Lithic Inclusions in the Taupo Pumice Formation

<p>The Taupo Pumice Formation is a product of the Taupo eruption of about 1800a, and consists of three phreatomagmatic ash deposits, two plinian pumice deposits and a major low-aspect ratio and low grade (unwelded) ignimbrite which covered most part of the central North Island of New Zealand. The vent area for the eruption is located at Horomatangi Reefs in Lake Taupo. Lithics in the phreatoplinian ash deposits are negligible in quantity, but the plinian pumice deposits contain 5-10% lithics by volume in most near-vent sections. Lithics in the plinian pumice deposits are dominantly banded and spherulitic rhyolite with minor welded tuff, dacite and andesite. The ground layer which forms the base of the ignimbrite unit consists of dominantly lithics and crystals and is formed by the gravitational sedimentation of the 'heavies' from the strongly fluidized head of the pyroclastic flow. Lithic blocks in the ground layer are dominantly banded and spherulitic phenocryst-poor rhyolite, welded tuff with minor dacite and andesite. Near-vent exposures of the ground layer contain boulders upto 2 m in diameter. Friable blocks of hydrothermally altered rhyolite, welded tuff and lake sediments are found fractured but are preserved intact after transportation. This shows that the fluid/pyroclastic particle mixture provided enough support to carry such blocks upto a distance of 10 km from the vent. The rhyolite blocks are subdivided into hypersthene rhyolite, hypersthene-hornblende rhyolite and biotite-bearing rhyolite on the basis of the dominant ferromagnesian phenocryst assamblage. Hypersthene is the dominant ferromagnesian phenocryst in most of the rhyolite blocks in the ground layer and forms the major ferromagnesian crystal of the Taupo Sub-group tephra. The rhyolite blocks have similar whole rock chemistry to the Taupo Sub-group tephra and are probably derived from lava extrusions associated with the tephra eruptions from the Taupo Volcanic Centre in the last 10 ka. Older rhyolite domes and flows in the area are probably represented by the intensely hydrothermally altered rhyolite blocks in the ground layer. The dacite blocks contain hypersthene and augite as a major ferromagnesian phenocryst. Whole rock major and trace element analyses shows that the dacite blocks are distinct from the Tauhara dacites and from the dacites of Tongariro Volcanic Centre. The occurrence of dacite inclusions in significant quantity in the Taupo Pumice Formation indicates the presence of other dacite flows near the vent area. Four types of andesite blocks; hornblende andesite, plagioclase-pyroxene andesite, pyroxene andesite and olivine andesite occur as lithic blocks in the ground layer. The andesites are petrographically distinct from those encountered in deep drillholes at Wairakei (Waiora Valley Andesites), and are different from the Rolles Peak andesite in having lower Sr content. The andesite blocks show similar major and trace element content to those from the Tongariro Volcanic Centre. The roundness of the andesite blocks indicates that the blocks were transported as alluvium or lahars in to the lake basin before being incorporated into the pyroclastic flow. Two types of welded ignimbrite blocks are described. The lithic-crystal rich ignimbrite is correlated with a post-Whakamaru Group Ignimbrite (ca. 100 ka ignimbrite erupted from Taupo Volcanic Centre) which crops out to the north of Lake Taupo. The crystal rich ignimbrite is tentatively correlated with the Whakamaru Group Ignimbrites. The lake sediment boulders, pumiceous mudstone and siltstone in the ground layer probably correlate to the Huka Group sediments or younger Holocene sediments in the lake basin. A comparative mineral chemistry study of the lithic blocks was done. A change in chemistry of individual mineral species was found to accompany the variation in wholerock major element constituents in the different types of lithics. The large quantity of lithic blocks in the ground layer suggests extensive vent widening at the begining of the ignimbrite eruption. A simple model of flaring and collapse of the vent area caused by the down ward movement of the fragmentation surface is presented to explain the origin of the lithic blocks in the ground layer. The lithics in the Taupo Pumice Formation are therfore produced by the disruption of the country rock around the vent during the explosion and primary xenoliths from depths of magma generation were not found. Stratigraphic relations suggest that the most important depth of incorporation of lithics is within the post-Whakamaru Group Ignimbrite volcanics and volcaniclastic sedimentary units.</p>

