武汉市陆家街地面塌陷的形成机制

发生于武汉市陆家街的地面塌陷,是隐伏岩溶区的一种地质灾害,由于它与人类工程及社会经济活动有关,所以也是一种环境工程地质问题。用潜蚀机制解释这种现象较为合理,它是一个累进变形破坏过程。地面塌陷的发生与一定的地质、地貌条件密切相关。在搞清地面塌陷的形成机制、地质背景和发生条件的基础上,这种地质灾害是可以预测和防治的。     

Geochronology and magmatic evolution of the Huautla volcanic field: last stages of the extinct Sierra Madre del Sur igneous province of southern Mexico

The Huautla volcanic field (HVF), in the Sierra Madre del Sur (SMS), is part of an extensive record of Palaeogene magmatism reflecting subduction of the Farallon plate along the western edge of North America. Igneous activity resulting from Farallon subduction is also exposed to the north, in the Sierra Madre Occidental (SMO) and Mesa Central (MC) provinces. We present the results of a stratigraphic and K–Ar, Ar–Ar, and U–Pb geochronological study of the Huautla volcanic successions, in order to refine our knowledge on the petrologic and temporal evolution of the northern SMS and gain insights on magmatic–tectonic contrasts between the SMS and the SMO–MC provinces. The HVF is made up of lava flows and pyroclastic successions that overlie marine Cretaceous sequences and post-orogenic continental deposits of Palaeogene age. In the study area, the main Oligocene succession is pre-dated by the 36.7 million years its caldera west of the Sierra de Huautla. The HVF succession ranges in age from ～33.6 to 28.1 Ma and comprises a lower group of andesitic–dacitic lava flows, an intermediate sequence of ignimbrites and dacitic lavas, and an upper group of andesitic units. The silicic succession comprises a crystal-poor ignimbrite unit (i.e. the Maravillas ignimbrite; 31.4 ± 0.6, 32.0 ± 0.4 Ma; ～260 km³), overlain by a thick succession of dacitic lavas (i.e. the Agua Fría dacite; 30.5 ± 1.9, 31.0 ± 1.1 Ma). Integration of the new stratigraphic and geochronological data with prior information from other explosive centres of the north-central SMS allows us to constrain the temporal evolution of a silicic flare-up episode, indicating that it occurred between 37–32 Ma; it consisted of three major ignimbrite pulses at ～36.5, ～34.5, and ～33–32 Ma and probably resulted from a progressive, mantle flux-driven thermomechanical maturation of the continental crust, as suggested in the HVF by the transition from andesitic to voluminous siliceous volcanism. The information now available for the north-central sector of the SMS also allows recognition of differences between the temporal and spatial evolution of magmatism in this region, and of that documented in the southern SMO and MC provinces, suggesting that such contrasts are probably related to local differences in configuration of the subduction system. At ～28 Ma, the MC and southern SMO provinces experienced a trenchward migration of volcanism, associated with slab rollback; on the other hand, the broad, more stable distribution of Oligocene magmatism in the central and north oceanic plate was subducting at a low angle.     

广阔渠截潜引水工程浸没灾害研究

在搜集广阔渠截潜引水工程研究区地下水资源勘察和评价成果的基础上,经现场调研后,采用三维数值模拟对该区枯水期浸没灾害做了预测,并据此采用类比法对汛期浸没灾害做了初步评价,研究了不同季节和不同截渗墙长度的相应浸没范围大小和受灾对象,提出了减少浸没灾害和增大自流引水流量措施的建议,不仅对该工程截潜方案设计具有重要指导意义,而且对其他冲积平原区截潜工程方案设计也有一定的借鉴作用.     

