塔里木盆地西南部的三维密度扰动成像

塔里木盆地西南部位于昆仑造山带东北方,地壳构造特殊,是中国天然气勘探的重要区域。在地面重力调查的基础上,笔者等对2~15 km的盆地西南部的密度扰动结构进行成像计算,并结合电阻率三维结构对地壳构造进行分析。本文根据重力场小波变换的尺度—源深度转换律,进行地面重力异常场多尺度分解,取得了反映中国地壳不同埋藏深度的小波细节,揭示了研究区地壳的密度结构。结果表明,网度足够密的区域高精度重力场测量可以获得关于沉积盆地深部构造的丰富信息,应用小波多尺度分析和三维反演方法可以把与深层构造有关的地质信息提取出来,客观地为沉积盆地内部构造演化和油气勘探提供依据。塔里木盆地西南部上地壳三维密度扰动成像揭示了昆仑山脉向北仰冲推覆构造楔和山前坳陷带的立体结构,为盆山耦合动力学研究和深层油气勘探提供了新的认识。大地电磁数据三维反演取得的盆地三维电阻率模型,从电性结构角度得到了盆地的三维构造,和盆地西南部的密度结构有很好的相关性,支持了密度扰动成像的有关结论。

汶川地震的岩石圈深部结构与动力学背景

中国西部地区由于受到印度板块向北推移挤压,青藏高原强烈变形,高原内部及其边缘的活断层上经常发生强烈地震,是大陆内部最活跃的地震区。汶川8级地震就发生在青藏高原东缘的松潘-甘孜地块与扬子地块交界的龙门山主中央断裂带上。作者利用面波层析成像、跨龙门山的被动源地震观测、爆破地震剖面的结果对震源附近的岩石圈结构和动力学特征进行研究,发现松潘-甘孜地块与扬子地块的岩石圈结构与性质有重大差异。扬子地块岩石圈显示为高速、坚固和稳定特性,而松潘-甘孜地块为低速、软弱及易于破碎。在松潘-甘孜地块中,中地壳内普遍存在一个低速层,它是引起中上地壳推覆运动的滑脱层,龙门山的推覆构造就是上部地壳仰冲的结果。汶川地震震源深度为14 km,正好位于龙门山推覆体的映秀-北川主中央断裂带上。

黏土-砂交互地层沉井下沉阻力研究

为明确交互地层中沉井下沉阻力特征,以常泰长江大桥6号墩沉井基础为背景,基于实测数据对黏土-砂交互式地层中大型沉井下沉过程中的刃脚踏面反力、侧壁压力及侧摩阻力的大小与分布规律进行研究。结果表明:沉井下沉阻力集中在外圈井壁,外圈井壁刃脚踏面反力与踏面埋置深度的相关性较高,且受沉井自重的影响显著,因下部粉质黏土层与粉砂、细砂层的极限承载力相当,随沉井底口由砂土层进入粉质黏土层,外圈井壁刃脚踏面反力均值并无显著变化;在第2次浇筑井壁混凝土阶段,沉井底面位于粉砂、细砂层与下部粉质黏土层分界面,随着沉井自重增大,砂土层内的刃脚踏面反力显著增加,粉质黏土层内的刃脚踏面反力因受土层的超孔隙水压力消散的影响反而有所减小;刃脚踏面由砂层进入粉质黏土层后,位于砂土层内的沉井侧壁压力及下沉侧摩阻力显著增大。

火焰山逆掩带成图方法探讨

火焰山构造带作为吐哈盆地近期勘探的主要区带,由于火焰山带地表条件恶劣、地震资料品质较差,且火焰山逆冲断层上盘山体的速度大、变化快,在时间剖面上造成下盘的假构造、假断层和构造高点偏移的现象,长期制约着该区的勘探进程。本文根据火焰山掩伏带的特点,针对性的开展变速成图方法攻关,利用地震正演模型分析的方法,分析和计算下盘构造是否落实和构造高点的偏移情况,寻找到一条适合火焰山下盘变速成图的方法,准确的落实了胜金口下盘的火焰山背斜构造圈闭,并通过火3井的钻探证实了背斜圈闭落实可靠。因此,该成图方法为揭开火焰山掩覆带构造内幕提供了一种相对有效的方法。

