塔里木盆地满加尔凹陷西缘奥陶系柯坪塔格组下段海相砂岩准层序成因与意义

通过精细岩芯描述、单井沉积微相分析与地震相、测井相综合研究,认为在塔里木盆地满加尔凹陷西缘奥陶系柯坪塔格组下段顶部含油气砂体中,发育3种类型的准层序：①粒级由底部粗—中下部细—上部粗的、反映整体向上变浅的海侵滞留沉积—海泛泥岩—滨岸沉积准层序,羊屋2井5460~5468 m含油气段位于该准层序内;②粒级向上变粗的滨外泥岩—临滨－前滨沉积,顶部受风暴影响的准层序,跃南2井6503~6512 m含油气段位于该准层序内;③粒级向上变细的潮下带—潮间带沉积的准层序,吉南1井5465~5486 m含油气段属于此准层序。发育于羊屋2井中的第一种准层序内含油气砂体在时间上属于较早的准层序3,发育于跃南2井、哈得13井中的第二种准层序与吉南1井中的第三种准层序内的含油气砂体属于稍晚的准层序4。早期沉积的、发育于羊屋2井顶部的第一种准层序是有利储层发育段,该井区以北靠近柯坪塔格组下段顶面尖灭线附近的准层序3时期沉积的临滨相储层是油气聚集成藏的有利部位。     

Ordovician eclogites from the Chinese Beishan: implications for the tectonic evolution of the southern Altaids

Numerous lenses of eclogite occur in a belt of augen orthogneisses in the Gubaoquan area in the southern Beishan orogen, an eastern extension of the Tianshan orogen. With detailed petrological data and phase relations, modelled in the system NCFMASHTO with thermocalc , a quantitative P–T path was estimated and defined a clockwise P–T path that showed a near isothermal decompression from eclogite facies (>15.5 kbar, 700–800 °C, omphacite + garnet) to high‐pressure granulite facies (12–14 kbar, 700–750 °C, clinopyroxene + sodic plagioclase symplectitic intergrowths around omphacite), low‐pressure granulite facies (8–9.5 kbar, ～700 °C, orthopyroxene + clinopyroxene + plagioclase symplectites and coronas surrounding garnet) and amphibolite facies (5–7 kbar, 600–700 °C, hornblende + plagioclase symplectites). The major and trace elements and Sm–Nd isotopic data suggest that most of the Beishan eclogite samples had a protolith of oceanic crust with geochemical characteristics of an enriched or normal mid‐ocean ridge basalt. The U–Pb dating of the Beishan eclogites indicates an Ordovician age of c. 467 Ma for the eclogite facies metamorphism. An ³⁹Ar/⁴⁰Ar age of c. 430 Ma for biotite from the augen gneiss corresponds to the time of retrograde metamorphism. The combined data from geological setting, bulk composition, clockwise P–T path and geochronology support a model in which the Beishan eclogites started as oceanic crust in the Palaeoasian Ocean, which was subducted to eclogite depths in the Ordovician and exhumed in the Silurian. The eclogite‐bearing gneiss belt marks the position of a high‐pressure Ordovician suture zone, and the calculated clockwise P–T path defines the progression from subduction to exhumation.     

