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We prove the existence of an elliptic Reeb orbit for some contact forms on the real projective three space R P³. The main ingredient of the proof is the existence of a distinguished pseudoholomorphic curve in the symplectization given by the U map on ECH. Also, we check that the first value on the ECH spectrum coincides with the smallest action of null-homologous orbit sets for 1/4-pinched Riemannian metrics. This action coincides with twice the length of a shortest closed geodesic. In addition, we compute the ECH spectrum for the irrational Katok metric example. [ABSTRACT FROM AUTHOR]

Satellite altimetry is somewhat unique among ocean remote sensing techniques because it provides much more than surface observations. By measuring sea surface topography and its change in time, altimeters provide information on the Earth’s gravity field, the shape and structure of the ocean bottom, the integrated heat and salt content of the ocean, and geostrophic ocean currents. Much progress has been made in the development of operational ocean applications, and altimeter data are now routinely assimilated in near-real-time to help forecast El Niño, monitor coastal circulation, and predict hurricane intensity. Although past missions have been flown largely for research purposes, altimetry is rapidly moving into the operational domain and will become a routine component of international satellite systems during the twenty-first century. Regarding the rapidly growing satellite altimetry database and corresponding products worldwide, the investigation of different mean dynamic ocean topography (MDT) models was carried out, which was assesses to be important for further use in geodetic applications. The efficiency and quality of different MDT models are discussed in view of the adopted geoids as reference surfaces. The region of the North Sea area was applied for the construction of the SST (Sea Surface Topography) model based on the altimetry data from 6 satellites for the total period of 15 years. Gravimetric quasigeoid and SST model were used for the comparison with independent data from 5 tide-gauges and led to the conclusion on the 44.73 cm level of accuracy of discussed models. Similar comparison of EGM2008 and computed normal heights for well-determined GPS-sites led to the low accuracy of this MDT. [ABSTRACT FROM AUTHOR]

Agate geodes contain spheroidal patterns characterized by spectacularly coloured and circularly concentric laminations with radially aligned quartz crystals, yet the origin of these geometric patterns has remained enigmatic. Here, detailed comparisons are documented between these kinds of patterns in a selection of geodes and concretions and those produced by abiotic chemically oscillating reactions. We find strikingly comparable self-similar, fractal patterns in both natural volcanogenic geodes and sedimentary concretions as well as in these benchtop experiments. In addition, the mineralogical composition of patterns and associated organic matter point to the oxidation of organic compounds in both geodes and concretions. This process occurred during diagenetic or supergene alteration, and it is consistent with spontaneous and abiotic chemically oscillating reactions. It is concluded that the oxidation of organic acids was involved in the formation of these patterns and that these rocks indicate oxidation–reduction reactions involving organic carbon, which itself may be abiotic or biological in origin. Hence, agate geodes and concretions represent the abiotic biosignatures of possible biological origin in volcanic and sedimentary rocks. [ABSTRACT FROM AUTHOR]

We performed an extensive optical and chemical analysis of a single Keokuk geode using electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy that revealed an extraordinary array of minerals and multiple, complex cycles of mineralization. We identified at least 15 minerals including 5 that, to our knowledge, have not been reported in previous studies of these geodes. Along with bitumen we have described the occurrence of REE's, and other unidentified phases containing metals such as chromium, nickel, molybdenum, tin, copper, zinc, and lead. Additionally, preliminary thin-section analysis reveals the occurrence of the tentatively identified minerals zircon, rutile, and xenotime as well as grains containing gold and silver within the chalcedony shell. The presence of these potentially economically valuable minerals warrants further investigation into the micro-minerology of Keokuk geodes. Our SEM/EDX analysis reveals an array of complex mineral assemblages, intergrowths, and inclusions that help chronologically link multiple stages of paragenesis occurring in different locations within the geode. Consequently, morphology and intricate microstructures provide a window into the extreme complexity of mineral crystallization. The majority of micro-minerals we have observed correspond with the later stages of geode paragenesis, thus providing a detailed record of the secondary mineralization processes which occurred over thousands to millions of years. [ABSTRACT FROM AUTHOR]