Lithic Inclusions in the Taupo Pumice Formation

<p>The Taupo Pumice Formation is a product of the Taupo eruption of about 1800a, and consists of three phreatomagmatic ash deposits, two plinian pumice deposits and a major low-aspect ratio and low grade (unwelded) ignimbrite which covered most part of the central North Island of New Zealand. The vent area for the eruption is located at Horomatangi Reefs in Lake Taupo. Lithics in the phreatoplinian ash deposits are negligible in quantity, but the plinian pumice deposits contain 5-10% lithics by volume in most near-vent sections. Lithics in the plinian pumice deposits are dominantly banded and spherulitic rhyolite with minor welded tuff, dacite and andesite. The ground layer which forms the base of the ignimbrite unit consists of dominantly lithics and crystals and is formed by the gravitational sedimentation of the 'heavies' from the strongly fluidized head of the pyroclastic flow. Lithic blocks in the ground layer are dominantly banded and spherulitic phenocryst-poor rhyolite, welded tuff with minor dacite and andesite. Near-vent exposures of the ground layer contain boulders upto 2 m in diameter. Friable blocks of hydrothermally altered rhyolite, welded tuff and lake sediments are found fractured but are preserved intact after transportation. This shows that the fluid/pyroclastic particle mixture provided enough support to carry such blocks upto a distance of 10 km from the vent. The rhyolite blocks are subdivided into hypersthene rhyolite, hypersthene-hornblende rhyolite and biotite-bearing rhyolite on the basis of the dominant ferromagnesian phenocryst assamblage. Hypersthene is the dominant ferromagnesian phenocryst in most of the rhyolite blocks in the ground layer and forms the major ferromagnesian crystal of the Taupo Sub-group tephra. The rhyolite blocks have similar whole rock chemistry to the Taupo Sub-group tephra and are probably derived from lava extrusions associated with the tephra eruptions from the Taupo Volcanic Centre in the last 10 ka. Older rhyolite domes and flows in the area are probably represented by the intensely hydrothermally altered rhyolite blocks in the ground layer. The dacite blocks contain hypersthene and augite as a major ferromagnesian phenocryst. Whole rock major and trace element analyses shows that the dacite blocks are distinct from the Tauhara dacites and from the dacites of Tongariro Volcanic Centre. The occurrence of dacite inclusions in significant quantity in the Taupo Pumice Formation indicates the presence of other dacite flows near the vent area. Four types of andesite blocks; hornblende andesite, plagioclase-pyroxene andesite, pyroxene andesite and olivine andesite occur as lithic blocks in the ground layer. The andesites are petrographically distinct from those encountered in deep drillholes at Wairakei (Waiora Valley Andesites), and are different from the Rolles Peak andesite in having lower Sr content. The andesite blocks show similar major and trace element content to those from the Tongariro Volcanic Centre. The roundness of the andesite blocks indicates that the blocks were transported as alluvium or lahars in to the lake basin before being incorporated into the pyroclastic flow. Two types of welded ignimbrite blocks are described. The lithic-crystal rich ignimbrite is correlated with a post-Whakamaru Group Ignimbrite (ca. 100 ka ignimbrite erupted from Taupo Volcanic Centre) which crops out to the north of Lake Taupo. The crystal rich ignimbrite is tentatively correlated with the Whakamaru Group Ignimbrites. The lake sediment boulders, pumiceous mudstone and siltstone in the ground layer probably correlate to the Huka Group sediments or younger Holocene sediments in the lake basin. A comparative mineral chemistry study of the lithic blocks was done. A change in chemistry of individual mineral species was found to accompany the variation in wholerock major element constituents in the different types of lithics. The large quantity of lithic blocks in the ground layer suggests extensive vent widening at the begining of the ignimbrite eruption. A simple model of flaring and collapse of the vent area caused by the down ward movement of the fragmentation surface is presented to explain the origin of the lithic blocks in the ground layer. The lithics in the Taupo Pumice Formation are therfore produced by the disruption of the country rock around the vent during the explosion and primary xenoliths from depths of magma generation were not found. Stratigraphic relations suggest that the most important depth of incorporation of lithics is within the post-Whakamaru Group Ignimbrite volcanics and volcaniclastic sedimentary units.</p>

Quality of coal seam D of Muara Enim Formation, Central Palembang Subbasin

Coal seam D belongs to Muara Enim Formation in Central Palembang Subbasin, South Sumatera Basin, which ages of Middle Miocene to Late Miocene. This study aims to determine the quality of the coal, especially sulphur content and form, ash content and composition, and trace elements of heavy metals. Those are important to know as a reference in suitability in the use of this coal. Methods of analysis is proximate, total of sulphur, form of sulphur, SEM-EDS, ash composition, and trace element. The coal is categorized as low rank coal or lignite with a very low total sulphur max 0.25%, dominated by the organic sulphur formed during the peatification and coalification process (syngenetic). The coal has a safe ash composition. It shows from a very low metal oxide content that causes slagging and fouling at low temperatures process. Likewise, the trace element content of the coal such as chromium (Cr), cadmium (Cd), manganese (Mn), lead (Pb), nickel (Ni) is still far below the threshold for trace element content in coal.