青藏高原新生代火山作用与构造演化

青藏高原的新生代火山作用是印度-亚洲大陆碰撞的火山响应,它显示了系统的时、空变化。随着印度-亚洲大陆碰撞从~65 Ma的接触-碰撞(即"软碰撞")转变到~45 Ma的全面碰撞(即"硬碰撞"),火山作用也逐渐从钠质+钾质变为钾质-超钾质+埃达克质。65~40 Ma的钾质和钠质熔岩主要分布于藏南的拉萨地块,少量分布于藏中的羌塘地块。从45~26 Ma,在藏中的羌塘地块中广泛发育钾质-超钾质熔岩和少量埃达克岩。随后的碰撞后火山作用向南迁移,在拉萨地块中产生~26~10 Ma间的同时代超钾质和埃达克质熔岩。尔后,从~18 Ma始,钾质和少量埃达克质火山作用重新向北,在西羌塘和松潘-甘孜地块中呈广泛和半连续状分布。此种时-空变异对形成青藏高原的深部地球动力学过程提供了重要约束。该过程包括:已消减的新特提斯大洋板片的回转、断离及随后增厚拉萨岩石圈根的去根作用,及因此而造成的印度岩石圈向北下插。青藏高原的隆升是自南向北穿时发生的。高原南部被创建于渐新世晚期,并保持至今;直到中新世中期,由于下插印度岩石圈的持续向北推挤,西羌塘和松潘-甘孜岩石圈的下部开始塌陷和拆离,高原北部才达到其现今的高度和规模。     

Caledonian high-pressure metamorphism in the Strona-Ceneri Zone (Southern Alps of southern Switzerland and northern Italy)

The Strona-Ceneri Zone comprises a succession of polymetamorphic, pre-Alpidic basement rocks including ortho- and paragneisses, metasedimentary schists, amphibolites, and eclogites. The rock pile represents a Late Proterozoic or Palaeozoic subduction accretion complex that was intruded by Ordovician granitoids. Eclogites, which occur as lenses within the ortho-paragneiss succession and as xenoliths within the granitoids record a subduction related high-pressure event (D1) with peak metamorphic conditions of 710 ± 30 °C at 21.0 ± 2.5 kbar. After isothermal uplift, the eclogites experienced a Barrowtype (D2) tectonometamorphic overprint under amphibolite facies conditions (570-630 °C, 7-9 kbar). U-Pb dating on zircon of the eclogites gives a metamorphic age of 457 ± 5 Ma, and syn-eclogite facies rutile gives a ²⁰⁶Pb/²³⁸U age of 443 ± 19 Ma classifying the subduction as a Caledonian event. These data show that the main tectonometamorphic evolution of the Strona-Ceneri Zone most probably took place in a convergent margin scenario, in which accretion, eclogitization of MOR-basalt, polyphase (D1 and D2) deformation, anatexis and magmatism all occurred during the Ordovician. Caledonian high-pressure metamorphism, subsequent magmatism and Barrow-type metamorphism are believed to be related to subduction and collision within the northern margin of Gondwana. Editorial handling: Edwin Gnos     

塔河油田四区奥陶系古岩溶流域的倒淌河及其成因研究

在现代岩溶区,由于构造运动、岩性差异以及地貌起伏等因素,常常出现水系袭夺现象,并随之伴生一系列反常的水文地貌现象,如分水岭迁移和破坏、袭夺肘、风峡、断头河和倒淌河等。基于三维地震资料,应用层拉平技术、精细相干分析技术及相关地震成图技术,对塔河油田四区中—下奥陶统顶部海西早期的岩溶古地貌和古水系进行了恢复识别,发现也存在类似的反常水文地貌现象。借鉴现代水系袭夺理论,证实了塔河油田四区东部岩溶流域早期为南向汇流结构,而后期由于构造运动引起西北部侵蚀基准面下降,并通过地下途径对邻近南向流域北缘进行逐步袭夺,形成了大型倒淌河,再现了本区岩溶古水系及流域的阶段性演化过程,从而为揭示塔河油田奥陶系古岩溶发育规律提供了重要的依据。     

鄂尔多斯盆地石炭纪中央古隆起形成机制

将鄂尔多斯盆地简化为受南北挤压的等厚各向同性弹性薄板模型进行应力—应变场数值模拟,力图揭示鄂尔多斯地区石炭纪出现的细腰状中央古隆起的形成机制。模拟中Z轴方向应变(εz)正值区对应于盆地内部的隆起区,zε正等值线形态对应于隆起形态;单轴挤压条件下,εz正等值线总会呈现沿应力轴方向延伸的细腰状形态;点作用力产生的zε正等值线范围局限,而线作用力产生的εz正值区分布较广。模拟结果表明鄂尔多斯盆地石炭纪细腰状隆起是在南北边界受挤压条件下,应力—应变在盆地内部传递过程中所必然出现的结果,南北向点作用力比南北向线作用力产生的zε等值线形态更接近于鄂尔多斯盆地中央古隆起形态;点作用力可能代表了石炭纪微板块间的点碰撞或者弧—陆碰撞。     

