Biodiversity reduction on contaminated sediments in the sea: contamination or sediment mobility?

Where contaminants in sediments correlate with biodiversity reductions, the contamination may not be the cause. Other physical factors may be responsible, and should be investigated so that any remedial action is directed properly. Two examples are given where unusual sediment mobility caused biodiversity reductions in sediments with elevated trace contaminants.     

The Kansas University meteorit

Abstract— A new 2.8 kg meteorite find from the United States, Kansas University, is classified as an L6 (S3) chondrite based on optical microscopy and electron microprobe analysis of mafic minerals. Natural thermo-luminescence (TL) and ¹⁴C measurements suggest that the Kansas University meteorite has a short terrestrial age compared to other meteorite finds from this area and is not paired with the other local meteorite finds, Densmore (1879), Lawrence, Kansas and Long Island, Kansas.     

SKETCHES IN THE HISTORY OF METEORITICS 2: THE EARLY CHEMICAL AND MINERALOGICAL WORK

The chemical and mineralogical work on meteorites over the period 1800 to 1840 is reviewed. The number of elements known to be present in meteorites rose from six to 19. Chemical techniques advanced rapidly so that by 1815 the procedure was essentially that of modern wet chemical analysts: removal of the magnetic material, dissolution of the acid-soluble portion and fusion of the remainder with alkali. After Bournon's work in 1802 much mineralogical progress was made during the 1820's, notably by G. Rose. Berzelius made important contributions by his own analyses and synthesis of the work of others. By 1840 ordinary chondrites, carbonaceous chondrites, plagioclase-pyroxene achondrites, Chassigny, pallasites and octahedrites could all be distinguished     

METAL OF HIGH Co CONTENT IN LL CHONDRITES

Measurements on the metal of the LL chondrites Appley Bridge, Jelica, Olivenza, and Khanpur have shown that the Co: Ni ratio of the metal is near 1.24 and that Prior's law appears to be followed to some extent within the LL group.     

THERMOLUMINESCENCE AND THE TERRESTRIAL AGE OF METEORITES

The use of thermoluminescence (TL) to determine the terrestrial age of meteorites is investigated. It is found that meteorites can be divided into two groups. One group, in which members lose their low temperature TL rather rapidly (the “low retentivity” group), may be dated up to about 100 years after fall, although with little accuracy. The other (the “high” group) is more retentive, and may still be dated several hundred years after fall. A meteorite of unknown date of fall may be assigned to the high or low group by laboratory determination of the rate of decay of the low temperature TL. Weathering coats the grains with limonite and lowers the intensity of the TL. The percentage reduction is constant for various intensities, but the peak height ratio is changed. Therefore, for weathered specimens, a method which examines the decrease in the intensity of a single peak is preferred to one which depends upon peak height ratios: this is made possible by artificially irradiating the meteorites. The following terrestrial ages for finds were obtained: Plainview 225–300 years; Dimmitt 280–330 years; Calliham 350–400 years. Bluff, Etter, Potter, Shields and Wellman (c) proved to be too old to be dated by our methods (≥ 500 years). None of the low group finds available to us proved to be young enough to be dated precisely. Terrestrial ages indicate an extremely low efficiency of recovery (≤ 1%) for meteorites that are not seen to fall. Artificially irradiating the meteorites also revealed the fact that 9 of our 19 meteorites were saturated with respect to thermoluminescence when they entered the atmosphere, and therefore that a technique based on this phenomenon would not be applicable to such specimens to obtain their cosmic ray exposure age.     

ARTIFICIALLY-INDUCED THERMOLUMINESCENCE GRADIENTS IN STONY METEORITES

Several meteorites show variations in natural thermoluminescence intensity with depth. To investigate this, the gamma-ray induced thermoluminescence of the Plainview, Ucera, and Lost City meteorites has been analyzed. The results show that the thermoluminescence gradients in the meteorites are related to the concentration of electron traps, probably as a result of some of them being produced by cosmic ray bombardment.     

Regional-scale Proterozoic IOCG-mineralized breccia systems: examples from the Wernecke Mountains, Yukon, Canada

A large scale Proterozoic breccia system consisting of numerous individual breccia bodies, collectively known as Wernecke Breccia, occurs in north-central Yukon Territory, Canada. Breccias cut Early Proterozoic Wernecke Supergroup sedimentary rocks and occur throughout the approximately 13 km thick deformed and weakly metamorphosed sequence. Iron oxide–copper–gold ± uranium ± cobalt mineralization is associated with the breccia bodies and occurs as veins and disseminations within breccia and surrounding rocks and locally forms the breccia matrix. Extensive sodic and potassic metasomatic alteration occurs within and around breccia bodies and is overprinted by pervasive calcite and dolomite/ankerite, and locally siderite, alteration, respectively. Multiple phases of brecciation, alteration and mineralization are evident. Breccia bodies are spatially associated with regional-scale faults and breccia emplacement made use of pre-existing crustal weaknesses and permeable zones. New evidence indicates the presence of metaevaporitic rocks in lower WSG that may be intimately related to breccia formation. No evidence of breccia-age magmatism has been found to date.