Trace element content in alluvial soils landscape of the flood plains of the Iput river

The results of research on the content and distribution of trace elements in alluvial soils of various elements of the floodplain landscape, and their relationship with fertility indicators are presented. It has been found that the maximum concentrations of most trace elements (Ni, Zn, Mn, Cr, Co, Mo, As) are characteristic of the alluvial overhanging-marsh heavy-coal pristine subsystem of the floodplain landscape. In the riverine and perish subsystems of the floodplain landscape in individual layers of the corresponding soils, an excess of clark was found: in the alluvial sour acid layered primitive shortened sandy loam Cu by 1.5; Zn in 1.1; Cd 9.2 times, in alluvial chilli-marsh heavy-coal Cu 1.05; Zn in 1.4; Mn in 1.01; Cr in 1,2; Cd 3.2 times. For the riverine and perch subsystems, the excess of Cu, Mn and Cr was observed in the soil layer 0-5 cm, the remaining exceedances are characteristic of deeper layers. Decreasing rows of trace elements in alluvial soils have a similar structure. The microelements in question, in the soils of the floodplain landscape of the Iput River, in terms of clark concentration, belong to the group of dispersing. There is no significant correlation between micronutrient content and fertility of the alluvial soils under consideration.

Accumulation of trace element content in the lungs of Sao Paulo city residents and its correlation to lifetime exposure to air pollution

Heavy metals are natural and essential elements of the environment and living beings, produced from natural (e.g. volcanic activity and cosmic ray-induced spallation) and anthropogenic processes (e.g. industrial and fossil fuel combustion). Studies showed increase of heavy metal and Polonium-210 concentrations in lung autopsies linked to urban and industrial air pollution. In this preliminary study, we analyzed the levels of heavy metals and Polonium-210 (210Po) in lung tissues in autopsies from residents of the city of Sao Paulo, SP, Brazil. In order to identify the generating sources of the heavy metals in lung a factor analysis was performed. Of the first four factors, which explain 66% of the total variability, three were associated with vehicular sources. The fitting of a regression model with Polonium-210 as the response variable and with the four factors as explanatory variables, controlling for age, sex and tobacco, showed a significant association between the concentration of polonium and the first factor that is generated by catalysts and brakes (coefficient = 0.90, standard error = 0.33, p = 0.016). Our findings suggest an association between the metals trace, from air pollution, and Polonium-210 in lung autopsies.

Evolution of a hydrothermal ore-forming system recorded by sulfide mineral chemistry: a case study from the Plaka Pb–Zn–Ag Deposit, Lavrion, Greece

Laser ablation-inductively coupled plasma-mass spectrometry and electron-probe microanalysis were used to investigate the trace-element contents of sphalerite, chalcopyrite and pyrite from the Plaka Pb–Zn–Ag deposit. Using petrographic observations, the analytical results could be linked to the temporal evolution of the Plaka ore-forming system. Sphalerite chemistry reliably records the temperature and fS2 evolution of the system, with estimated formation temperatures reproducing the microthermometric results from previous fluid-inclusion studies. Chalcopyrite chemistry also shows systematic variations over time, particularly for Cd, Co, Ge, In, Sn and Zn concentrations. Measurable pyrite was only found in association with early high-temperature mineralisation, and no clear trends could therefore be identified. We note, however, that As and Se contents in pyrite are consistent with formation temperatures estimated from co-existing sphalerite. Statistical analysis of the sphalerite data allowed us to identify the dominant geological controls on its trace-element content. The three investigated factors temperature, fS2, and sample location account for > 80% of the observed variance in Mn, Fe, Co, Ga, Ge, In, Sb and Hg concentrations, and > 60% of the observed variance in Cd and Sn concentrations. Only for Cu and Ag concentrations is the explained variance < 50%. A similarly detailed analysis was not possible for chalcopyrite and pyrite. Nevertheless, comparison of the results for all three investigated minerals indicates that there are some systematic variations across the deposit which may be explained by local differences in fluid composition.

