PETRIFIED WOOD OCCURRENCES IN WESTERN THRACE AND LIMNOS ISLAND: MINERALOGY, GEOCHEMISTRY AND DEPOSITIONAL ENVIRONMENT

The present study describes the geology and mineralogy of the main petrified wood occurrences in Evros-Rhodopi and Limnos and integrates them in a volcanichydro thermal framework taking into consideration the nature of hydrothermal solutions during the silicification process. In the Lykofi-Fylakto-Lefkymi area, quartz and opal-CT are the main silica polymorph within the wood. The hostrocL· exhibit a zeolitic alteration suggesting reduced and slightly alkaline fluids for the silicification of wood. At Kassiteres/Sappes area the presence ofsilicified wood within kaolinite± alunite altered tuffbreccias indicates that slight acidic fluids were involved in the silicification processes. In Limnos Island the fossiliferous Portianou, Varos- Roussopouli and Moudros-Roussopouli areas occur in the periphery of an eroded volcanic edifice exposed at Fakos peninsula. The silicified wood occurs: (a) within weakly altered pyroclastics and (b) associated to several horizons of sinters interbedded within the pyroclastics. Transformation of amorphous silica to opal-CT and then to quartz is postulated based on XRD and SEM studies. The studied areas represent unique natural monuments, comparable to the petrified forest of Lesvos island.

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Genesis of chemical sediments in Birimian greenstone belts: evidence from gondites and related manganese-bearing rocks from Northern Ghana

Mineralogical Magazine ◽

10.1180/minmag.1995.059.395.08 ◽

1995 ◽

Vol 59 (395) ◽

pp. 229-251 ◽

Cited By ~ 21

Author(s):

Frank Melcher

Keyword(s):

Transition Metals ◽

Manganese Oxide ◽

Depositional Environment ◽

Northern Ghana ◽

Hydrothermal Solutions ◽

Geochemical Conditions ◽

Mineral Assemblages ◽

Greenstone Belts ◽

Chlorite Schist ◽

Chemical Sediments

AbstractEarly Proterozoic chemical sediments of the Birimian Supergroup in northern Ghana host several types of metamorphosed manganese-bearing rocks. Differences in the mineralogy and geochemistry can be attributed to facies changes in a mixed volcanic-volcaniclastic depositional environment. Manganese oxide-bearing phyllite, which is enriched in transition metals (Cu, Ni, Co, Zn), formed on the flanks of submarine volcanic edifices above an oxidation boundary. Towards the deeper basin, manganese silicate-rich gondites occur. These consist either of spessartine + quartz + ilmenite, or of spessartine + quartz + Mn amphiboles ± rhodonite ± hyalophane ± Mn stilpnomelane ± ilmenite. The Mn amphiboles are identified as manganoan actinolite, tirodite, and dannemorite. Sulphides are widespread as premetamorphic inclusions in Mn garnet grains. In the basin centre, chlorite schist containing garnet with 50–60 mol.% spessartine represents the most distal manganese-bearing rock which is highly diluted by volcanogenic background sedimentation. The origin of Mn-rich rocks is explained by heat-driven seawater convection systems active in submarine volcanic centres that provided hydrothermal solutions. Precipitation of different minerals depended on the geochemical conditions prevailing on the seafloor. During the Eburnean event (around 2000 Ma), the chemical sediments were metamorphosed to upper greenschist or lower amphibolite facies. Mineral assemblages in the gondites point to metamorphic conditions in the range of 450–500°C at 2–3 kbar.

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Reducing Theft of Petrified Wood at Petrified Forest National Park

Journal of Interpretation Research ◽

10.1177/109258720000500101 ◽

2000 ◽

Vol 5 (1) ◽

pp. 1-18 ◽

Cited By ~ 15

Author(s):

Carolyn J. Widner ◽

Joseph Roggenbuck

Keyword(s):

Field Experiment ◽

National Park ◽

Primary Resource ◽

Resource Protection ◽

Petrified Wood ◽

Petrified Forest National Park ◽

Petrified Forest

The theft of petrified wood from Petrified Forest National Park is the park's primary resource-protection problem. Several interventions to control theft currently exist in the park, yet an estimated 12 tons of wood disappear from the park each year. This study evaluated three interventions to reduce the theft of wood from the park. Tested interventions included a sign, a signed pledge, and a uniformed volunteer. A field experiment revealed that all three interventions significantly reduced theft of wood over control conditions. In addition, the interventions were not significantly different from each other in their effectiveness.

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The fossil wood of East Cairo, Egypt: A mineralogical view

Mineralogia ◽

10.1515/mipo-2015-0003 ◽

2015 ◽

Vol 45 (1-2) ◽

pp. 47-57

Author(s):

Kamaleldin M. Hassan

Keyword(s):

Optical Microscopy ◽

Powder Diffraction ◽

Xrd Analysis ◽

Optical Microscope ◽

Fossil Wood ◽

X Ray ◽

Petrified Wood ◽

Representative Samples ◽

Petrified Forest

AbstractAs part of the characterization of the petrified wood of East Cairo at the New Cairo Petrified Forest, representative samples collected from the area were studied by X-ray powder diffraction (XRD) and optical microscopy. The samples, as indicated by XRD analysis, are composed of quartz ± some goethite ± minor moganite ± minor gypsum ± trace calcite. The absence of moganite in some samples has been attributed to the transformation of moganite to quartz or to leaching processes. Under the optical microscope, some of the 10 petrified-wood samples are permineralized with mainly microcrystalline quartz (chalcedony), some with a combination of chalcedony and microgranular quartz, and some with microgranular quartz. The sequence of silicification is likely to have been either opaline precursor to chalcedony and quartz, or directly to chalcedony and quartz. The crystallinity indices (C.I.) of the quartz in the samples studied, measured using a standard X-ray powder diffraction procedure, are consistent with the petrographic findings. The chalcedonic samples have the least C.I. values, and the microgranular quartz samples the highest values.

