During explosive eruptions, a suspension of gas and pyroclasts rises rapidly within a conduit. Here, we have analysed textures preserved in the walls of a pyroclastic feeder dyke of the AD 1886 Tarawera basaltic Plinian fissure eruption. The samples examined consist of basaltic ash and scoria plastered onto a conduit wall of a coherent rhyolite dome and a welded rhyolitic dome breccia. We exami...

biotite samples from different units of boroujerd granitoid complex (bgc) of the sanandaj-sirjan zone, western iran, have beenanalyzed by electron microprobe for major elements. biotite analyses from three units of quartzdiorite, granodiorite and monzograniteof bgc have their own distinct non-overlapping compositional fields in the annite – siderophyllite – phlogopite – eastonitequadrilateral (...

reflect the dewatering of structurally lower levels after nappe emMuscovite and biotite dehydration-melting reactions near the peak placement. If so, then nappe emplacement occurred at T~475°C. of metamorphism played a significant role in the reaction and fluid history of the Rangeley Formation in southwestern New Hampshire, USA. Evidence for in situ melting includes: (1) the consistency among ...

a particular feature of biotite grains from some of the canadian appalachian granitic rocks is the presence of lenses of ca-al silicates developed along cleavage planes. these from the more to less common are prehnite, pumpellyite and grandite garnet, an intermediate composition between andradite and grossular. rarely all three minerals can be observed together in one single biotite grain. micr...

Detailed electron-microprobe line profiles and small-area compositional maps of zoned garnets in a sample of high-pressure–high-temperature granulite show features inconsistent with commonly applied diffusion models. Larger grains of an early garnet generation have their highest Ca contents in domains away from the rim or inclusions but show a sharp fall in Ca balanced by increased Mg and Fe (a...

Chemical analysis of the Water-rock interaction showed that hydrothermal altered rock contains large amount of fluoride. Considering that alteration has mainly occurred at the fractures’ cleavages, the aim of this paper is to investigate the change of the mineral composition between the cleavages and other parts of the granite surfaces. Scanning electron microscope with energy-dispersive spectr...

We performed batch dissolution experiments on different sized granite and biotite in pure water, in order to better understand the source and geochemical behavior of fluoride in groundwater. Very high concentrations of fluoride (up to 6–10 mg/l) were observed from granite leaching. Correlations between leached ions suggest that fluoride possibly originates from dissolution of biotite. After ~50...

A nearly complete and undisturbed Miocene carbonate sequence is present in the easternmost part of the UmbriaMarche basin, Italy, which is ideal for detailed and integrated stratigraphic investigations of the Miocene Epoch. In this study, we were trying to obtain evidence for the presence or absence of distal ejecta from the 15 Ma Ries impact structure in southern Germany, located about 600 km ...

A sandstone outcrop exposed to freshwater seepage supports a diverse assemblage of photosynthetic microbes. Dominant taxa are two cyanophytes (Oscillatoria sp., Rivularia sp.) and a unicellular green alga (Palmellococcus sp.). Less abundant taxa include a filamentous green alga, Microspora, and the desmid Cosmarium. Biologic activity is evidenced by measured levels of chlorophyll and lipids. Bi...

Cesium adsorption/desorption experiments for various clay minerals, considering actual contamination conditions in Fukushima, were conducted using the (137)Cs radioisotope and an autoradiography using imaging plates (IPs). A 50 μl solution containing 0.185 ~ 1.85 Bq of (137)Cs (10(-11) ~ 10(-9 )molL(-1) of (137)Cs) was dropped onto a substrate where various mineral particles were arranged. It w...