红层软岩隧洞围岩变形破坏机制研究

红层软岩的物质组成、化学成分、物理力学性质等方面在国内外已有较系统的研究,但对软岩隧道围岩的变形破坏机理及其治理一直是工程技术人员关心问题。通过对回龙宫隧洞的地质环境分析及有限元数值计算,阐明了红层隧洞围岩的膨胀变形破坏机理,最后提出了在此类围岩中修建水工隧洞的过程中,防止围岩变形破坏的建议。     

Regional stratigraphy and distribution of epigenetic stratabound celestine, fluorite, barite and Pb–Zn deposits in the MVT province of northeastern Mexico

Northeastern Mexico hosts numerous epigenetic stratabound carbonate-hosted low-temperature hydrothermal deposits of celestine, fluorite, barite and zinc-lead, which formed by replacement of Mesozoic evaporites or carbonate rocks. Such deposits can be permissively catalogued as Mississippi Valley-type (MVT) deposits. The deposits studied in the state of Coahuila are associated with granitic and metasedimentary basement highs (horsts) marginal or central to the Mesozoic Sabinas Basin. These horsts controlled the stratigraphy of the Mesozoic basins and subsequently influenced the Laramide structural pattern. The Sabinas Basin consists of ~6,000-m-thick Jurassic to Cretaceous siliciclastic, carbonate and evaporitic series. The MVT deposits are mostly in Barremian and in Aptian-Albian to Cenomanian formations and likely formed from basinal brines that were mobilized during the Laramide orogeny, although earlier diagenetic replacement of evaporite layers (barite and celestine deposits) and lining of paleokarstic cavities in reef carbonates (Zn–Pb deposits) is observed. Fluid inclusion microthermometry and isotopic studies suggest ore formation due to mixing of basinal brines and meteoric water. Homogenization temperatures of fluid inclusions range from 45°C to 210°C; salinities range from 0 to 26 wt.% NaCl equiv., and some inclusions contain hydrocarbons or bitumen. Sulfur isotope data suggest that most of the sulfur in barite and celestine is derived from Barremian to Cenomanian evaporites. Regional geology and a compilation of metallogenic features define the new MVT province of northeastern Mexico, which comprises most of the state of Coahuila and portions of the neighboring states of Nuevo León, Durango and, perhaps extends into Zacatecas and southern Texas. This province exhibits a regional metal zonation, with celestine deposits to the south, fluorite deposits to the north and barite and Zn–Pb deposits mostly in the central part.     

四川南部城市群主要环境工程地质问题

四川南部城市群为成渝经济区区域规划中四大城市群之一,有望成为四川省第二大增长极。区内多为丘陵山地型城市,有限的发展空间迫使城市建设活动中频繁的削坡、回填,在获得发展空间的同时也引发了大量的环境工程地质问题。地震活动、红层风化,地质灾害是区内最主要的环境工程地质问题。通过分析前人研究成果结合收集资料分析得出：华（？）山断裂及荥经-马边-盐津断裂在区内均表现为强活动性,地震活动频繁。侏罗系-白垩系红层泥岩具有快速风化的特性,红层边坡具有剥落、崩塌、落石、表层溜塌、滑塌、浅层滑坡六大破坏方式。区内地质灾害频发,发育密度达7.81处/100km~2,地质灾害类型以滑坡、崩塌为主。     

湖南红层找水初探

红层含水性弱,找水难度大,是找水难点中的难点．我省红层分布广泛且多集中在经济发达的大中城市,如长沙、湘谭、株洲、常德、怀化等．所以红层找水对湖南经济发展的重要性尤为突出．在系统分析了红层的分布与水文地质特征的基础上,从宏观上阐述了红层找水的基本条件和方法过程;并以凌津滩电厂找水为例,介绍了因地制宜,具体问题具体分析的找水方法,对在红层找水有重要的参考价值．     

Pore fluid evolution,distribution and water-rock interactions of carbonate cements in red-bed sandstone reservoirs in the Dongying Depression,China

The compositions, distribution and its interaction with rocks of the evolving pore fluids controls the distribution of carbonate cements and reservoir storage spaces. The reservoir quality of the red-bed sandstone reservoirs in the Dongying Depression was investigated by an integrated and systematic analysis including carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and fluid inclusions. The investigation was also facilitated by probing the mineral origins, precipitation mechanisms, pore fluid evolution and distribution, and water-rock interaction of carbonate cements and their influences on reservoir quality. Diagenetic-evolving fluids in the interbedded mudstones are the main source for the precipitation of calcite cements that completely fill the intergranular volume (CFIV calcite) with heavier oxygen and carbon isotopes. The ferro-carbonate cements in the reservoir sandstone are enriched in lighter carbon and oxygen isotopes. In addition to the cations released by the conversion of clay minerals in reservoirs, products of organic acid decarboxylation and the associated feldspar dissolution process provide important sources for such carbonate cementation. The carbon isotopes of CO₂ and the oxygen isotopic composition of fluids equilibrated with the CFIV calcite, ferro-calcite, dolomite and ankerite cements indicate that the pore in the red-bed reservoirs experienced high salinity fluids, which evolved from the early-formed interbedded mudstones, through organic acid input and to organic acid decarboxylation. Pore fluids from nearby mudstones migrated from the edge to the centre of sandbodies, causing strong calcite cementation along the sandbody boundaries and forming tight cementation zones. Pore fluids associated with organic CO₂ and acids and organic acid decarboxylation are mainly distributed in the internal portion of sandbodies, causing feldspar dissolution and precipitation of ferro-carbonate cements. The distribution of pore fluids caused the zonal distribution of carbonate cements in sandbodies during different periods. This may be advantageous to preserve the porosity of reservoirs as exemplified by the distribution of high-quality reservoirs in the red-bed sandbodies.