廊固凹陷近岸水下扇特征及控制因素   总被引：2，自引：0，他引：2  

宋荣彩  张哨楠  董树义  周文 《地球科学与环境学报》2007,29(2):145-148,157

通过对廊固凹陷18口井541 m岩心的系统观察、156口井测井序列的建立、1km×1 km三维地震测网密度的地震相识别,分析了该沉积体系的相带展布特征。该砂砾岩层总体趋势为向上厚度减薄、层数减少,共识别出5期扇体,多呈条带状沿大兴断层断面分布,每期之间发育稳定的暗色泥岩段。该近岸水下扇的形成受3级层序、大兴断层、古构造、古气候、古地形以及物源供给等多种因素的控制。3级层序的发育特点、大兴断层的分段活动以及特殊的物源供给背景因素的匹配对近岸水下扇形成起到决定性作用。2~3期扇体扇中分布范围广,储集条件好,是凹陷下一步开发工作的有利目标。  相似文献   

Metal-residence sites in lavas and tuffs from Volcán Popocatépetl, Mexico: implications for metal mobility in the environment     

A. C. L. Larocque  James A. Stimac  Claus Siebe 《Environmental Geology》1998,33(2-3):197-208

 Volcan Popocatépetl is a Quaternary stratovolcano located 60 km southeast of Mexico City. The summit crater is the site of recent ash eruptions, excess degassing, and dacite dome growth. The modern cone comprises mainly pyroclastic flow deposits, airfall tephras, debris flows, and reworked deposits of andesitic composition; it is flanked by more mafic monogenetic vents. In least-degassed fallout tuffs and mafic scoria, transition metals are concentrated in phases formed before eruption, during eruption, and after eruption. Preeruptive minerals occur in both lavas and tephra, and include oxides and sulfides in glass and phenocrysts. The magmatic oxides consist of magnetite, ilmenite, and chromite; the sulfides consist of both (Fe,Ni)_1-xS (MSS) and Cu–Fe sulfide (ISS). Syn- and posteruptive phases occur in vesicles in both lavas and tephra, and on surfaces of ash and along fractures. The mineral assemblages in lavas include Cu–Fe sulfide and Fe–Ti oxide in vesicles, and Fe sulfide and Cu–Fe sulfide in segregation vesicles. Assemblages in vesicles in scoria include Fe–Ti oxide and rare Fe–Cu–Sn sulfide. Vesicle fillings of Fe–Ti oxide, Ni-rich chromite, Fe sulfide, Cu sulfide, and barite are common to two pumice samples. The most coarse-grained of the vesicle fillings are Cu–Fe sulfide and Cu sulfide, which are as large as 50 μ in diameter. The youngest Plinian pumice also contains Zn(Fe) sulfide, as well as rare Ag–Cu sulfide, Ag–Fe sulfide, Ag bromide, Ag chloride, and Au–Cu telluride. The assemblage is similar to those typically observed in high-sulfidation epithermal mineralization. The fine-grained nature and abundance of syn- and/or posteruptive phases in porous rocks makes metals susceptible to mobilization by percolating fluids. The abundance of metal compounds in vesicles indicates that volatile exsolution prior to and/or during eruption played an important role in releasing metals to the atmosphere. Received: March 1997 · Accepted: 27 May 1997  相似文献   

