水下分流河道砂体的叠置样式及其储层非均质性变化特征

在研究区目的层进行高分辨率层序地层研究的基础上,对分流河道微相的储层质量非均质性进行分析,应用不同级次基准面旋回成因的沉积学分析和表征储层质量非均质性的各项岩芯化验、统计学数据定量分析,指出基准面旋回因素对不同级次水下分流河道主体储层质量非均质性影响存在差异:单一水下分流河道和单期复合水下分流河道的储层质量非均质性呈正韵律变化,多期复合水下分流河道储层质量非均质性分布呈不规则趋势,多级次的基准面旋回及其伴随的可容纳空间变化所引起的沉积环境的变化影响水下分流河道储层非均质性.     

Evaporites,brines and base metals: Low‐temperature ore emplacement controlled by evaporite diagenesis

Salt beds and salt allochthons are transient features in most sedimentary basins, which through their dissolution can carry, focus and fix base metals. The mineralisation can be subsalt, intrasalt or suprasalt, and the salt body or its breccia can be bedded or halokinetic. In all these evaporite‐associated low‐temperature diagenetic ore deposits there are four common factors that can be used to recognise suitably prepared ground for mineralisation: (i) a dissolving evaporite bed acts either as a supplier of chloride‐rich basinal brines capable of leaching metals, or as a supplier of sulfur and organics that can fix metals; (ii) where the dissolving bed is acting as a supplier of chloride‐rich brines, there is a suitable nearby source of metals that can be leached by these basinal brines (redbeds, thick shales, volcaniclastics, basalts); (iii) there is a stable redox interface where these metalliferous chloride‐rich waters mix with anoxic waters within a pore‐fluid environment that is rich in organics and sulfate/sulfide/H₂S; and (iv) there is a salt‐induced focusing mechanism that allows for a stable, long‐term maintenance of the redox front, e.g. the underbelly of the salt bed or allochthon (subsalt deposits), dissolution or halokinetically maintained fault activity in the overburden (suprasalt deposits), or a stratabound intrabed evaporite dissolution front (intrasalt deposits). The diagenetic evaporite ‐ base‐metal association includes world‐class Cu deposits, such as the Kupferschiefer‐style Lubin deposits of Poland and the large accumulations in the Dzhezkazgan region of Kazakhstan. The Lubin deposits are subsalt and occur where long‐term dissolution of salt, in conjunction with upwelling metalliferous basin brines, created a stable redox front, now indicated by the facies of the Rote Faule. The Dzhezkazgan deposits (as well as smaller scale Lisbon Valley style deposits) are suprasalt halokinetic features and formed where a dissolving halite‐dominated salt dome maintained a structural focus to a regional redox interface. Halokinesis and dissolution of the salt bed also drove the subsalt circulation system whereby metalliferous saline brines convectively leached underlying sediments. In both scenarios, the resulting redox‐precipitated sulfides are zoned and arranged in the order Cu, Pb, Zn as one moves away from the zone of salt‐solution supplied brines. This redox zonation can be used as a regional pointer to both mineralisation and, more academically, to the position of a former salt bed. In the fault‐fed suprasalt accumulations the feeder faults were typically created and maintained by the jiggling of brittle overburden blocks atop a moving and dissolving salt unit. A similar mechanism localises many of the caprock replacement haloes seen in the diapiric provinces of the Gulf of Mexico and Northern Africa. Evaporite‐associated Pb–Zn deposits, like Cu deposits, are focused by brine flows associated with both bedded and halokinetic salt units or their residues. Stratabound deposits, such as Gays River and Cadjebut, have formed immediately adjacent to or within the bedded salt body, with the bedded sulfate acting as a sulfur source. In allochthon/diapir deposits the Pb–Zn mineralisation can occur both within a caprock or adjacent to the salt structure as replacements of peridiapiric organic‐rich pyritic sediments. In the latter case the conditions of bottom anoxia that allowed the preservation of pyrite were created by the presence of brine springs and seeps fed from the dissolution of nearby salt sheets and diapirs. The deposits in the peridiapiric group tend to be widespread, but individual deposits tend to be relatively small and many are subeconomic. However, their occurrence indicates an active metal‐cycling mechanism in the basin. Given the right association of salt allochthon, tectonics, source substrate and brine ponding, the system can form much less common but world‐class deposits where base‐metal sulfides replaced pyritic laminites at burial depths ranging from centimetres to kilometres. This set of diagenetic brine‐focusing mechanisms are active today beneath the floor of the Atlantis II Deep and are thought to have their ancient counterparts in some Proterozoic sedex deposits. The position of the allochthon, its lateral continuity, and the type of sediment it overlies controls the size of the accumulation and whether it is Cu or Pb–Zn dominated.     

