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The mineralogical and chemical changes of bentonites were studied under the boundary conditions of a repository in salt formations by means of a literature review, a natural analogue study, and laboratory experiments. In the natural analogue study the expandability of clays from deep boreholes in the East Slovakian Basin was found to be dependent not only on depth and temperature but also on the salinity of the pore waters. In laboratory experiments the fraction

The Odra river flood of 1997 was a rare hydrological as well as an interesting sedimentological event. At Hohenwutzen (Lower Odra River) we observed the suspended particulate matter transport and the temporal development of water and solids' pollution with heavy metals and As. While the suspended particulate matter concentration decreased the trace element concentrations increased during the flood by fractionation of particles and solution processes. Because of a successive flooding of differently contaminated sedimentary sources and polluted regions the contents of heavy metals developed irregularly. Their median particulate concentrations did not exceed the values of older samples taken under mean discharge conditions between 1989 and 1995. The dissolved amounts correspond to those ofthe Elbe river in 1990. During the flood the dissolved share of all analyzed total element contents increased. The total loads increased 4fold (Cr) to 17fold (Cd).

In western Peru kaolin-alunite deposits occur in Lower Cretaceous and Tertiary clastic, volcaniclastic and volcanic, mostly rhyolitic, rocks. Alunites from␣hypogene kaolin deposits yield K /Ar ages of 11.5 ±␣0.7␣Ma and 13.3 ± 0.4 Ma. In addition to kaolin and alunite, the following minerals are present: white mica, smectite, barite, pyrophyllite, tridymite, cristobalite, α- and β-quartz, chamosite, gibbsite, and aluminum-phosphate-sulphate minerals (APS). APS mineralizations with REE-bearing svanbergite and florencite originate from supergene alteration. Woodhouseite, goyazite, crandallite and pure svanbergite develop in hypogene and supergene kaolin deposits. The distinction between hypogene and supergene kaolinization can be made using various element ratios in kaolin (P vs. S, Zr vs. Ti, Cr + Nb vs. Ti + Fe, and Ce + Y + La vs. Ba + Sr). S,␣Ba, and Sr are considerably enriched in kaolin during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated mainly during weathering. Au and Ag become enriched during hypogene kaolinization (advanced argillitization). Kaolinization is associated with the evolution of the Central Andes as follows: (1) during the Lower Cretaceous kaolinization characterizes phases of relative tectonic quiescence during mountain building and took place in a miogeosynclinal back-arc basin. The kaolin-bearing sediments were laid down in flood plain to delta plain environments; (2) in the magmatic arc/back-arc basin (eugeosyncline) kaolinization was mainly associated with uplift and peneplanation; (3) in the magmatic arc proper, late Miocene kaolinization of volcanic and volcaniclastic rocks has many features in common with the high sulphidation epithermal Au deposits.

Two types of aluminium-phosphate-sulfate minerals are described for the first time from the Lohrheim kaolinitic clay deposit which was laid down during the Tertiary on Devonian rocks of the Rheinisches Schiefergebirge: type A is dominant in gorceixite BaAl3(PO4)2(OH)5 · H2O, type B is abundant in florencite-(Ce) CeAl3(PO4)2(OH)6 and goyazite SrAl3(PO4)2(OH)5· H2O. Both types resulted from weathering of pyritiferous parent material, which caused the low pH of the meteoric water. Their cations Ba and REE, however, were derived from different sources. The Ba in gorceixite was provided by supergene alteration of barite-bearing Eifelian bituminous shales and volcanics which locally underlie the kaolinitic saprolite, whereas the REE are likely to have been derived from the Devonian keratophyres which form the direct substrate of the loam of the weathering zone. In the saprolite profile an overall decrease of the REE content from bottom to top as well as HREE/LREE changes may be observed; they are a function of pH. During the incipient stages, HREE were preferentially removed, while during later stages a moderate rise in the pH led to a marked depletion in LREE relative to HREE. Chemical analyses of different size fractions of kaolin demonstrate that goyazite-florencite (type B) is LREE selective, whereas gorceixite (type A) is HREE selective.

In the region of Illapel, Chile, dioritic and andesitic rocks of Cretaceous to Paleocene age from the Unidad San Lorenzo Formation have suffered strong alteration resulting in the formation of a kaolin-rich zone, which is mined in the La Vanguardia open pit near Combarbalá. Detailed mineralogical and chemical investigations of channel samples from this mine, involving a combination of optical microscopy, XRD, SEM-EDX, XRF and TEM, permitted recognition of a zone of silicification and a zone of advanced argillic alteration, both of which contain alunite s.s. and aluminium-phosphate-sulphate (APS) minerals of the woodhouseite group with subordinate amounts of gorceixite, florencite and goyazite. These minerals are found to have originated from infiltration of meteoric waters. The passage from silicification into advanced argillic alteration was associated with an increase in sulphate activity as manifested by the increase of SO42— at the expense of PO43— in the alunite s.s. and by an increase of the Au content from 0.01 to 0.03 mg/kg Au. This high sulphidation type of wallrock alteration may be roughly compared with the Nansatu type of White (1991).