The article describes the establishment of the location of agate geodes using the GPR method in the area of the Simota gully (Lesser Poland Voivodeship). Agates (a multicolored variety of gemstone of chalcedony group) have multifaceted values that informed their study. Traditional methods of geode location are less reliable, hence the attempt to use the GPR method. Measurements were taken at two study test sites with subsurface geology of weathered melaphyre and pyroclastic deposits using a GPR system (ProEx). A high-frequency antenna (1.6 GHz) was used along with the pre-established profiles of lengths of 6-m and 10-cm intervals. Furthermore, simple soil tests using the soil sampler tool were made prior to the GPR measurement. The GPR results show significant high attenuation of the electromagnetic energy interpreted to be due to clay components of the regolith. Advanced signal processing procedures (such as the attribute of the signal) were used on the data for better enhancement that aided interpretation. Other anomalies depicted on the radargrams were thought to be the presence of roots, pieces of melaphyres-targeted agates. Furtherance to ascertain the reflection coefficients as recorded on the GPR data, in situ samples (root pieces, melaphyres, agates) taken were tested in the laboratory for electric permittivity property. Based on the interpretation results, several agate geodes were dug out from the ground. [ABSTRACT FROM AUTHOR]

Pathological lesions and fractures in the proximal femur are a common presentation to orthopaedics. Key to getting the management right first time is careful assessment using a multidisciplinary approach. Early discussion with the local orthopaedic oncology service is paramount before any biopsy or surgical intervention is planned. This paper discusses several key pathologies that can result in lesions of the proximal femur and their optimal management. [ABSTRACT FROM AUTHOR]

Voronoi tessellation, and its dual the Delaunay triangulation, provide a cohesive framework for the study and interpretation of phenomena of geographical space in two and three dimensions. The planar and spherical solutions introduce errors in the positional accuracy of both Voronoi vertices and Voronoi edges due to errors in distance computations and the path connecting two locations with planar lines or great circle arcs instead of geodesics. For most geospatial applications the introduction of the above errors is insignificant or tolerable. However, for applications where the accuracy is of utmost importance, the ellipsoidal model of the Earth must be used. Characteristically, the introduction of any positional error in the delimitation of maritime zones and boundaries results in increased maritime space for one state at the expense of another. This is a situation that may, among others, have a serious impact on the financial activities and the relations of the states concerned. In the context of previous work on maritime delimitation we show that the Voronoi diagram constitutes the ideal solution for the development of an automated methodology addressing the problem in its entirety. Due to lack of a vector methodology for the generation of Voronoi diagram on the ellipsoid, the aforementioned solution was constrained by the accuracy of existing approaches. In order to fill this gap, in this paper we deal with the inherent attributes of the ellipsoidal model of the Earth, e.g. the fact that geodesics are open lines, and we elaborate on a methodology for the generation of the Voronoi diagram on the ellipsoid for a set of points in vector format. The resulting Voronoi diagram consists of vertices with positional accuracy that is only bounded by the user needs and edges that are comprised of geodesics densified with vertices equidistant to their generators. Finally, we present the implementation of the proposed algorithm in the Python programming language and the results of two case studies, one on the formation of closest service areas and one on maritime boundaries delimitation, with the positional accuracy set to 1 cm. [ABSTRACT FROM AUTHOR]

Tumuli are a common feature of pahoehoe basaltic flows, interspersed with pits, and furnished the necessary volume of rock in the Paraná volcanic province for hydrothermal alteration and ballooning to form large cavities (1–2 m common). Filling by amethyst and other minerals resulted in the largest world deposit of geodes, Ametista do Sul. The flat-lying fracture positioned 1 m below the 2–3 m thick geodic level crosses the plateau and is a major guide for exploration and gallery opening. The geodes are limited on the top by the platy joint layer, which is covered by an auto-breccia with undulating lower limit. This wave mimicks and is internal to the structure of tumuli and pits at the surface. This field-oriented survey of galleries selected out of 300 active mines resulted in the description of the internal structure of the remarkable Veia Alta pahoehoe flow, in addition to observations in Uruguay. [ABSTRACT FROM AUTHOR]

As part of an international research project, the marine fungal strain collection of the Helmholtz Centre for Ocean Research (GEOMAR) research centre was analysed for secondary metabolite profiles associated with anticancer activity. Strain MF458 was identified as Tolypocladium geodes, by internal transcribed spacer region (ITS) sequence similarity and its natural product production profile. By using five different media in two conditions and two time points, we were able to identify eight natural products produced by MF458. As well as cyclosporin A (1), efrapeptin D (2), pyridoxatin (3), terricolin A (4), malettinins B and E (5 and 6), and tolypocladenols A1/A2 (8), we identified a new secondary metabolite which we termed tolypocladenol C (7). All compounds were analysed for their anticancer potential using a selection of the NCI60 cancer cell line panel, with malettinins B and E (5 and 6) being the most promising candidates. In order to obtain sufficient quantities of these compounds to start preclinical development, their production was transferred from a static flask culture to a stirred tank reactor, and fermentation medium development resulted in a nearly eight-fold increase in compound production. The strain MF458 is therefore a producer of a number of interesting and new secondary metabolites and their production levels can be readily improved to achieve higher yields. [ABSTRACT FROM AUTHOR]

