渤海南部新生代构造发育与演化特征

利用三维地震资料及钻井资料,在对断裂体系精细刻画的基础上,结合区域地球动力学背景,就渤海湾盆地渤海海域南部地区(包括渤南低凸起、黄河口凹陷、莱北低凸起、莱州湾凹陷)新生代的构造发育演化特征及沉积–沉降中心迁移规律进行了详细分析。研究结果表明:断裂体系存在三组优势发育方向,NNE向断裂属郯庐断裂带渤南段,可分为西、中、东三个分支带,走滑特征明显;近EW向及NE向为伸展性质的控凹、控带断裂;三组断裂相互切割,形成了渤海南部地区"东西分带、南北分块"的构造格局;古近纪具有两个沉积–沉降中心,黄河口凹陷中心受控于近EW向断裂,莱州湾凹陷的沉积中心受近EW向和NNE向断裂共同控制,至新近纪,沉积中心呈由南向北迁移的规律;渤海南部地区构造演化体现了断–拗与走滑的叠加效应,可以划分为孔店组–沙四段沉积期的初始裂陷、沙三段沉积期的伸展裂陷、沙二段–东营组沉积期的走滑–伸展和馆陶组沉积期以来的走滑–裂后拗陷四个阶段。     

黑龙江铜山断裂的变形特征及铜山铜矿床蚀变带-矿体重建

黑龙江铜山铜矿床系多宝山铜矿田的重要组成部分,它和多宝山矿床同是中亚造山带东段最古老的斑岩铜矿床(奥陶纪)。铜山断裂为铜山斑岩铜矿床内最为重要的一条成矿后断裂,它截切矿体和蚀变带,因而导致矿化中心、深部找矿方向不明。现阶段的研究对其运动学特征还存有较大争议,缺乏对该带变形特征与性质的细致观察与鉴别。据此,本文开展详细地野外及室内研究工作,取得如下新认识:1)铜山断裂为近东西走向的压扭性断裂,最典型的构造几何学特征为发育北东-北东东走向劈理、构造透镜体、以及岩脉及热液脉扭曲现象。2)断裂带内石英、黄铜矿、黄铁矿、闪锌矿的镜下变形特征和石英C轴组构特征显示低温变形条件,依据矿物和岩石变形特点判断铜山断裂主体为脆性断裂。3)构造解析表明铜山断裂运动学特征为:上盘由南东向北西方向斜向逆冲。综合断裂上、下盘地质体界线、蚀变和脉系分布特征等,判断上盘相对下盘大致沿NW320°方向水平移动距离700~800m,垂向抬升550~700m,错开蚀变外带(青磐岩化带、石英-绢云母-伊利石-绿泥石化带)和矿化带。4)铜山断裂的次级断裂截切了中晚三叠世白云母花岗岩,推测铜山断裂活动时限晚于中晚三叠世。5)复原铜山断裂上盘和下盘的空间位置至铜山断层活动前,重建铜山铜矿床蚀变带-矿化体,初步判断铜山断裂活动前铜山矿床为纺锤形态。根据重建后矿化和蚀变的分布规律推断下盘Ⅲ号矿体的南侧位置应有尚未发现的成矿斑岩和矿体,为深部找矿提供了依据。     

西准噶尔达拉布特断裂带中段晚古生代构造分析

走滑断裂构造在中亚造山带增生及演化过程的研究中扮演了重要角色,其主要构造单元均被走滑断裂带所分割。西准噶尔造山带是中亚增生型造山带的重要组成部分,达拉布特断裂是西准噶尔造山带中一条重要的走滑断裂,其复杂的构造表现吸引了大量研究者的关注。前人不仅在其构造解释上存在着走滑断层、逆冲断层或压扭性断层等诸多争议,且在其活动时代问题上也有不同的看法。本文依据在达拉布特断裂带中段开展的详细野外构造学工作,结合前人针对该地区石炭纪火山岩、浊积岩和造山后花岗岩侵入体所做的同位素年代学工作成果,对达拉布特断裂的活动性质和活动时代进行了讨论。结果确认在中二叠统沉积之前,达拉布特断裂带存在两期变形事件,分别对应于320Ma左右沿NE-SW的较深层次的左行走滑事件D1和表现为脆-韧性转换域的轴面倾向SE的褶皱作用构造事件D2。前者为主期变形事件,而后者发生在中二叠统沉积之前。本文同时报道了沿达拉布特断裂带出露右行走滑构造形迹,并讨论了其可能的成因。沿达拉布特断裂带的多期构造事件记录了西准噶尔地区造山后大规模走滑构造调整过程,是晚古生代晚期中亚各个陆块拼合后大规模陆内调整在西准噶尔造山带的具体体现。     