Two different types of APS minerals are described for the first time from the Desa Toraget kaolin deposit (Sulawesi, Indonesia). Type I is a near end member alunite with some PO 4 3− substituting for (SO 4 ) 2− . The second type contains Ca at a maximum of 0.28 in the structural formula and as a consequence of this, phosphate (−0.47) increased at the expense of SO 4 2− (1.53). The compositional data attest to a solid solution between woodhouseite and pure alunite. Desa Toraget kaolin mineralization, hence may be classified as “advanced argillic alteration” which requires high oxidation and sulfidation and is related in time and space to the Quaternary volcanic activity. In view of the genetic linkage between epithermal Au mineralization and high sulphidation kaolinitic alteration elsewhere, the study area might be considered as a potential target for Au exploration.

Im Rahmen des DFG-Projektes „Mineralogisch-geochemisch-sedimentologische Untersuchungen der Schwebstoffe und Sedimente in der deutschen Mittel- und Oberelbe“ (HENNING u.a. 1993) wurden Schwebstoff-Flocken phasenanalytisch untersucht: u.a. die Menge der anorganischen Schwebstoffe in den Flocken, der Mineralbestand im anorganischen Anteil, der Anteil an biogenem Opal, die Korngrosenverteilung, die Schwermineral- und Schwerepartikelassoziation und der Aufbau und das Gefuge der Schwebstoff-Flocken. In der folgenden kurzen Zusammenfassung werden einige vorlaufige Ergebnisse vorgestellt, wobei auf das Poster und die ubrigen Zusammenfassungen und Poster unserer Arbeitsgruppe zum „6. Magdeburger Gewasserschutzseminar“ in Cuxhaven verwiesen werden kann. Zur Untersuchung gelangten und gelangen Schwebstoff-Proben von ca. 25 Probenahmepunkten auf ca. 380 km Lange von Schmilka bis Geesthacht von 10 Bereisungen im Zeitraum von Februar 1989 bis Juli 1994. Dabei sollten sowohl saisonale jahreszeitliche Trends als auch besondere Ereignisse (z.B. Hochwasser-Beprobung April 1992) erfast werden.

Die relativen Mineralverhaltnisse in den Schwebstoffen, insbesondere das Quarz/Tonmineralverhaltnis, in Verbindung mit der Erfassung verschiedener Begleitparameter (Feststoffkonzentration, POC, Korngrosenverteilung etc.) geben Informationen zur Herkunft der Schwebstoffe, zur Schwebstoffzusammensetzung und der damit einhergehenden Transportkraft der Schwebstoffflocken. Das Relief im Einzugsgebiet, der daraus resultierende Stromausbau, die hydrologische Situation sowie die saisonalen Veranderungen der biogenen Phasen zeichnen sich als die entscheidenden Einflusgrosen auf die Schwebstoffzusammensetzung ab.

Seit 1989 sind in mehrmonatigen Abstanden an gleichen Mespunkten der Elbe im Flusabschnitt zwischen Schmilka und Wahrenberg bzw. Geesthacht (seit 1990) Schwebstoffe zur mineralogisch-phasenanalytischen Untersuchung entnommen worden. Die Proben wurden als Punktproben mit einem Volumen von jeweils 200 Litern Fluswasser aus einer Wassertiefe von ca. 1 m mittels Schopfern von Brukken, Fahren oder ausladenden Pontons entnommen. Die Feststoffanteile sind durch Sedimentation angereichert und mittels Vakuumfiltration uber Membranfilter der Porenweite 0,45 µm gewonnen und gefriergetrocknet worden.

Im Rahmen des DFG-Projektes „Mineralogisch-geochemisch-sedimentologische Untersuchungen der Schwebstoffe und Sedimente in der deutschen Mittel- und Oberelbe“ (HENNING u.a. 1993) wurden Schwerminerale und Schwerepartikel (Dichte > 2,9 g/cm3) nach der in der Petrographie ublichen Methode der Schwermineraltrennung aus Schwebstoff-Flocken gewonnen und lichtmikroskopisch sowie rasterelektronenmikroskopisch unter Einbeziehung der Elektronenstrahlmikroanalyse untersucht. Dabei sind in den Sedimenten und Schwebstoffen der Elbe, wie auch anderer Flusse, in den Schwermineralassoziationen auser geogenen Mineralanteilen auch anthropogene und biogene Schwerepartikel zu erwarten. Die Untersuchungen wurden zunachst an Proben aus dem Raum Schmilka und Roslau durchgefuhrt.

In der Diskussion um die Schadstoffdynamik der Elbe hat es sich gezeigt, das neben den Schwebstoff- und Schadstoffkonzentrationen im Gewasser die Veranderungen der Schwebstoffzusammensetzung erfast werden mussen. Zunehmendes Interesse gilt dabei der Klarung des jahreszeitabhangigen, biogenen Einflusses auf den partikularen Schadstofftransport.