The Deep-Water Peyssonnelia Beds from the Balearic Islands (Western Mediterranean)

Abstract. Peyssonnelia bed distribution on continental shelf bottoms of the Balearic Islands (Western Mediterranean) ranges from 40 to 90 m depth. Different species of Peyssonnelia dominate these bottoms and, according to multivariate techniques, two main assemblages have been distinguished: the Peyssonnelia rosa-marina beds and the Peyssonnelia sp. beds, together with some transition samples between Peyssonnelia and maërl beds. Erect red algae are always abundant. Although average yearly irradiance reaching these beds is only 6.4-0.3% of subsurface irradiance, the species richness averages 45 species per sample (1600 cm²) and mean biomass is 2835 g dw. m^-2. The high carbonate content of the living algae of these bottoms suggests that they are important contributors to the production of sediments in the Balearic continental shelf.     

In situ and satellite observations of the eastward migration of the Western Alboran Sea Gyre

During October 2003 an intensive oceanographic survey (BIOMEGA) was carried out in the Alboran Sea, coinciding with a migration event of the Western Alboran Sea Gyre (WAG). The observations gathered during that cruise constitute the first field evidence of a migrated stage of the WAG. In this work we present the main differences between the 3D hydrodynamic fields observed during BIOMEGA and those corresponding to a WAG located at its usual position. The migration of the gyre was followed by satellite (altimetry and sea surface temperature) imagery. The causes of the gyre migration are explored in terms of the quasi-geostrophic tendency equation, in particular of the dynamics governing scales larger than the Rossby radius of deformation. It is shown that the steady state gyre must be almost equivalent barotropic and that the key process to break down the stationarity would be a density advection at gyre scale. The mechanisms to explain the migration of the WAG proposed by previous authors are discussed in light of the explanation proposed in this work.     

Granitoids in the Rozvadov Pluton,Western Bohemia and Oberpfalz

The Rozvadov Pluton is a complex of mainly Variscan granitoid rocks situated near the Bohemian-Bavarian border between Bärnau, Tachov, Rozvadov and Waidhaus, 25 km ESE of the KTB site. Five mappable units can be distinguished, which intruded as folows: (1) slightly deformed leucocratic meta-aplite/metapegmatite dykes with garnet and tourmaline; (2) a complex of cordierite-bearing granitoids, which have been divided into three facies (a) biotite granite with cordierite (at the margin of the complex), (b) biotite-cordierite granite and (c) cordierite tonalite (in the centre of the complex; (3) fine-grained biotite granite of the Rozvadov type with associated pegmatite bodies; (4) two-mica Bärnau granite; and (5) geochemically specialized albite-zinnwaldite-topaz granite (Kríový kámen/Kreuzstein granite) with indications of Sn-Nb-Ta mineralization and associated phosphorus-rich pegmatite cupolas. Rare earth element data suggest that meta-aplite/pegmatite dykes are the result of a batch partial melting process, whereas the compositional variation of the other rock types was mainly controlled by fractional crystallization. The genesis of the cordierite granitoid suite is best explained in terms of a batch melting of metapelitic source followed by crystallization of a cordierite-rich cumulate and K-feldspar enriched melt. The leucocratic pluton constituents — the meta-aplites and the Bärnau and Kíový kámen granites are rich in phosphorus (0.5–0.8%). The main carriers of phosphorus are alkali feldspars, especially K-feldspar (up to 0.8% P₂O₅). The presence of P-rich leucocratic granites is one of the features distinguishing the Variscan granitoids within the Moldanubian zone from the nearly contemporaneous granitoids in the Saxothuringian zone.     

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement (MEIFR) is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique (corresponding to the maximum curvature) and slope technique (slope being 1) are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.     

