青海锡铁山铅锌矿构造控矿型式与特征

锡矿山铅锌矿受含矿岩系主褶皱和韧性剪切带的双重控制。矿体主要形成于主褶皱转折端厚层大理岩与含碳石英片岩间的构造虚脱及转折端附近。后期韧性剪切带内强弱不同的构造置换型式，是导致Ⅰ、Ⅱ、Ⅲ矿带矿体规模和形态差异的主要因素。因此，矿体最终规模和形态，不但取决于主褶皱的几何形态和空间展布形式，也取决于韧性切剪带对其叠加和改造的程度。     

中国新疆北天山的活动逆断裂褶皱带及其大地震的位置预测(英)

发育在北天山山麓的活动断裂褶皱带属于向前扩展的薄皮构造，且所有的背斜都是断裂扩展褶皱，主滑脱面距地表8～9km深。距今292万年以来，地壳缩短13．5～14．6km，缩短率是4.62～5．0mm／a。自30000年前至今，准噶尔南缘断裂和齐古道断裂褶皱带的活动十分微弱，而独山子和玛纳斯道断裂-褶皱带则是活动褶皱-断裂带。北天山地区普遍发育三级阶地,受活动逆断裂和褶皱的影响，均产生褶曲变形和错断。距今12000～13000年以来，吐谷鲁逆断裂-背斜的垂直滑动速率、抬升速率、缩短速率分别是0．83～0．91、3.46～3.75和1.23～1．33mm／a。1906年的玛纳斯地震发生在一条盲断坡上，但是其同震破裂和褶皱隆升却出现在玛纳斯逆断裂-褶皱带上，震中距玛纳斯逆断裂-褶皱带约40km。揭示出北天山挤压拗陷区的孕震构造是一个由深部盲断坡-滑脱断层-浅层断坡构成的复杂构造系统。通过上述活动构造和古地震研究的结果可以推测，天山北麓未来发生大震（M≥7．0）的位置可能是在呼图壁河至金沟河段和金沟河至奎屯河段的齐古道断裂-褶皱带上，其震级相当于1906年玛纳斯地震。乌鲁木齐挤压坳陷中的活动逆断裂褶皱带上只有发生M≤6．0地震的可能性。     

阜平猴石顶太古界褶皱的岩石磁性组构

猴石顶太古界重褶皱位于阜平太古宙穹状复合褶皱群中一个钩状褶皱的“钩子”部位。其中一层斜长角闪岩标志层的岩石磁性组构的分布情况为:1.在翼部的磁化率量值椭球是压扁形的,磁性叶理面的方向与变质层面及片麻理的方向基本一致,表现为向北西倾斜的倒转褶皱;2.在太古宙再次变形阶段所形成的转折端部位,磁性叶理面的走向变化较大,并出现拉长形的磁化率量值椭球,反映了经受过拉张作用的变形和多于一次的不同方向应力的作用;3.西翼的磁性线理值与磁性叶理值以及磁化率各向异性度都大,反映它经受过较强的剪切应力与压应力的作用;4.磁性线理主要倾向北半球,而且部分磁性线理近南北方向分布。 推测猴石顶重褶皱可能处于向北倾伏的主体构造的东侧。 上述岩石磁性是由自行设计的静态测量方法,用国产的数字式无定向磁力仪测定的。     

四川盆地的地震地质特征

四川盆地是我国具有代表性的中新生代沉积盆地,喜马拉雅运动使之发生褶皱变形。野外观察和深部探测资料表明,褶皱及与之相伴的断裂通常在3～5千米的深度上消失,为典型的浅层构造。上下层位构造形态的不协调现象是沿软弱层位发生滑脱作用的结果。盆地内的地震活动性比四川西部活动构造区明显减弱,仅有的几个中强地震震例表明,它们具有震源浅、震级低,烈度高且震中位置与背斜构造关系密切的特点。本文旨在通过盆地内盖层滑动及其与盖层沼皱、断裂的成因机制的讨论,探索导致盆地内地震活动特殊现象的原因。并预测盆地内未来地震的可能强度。     

Evolution of the Komiji Syncline in the North Fossa Magna, central Japan: Paleomagnetic and K–Ar age insights

Abstract We carried out paleomagnetic measurements and K–Ar dating on Neogene andesitic lavas and sills of the Shigarami Formation in North Fossa Magna, central Japan. The Shigarami Formation is distributed in the axial part of the Komiji Syncline in the folding zone of the southwestern North Fossa Magna. Results of the present study indicate that the Komiji Syncline was formed shortly after 4.42 ± 0.12 Ma during the Pliocene. The sedimentary rocks of the Shigarami Formation consist of shallow marine and fluvial deposits. Intrusions of andesitic sills are found in the shallow marine deposits and two andesitic lava flows are present in the fluvial deposits. Oriented samples were taken from the sills at four sites and from the lavas at three sites. The samples produced stable remanent magnetization through stepwise alternating field and thermal demagnetizations. Results of a positive fold test indicate that the stable remanent magnetizations concentrate around a mean reversed polarity of declination = 169.0°, inclination = ?58.5° and 95% confidence limit = 9.0° after corrections have been made according to the direction of the bedding of the sedimentary rocks. Four fresh samples were selected for K–Ar dating from the samples used for paleomagnetic measurements. The groundmass of three samples taken from the sills yield ages of 4.42 ± 0.12, 4.49 ± 0.22 and 4.69 ± 0.13 Ma, whereas the one taken from the lower lava has an age of 5.91 ± 0.26 Ma. We believe that the Komiji Syncline was formed after the emplacement of lavas and sills in the area, because the descending Miocene strata were folded concordantly with the Shigarami Formation. The Pliocene and Pleistocene strata rest unconformably on the folded strata. The deformation might have progressed during the Pliocene, then slowed down in the Early Pleistocene. Our results suggest that the northwestward motion of the Philippine Sea Plate and the collision of the Tanzawa Block affected not only the South Fossa Magna, but also the North Fossa Magna.     