Tectono-sedimentary evolution of the Upper Prealpine nappe (Switzerland and France): nappe formation by Late Cretaceous-Paleogene accretion

Abstract

The Upper Prealpine nappe of the Swiss and French Prealps consists of a composite stack of various tectonic slivers (Gets, Simme, Dranse and Sarine sub-nappes, from top to bottom). The structural superposition and stratigraphic content of the individual sub-nappes suggests a successive stacking at the South Penninic/Adriatic transition zone during the Late Cretaceous and Early Paleogene. The present paper deals with two aspects. (1) new data obtained from the Complexe de base Series of the Dranse sub-nappe which underlies the Helminthoid Sandstone Formation, and (2) the development of a geodynamic accretionary model for the Upper Prealpine nappe stacking.

The Complexe de base Series reveals a succession of black shales at the base, grading upward into variegated red/green and red shales which were deposited in an abyssal plain environment starved of clastic input. It is overlain by the Helminthoid Sandstone Formation. The combined analysis of planktic and agglutinated benthic foraminifera and comparisons with other Tethyan series suggest an Albian to Campanian age of the Complexe de base succession. Tectonic transport of the abyssal plain segment into a trench environment allowed for the stratigraphic superposition by the Helminthoid sandstone sequence. The present findings combine well with the general scheme of the Upper Prealpine nappe stack and several single results on parts of the nappe stack. We take that opportunity to present a comprehensive model for the tectono-sedimentary evolution of the Upper Prealpine nappe.

We suggest that Late Jurassic-Early Cretaceous asymmetric (?) extension at the South Penninic-Adriatic margin created an extensional alloehthon. Later during the mid-Cretaceous, the start of convergence drove the obduction of oceanic crust on the northern margin of the extensional allochthon. The resulting ophiolitic/continental source supplied clasts to the trench basin in front (Manche turbidite series), and the backarc basin (Mocausa Formation) and abyssal plain (Perrières turbidite series) to the South. During Middle to Late Coniacian the main Adriatic margin was thrusted over the obductionrelated mixed belt and established an incipient accretionary prism containing the former trench, backarc and abyssal plain basin fill series. During this stage the Gueyraz (melange) Complex formed, which separates the trench series from the retroarc and abyssal plain formations. On top of the incipient accretionary prism a forearc basin developed hosting the Hundsrück Formation. The frontal abyssal plain formation (Complexe de base) still received few turbiditic intercalations. From Campanian time on, the forearc basin was bypassed and deposition of the Helminthoid Sandstone Formation occurred on the Complexe de base succession. During the Maastrichtian the abyssal plain and trench fill succession (Dranse nappe) was accreted to the incipient wedge, and in front of a newly active buttress, the Gurnigel trench basin was established. Another accretionary event during latest Paleocene/earliest Eocene added parts of that trench series to the base of the wedge (Sarine nappe). During the Late Eocene the accretionary wedge and remaining trench fill series (Gurnigel nappe) were thrusted en-bloc over the Middle Penninic limestone nappes and partly overtook the latter. Continued shortening of the resulting nappe pile and out-of-sequence thrusting accomplished the overriding of the Middle Penninic units over the former South Penninic Gurnigel trench series (inversion of palaeogeographic domains).     

系列地图批处理自动成图解决方案——以勘查地球化学系列图为例

勘查地球化学系列图是化探地质工作成果的主要载体之一,是探索资源与环境问题的重要资料。在分析勘查地球化学数据的特点、常用图型及批处理自动成图含义的基础上提出了"地图模板+变量"驱动的解决方案,地图模板图记录系列地图间的共性,图系变量库刻画了系列地图间的个性,两者有机结合保证了系列地图批处理自动成图的高效性。采用ArcGIS环境下ArcMap软件与ArcPy脚本开发相结合的方式,阐述了系列地图批处理自动成图的实施过程。     

Experimental validation of semi‐active resetable actuators in a ⅕th scale test structure

The seismic performance of a test structure fitted with semi‐active resetable devices is experimentally investigated. Shaking table tests are conducted on a ?th scale four‐storey building using 27 earthquake records at different intensity scalings. Different resetable device control laws result in unique hysteretic responses from the devices and thus the structure. This device adaptability enables manipulation or sculpting of the overall hysteresis response of the structure to address specific structural cases and types. The response metrics are presented as maximum 3rd floor acceleration and displacement, and the total base shear. The devices reduce all the response metrics compared with the uncontrolled case and a fail‐safe surrogate. Cumulative probability functions allow comparison between different control laws and additionally allow tradeoffs in design to be rapidly assessed. Ease of changing the control law in real‐time during an earthquake record further improves the adaptability of the system to obtain the optimum device response for the input motion and structural type. The findings are an important step to realizing full‐scale structural control with customized semi‐active hysteretic behaviour using these novel resetable device designs. Copyright © 2008 John Wiley & Sons, Ltd.     

