A coupling of mixed and discontinuous Galerkin finite-element methods for poroelasticity

In this paper, we formulate a finite-element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation model of poroelasticity. We approximate the flow variables by a mixed finite-element space and the displacement by a family of discontinuous Galerkin methods. Theoretical convergence error estimates are derived and, in particular, are shown to be independent of the constrained specific storage coefficient, c _o . This suggests that our proposed algorithm is a potentially effective way to combat locking, or the nonphysical pressure oscillations, which sometimes arise in numerical algorithms for poroelasticity.     

Fractional crystallization models and B–Be–Li systematics at Mt Somma-Vesuvius volcano (Southern Italy)

A compilation of B–Be–Li data on rocks that cover the entire eruptive history of Somma-Vesuvius is presented and interpreted in the light of evolution models for the Somma-Vesuvius rocks. Using major and trace element data, fractional crystalllization models are presented for different geochemical units. These data were used to constrain the source mineralogy of the Somma-Vesuvius rocks (ol-opx-cpx-gar-amp of 0.4-0.3-0.1-0.1-0.1), the amount of sediment added (5–10%) and the melt fraction from batch partial melting computations (0.05–0.1). From the B–Li data it is inferred that the main process responsible for the B isotopic signature is sediment recycling. However, the B–Li data show a major variation in Li abundances respect to B which is explained with Li dehydration before the fluid enriched the mantle wedge that produced the arc magmas. The Somma-Vesuvius B isotope composition is intermediate between that of the Campi Flegrei and the broad field of the Eolian Island arc. A low Be isotopes in the recent volcanic rocks can be explained as: (a) the top 1–22 m of the incoming sediment is accreted, (b) large amounts of sediment erosion, (c) a slow rate of subduction which have provoked a long magmatic history for the Vesuvius magma, (d) the sediment component takes several Myr longer than the subducting plate to reach the magma source region beneath Italy.     

太原盆地农田区大气降尘对土壤重金属元素 累积的影响及其来源探讨

通过研究太原盆地大气干湿沉降中重金属元素的含量分布特征及年输入通量,讨论其对土壤中重金属元素累积的影响。同时采用富集因子法探讨降尘物质的来源。研究结果表明,降尘中重金属元素As、Cd主要来源于人为活动,Pb的来源可能是人为源和自然源。而Hg则主要来源于自然源。     

滇西沘江流域水体中重金属元素的地球化学特征

通过测定流经兰坪金顸铅锌矿区的沘江水体中Pb、Zn、Cd、As的含量和底泥中重金属元素的化学形态的含量,分析了重金属元素的分布和化学形态的变化。结果表明,沘江水遭到了Cd污染,底泥已经成为重金属元素的蓄积库,以国家土壤环境质量标准（Ⅲ级）衡量,Pb、Zn、Cd和舡分别超标3．4倍、15．8倍、106倍和2．6倍。沘江水中重金属元素含量的峰值在矿山附近的下游,而底泥中重金属元素的峰值在矿山下游30-50km的地方,矿业活动、水流变缓、pH等水体环境条件的变化都能影响水和底泥中重金属元素的含量。底泥中的Pb以碳酸盐结合态为主,Zn和Cd以铁锰氧化物结合态为主,而As以残渣态为主。Pb、Cd、Zn三种元素的环境有效态含量比较高,对沘江流域生态环境具有潜在的巨大的危害。     

Spatial distribution features and environment effect of heavy metal in intertidal surface sediments of Guanhe estuary, Northern Jiangsu Province

In northern Jiangsu coastal zone area, Guanhe River is the biggest river and has the best navigation conditions among rivers which flow into the Yellow Sea. The grain sizes show gradual increase from the high intertidal zone to lower intertidal zone. The heavy metal values have slight changes along both sides of the river mouth, but show an evident change perpendicular to the tidal flat. In the latter case, they show a good correlation with grain size fluctuation, that is, the heavy metal values gradually decline when the grain size increases from the high intertidal zone to the lower intra-tidal zone. Analyses of the heavy metal elements show that on the Guanhe estuary surface sediment, the content of the elements Hg, As and Cu is above background values; Pb and Zn contents are rather close to the background values; and Cd content is less than the background values. The element Hg comes out to be harmful in a medium level to ecological environment, while the elements of Cr, As, Cu, Pb, Zn and Cd fall in a safe range of MPL. On the whole, Guanhe estuary tidal flat is not very harmful to the ecology in terms of the heavy metals. __________ Translated from Marine Geology & Quaternary Geology, 2007, 27(5): 23–32 [译自: 海洋地质与第四纪地质]     

广州航空邮件处理中心土洞及桩端软土层处理工艺研究

广州航空邮件处理中心位于岩溶发育地区,场区内存在大量土洞、溶洞等不良地质现象。该建筑物拟采用静压桩基础。为保证建筑物及场道安全,须对场区土洞进行处理。结合场地具体情况和施工工期要求,首先对大体积土洞进行泵注细石砼骨料充填处理,以消除地面大面积塌陷的危险,消灭压桩机械施工安全隐患,然后开始进行静压桩基础施工,同时在场地允许区域对中小体积土洞、桩端软土层等分别进行泵注砂浆骨料和袖阀注浆处理．以确保洞体密实和保证桩基承载力。通过对处理工艺、处理范围的比较筛选和对质量控制要点、施工技术要点的分析提炼．达到了施工简便、造价合理、安全高效的目的,并采用骨料取芯检测、土体标贯试验和压缩试验、洞体物探等多种检测手段,完全达到了设计要求,取得了良好的工程效果和经济效益。     