1949年新疆库车7.4/级地震的地震构造条件

前人研究认为 ,库车 194 9年 7 级地震主要与天山南麓活动构造带的NEE向秋立塔格断裂有关。最近笔者根据深地震地壳测深、石油地质及活断裂等研究的新成果 ,对这次地震的构造条件进行了较深入的分析。塔里木陆块向天山俯冲 ,天山上地壳被挤压块断隆升并侧向推覆扩展 ,于天山南缘形成库车盆地及由秋立塔格等一系列逆断裂组成的逆断 -褶皱系 ,这是发育于沉积盖层的薄皮构造。NE向库车 -依西 1井断裂是库车盆地构造中重要的传递断裂 ,位于NE向的乌鲁木齐 -库车 -柯坪构造带中。有关 7 级地震的地震学研究结果与秋立塔格断裂完全不符 ,而与库车 -依西 1井断裂基本一致     

1949年新疆库车7.4/级地震的地震构造条件

前人研究认为 ,库车 194 9年 7 级地震主要与天山南麓活动构造带的NEE向秋立塔格断裂有关。最近笔者根据深地震地壳测深、石油地质及活断裂等研究的新成果 ,对这次地震的构造条件进行了较深入的分析。塔里木陆块向天山俯冲 ,天山上地壳被挤压块断隆升并侧向推覆扩展 ,于天山南缘形成库车盆地及由秋立塔格等一系列逆断裂组成的逆断 -褶皱系 ,这是发育于沉积盖层的薄皮构造。NE向库车 -依西 1井断裂是库车盆地构造中重要的传递断裂 ,位于NE向的乌鲁木齐 -库车 -柯坪构造带中。有关 7 级地震的地震学研究结果与秋立塔格断裂完全不符 ,而与库车 -依西 1井断裂基本一致     

Geometrical relationships between unconformities and subsequent folding: the Arro fold system (southern Pyrenees)Relations entre discordances et plissement dans le système de plis et chevauchements d'Arro (bassin de Graus-Tremp,Pyrénées)

The Arro system is an oblique fold system involving the Eocene sediments of the Graus-Tremp basin. It consists of westward-verging folds, trending NNW–SSE, some of them related with thrusts, in piggyback sequence. Seismic profiles allow to infer the geometry of structures at depth: folds and thrusts are ‘decolled’ over an unconformity between turbiditic and platform sediments. Re-activation of bedding surfaces by folding in the underlying units resulted in folding and thrusting in the upper series. To cite this article: A.M. Casas et al., C. R. Geoscience 334 (2002) 765–772.     

Tectonic analysis of progressive secondary deformation in the hinge of a major Caledonian fold nappe,north-western Ireland

Polyphase deformation chronologies established within the mid-crustal portions of orogenic belts have classically been attributed to regional-scale ‘events’ which generate distinct structural sequences that can be directly correlated across large tracts of the orogenic belt. However, concepts of progressive deformation in which minor structures may be continually generated, amplified and redeformed within a unifying kinematic framework suggest that regional correlation of minor structures is both misguided and misleading. Detailed structural analysis of lower amphibolite facies Dalradian metasediments in north-west Ireland does, however, demonstrate that a coherent and meaningful deformation chronology can be established within the framework of individual fold nappes. Protracted deformation has resulted in the generation of a series of overprinting, secondary structures (D₄–D₉), which are kinematically linked to the continued structural evolution and south-east directed translation of the crustal-scale (D₃) Ballybofey (fold) Nappe. Secondary (D₄) crenulation axes initiated at an oblique angle to the direction of nappe transport both rotate and amplify into larger scale folds, which are subparallel to transport and demonstrate successive stages of diachronous folding. Continued nappe-related deformation induces southwards verging contractional (D₅) folds, which are particularly well developed and focused into reactivated ductile (D₃) thrust zones generated during the initial stages of nappe translation. Subsequent to thickening-induced ductile extension and collapse of the nappe, a return to contractional tectonics is marked by major episodes of broad, open buckle folding developed orthogonal to both the overturned limb (D₇) and upper limb (D₈) of the nappe. Detailed structural analysis and investigation of secondary folds and overprinting fabrics provides a valuable insight into the protracted kinematic evolution of major fold nappes.