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Tourmalinites in supracrustal rocks in the Bjørnesund area, West Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v155.8184 ◽

1992 ◽

Vol 155 ◽

pp. 73-78

Author(s):

P.W.U Appel

Keyword(s):

Depositional Environment ◽

Massive Sulphide ◽

Hydrothermal Solutions ◽

West Greenland ◽

Alteration Zones ◽

Sulphide Ore ◽

Hydrothermal Processes ◽

Hydrothermal Origin ◽

Ore Bodies ◽

Geologic Setting

In the mid-Archaean supracrustal rocks of Bjørnesund south of Fiskenæsset metre wide anthophyllite-rich zones are found hosted in mafic volcanics. These zones, which are locally associated with sulphides, are interpreted as alteration zones from hydrothermal solutions which circulated through the volcano-sedimentary pile; in places they contain thin tourmalinites. The tourmaline composition and geologic setting of the occurrences closely resemble stratabound tourmalinites of submarine hydrothermal origin which elsewhere are associated with metalliferous deposits. It is concluded that the presence of the Bjørnesund tourmalinites associated with anthophyllite zones indicates that hydrothermal processes were once active in the depositional environment where the Bjørnesund supracrustals were formed; in other regions such processes are known to have generated massive sulphide ore bodies.

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Understanding Park Visitors’ Response to Interventions to Reduce Petrified Wood Theft

Journal of Interpretation Research ◽

10.1177/109258720300800106 ◽

2003 ◽

Vol 8 (1) ◽

pp. 67-82 ◽

Cited By ~ 7

Author(s):

Carolyn Widner Ward ◽

Joseph Roggenbuck

Keyword(s):

National Park ◽

Structured Interviews ◽

Subjective Responses ◽

Petrified Wood ◽

Petrified Forest National Park ◽

Petrified Forest

This study examined why theft of petrified wood at Petrified Forest National Park occurred and how designed interventions worked to inhibit the performance of that behavior. This evaluation was based on semi-structured interviews with observed thieves and non-thieves. Subjective responses revealed that theft was not a thoughtless act, but instead occurred because thieves rationalized that their particular act of theft was acceptable. The primary rationalization given by thieves was that their piece of stolen wood was so small that taking it would not hurt anything. It appeared as though anti-theft messages were received by all of those interviewed, but that thieves only applied these messages to the larger pieces of wood. In addition, most thieves did not view taking a little chip as stealing. There was not one primary message from the interventions processed by respondents, but instead many different messages were received and may have been impacting behavior.

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PALAEOXYLOTOMICAL STUDY OF A NEW COLLECTION FROM ZARAND MIOCENE PETRIFIED FOREST, SOUTH APUSENI MTS.

Acta Palaeontologica Romaniae ◽

10.35463/j.apr.2020.01.02 ◽

2019 ◽

pp. 19-34

Author(s):

Stanila Iamandei ◽

Eugenia Iamandei ◽

Petru Todea

Keyword(s):

Knowing That ◽

Quercus Frainetto ◽

Private Collection ◽

Petrified Wood ◽

Petrified Forest

We had in study some samples from a private collection of petrified wood, from South Apuseni mts., found in an area where numerous Miocene petrified woods were already described and tens lignotaxa were identified. These new petrified woods were collected from Ociu area, on the Church’s brook. They could contribute to better knowing that fabulous Mid-Miocene forest, and by palaeoxylotomic study the following arboreal taxa were identified: Thu-joxylon sp., Magnolioxylon kräuselii (Greguss) Van der Burgh, Spiroplatanoxylon densiradiatum (Petrescu) Süss, and Quercoxylon sp. cf. Quercus frainetto Tenore.

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Ultrastructural Alterations in Sinusoidal Endothelial Fenestrae as a Result of Hypoxia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100090828 ◽

1976 ◽

Vol 34 ◽

pp. 168-169

Author(s):

Waykin Nopanitaya ◽

Raeford E. Brown ◽

Joe W. Grisham ◽

Johnny L. Carson

Keyword(s):

Endothelial Cells ◽

Experimental Model ◽

Hepatic Lobule ◽

Ultrastructural Alterations ◽

Large Type ◽

Sinusoidal Endothelial Fenestrae ◽

General Size ◽

Sem Studies

Mammalian endothelial cells lining hepatic sinusoids have been found to be widely fenestrated. Previous SEM studies (1,2) have noted two general size catagories of fenestrations; large fenestrae were distributed randomly while the small type occurred in groups. These investigations also reported that large fenestrae were more numerous and larger in the endothelial cells at the afferent ends of sinusoids or around the portal areas, whereas small fenestrae were more numerous around the centrilobular portion of the hepatic lobule. It has been further suggested that under some physiologic conditions small fenestrae could fuse and subsequently become the large type, but this is, as yet, unproven.We have used a reproducible experimental model of hypoxia to study the ultrastructural alterations in sinusoidal endothelial fenestrations in order to investigate the origin of occurrence of large fenestrae.

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Amorphous silica coating on α-alumina particles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137422 ◽

1995 ◽

Vol 53 ◽

pp. 210-211

Author(s):

J. W. Mellowes ◽

C. M. Chun ◽

I. A. Aksay

Keyword(s):

Amorphous Silica ◽

Heterogeneous Nucleation ◽

Homogeneous Nucleation ◽

Silica Coating ◽

Full Density ◽

Optimal Conditions ◽

Fine Grained ◽

Alumina Particles ◽

Complete Mullitization ◽

Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

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