Platinum-group element distribution in chromite ores from ophiolite complexes: implications for their exploration

Compilation of some new data on ophiolites for Greece and Yugoslavia, and published data from previous studies, indicate that platinum-group element (PGE) and gold concentrations in chromite ores are generally low, ranging from less than 100 ppb to a few hundred ppb. However, samples from several ophiolite complexes exhibit an enrichment (of a few ppm) (a) only in Os, Ir and Ru,(b) only in Pt and/or Pd or (c) in all PGE. This enrichment (up to 10s ppm) is mainly related with chromitites hosted in supra-Moho dunites and dunites of the uppermost stratigraphic levels of the mantle sequence and it seems to be local, independent of the chromitite major element composition and the chromite potential of the ophiolite complexes. The contents of PGE combined with less chalcophile elements (Ni, Co, Cu), the ratios of incompatible/compatible elements, and PGE-patterns provide evidence for discrimination between chromitites derived from primitive magmas and those derived from partially fractionated magmas, although they have a similar major element composition. Thus, they can be used for a stratigraphic orientation in the mantle sequence, and therefore for exploration targets. Moreover, PGE data offer valuable information for the evaluation of the chromite potential in ophiolite complexes. The most promising ophiolites seem to be those which apart from the petrological and geochemical characteristics indicating extensive degree of partial melting in the mantle source contain only one chromite ore type (the other type being only in small proportion) of limited compositional variation, in both major elements and PGE, low ratios of , while PGE-enriched chromitites in the mantle sequence are only occasionally present. In contrast, ophiolites which contain both high-Cr and -Al chromitites, and where their chalcophile element data implies relatively extensive fractionation trend are not good exploration targets for chromite ores, although they are related with a SSZ environment.     

A dynamic box model of bioactive elements in the southern Taiwan Strait

A dynamic box model was applied to study the characteristics of biogeochemical cycling of PO_4-P,NO_3-N,AOU,POC and PON in the southern Taiwan Strait region based on field data of the"Minnan Taiwan Bank Fishing Ground Upwelling Ecosystem Study" during the period of Dec.1987-Nov.1988.According to the unique hydrological and topographical features of the region,six boxesand three layers were considered in the model.The variation rates and fluxes of elements induced by hor-izontal current,upwelling,by diffusion,sinking of particles and biogeochemical processes were estimatedrespectively.Results further confirmed that upwellings had important effects in this region.Thenearshore upwelling areas had net input fluxes of nutrients brought by upwelling water,also had high de-pletion rates of nutrients and production rates of particulate organic matter and dissolved oxygen.Theabnormal net production of nutrients in the middle layer(10-30m) indicated the important role of bacte-ria in this high production region.Th     

“Tripoli”的含义及译名的讨论

“Tripoli”是一种新型的石英质工业矿物原料,在我国长期被误译为硅藻土,影响地质部门对这一新矿种的认识和寻找。本文追溯了“Tripoli”一名的由来,正确地阐述了“Tripoli”的本质特征,分析了在国内文献中长期被误译的根源,指明了其正确含义,并建议废除各种不正确的中译名,译为“粉石英”。     

胶东海阳所超镁铁岩中强亲铁元素的地球化学特征及其构造环境探讨

强亲铁元素与亲石元素具有不同的地球化学行为，因此能够从不同的角度为造山带中超镁铁岩的成因及演化提供重要信息。位于苏鲁造山带东北端的胶东海阳所超镁铁岩主要由橄榄岩和辉石岩组成，它们常以团块状赋存于花岗质片麻岩中。虽然前人对这些超镁铁岩已经开展大量岩石学研究，但关于其成因及构造属性仍存在较大争议。本文开展了海阳所超镁铁岩的全岩主微量元素、强亲铁元素及Re-Os同位素的分析工作，结果显示蛇纹石化橄榄岩具有较高的MgO和Fe₂O₃^T含量，较低的Al₂O₃、TiO₂和CaO含量，明显富集流体迁移元素（U、Pb），亏损高场强元素（Zr、Hf），强亲铁元素没有发生明显分异，但Ru显示正异常，表明海阳所蛇纹石化橄榄岩是经历了低-中等程度部分熔融及熔/流体交代作用影响的残余地幔橄榄岩。海阳所辉石岩的主量元素表现出明显的结晶分异特征，稀土元素较原始地幔富集，铂族元素（PGEs）含量较低且发生了明显的分异，表明辉石岩的地幔源区经历过高程度的部分熔融和硫化物的分离。海阳所蛇纹石化橄榄岩的Os同位素地球化学特征表现出大洋亲和性，与辉石岩不具有熔体-残留体的关系。由于该地区发育较深层次的韧性剪切带，蛇纹石化橄榄岩中的橄榄石与辉石表现出韧性变形的特征，同时有辉石岩侵入到橄榄岩的现象，表明该地区的蛇纹石化地幔橄榄岩与辉石岩既不同时，也不同源，因此，暗示了该套岩石组合可能形成于大洋核杂岩（OCC）与洋脊型蛇绿岩（MOR）堆晶岩交互发育环境。