西藏羌塘盆地白垩纪中期构造事件的磷灰石裂变径迹证据

拉萨与羌塘地块于白垩纪中期的碰撞造山对羌塘原型盆地的热体制和构造演化有着重要影响.运用磷灰石裂变径迹方法,对羌塘盆地隆鄂尼夏里组和托纳木雪山组砂岩分析表明,裂变径迹年龄集中在120～ 80Ma之间,表明在白垩纪中期,羌塘盆地普遍发生了一次构造抬升事件,该期构造事件的年龄与盆地内早白垩世的岩浆热事件、主要构造变形作用发生在晚白垩世以及雪山组和阿布山组角度不整合的时代(125～75Ma)较一致,是拉萨与羌塘地块碰撞造山事件的记录.热历史模拟表明,白垩纪中期构造事件对羌塘盆地南部和北部的热演化历史有着差异影响,羌塘盆地南部降温速率相对不大,抬升剥蚀厚度约1500m,而北部古地温迅速降温到近地表温度,抬升剥蚀厚度近4000m.这种差异抬升剥蚀可能与班公湖-怒江洋壳向南俯冲使得因拉萨地块构造负载而导致羌塘地块的挠曲有关.     

Advances in the study of the Crop Evapotranspiration in Changing Environment

Significant changes in the regional energy process, water recycling and the biological process have taken place due to the climate change and human activities, and the regional agriculture has been affected by these changes. It is therefore a key issue for the regional agricultural water resource management to accurately monitor and evaluate the change of crop evapotranspiration under a changing environment. The development of the evapotranspiration theory was first reviewed, and then, the driven mechanisms and the research progress of crop evapotranspiration were illustrated. The suitability of the current monitoring method and evaluation model of the evapotranspiration in the crop evapotranspiration research under climate change were analyzed. After that, the current studies of the agricultural water resources management of “ET-based” were reviewed, and finally, the research tendency of the crop evapotranspiration on the theory, methods and application management in the future were prospected.     

U–Pb and Ar–Ar geochronology of the Fujiawu porphyry Cu–Mo deposit,Dexing district,Southeast China: Implications for magmatism,hydrothermal alteration,and mineralization

The Fujiawu porphyry Cu–Mo deposit is one of several porphyry Cu–Mo deposits in the Dexing district, Jiangxi Province, Southeast China. New zircon SHRIMP U–Pb data yield a weighted mean ²⁰⁶Pb/²³⁸U age of 172.0 ± 2.1 and 168.5 ± 1.4 Ma from weakly altered granodiorite porphyry and quartz diorite porphyry, respectively. Two hydrothermal biotites from granodiorite porphyry give an Ar–Ar step-heating plateau age of 169.9 ± 1.8 and 168.7 ± 1.8 Ma. Hydrothermal apatite exsolved from altered biotite yields an isotope dilution thermal ionization mass spectrometry isochron age of 164.4 ± 0.9 Ma. The apatite age is similar to the ages obtained from hydrothermal rutile (165.0 ± 1.1 and 164.8 ± 1.6 Ma) and indicates that the magmatism and hydrothermal activity in the Fujiawu deposit occurred in the Middle Jurassic. Hydrothermal fluid circulation related to multiple stages of magma emplacement resulted in Cu–Mo mineralization in the Fujiawu porphyry deposit. The zircon SHRIMP U–Pb ages and the published molybdenite Re–Os age (170.9 ± 1.5 Ma) represent the timing of magma crystallization and Mo mineralization, whereas the rutile and apatite U–Pb ages reflect the timing of Cu mineralization following quartz diorite emplacement. The data suggest slow cooling after emplacement of the quartz diorite porphyry.     

中国海相油气田勘探实例之三渤海湾盆地任丘古潜山大油田的发现与勘探

任丘油田发现于1975年,是我国最大的海相碳酸盐岩潜山高产油田,1996年探明储量4×108t。油田为一古潜山复式油气聚集带,由蓟县系雾迷山组、奥陶系马家沟组和亮甲山组、寒武系府君山组三个古潜山油藏以及古潜山上覆的下第三系沙河街组油藏构成。古潜山油藏为缝洞孔十分发育的碳酸盐岩储集体,油源为上覆的下第三系沙河街组,具独特的“新生古储”的油藏地质特征。论述了油田的发现和勘探历程、古潜山油藏的成藏特征,以及寻找古潜山油田的启示。     

地史早期岩石中的铅锌演化--狼山-渣尔泰山中元古代铅锌成矿的物质基础

以中国内蒙古狼山一渣尔泰山中元古代SEDEX型铅．锌成矿带为例，研究了该区从太古代到中元古代地壳岩石的铅锌含量和变化关系以及与成矿的关系。研究发现，从早到晚，岩石SiO2和K2O含量升高，铅含量也与二者同步增加；FeO、MgO、CaO及Na20含量呈下降趋势，锌含量也同步降低。在太古代时，岩石的Zn／Pb比值一般〉8，中元古代时这一比值降低为2～4。矿石的Zn／Pb比值与基底岩石Zn／Pb比值具有很好的一致性。铅锌这种随时间的变化与中元古代铅的暴发性成矿及大规模铅锌共生矿床的形成是同步的，说明基底岩石中的铅和锌是该成矿带SEDEX矿床成矿的物质基础。     