The article reports on geodes from the American Midwest. It mentions its formation in sedimentary layers deposited in hot shallow seas near the equator. An overview of various minerals found in mine fields including quartz, kaolinite and pyrite which are crystal groups in geode deposits is also presented.

The article reports on geodes and their formation. It mentions its definition by the American Geological Institute (AGI) as a hollow and globular body located in limestone beds and in shales featuring a thin and partial layer of dense chalcedony. An overview of its morphologic attributes is also presented.

The article reports on Earth science symbols in various American states. These include diamond in Arkansas, geode in Iowa and the Salem Limestone in Indiana. It mentions that the Midwest minerals will be the theme for the Tucson Gem and Mineral Show in 2017 featuring fossils of Mesozioc dinosaurs as well as Cambrian and mammalian vertebrates.

Objective: To assess CT features of the sternoclavicular joint (SCJ) and first costochondral junction in asymptomatic patients.Materials and Methods: In 66 patients transverse and coronal oblique high-resolution multiple detector CT images of the SCJ and first costochondral junction were obtained. Images were reviewed by consensus of two radiologists. Joint space width was measured at three levels, and osteophytes, geodes, and erosions were evaluated. Variants and degree of ossification were noted. Statistical analysis consisted of Shapiro-Wilk test, Pearson's test, and paired sample t test.Results: There were 34 men and 32 women with a mean age of 60 years (age range, 17-98 years). The width of the joint spaces showed a normal distribution. There was no significant difference between the left and right sides. On coronal images the joint space was wider superiorly and on transverse images posteriorly. There was a trend toward decreasing joint space with age, although it did not reach significance (p > 0.05). Clavicular osteophytes were seen in 16 out of 66 patients (24 %) and sternal osteophytes in 16 out of 66 patients. Clavicular geodes were seen in 10 out of 66 patients (15 %) and sternal geodes in 14 out of 66 patients (14 %). No erosions were seen. Clefts of the first costochondral junction were seen in 31 out of 66 patients (47 %).Conclusion: In asymptomatic patients, there is no significant asymmetry of the SCJ. The joint spaces did not significantly decrease with age, although such a trend could be observed. Pronounced joint space narrowing with large geodes and osteophytes was not seen. Clefts of the first costochondral junction are common and not significant. [ABSTRACT FROM AUTHOR]

The article offers information about the production of celestine-bearing geodes, which occur in the Jurassic Curtis Formation of Emery and Wayne counties off the east and south flanks of the San Rafael Swell in Utah. It notes that the two counties produce geodes to 25 centimeter wide which contain bladed to tabular celestine crystals. Information about evaporative littoral system as well as the formation of anhydrite nodules and silicification of the nodules is presented.

Dudgeodes bharathidasani sp. nov. is described from the Western Ghats of South India. The nymphs of this species were found in the seepage areas of a stream, and they were associated with the nets constructed by trichopteran larvae (Hydropsychidae: Hydropsyche). [ABSTRACT FROM AUTHOR]

The archaeological research carried out at Cioarei-Boroşteni Cave, Romania, exposed, in the H Mousterian layer (GrN 15054: 47.900 + 1800/–1500 BP), a spherical-ellipsoidal geode. Its structure was determined using a tomograph with special resolution. The particular morphology, aspect and features of the geode drew the attention of the Neanderthal man who introduced it into the cave due to its unusual look as compared to the other rocks. Using a fibre-optic digital microscope, it has been observed that the geode was painted with ochre. The Neanderthal man must have certainly attached an aesthetic importance to it, while its having been painted with ochre was an addition meant to confer symbolic value. Also, in Cioarei Cave, in addition to the ochre samples, the oldest ochre preparation containers made of stalagmites and stalagmite crusts were uncovered. [ABSTRACT FROM AUTHOR]

Fluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Paraná continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low δS values of pyrite (−25 to −32 ‰) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in δO values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80-90 °C infiltrating a basaltic host rock of less than 45 °C. Colourless quartz and amethyst formed at temperatures between 40 and 80 °C, while the different calcite generations and late gypsum precipitated at temperatures below 45 °C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with δD values of amethyst-hosted fluid inclusions (−59 to −51 ‰) show a significant O-shift from the meteoric water line. This O-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high δS values of anhydrite and barite (7.5 to 9.9 ‰) suggest that sedimentary brines from deeper parts of the Guaraní aquifer system must have been responsible for the amethyst mineralisation. [ABSTRACT FROM AUTHOR]

Spectacular celestine geodes occur in a Jurassic peri-evaporitic sequence (Ardon Formation) exposed in Makhtesh Ramon, southern Israel. The geodes are found only in one specific location: adjacent to an intrusive contact with a Lower Cretaceous basaltic dyke. Celestine, well known in sedimentary associations worldwide and considered as a low temperature mineral, may therefore be associated with magmatic-induced hydrothermal activity. Abundant fluid inclusions in celestine provide valuable information on its origin: gas-rich inclusions in celestine interiors homogenized at T≥200°C whereas smaller liquid-rich inclusions record the growth of celestine rims at T≤200°C. Near 0°C melting temperatures of some fluid inclusions and the occurrence of hydrous Ca-sulphate solid crystals in other inclusions indicate that celestine precipitated from variably concentrated Ca-sulphate aqueous solutions of meteoric origin. Celestine crystallized from meteoric water heated by the cooling basaltic dyke at shallow levels (c. 160 m) during a Lower Cretaceous thermal perturbation recorded by regional uplift and magmatism. The 87Sr/86Sr ratio of geode celestine, 0.7074, is similar to that measured in the dolostones of the host Jurassic sequence, but differs markedly from the non-radiogenic ratio of the dyke. Strontium in celestine was derived from dolostones preserving the 87Sr/86Sr of Lower Jurassic seawater, while sulphur (δ34S = 19.9‰) was provided by in situ dissolution of precursor marine gypsum (δ34S = 16.8‰) indicated by relict anhydrite inclusions in celestine. Low-temperature meteoric fluid flow during the Campanian caused alteration of the dyke into secondary clays and alteration of geodal celestine into quartz, calcite and iron oxides. [ABSTRACT FROM AUTHOR]

The article focuses on the emergence of pseudomorphs of quartz after crystals of an undetermined mineral or minerals in Morocco since 1984. It mentions that such mysterious objects have been found in regions including Sidi Rahal, El Kelaa des Sraghna Province, and Marrakech-Tensift-El Haouz. It also notes the mystery surrounding objects where most of them appear to have developed inside of geodes.

The article presents information on polyhedroid minerals which are described as flat-sided, geometric-appearing blocks of polycrystalline quartz. It says that the polyhedroids tend to be hollow, and encrusted by druses of usually colorless quartz crystals, therefore they may be a type of geodes. It also discusses different theories of the formation of polyhedroids.

Abstract: We report the discovery of a large number (probably thousands) of gossans in the intraplate Paraná volcanic province in South America, based on observations from satellite images and field work supplemented with rock geochemistry and geophysics. We also provide a straightforward prospecting guide for agate and amethyst deposits. The study area is located on the border between Brazil and Uruguay, encompassing the Quaraí mining district and the Los Catalanes gemological district. Anomalies in Google Earth satellite images were identified above six underground mines in the Los Catalanes gemological district, characterized in the pampas of the region as irregular structures of intense green color and sometimes with some brownish tints. These vegetation, gamma-spectrometric, and geochemical anomalies occur at several stratigraphic levels in the volcanics. Three gamma-spectrometric sections performed on the Maurício mine of the Los Catalanes gemological district indicate low emission rates near 55cps (sd=4.7) in the gossan compared with the regional average of Cordillera flow (63cps). LOI higher than 2% is considered a strong indicator of intense hydrothermal alteration in the gossan. In the Quaraí mining district, gossans were studied in five areas, two in the Catalán flow, two in the Muralha flow, and one in Cordillera flow. Negative gama-spectrometric anomalies (higher than one standard deviation) occur in these gossans. The detailed study of one gossan included a gamma-spectrometric grid spacing of 50×50m (K, U, Th and total emission rate) and whole-rock geochemical analyses (ACME, Canada). The whole-rock geochemical analyses (20 samples) collected inside and outside the gossan demonstrate that these rocks are basaltic andesites of the low‐Ti Gramado chemical type. The samples within the gossan have high values of loss on ignition (2.3, 2.8, 2.9, 2.8, 2.9, 2.4, 2.6, 2.6, 2.3 and 2.3wt.%), whereas outside the gossan the values are lower (0.8, 2.3, 0.5, 0.5, 1.6, 0.5, 0.6, 0.9, 1.3 and 1.9wt.%). SiO2, K2O and Rb show strong negative correlations with a loss on ignition, whereas MgO shows a slight enrichment. The low gamma-spectrometric signal in the gossan is defined primarily by the lower K2O of the altered rock. We thus report the discovery of gossans above amethyst geodes in the world-class deposits of the Paraná volcanic province and present a first description of the structure. A straightforward prospecting guide will facilitate future exploration for new deposits. [Copyright &y& Elsevier]