甘肃疏勒河冲积扇发育特征及其对构造活动的响应   总被引：7，自引：2，他引：5  

王萍  卢演俦  丁国瑜  陈杰 《第四纪研究》2004,24(1):74-81

甘肃疏勒河冲积扇是面积达2400km²的一个巨型冲积扇,位于青藏高原北缘阿尔金断裂带东端。区域构造上该扇发育在阿尔金主断裂、三危山断裂和南截山断裂组成的阿尔金断裂带左旋走滑构造域。根据野外调查获得的沉积层序、地貌形态和构造变形等资料,该冲积扇可划分为老冲积扇和新冲积扇。老冲积扇扇顶紧靠阿尔金主断裂,由已显著构造变形的早更新统玉门砾岩组成;新冲积扇是在老冲积扇基础上发育的,扇顶已向下游移动到大坝附近,距阿尔金主断裂4km,主要由中更新统酒泉砾石和晚更新统戈壁砾石组成。疏勒河冲积扇发育对区域构造活动的响应主要表现为:1)在第四纪早期,阿尔金断裂的左旋走滑兼逆冲运动,导致了由玉门砾岩组成的疏勒河老冲积扇扇头被左旋错动约8km,同时扇体,尤其扇头明显褶皱隆升,扇顶向山外移动;2)此后随着阿尔金断裂继续作左旋走滑兼逆冲运动,老冲积扇扇头又被左旋错动了约2km,总共左旋位移了约10km,并且扇顶下移了约4km,形成新的冲积扇;3)在冲积扇内从早更新世至晚更新世沉积中心不断向下游移动,呈现向下游超覆沉积的特征,这也一定程度上反映了祁连山隆升、向外扩展和侵蚀作用显著  相似文献   

共反射元弧叠加方法在火山岩成像中的应用   总被引：14，自引：5，他引：9       下载免费PDF全文

裴江云  刘洪  李幼铭  朱振宇 《地球物理学报》2004,47(1):106-111

常规叠加方法假设叠加的地震道集的反射波来自地下同一个反射点,而地表观测到 的反射波场在空间上小于菲涅尔体范围是不可分辨的. 本文根据火山岩体特征,用元弧描述 火山岩的反射界面. 将来自菲涅尔体范围内的反射波沿着元弧界面求和,进而扩大叠加次数 ,达到增加反射信号能量提高地震反射波的叠加成像质量的目的. 文中给出了反射波走时参 数与地下元弧反射界面之间的联系和叠加实现的步骤. 计算结果表明,元弧叠加方法能够提 高剖面的信噪比,增加反射波同相轴的连续性.  相似文献   

胶北地块与金成矿有关的郭家岭岩体和上庄岩体年代学及地球化学研究   总被引：4，自引：0，他引：4  

罗贤冬  杨晓勇  段留安  孙卫东 《地质学报》2014,88(10):1874-1888

胶东半岛是我国最主要的原生金矿矿集区,金矿的主要控矿围岩是郭家岭花岗岩,通过研究郭家岭花岗岩的地球化学特征对研究金矿的成因和物质来源具有指示性意义。本文研究的两个花岗岩岩体为上庄岩体和郭家岭岩体,两岩体同属郭家岭型花岗岩。通过对两岩体的花岗岩样进行岩相学矿相学观察、全岩主、微量元素和U-Pb同位素分析,获得胶东半岛中生代岩浆岩的成因机制与源区性质及自然金的产出形式等科学信息。LAICP MS锆石U-Pb年龄得出郭家岭岩体年龄125.4±2.2 Ma,上庄岩体U-Pb年龄128.8±2.0 Ma,都为中生代早白垩世,两岩体年龄相差3Ma,在年龄误差范围来看可以把两岩体作为同一期岩体,也在年龄角度证实两岩体都同属郭家岭花岗岩。两岩体的锆石组成都含有太古宙和晚侏罗纪的继承锆石,指示两岩体的成岩物质来源具相似性,都包含太古宙岩石成分和晚侏罗世花岗岩成分。两岩体具有相似的稀土元素和微量元素分配模式,表现出明显的LREE富集和HREE极度亏损,没有明显的铕负异常。郭家岭岩体和上庄岩体花岗岩都具有类似埃达克岩的特征,都具有高的Sr含量(913×10-6~1325×10-6),低的Y含量(2.2×10-6~8.4×10-6)和Yb含量(0.21×10-6~0.68×10-6),较高的(Dy/Yb)N比值1.62~2.28,暗示花岗岩岩浆形成时石榴石是一个重要的残留相,而没有斜长石作为残留相。两岩体具有较低的MgO、Cr、Ni含量和Mg#,反映郭家岭型花岗岩岩浆的形成可能是岛弧环境榴辉岩相压力条件下洋壳玄武质岩石的部分熔融。  相似文献   