西藏台错沉积记录与更新世晚期—全新世气候变化

西藏西部台错湖T1阶地的两个剖面沉积中,除下部10余厘米含碳化植物和50-70 cm处为暗色碳酸盐粘土及粘土外,中、上部全系粘土碳酸盐层,含丰富的介形类和轮藻类。据碳酸盐、介形类、轮藻类的碳、氧稳定同位素值与微体古生物群落生态特征等提供的环境气候变化指标,指示该区距今41.4~4.5 ka BP间气候变化为：在41.4~26.2 ka BP气候较湿润;26.2~25.5 ka BP偏暖稍干;25.5~22.5 ka BP气候暖湿;22.5~21.0 ka BP气候偏冷湿;20.5~17.5 ka BP气候骤冷、偏湿,反映本区处于末次冰期盛冰期;17.5~16.0 ka BP偏冷偏干;16.0~11.8 ka BP气候偏暖湿,为全球间歇性暖事件的响应;11.8~10.4 ka BP气候较冷干,大致相当于新仙女木期,10.4 ka BP气温开始回升;10.4~9.4 ka BP气候偏暖湿;9.4~8.5 ka BP气候呈现短暂暖湿颤动;8.5~7.9 ka BP气候偏干冷,为冰后期强烈降温偏干事件;7.8~6.3 ka BP气候偏暖湿;6.3~4.5 ka BP气候趋向冷干,4.5 ka BP记录到晚更新世晚期以来最大的干燥期。     

Late Panafrican evolution of the main Hoggar fault zones: Implications of magnetic fabric study in the In Telloukh pluton (Tin Serririne basin, Algeria)

The Late Panafrican evolution of the Hoggar shield is characterized by emplacement of magmatic intrusions and by occurrence of major shear zones separating different terranes. In Telloukh granite is close to the In Guezzam faults (western border of the Tin Serririne basin). Analysis of its visible and magnetic fabrics suggests an emplacement mode and deformation that are not related to the In Guezzam faults, but most likely to a N–S compression, an event not yet identified. Dioritic dykes crosscutting the granite have a very different magnetic fabric, which is related on the contrary to dextral strike-slip movements along the In Guezzam faults. In both cases, no visible fabric can be correlated with the magnetic fabric, which has been likely acquired during late magmatic stages. This magnetic fabric was not significantly affected by the tectonic events that took place after entire crystallization of the magma. The In Guezzam faults and the major 7°30 and 4°50 shear zones are close to intrusions such as In Telloukh dykes and the Alous En Tides and Tesnou plutons where quite similar magnetic fabrics are observed, all related with dextral strike-slip movements along these structures.     

西藏许如错地区洁居纳卓组碎屑锆石U-Pb年龄及其地质意义

在西藏许如错地区新识别出的洁居纳卓组为一套固结—半固结的粗碎屑岩建造。为探讨该地层的沉积时代和沉积物源,对1个砂岩样品进行了碎屑锆石U-Pb年代学分析。获得了4组有效年龄:10.1~17.2Ma、41.7~72.2 Ma、77.9~87.8Ma、463~1610Ma。结合岩石组合特征、ESR测试结果和区域年龄资料,认为洁居纳卓组可能形成于上新世。物源分析结果显示,许如错以南的查孜及附近地区的林子宗群、布嘎寺组火山岩是洁居纳卓组沉积物质的主要来源,古新世—中新世的侵入岩和晚古生代地层也为其提供了少量的沉积物质。洁居纳卓组发育于许如错南北向地堑盆地之内,是上新世高原隆升在冈底斯地区的沉积响应,是青藏高原局部构造差异隆升的结果。     

断陷盆地岩性油气藏快速勘探的实用地质-地震相结合配套技术

陆相断陷盆地岩性圈闭目标的快速识别和优选,需要先进地质理论指导与地震技术应用两方面的有机结合。本文通过对塔南凹陷岩性油气藏快速勘探过程中使用的地质理论和地震技术进行总结,建立了一套复杂断陷盆地岩性油气藏快速探明储量规模的实用地质—地震配套技术系列。在岩性油气藏勘探程度不断加深的过程中,综合采用构造分析、层序分析、相带分析和成藏分析等地质分析方法进行指导,配合使用精细构造解释、地震多属性分析、井—震约束下的拟声波波阻抗反演等地震技术,实现岩性圈闭的“定背景、定层系、定区带和定目标”,有效地解决了塔南凹陷岩性油藏勘探中遇到的地质难题,在较短的时间内实现了岩性油藏勘探的突破和基本探明。这一技术系列对同类断陷盆地岩性油气藏的勘探具有重要的借鉴和指导意义。     