Content of rare earth elements in basalt aggregate from Winna Góra, Poland

Seek for new Rare Earth Elements (REE) sources encourage looking for easily available sources located in Europe. REE in evolved magmatic systems are predominantly associated with alkali environments. Therefore, it was decided to identify the content of REE in alkali igneous rocks of the Winna Góra basalt quarry located in Lower Silesia, Poland. In this study, a commercially available basalt aggregate from Winna Góra deposit located in the south-western part of Poland near Jawornik was examined for REE content. Mineral content and chemical composition were examined with a light microscope, XRD and XRF, whereas trace element content was measured with the ICP-MS technique. A new method of sample preparation for the purpose of REE identification in basalt aggregate based on pressure microwave mineralisation was developed. Mineral composition and TAS diagram classify aggregate as tephrite. The mineral composition of samples reflects typical mafic and ultramafic rocks. Quantitative mineralogical analysis by the Rietveld method showed that the main minerals are anorthite (46.7%) and augite (37.4%) with a minor content of forsterite (7.5%), nepheline (7.4%) and apatite below 1%. The total content of REE does not exceed 132 ppm. Chondrite normalised curves show the highest concentration of La and Pr. In the case of HREE, the majority of elements (Eu, Tb, Dy, Ho, Er, Yb) concentrations were below 1 ppm, a Tm and Lu were not detected. The low enrichment in HREE was also reflected in La/Gd ratios. Obtained results are comparable to the REE contents in the western part of the Cenozoic European Volcanic Province.

Geochemistry of Framboids

The stoichiometry of pyrite in framboids is unknown. The trace element content of framboids has been reported since framboids usually constitute the earliest pyrite phase in a sediment and therefore are more likely to pick up trace element variations in contemporary seawater. The trace element ratios in sedimentary framboids are similar to those in the host shales. Analyses of hydrothermal framboids are fewer, and As, Sb, and Tl appear to be enriched in hydrothermal framboids, with As, Sb, Ni, and Co also being enriched in framboids formed during metamorphism. In contrast with trace element distributions, no spatial variations in sulfur isotopic compositions have been reported within individual framboids. Framboids pick up a more accurate measure of the sulfur isotopic composition of the prevailing dissolved sulfide and are likely to retain this over geologic time. Although it is probable that pyrite framboids collect the local environmental trace element variations, interpretations of the results in terms of paleoenvironmental reconstructions are currently complex. The original sequestration of trace elements is likely to be in part determined by the pyrite crystal chemistry, and there may be a limit to how much of any given trace element can be sequestered by pyrite. This is likely to be enhanced during late diagenesis and early metamorphism and it is not altogether clear how individual trace elements behave over geologic time.

Hydrogeochemical features of Lake Kotokel

The purpose of this study is to determine the main hydrochemical parameters of Lake Kotokel deep waters, to identify the role of groundwater feeding it, as well as to establish the features of spatial distribution of macro- and microelements in the lake. Field work was carried out during the ice and ice-free seasons. A special sampler was used to take water samples from the bottom of the lake. Water samples were filtered through the filters with a pore size of 0.45 μm at the sampling site. Plastic bottles were used for the water samples for analysis. Polypropylene containers (15 ml) pretreated with 0.1 N nitric acid were used for the water samples for trace elements. The analysis of the macrocomponent composition of water was carried out in a certified Laboratory of Hydrogeology and Geoecology of the Geological Institute of the Siberian Branch of the Russian Academy of Sciences (Ulan-Ude) according to the standard methods intended for fresh and saline waters. Cations (Ca2+, Mg2+, Na+, K+) were determined by atomic absorption, F-, SiO2 – by the colorimetric method, HCO3- , CO32- and Cl- – by the titrimetric method, SO42- – by the turbidimetric method. The analysis of the trace element content was carried out in the Laboratory of Aquatic Microbiology at the Limnological Institute of the Siberian Branch of the Russian Academy of Sciences (Irkutsk) by the method of inductively coupled plasma on Agilent 7500ce quadrupole mass spectrometer. Conducted research made it possible to determine an inhomogeneous chemical composition of lake water associated with the discharge of fissure-vein waters along the faults that bound the depression from the southeast and northeast and intersect the lake water area from the island to the Istok river. The highest content of dissolved substances was recorded in the strait between Monastyrsky island and the western shore of the lake; the maximum values of hydrocarbonate ion and total mineralization were found here. The maximum content of sulfate ion was found in the southern and southeastern parts of the lake. The dispersion in microelement distribution reaches several mathematical orders. The most variable concentration is characteristic of iron, manganese, copper, zinc, lead, phosphorus, molybdenum, tungsten, strontium. Their high contents were found in the lake water within the location of faults of northeast strike. Therefore, the chemical composition of the water of Lake Kotokel is largely formed by fissure-vein waters. This water is discharged along the tectonic faults of the northeastern strike. The research revealed two centers of subaqueous discharge, which are characterized by the formation of two different associations of microelements in the lake water. The composition of microelements in fissure-vein waters is determined by their interaction degrees with rocks.