沉积盆地下古生界碳酸盐岩地区热历史恢复方法探索

古温标是目前恢复沉积盆地热历史最常用方法之一,但在下古生界高过成熟碳酸盐岩由于没有合适的成熟度标定参数(古温标),对其经受的热历史和成烃史的恢复一直是困扰中国海相碳酸盐岩油气勘探的问题。目前常用的沥青反射率、牙形石色变指数、镜状体反射率等各类古温标,在用于早古生代碳酸盐岩地区的热历史恢复时都是借助于它们各自与镜质体反射率之间的关系,再利用现有的镜质体反射率模拟热历史方法来恢复热历史,因而存在不同的缺陷。重点介绍了利用有机质自由基浓度作为碳酸盐岩地区古温标的可能性。通过不同时间和温度下的热模拟得到的有机质自由基浓度数据,初步建立了三种类型有机质的自由基浓度(N)与时间-温度指数(TTI)的定量模型。这种有机质自由基浓度与TTI的关系式为碳酸盐岩地区古地温的恢复提供了新的方法。     

华北东部地区盆地叠合特征与古生界生烃史

华北东部地区下古生界沉积了海相碳酸盐岩潜在的烃源岩,上古生界发育良好的煤系气源岩。由于经历了多期次、不同规模盆地的多种样式的叠合,其间又经历多期次的抬升、剥蚀与改造,因此,不同地区的古生界烃源岩生烃史具有显著的差异。地层对比和上古生界RO特征指示研究区北部的济阳坳陷具有较厚的三叠系原始沉积,三叠纪盆地的叠合对古生界烃源岩生烃史具有重要影响。依据盆地叠合方式、上古生界热演化程度,将上古生界生烃史划分为三叠纪、侏罗纪-白垩纪、早第三纪以来等3个阶段,分别对应生烃史的早期、中期和晚期,早期浅埋、中期抬升、晚期深埋型地区的“二次生烃”潜力大,如济阳坳陷和东濮凹陷。上古生界盆地的均衡面式叠合使下古生界的热演化程度比上古生界至少高0.3%以上,因此,在三叠纪末下古生界基本达到生烃高峰,在一定程度上损耗了其原始有机质并降低其“二次生烃”潜力。     

沁水盆地地层剥蚀量研究

[摘 要]沁水盆地自晚三叠世以来不断抬升,遭受了多次剥蚀,但其累积剥蚀量一直悬而未决,对盆地模拟和资源评价产生了不良影响。本文在沁水盆地沉积-构造演化史、热演化史研究的基础上,根据野外露头和钻井资料,以镜质体反射率反演方法为主,辅以声波时差法和构造剖面法,较为准确地确定了沁水盆地中新生代以来的累积地层剥蚀量。研究表明,沁水盆地石炭-二叠系煤层在燕山运动时期遭受最高地温,其后回返抬升并伴有地温梯度下降。参照济阳坳陷连续沉积剖面建立了镜质体反射率与深度关系,经地温梯度校正后,计算出了沁水盆地石炭-二叠系最大埋深,从而得到其此后抬升过程中的累积剥蚀量,经与声波时差法、构造剖面法计算结果对比,三者计算结果较为符合。研究结果表明,晚三叠世以来沁水盆地累积地层剥蚀量在1400～3300m之间,其中盆地中部剥蚀量较少,一般小于2500m,盆地边缘剥蚀量较大,可达3000m以上。主要剥蚀时期为晚白垩世至新近纪,地层剥蚀量可达2000m以上;其次为晚三叠世至早侏罗世,地层剥蚀量一般小于1000m。     

The Glueckstadt Graben, a sedimentary record between the North and Baltic Sea in north Central Europe

The Glueckstadt Graben is one of the deepest post-Permian structures within the Central European Basin system and is located right at its “heart” at the transition from the North Sea to the Baltic Sea and from the Lower Saxony Basin to the Rynkoebing–Fyn High.The Mesozoic to recent evolution is investigated by use of selected seismic lines, seismic flattening and a 3D structural model. A major tectonic event in the latest Middle–Late Triassic (Keuper) was accompanied by strong salt tectonics within the Glueckstadt Graben. At that time, a rapid subsidence took place within the central part, which provides the “core” of the Glueckstadt Graben. The post-Triassic tectonic evolution of the area does not follow the typical scheme of thermal subsidence. In contrast, it seems that there is a slow progressive activation of salt movements triggered by the initial Triassic event. Starting with the Jurassic, the subsidence centre partitioned into two parts located adjacent to the Triassic “core.” In comparison with other areas of the Central European Basin system, the Glueckstadt Graben was not strongly affected by additional Jurassic and Cretaceous events. During the late Jurassic to Early Cretaceous, the area around the Glueckstadt Graben was affected by relative uplift with regional erosion of the elevated relief. However, subsidence was reactivated and accelerated during the Cenozoic when a strong subsidence centre developed in the North Sea. During Paleogene and Quaternary–Neogene, the two centres of sedimentation moved gradually towards the flanks of the basin.The data indeed point toward a control of post-Permian evolution by gradual withdrawal of salt triggered by the initial exhaustion along the Triassic subsidence centre. In this sense, the Glueckstadt Graben was formed at least partially as “basin scale rim syncline” during post-Permian times. The present day Hamburger, East and Westholstein Troughs are the actual final state of this long-term process which still may continue and may play a role in terms of young processes and, e.g., for coastal protection.