Extensional deformation structures within a convergent orogen: The Val di Lima low-angle normal fault system (Northern Apennines,Italy)     

《Journal of Structural Geology》2014

A low-angle extensional fault system affecting the non metamorphic rocks of the carbonate dominated Tuscan succession is exposed in the Lima valley (Northern Apennines, Italy). This fault system affects the right-side-up limb of a kilometric-scale recumbent isoclinal anticline and is, in turn, affected by superimposed folding and late-tectonic high-angle extensional faulting.The architecture of the low-angle fault system has been investigated through detailed structural mapping and damage zone characterization. Pressure-depth conditions and paleofluid evolution of the fault system have been studied through microstructural, mineralogical, petrographic, fluid inclusion and stable isotope analyses. Our results show that the low-angle fault system was active during exhumation of the Tuscan succession at about 180°C and 5 km depth, with the involvement of low-salinity fluids. Within this temperature - depth framework, the fault zone architecture shows important differences related to the different lithologies involved in the fault system and to the role played by the fluids during deformation. In places, footwall overpressuring influenced active deformation mechanisms and favored shear strain localization.Our observations indicate that extensional structures affected the central sector of the Northern Apennines thrust wedge during the orogenic contractional history, modifying the fluid circulation through the upper crust and influencing its mechanical behavior.  相似文献   

Influence of carbonate facies on fault zone architecture     

《Journal of Structural Geology》2014

Normal faults on Malta were studied to analyse fault propagation and evolution in different carbonate facies. Deformation of carbonate facies is controlled by strength, particle size and pore structure. Different deformation styles influence the damage characteristics surrounding faults, and therefore the fault zone architecture. The carbonates were divided into grain- and micrite-dominated carbonate lithofacies. Stronger grain-dominated carbonates show localised deformation, whereas weaker micrite-dominated carbonates show distributed deformation. The weaker micrite-dominated carbonates overlie stronger grain-dominated carbonates, creating a mechanical stratigraphy. A different architecture of damage, the ‘Fracture Splay Zone’ (FSZ), is produced within micrite-dominated carbonates due to this mechanical stratigraphy. Strain accumulates at the point of juxtaposition between the stronger grain-dominated carbonates in the footwall block and the weaker micrite-dominated carbonates in the hanging wall block. New slip surfaces nucleate and grow from these points, developing an asymmetric fault damage zone segment. The development of more slip surfaces within a single fault zone forms a zone of intense deformation, bound between two slip surfaces within the micrite-dominated carbonate lithofacies (i.e., the FSZ). Rather than localisation onto a single slip surface, allowing formation of a continuous fault core, the deformation will be dispersed along several slip surfaces. The dispersed deformation can create a highly permeable zone, rather than a baffle/seal, in the micrite-dominated carbonate lithofacies. The formation of a Fracture Splay Zone will therefore affect the sealing potential of the fault zone. The FSZ, by contrast, is not observed in the majority of the grain-dominated carbonates.  相似文献   