Shake table study on an ordinary low‐rise building seismically isolated with SU‐FREIs (stable unbonded‐fiber reinforced elastomeric isolators)

This paper reports on the investigation of novel fiber reinforced elastomeric isolator (FREI) bearings, which do not have thick end plates, and are used in an unbonded application. Owing to the stable lateral load‐displacement response exhibited by the unbonded FREI bearings, the proposed bearings are referred to as stable unbonded (SU)‐FREIs. A shake table test program was conducted on a two‐story test‐structure having well‐defined elastic response characteristics. Compared with the results for the corresponding fixed base (FB) structure, the peak response values, distribution of lateral response throughout the height of the structure, and response time histories of the tested base isolated (BI) structure indicate that significantly improved response can be achieved. This study clearly indicates that SU‐FREI bearings can provide an effective seismic isolation system. Copyright © 2009 John Wiley & Sons, Ltd.     

Fluid evolution in base‐metal sulphide mineral deposits in the metamorphic basement rocks of southwest Scotland and Northern Ireland

The Dalradian and Ordovician–Silurian metamorphic basement rocks of southwest Scotland and Northern Ireland host a number of base‐metal sulphide‐bearing vein deposits associated with kilometre‐scale fracture systems. Fluid inclusion microthermometric analysis reveals two distinct fluid types are present at more than half of these deposits. The first is an H₂O–CO₂–salt fluid, which was probably derived from devolatilization reactions during Caledonian metamorphism. This stage of mineralization in Dalradian rocks was associated with base‐metal deposition and occurred at temperatures between 220 and 360°C and pressures of between 1.6 and 1.9 kbar. Caledonian mineralization in Ordovician–Silurian metamorphic rocks occurred at temperatures between 300 and 360°C and pressures between 0.6 and 1.9 kbar. A later, probably Carboniferous, stage of mineralization was associated with base‐metal sulphide deposition and involved a low to moderate temperature (T_h 70 to 240°C), low to moderate salinity (0 to 20 wt% NaCl eq.), H₂O–salt fluid. The presence of both fluids at many of the deposits shows that the fractures hosting the deposits acted as long‐term controls for fluid migration and the location of Caledonian metalliferous fluids as well as Carboniferous metalliferous fluids. Copyright © 2004 John Wiley & Sons, Ltd.     

Curie point depth from spectral analysis of aeromagnetic data from Cerro Prieto geothermal area,Baja California,México

Using aeromagnetic data acquired in the area from the Cerro Prieto geothermal field, we estimated the depth to the Curie point isotherm, interpreted as the base of the magnetic sources, following statistical spectral-based techniques. According to our results the Curie point isotherm is located at a depths ranging from 14 to 17 km. Our result is somewhat deeper than that obtained previously based only in 2-D and 3-D forward modeling of previous low-quality data. However, our results are supported by independent information comprising geothermal gradients, seismicity distribution in the crust, and gravity determined crustal thickness. Our results imply a high thermal gradient (ranging between 33 and 38 °C/km) and high heat flow (of about 100 mW/m²) for the study area. The thermal regime for the area is inferred to be similar to that from the Salton trough.     

地震前兆资料的快速应用

陕西省地震局研制的一套软件解决了地震前兆数字化和大华北资料共享后的大量数据在分析预报中的快速应用问题。内容有“九五”、“十五”、模拟和大华北资料的下载、处理、保存、计算、统计和制图等功能。采取了简化操作、成批处理、自动成图等方法,有效地提高了分析速度,与Mapsis互相兼容,取长补短,能在20分钟内完成地震趋势会商前的准备工作,在震情分析中发挥了良好的作用。     

PHC管桩和预制方桩受力性状试验对比分析

通过在同一场地的预应力高强混凝土管桩（PHC桩）和预制方桩中埋设钢筋应力计的静载对比试验,比较了两类桩的荷载-沉降曲线、桩身轴力分布情况、桩侧摩阻力和桩端摩阻力发挥性状的异同,研究了PHC管桩的荷载传递机制,发现其侧阻和端阻的发挥规律与预制方桩相同,但在PHC管桩和方桩侧表面积相近的条件下,在最大试验荷载作用时,两者的侧阻和端阻发挥程度不同,PHC管桩平均单位侧阻比预制方桩低8.1 %,而端阻比方桩高24 %以上。