqua basement resulted in erosion of the Beaufort cover. East of the Cape fold belt, contemporaneous subsidence and tilting of the Natal basement created a late Karoo transtensional foreland basin, the Stormberg depocentre. Early Jurassic tectonic resetting and continental flood basalts terminated the Karoo basin.     

Molecular and isotopic compositions of bitumens in Silurian tar sands from the Tarim Basin,NW China: Characterizing biodegradation and hydrocarbon charging in an old composite basin

Biodegradation and oil mixing in Silurian sandstone reservoirs of the Tarim Basin, one of the largest composite basins in China, were investigated by analyzing the molecular characteristics and stable carbon isotopic signatures of low-molecular-weight (LMW) saturated hydrocarbons and high-molecular-weight (HMW) asphaltenes. Detection of 25-norhopanes and 17-nortricyclic terpanes in most Silurian tar sands from the Tabei Uplift in the Tarim Basin suggests a much greater degree of biodegradation here than in the Tazhong Uplift. This explains the relatively more abundant tricyclic terpanes, gammacerane, pregnane and diasteranes in tar sands from the Tabei Uplift than in those from the Tazhong Uplift. Hence, care must be taken when assigning oil source correlations using biomarkers in tar sands because of the biodegradation and mixing of oils derived from multiple sources in such an old composite basin. Asphaltenes in the tar sands seem to be part of the oil charge before biodegradation, depending on the relative anti-biodegradation characteristics of asphaltenes, the similarity in carbon isotopic signatures for asphaltenes and their pyrolysates, and the consistent product distribution for flash pyrolysis and for regular steranes in asphaltene pyrolysates, regardless of whether the tar sands were charged with fresh oil. According to the relative distributions of regular steranes and the relatively abundant 1,2,3,4-tetramethylbenzene significantly enriched in ¹³C, the oil sources for asphaltenes in the tar sands might be related to lower Paleozoic marine source rocks formed in euxinic conditions. Nevertheless, the relatively low abundance of gammacerane and C₂₈ regular steranes observed in asphaltene pyrolysates and residual hydrocarbons, within limited samples investigated in this work, made a direct correlation of oils originally charged into Silurian tar sands with those Cambrian source rocks, reported so far, seem not to be possible. Comparison of carbon isotopic signatures of n-alkanes in asphaltene pyrolysates with those of LMW saturated hydrocarbons is helpful in determining if the abundant n-alkanes in tar sands are derived from fresh oil charges after biodegradation. The limited carbon isotopic data for n-alkanes in LMW saturated hydrocarbons from the tar sands can be used to classify oils charged after biodegradation in the composite basin into four distinct groups.     

下扬子区下古生界油气有利勘探区带探讨

下扬子区下古生界具有良好的油气地质条件,具备形成大型油气藏的物质基础,但一直未获得油气勘探的突破。本文通过地质、地球物理综合解释,结合部分地质露头、钻井资料及上扬子勘探成果,重点对下扬子区下古生界构造地质特征与油气地质条件等开展了综合分析研究。从构造沉积充填角度将下扬子区分为4个二级构造单元,中部地区的无锡-黄山断隆带构造相对稳定,分析认为其西北部的无锡-黄桥低褶带为油气勘探的有利区带,具有形成下古生界弱改造型油气藏的勘探前景。     

构造-岩浆作用对热液活动的控制机理: 马努斯海盆为例

综述了马努斯海盆热液区构造特征、基底差异, 结合马努斯海盆热液区热液活动与构造-岩浆特征, 探讨了二者的耦合关系, 以及构造-岩浆作用对热液活动的影响和控制。马努斯海盆位于西南太平洋俾斯麦海的东北部, 是世界上扩张速度最快的海盆之一。马努斯海盆西部(马努斯扩张中心, Manus Spreading Center, MSC)主要由海盆扩张成熟期产生的大洋中脊玄武岩组成, 属于成熟弧后扩张中心,发育Vienna Woods热液区; 海盆东部(东南裂谷, Southeast Rift, SER)则是一个拉张裂谷, 处于扩张的早期阶段, 属于不成熟弧后扩张中心, 发育PACMANUS、DESMOS、SuSu Knolls三大热液区。MSC与大洋中脊的热液活动相似, 而SER因受到火山、俯冲作用影响更为显著, 其热液流体具有岩浆流体和俯冲流体的特征。与Vienna Woods热液压相比, PACMANUS、DESMOS以及SuSu Knolls三个热液区的水深相对较浅(1 150～1 740 m), 是地球内部热物质由内向外迁移的结果, 其下部岩浆作用强烈。此外,岩浆脱气作用和数值模拟结果表明, PACMANUS热液系统中具有岩浆流体的输入。与Vienna Woods热液区相比, PACMANUS、DESMOS、SuSu Knolls热液区的热液活动强度及流体组成主要受控于岩浆作用。