直流电弧原子发射光谱法测定钛和钛合金中微量杂质元素          下载免费PDF全文

王辉  马晓敏  郑伟  王宽 《岩矿测试》2014,33(4):506-511

高纯度的钛及钛合金具有良好的可塑性,当有杂质存在时变得脆而硬而影响其性能,准确分析杂质元素的含量有利于对钛生产工艺进行质量控制。对于杂质元素的分析,现行国家标准方法是采用样品蒸发温度较高的直流电弧作为光源,摄谱仪测定,需要经过显影、定影、测量黑度等步骤,操作繁琐,流程长,测量误差较大。本文应用中阶梯光栅和电荷耦合器件(CCD)组成的直流电弧(DC Arc)原子发射光谱仪(波长范围200~800nm),谱线干扰分析和谱线强度测量可以同时进行,能更大限度地获取光谱信息,建立了快速测定钛及钛合金中10种微量杂质元素(锰锡铬镍铝钼钒铜锆钇)的分析方法。实验讨论了测定过程中的四类谱线干扰,包括钛作为基体元素的谱线干扰、钛合金中添加的化学成分元素干扰、铁谱线的干扰、杂质元素之间的干扰,确定了适当的分析线;并应用一种浅孔薄壁细颈杯形电极装入试样,提高了样品的蒸发效果;用氯化银和碳粉的混合物作缓冲剂,提高了待测元素的谱线强度。本方法的检测范围为0.001%~0.06%,精密度小于15%,回收率为90.0%~110.0%,适合于大批量钛及钛合金样品中杂质元素的同时检测。  相似文献   

断层输导作用与油气充注作用关系分析   总被引：2，自引：0，他引：2       下载免费PDF全文

刘震  张旺  曹尚  刘明洁  张威  董冬 《地质科学》2014,49(4):1302-1313

断层是控制油气藏形成的重要因素之一;断层的开启及闭合影响到油气运移与聚集的效率。但油气在断层中的运移与在砂层中的充注存在差异性这一问题长期被忽视。一般认为;只要发育断层;其断开的渗透层就会被油气充注;极少关注地层水和石油的压缩特性对充注的影响。本文提出;地下单断层活动时;深部油气在超压作用下以涌流方式难以快速充注进入中浅层被切割的砂体;因此;单砂体至少要存在一条断层作为泄水出口;石油才能通过其余断层充注进入砂体;即单砂体要发育两条及两条以上断层;石油才能注入砂体。在断层静止期;油气通过渗流方式沿特定深度范围断面垂向运移;对油气垂向运移距离影响较小。本文运用4个大型盆地的典型油气藏与断层分布关系讨论了本文观点。该观点对油气成藏规律研究及成藏目标评价有较重要参考意义。  相似文献   

Tectonomagmatic origin of Precambrian rocks of Mexico and Argentina inferred from multi-dimensional discriminant-function based discrimination diagrams     

《Journal of South American Earth Sciences》2014

Several new multi-dimensional tectonomagmatic discrimination diagrams employing log-ratio variables of chemical elements and probability based procedure have been developed during the last 10 years for basic-ultrabasic, intermediate and acid igneous rocks. There are numerous studies on extensive evaluations of these newly developed diagrams which have indicated their successful application to know the original tectonic setting of younger and older as well as sea-water and hydrothermally altered volcanic rocks. In the present study, these diagrams were applied to Precambrian rocks of Mexico (southern and north-eastern) and Argentina. The study indicated the original tectonic setting of Precambrian rocks from the Oaxaca Complex of southern Mexico as follows: (1) dominant rift (within-plate) setting for rocks of 1117–988 Ma age; (2) dominant rift and less-dominant arc setting for rocks of 1157–1130 Ma age; and (3) a combined tectonic setting of collision and rift for Etla Granitoid Pluton (917 Ma age). The diagrams have indicated the original tectonic setting of the Precambrian rocks from the north-eastern Mexico as: (1) a dominant arc tectonic setting for the rocks of 988 Ma age; and (2) an arc and collision setting for the rocks of 1200–1157 Ma age. Similarly, the diagrams have indicated the dominant original tectonic setting for the Precambrian rocks from Argentina as: (1) with-in plate (continental rift-ocean island) and continental rift (CR) setting for the rocks of 800 Ma and 845 Ma age, respectively; and (2) an arc setting for the rocks of 1174–1169 Ma and of 1212–1188 Ma age. The inferred tectonic setting for these Precambrian rocks are, in general, in accordance to the tectonic setting reported in the literature, though there are some inconsistence inference of tectonic settings by some of the diagrams. The present study confirms the importance of these newly developed discriminant-function based diagrams in inferring the original tectonic setting of Precambrian rocks.  相似文献