鄂尔多斯地区奥陶系马家沟群中部块状白云岩的深埋藏白云石化机制

鄂尔多斯地区奥陶系马家沟群中部发育一套厚层块状白云岩。在西部地区定边至鄂托克旗一带,这套块状白云岩连续厚度达数百米。定探l井揭示的最大厚度为431 m。自西向东,白云岩体由厚变薄,并与石灰岩呈指状交织。这套块状白云岩由粗粉晶－细晶白云石组成,斑状结构发育。常见云斑的边界为缝合线,这表明斑状白云石化明显受缝合线控制。 白云岩有序度平均值为摩尔含量平均为50.65 g／mol。δ13C的平均值为0.6‰(PDB),的平均值为-7.4‰(PDB)。主体细晶白云石中液态包体常见,最低均－温度为104℃,包体成分中含有大量的有机成分和无机成分 上述特征表明,这套白云岩是由深埋藏白云岩化作用形成的,它显示出良好的储集性能,是重要的后备储集岩。     

大别山榴辉岩一片麻岩杂岩的成因

大别山榴辉岩由辉长岩、大陆拉斑玄武岩和少量泥灰质经高压变质作用形成。大别地块可划分出四个形成条件不同的榴辉岩区,它们代表一种构造－岩石组合体。片麻岩杂岩中各种高压变质岩类的发现证明它们与榴辉岩一起经历了原地高压变质过程。二者变质作用Ｐ－Ｔ参数的差异归因于抬升过程中退变质反应速度的不同。不同地区榴辉岩退变质组合及Ｐ－Ｔ条件与围岩的一致性表明,大别杂岩现今所展示的“递增”变质带是由榴辉岩相退变质作用形成的。高压榴辉岩－片麻岩杂岩的产生是印支期扬子与华北两个大陆板块碰撞的结果。     

秦岭祁连山昆仑山构造发展史与南北中国板块的拼合

按秦岭祁连山昆仑山发展演化，中国大陆的形成可总结为3阶段板块拼贴“焊合”模型即：中元古代至新元古代早期，原始秦昆洋俯冲—消减，塔里木—华北古陆（北中国板块）与华南洋域新生陆壳（南中国板块）拼贴增生，形成原始中国古陆；震旦纪至志留纪，原始中国古陆裂解，秦祁海洋扩张—俯冲—消减，阿拉善—华北板块（北中国板块）与塔里木、柴达木、华南组成的联合板块（南中国板块）缝合统一，形成古中国板块，泥盆纪至三叠纪早期，古特提斯洋俯冲—消减，藏滇板块（基梅里大陆一部分）与古中国板块碰撞拼贴，滨邻古特提斯洋的中国大陆西南缘（秦祁昆地区）全面皱起，造就中国大陆轮廓；中生代以来，板内超长期继承性汇聚和滨西太平洋边缘构造带、新特提斯—喜马拉雅构造叠加、改造，造就现令中国大陆构造、地势。     

安徽长江沿岸地区红花园组生物地层特征

安徽沿长江地区．下奥陶统红花园组发育良好．产大化石Ｃａｌａｔｈｉｕｍ－Ｍａｎｃｈｕｒｏｃｅｒａｓ－Ｃｏｒｅａｎｏｃｅｒａｓ组合及牙形石Ｓｅｒｒａｔｏｇｎａｔｈｕｓ带等。其时代相当皖南下奥陶世宁国阶早期Ｎ１至Ｎ２笔石带；其生物地层特征与扬子地层区基本一致。据此．本文揭示宁国阶早期扬子海与华北海可能是相通的。