小水井金多金属矿集区构造变形及成矿作用

小水井金多金属矿集区 ,处于哀牢山造山带锋带或后陆 (盆 )缘地带 ,集中分布在哀牢山主造山期后残留的石羊江复式背斜变形区域。在该区多年矿产勘查与开发工作后 ,发现石羊江复式背斜实为一个由边缘或基底主干断裂控制、并在后期的变形变质过程中形成的冲起构造 ,原东翼发育的断裂属一组与边缘主干断裂倾向相反、上盘上升的前展式叠瓦状反冲断裂系 ,总体构成陆缘背冲型叠瓦状逆冲推覆构造格架。该构造系统在垂向上、水平方向上均控制了区内成矿元素或含矿热液的矿化范围、强度与规模 ,多层次成矿系统或成矿条件的耦合 ,即构成了以冲起构造为轴心的离散型陆缘构造———成矿系统。运用上述成矿模式在该区内实践 ,先后发现十余处以金矿为主的矿床 (点 ) ,取得找矿重大突破 ,亦为在类似区域找矿提供了新的思路和方向。

New ideas on the tectonic of the Kurveleshi anticlinal belt in Albania, and the perspective for exploration in its subthrust

The external thrustbelt of Albania consists of some tectonic zones(Ionian,Kruja and Krasta-Cukali zones),that are westward overthrust,with a large amplitude(50e100 km),above the Apulian platform and South Adriatic Basin.The relative movement of the Adriatico-Apulian sub-plate between,the Euro Asiatic and African plates during from the Mesozoic to the Tertiary period,mainly controlled the tectonic evolution of the Albanides.The Ionian zone consists of anticline belts(Berati,Kurveleshi and Cika),that are overthrust toward the west with an amplitude about 20e30 km Their overthrustings was realized through regional sliding evaporitic horizons,which caused the masking of folded structures in the subthrust,with the perspective plays.The Kurveleshi anticlinal belt represents a mega-anticlinal with a length of 210 km and a width of about 20 km,and it is characterized by anticline structures with heterogeneous dimensions,predominantly those of great dimensions and linear type.The overthrusting of the anticline units has a local character,and it is more developed in the Kurveleshi anticlinal belt.Its magnitude is about 8e10 km.As a result of these overthrusts,imbrication and duplex styles are formed,leadind to the masking of the subthrust complex with structures of large interest(e.g.Delvina,Karbunara,etc.)where two oil fields have been dioscovered beneath the Mali Gjere anticline(Delvina oil field)and the Kremenara anticline(Karbunara oil field).Backthrust faults phenomena are secondary and they taken place in the post-collision stage.Generally they are easterward thrust faults of structural units with an amplitude of 5e10 km.The Kurveleshi anticlinal belt,based on tectonic features,is divided into two parts:The southern part,from Qafa Sevaster in the north down to Greece to the south.and northern part,from Qafa Sevaster in the south up to the end of the Patos-Verbas structure.In the southern part these features predominate:The anticline structures are large in size,and overthrust with a large amplitude(8e10 km)westward.The evaporitic diapirs have erupted through local faults of the anticline structures of the Kurveleshi anticlinal belt(Mali Gjere,Kurveleshi and Fterra anticlines).These eruptions(Delvina,Picar-Kapariel-Bashaj,etc.)have helped in the overthrusting of these structural units.It must be mentioned that the backthrusting is also affected by the diapir action.Moreover,vertical diapir occur,in the center of the structures like Navarica.In the northern part,the anticline structures are generally small to medium in size.Only the Patos-Verbas anticline is larger in size.In the Kurveleshi anticlinal belt the Ballsh and Visoka oilfields have developed.The eastern flank of the Shushica synclinal belt apears folded,and the carbonate anticline structures have developed.Existing oil fields include the Gorisht-Kocul,Cakran-Moallaj-Kreshpan and Amonica.These oil fields shoud continue towards the north(under the overthrust of the Patos-Verbas antcline)and in the south(under the regional ovethrust of the Kuervelesh anticlinal belt).