Western Alpine back-thrusting as subsidence mechanism in the Tertiary Piedmont Basin (Western Po Plain, NW Italy)

Basin formation dynamics of the Tertiary Piedmont Basin (TPB) are here investigated by means of cross-section numerical modelling. Previous works hypothesised that basin subsidence occurred due first to extension (Oligocene) and then to subsequent loading due to back-thrusting (Miocene). However, structural evidence shows that the TPB was mainly under contraction from Oligocene until post Pliocene time while extension played a minor role. Furthermore, thermal indicators strongly call for a cold (flexure-induced) mechanism but are strictly inconsistent with a hot (thermally induced) mechanism. Our new modelling shows that the TPB stratigraphic features can be reproduced by flexure of a visco-elastic plate loaded by back-thrusts active in the Western Alps in Oligo-Miocene times. Far-field compression contributed to the TPB subsidence and controlled the basin infill geometry by enhancing basin tilting, forebulge uplift and erosion of the southern margin of the basin. These results suggest that the TPB subsidence is the result of a combination of mechanisms including thrust loading and far-field compressional stresses.     

Structural improvement of age-hardened gypsum-treated bauxite red mud waste using readily decomposable phyto-organics

Several years (7) after incidental lithification by added gypsum, the effect of crushing and phyto-organics on some physical properties of red mud wastes (RMW) was examined under laboratory conditions. It was hypothesized that mechanically breaking up the hardened masses would increase their permeability. However, on the contrary, crushing these rock-hard masses into <2-mm particles did not increase permeability. A phyto-organic treatment on the other hand greatly improved permeability of the crushed entities such that infiltration rates increased from 0 to 10 cm/h. After 24 weeks of incubation, the structure of the newly formed phyto-organically treated gypsum-hardened RMW aggregates was also substantially improved over that of the controls, as a >3-fold increase in resistance to disintegration during wet sieving was exhibited by the phyto-organically treated samples. The increase in water infiltration by combining crushing with phyto-organic applications was ascribed to a decrease in particle dispersion, creating more stable clay clusters, which in turn stabilized channels and pores. Conversely, it was concluded that the singular crushing of gypsum-hardened bauxite waste in the waste dumps is potentially wasteful and ineffective.     

西天山特克斯达坂库勒萨依序列埃达克岩的确立及钼找矿意义

库勒萨依序列斑岩体δ平均3.05,属于钙碱性系列岛弧浅成岩。 SiO₂含量为57.06％~70.74％,高Al₂O₃、Na₂O、Sr和相对富集LREE,低MgO、Y、Yb,强烈亏损HREE。Na₂O/K₂O＞1,Sr/Y平均57.67,正Eu异常,因而具有典型O型埃达克岩特征。库勒萨依序列斑岩体与Mo异常套合好,已发现钼矿体,找矿前景良好。该埃达克岩的确立,对深化西天山区域成矿规律和指导今后找矿具有借鉴和指导意义。     

一种尚未定名的Ni—As—S—Se矿物相

Ｎｉ－Ａｓ－Ｓ－Ｓｅ矿物相首次发现于西秦岭南亚带拉尔玛－邛莫金－铜－铀建造矿床中。与其共生的矿物有：硒汞矿、硒铅矿、硒梯矿、硒硫锑矿、硒硫锑铜矿、自然金、重晶石、石英等。该矿物颗粒细小，粒度小于１０μｍ。在反光显微镜下呈白色，无内反射现象，为一均质矿物。两个点的电子探针分析结果（ＷＢ％）：Ｎｉ２４．１２３￣２９．３７８，Ａｓ２７．５７４￣３３．８９５，Ｈｇ７．５９１￣５．３５９，Ｓ１３．９３９￣１     

布尔津盆地西部凹陷铀成矿水文地球化学条件初探

根据水成铀矿床理论，本在论述布尔津盆地水动力及水化学特征的基础上，通过资料综合整理，着重分析西部凹陷第三系层间水的铀水迁移分带规律，对层间氧化带砂岩型铀矿成矿水地球化学条件进行初步探讨。