渤海莱州湾夏季悬浮体的分布和运移(英文)

本文以1985年夏季中法SCO—PSU联合黄河口调查第二航次所取的渤海莱州湾水深大于10米区域的悬浮体资料,研究了莱州湾内悬浮体的分布和运移规律,并讨论了它们与诸如黄河径流、潮流、环流、风和浪等动力因素之间的关系。     

Modelling of hydrocyclone performance based on spray profile analysis

Spray profile measurements can be used to calculate the underflow rate, and consequently, be related to hydrocyclone performance. The flow geometry of the spray discharge is found to arise from velocity patterns at the outlet orifice. Through a videographic example of an industrial hydrocyclone, it is shown that underflow profiles are typically parabolic, a feature which is indicative of the velocity at which the fluid exits. The inclusion of gravity in this model clearly highlights deficiencies in currently used models. Moreover, an intimate knowledge of factors affecting the profiles of the underflow of a cyclone is essential for the correct interpretation of videographic images. Subsequently, image data are used to estimate outlet velocities, which give an excellent insight into various fluid mechanical phenomena that are not appreciated by analysing basic operational variables. The exit velocities are used to calculate underflow rates, which are related to mass recovery in the underflow.     

Studies on sedimentary events in Mariana Trough and characteristics of geomagnetic field change

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Geologic evolution of a Cretaceous tectonometamorphic unit in the Franciscan Complex,western California

ABSTRACT

The Franciscan Yolla Bolly terrane of the NE California Coast Ranges consists mainly of quartzose metagreywackes containing sparse high-pressure/low-temperature (HP/LT) neoblastic minerals, including ubiquitous lawsonite. Some Yolla Bolly rocks also contain one or more of the newly grown phases, pumpellyite, aragonite, glaucophane, and/or jadeitic pyroxene. These blueschist-facies metasandstones recrystallized under physical conditions of ~200–300°C and ~8 kbar at subduction-zone depths approaching 30 km. Petrologically similar Franciscan metaclastic-rich map units – Yolla Bolly terrane-like rocks, here designated the ‘YB’ unit – crop out in the central and southern California Coast Ranges. Recently published detrital zircon U?Pb SIMS and LA-ICPMS data for 19 ‘YB’ metagreywackes indicate maximum ages of formation as follows: ~110–115 Ma (8) in the NE California Coast Ranges; ~95–107 Ma (7) in the San Francisco Bay area + Diablo Range; and ~85–92 Ma (4) in the dextrally offset Nacimiento Block. These fault-bounded ‘YB’ strata do not constitute coeval parts of a single tectonostratigraphic unit. Instead the term tectonometamorphic is proposed for such time-transgressive map units. Based on the current and likely Cretaceous 30° angular divergence between NS-palaeomagnetic stripes of the Farallon oceanic plate and the NNW-trending California convergent margin, I infer that arrival at the arc margin and underflow of a relatively thick segment of oceanic crust and its largely clastic sedimentary blanket may have resulted in progressive southeastward migration of an accreted, subducted, then exhumed HP/LT metagreywacke section. During the ~30 million year interval, ~115–85 Ma, the locus of ‘YB’ accretion, underflow, and tectonic regurgitation evidently moved SE along an ~1000 km stretch of the accretionary margin of western California.     

无资料地区小流域设计径流若干技术问题

从研究小流域水文特性及其影响因素入手,提出了在同一气候区内,应用小流域高度分布曲线与年降雨是随高度呈线性变化关系,来确定小流域面平均年降雨量,并应用年降雨径流关系分解小流域不闭合的河床地下水潜流量,以提高无资料地区小流域设计径流的技术水平。     

郏县截潜自流引水工程环境负效应及对策研究

在干旱半干旱冲积平原区,采用地下截潜工程自流引用较丰富的地下水资源的措施在技术上是可行的,但这种方案实例极少,且地下截潜工程的设置极易引起浸没灾害和生态环境恶化等问题。以郏县截潜自流引水工程的规划为例,从环境负效应出发,探讨该方案的合理性。在地下水资源勘察评价成果的基础上,采用三维数值模拟方法对研究区枯水期不同长度截潜工程的浸没范围作了预测,并在综合分析该区水文地质条件的基础上,采用类比法对汛期浸没范围也作了预测,基于影响因素分析法对水质污染作了初步评价,采用解析法对堤防地基渗透变形作了预测评价。结果表明:该方案所导致的环境负效应严重,在本区不宜采用截潜自流引水方案,并提出了新的开发水资源的合理方案和避免环境负效应的有效对策。     

黑龙江小金山砾岩型金矿地质特征及成矿机理

叙述了产于上侏罗统砾岩型金矿的矿床地质特征,赋存与富集规律,金的物质来源和砾岩金的成矿机理,侧重阐明了“底流”对砾岩金形成的作用。