因子分析在藏北商旭金矿床地球化学勘查中的应用

西藏双湖县商旭金矿床位于班公湖—怒江成矿带中部,矿体受NWW向断裂构造控制,呈脉状、透镜状产出,赋矿围岩为木噶岗日群炭质板岩及变质砂岩,矿石矿物为自然金,矿石类型主要为石英脉型与绢英岩型,为一典型的造山型金矿床。在对矿床地质特征、成矿条件分析的基础上,利用矿区岩屑地球化学数据,运用因子分析等多元统计方法,研究矿区地球化学元素组合,共划分出Cu-Pb-Zn元素组合分区、Au-Ag元素组合分区、As-Sb元素组合分区以及W-Mo-Bi元素组合分区等4个地球化学分区,绘制了因子得分等值线图,并在此基础上探讨找矿方向。结合矿区地质特征认为,Au、Ag元素组合和As、Sb组合为商旭金矿床的最佳地球化学标志元素,下一步地质工作重点应放在Ⅱ_1号、Ⅲ_1号矿体深部及周围,同时可布置适当的工程在Ⅲ号矿段西部A预测区,以追索Ⅲ_1系列矿体向西的延伸。     

Transformation,partitioning and flow–deposit interactions during the run‐out of megaflows

Four megabeds (I to IV) were recognized throughout the Cerro Bola inlier, a glacially influenced depositional area of the Carboniferous Paganzo Basin, south‐western La Rioja Province, Argentina. Such anomalous thick beds are associated with the collapse of an unstable basin margin after periods of large meltwater discharge and sediment accumulation. Failure of these previously deposited sediments triggered mass flows and associated turbidity currents into the basin. Megabed I is up to 188 m thick and was deposited during a transgressive stage by re‐sedimentation of ice‐rafted debris. Also part of the transgressive stage, Megabeds II, III and IV are up to 9 m thick and are associated with a dropstone‐free period of flooding. Megabeds were subdivided into three divisions (1 to 3) that represent a spectrum of flow properties and rheologies, indicative of a wide range of grain support mechanisms. These divisions are proposed as an idealized deposit that may or may not be completely present; the Cerro Bola megabeds thus display bipartite or tripartite organization, each division inferred to reflect a rheologically distinct phase of flow. Division 1 is a basal layer that consists of clast‐supported and matrix‐supported, pebble conglomerate, rarely followed by weak normally graded to ungraded, very coarse‐ to coarse‐grained sandstone. This lower interval is interpreted to be the deposit of a concentrated density flow and is absent in bipartite megabeds. Division 2 is represented by a mud‐rich sandstone matrix with dispersed granule to pebble‐size crystalline and mudstone clasts. It also includes fragments of sandstone up to boulder size, as well as rafts of cohesive muddy material and wood fragments. Division 2 is interpreted to be a result of debris‐flow deposition. A debrite‐related topography, resulting from the freezing of high yield strength material, captures and partially confines the succeeding upper division 3, which fills the topographic lows and pinches out against topographic highs. Division 3 is rich in mudstone chips and consists of very coarse‐grained, dirty sandstones grading upward to siltstones and mudstones. It is interpreted to be a deposit of a co‐genetic turbidity current. Spectral gamma ray and petrographic analyses indicate that both debrite and co‐genetic turbidite have high depositional mud content and are of similar composition. One of the megabeds is correlated with an initial slump‐derived debris flow, which suggests that the mass flow becomes partitioned both at the top, generating a co‐genetic turbidity current and, at the base, segregating into a concentrated density flow that seems to behave as a gravelly traction carpet.     

云南小湾断层泥矿物特征及其构造意义

通过显微镜观察、X射线衍射、红外光谱和化学分析等方法研究云南小湾断层泥中伊利石矿物特征,结果显示:(1)断层泥中的伊利石发育定向排列,其集合体呈扭折褶皱变形,有时呈流状构造充填在碎屑之间;(2)伊利石的X射线衍射特征为△[(002)-(001)]>8°,Ir>1,BB₁<4°,属ISII有序混层,膨胀层约占15%,晶胞参数b₀=8.993Å,1M多型结构;(3)层间阳离子2Ca+Na+K≈1,MgO含量变化1.05%-2.89%,结晶水(H₂O⁺)含量变化4.43%-5.23%。综合上述特征认为,断层泥伊利石不同于其它成因的伊利石,它是断层活动的直接产物,因此,根据它的特征可以推测断层活动机制。