Standard Liesegang banding is the display of parallel bands of precipitate formed periodically when co-precipitate ions interdiffuse in a gel medium. The most striking resemblance with Liesegang patterns in Nature lies in the diverse scenery of banded textural features commonly observed in some geological materials, such as geodes, agates, malachites, as well as stratigraphic units of certain rock formations. Here, we explore the possible relationship between the Liesegang banding scenario and magmatic-type pattern formation, such as zonations in km-scale circular zoned plutons and anorogenic ring complexes, cyclic layering in large mafic-ultramafic layered intrusions and orbicular granites, as well as in mm-scale crystal zonations. We also investigate magmatic processes such as fractional crystallization, and the ranges of T and p that are compatible with operating conditions for Liesegang banding. For geochemical self-organization to operate via a Liesegang-type mechanism, a necessary condition is that the system be transiently out of equilibrium, and be described by complex nonlinear kinetic laws. We examine the viability of the development of geochemical patterns, in relation with the various requirements for the growth of Liesegang structures. [ABSTRACT FROM AUTHOR]

This paper reviews the case of a 45-year-old male, farmer, who presented with a localized lesion on the left foot (back and both sides) with increased volume, and fistulae of a 5-year evolution. Clinically, micetoma was suspected and micribiological studies identified the causative agent to be Actinomadura madurae. The radiography showed involvement (geodes) at the metatarsal bones. Treatment was initiated with trimethoprim sulfamethoxazole, diaminodiphenylsulphone and proteolytic enzymes, showing improvement after three months of treatment. [ABSTRACT FROM AUTHOR]

Objective: To determine diagnostic performance statistics of extra-labral magnetic resonance (MR) findings for detection of labral tears in a population of patients with clinical suspicion of this diagnosis. Materials and Methods: Seventy-nine patients clinically suspected of having a labral tear (who underwent arthroscopy) had their MR studies retrospectively reviewed to determine the presence of lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes. These findings were then correlated with the arthroscopic presence (or absence) of a labral tear. Results: All findings (lateral acetabular oedema-like marrow signal, ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) had a specificity and positive predictive value (PPV) of 100%. Lateral acetabular oedema-like marrow signal had a sensitivity of 35% and 20% negative predictive value (NPV). This was the only statistically significant finding ( P < 0.05). The sensitivity and NPV of ganglia were 12% and 16%, dysplastic femoral bumps (12%, 16%), synovial herniation pits (4%, 14%) and geodes (6%, 15%) respectively, ( P > 0.05). Conclusion: Lateral acetabular oedema-like marrow signal is a useful sign (100% PPV) in the MR diagnosis of a labral tear, if one is clinically suspected. The other findings (ganglia, dysplastic femoral bumps, synovial herniation pits and geodes) were not statistically significant. Further studies are required to evaluate these. [ABSTRACT FROM AUTHOR]

Numerical modelling by finite element methods provides two significant insights into the formation of the giant amethyst geodes of the Paraná volcanic province: the conditions needed to open the cavities and the conditions that control their size and shape. Giant amethyst geodes were formed in the Cretaceous (135 Ma) in altered volcanic rocks by water vapour pressure (Δp) at about 0.5 MPa under an altered basalt cover of 5-20 m. Only rocks with Young's modulus values (E) in the range 1-2 GPa can sustain ballooning, which is the growth of a cavity in a ductile medium by the pressure of water and its vapour. The size of the proto-geode is dependent on the water vapour pressure, which is directly related to thickness of the overlying basalt. Varying the yield points causes the formation of either prolate or oblate cavities. A low transition point (smaller than 0.18 MPa) generates a prolate-shaped cavity, whereas a high transition point (larger than 0.18 MPa) generates oblate proto-geodes. Proto-geodes are smaller when Young's modulus is higher (rock is less altered) or when water vapour pressure is lower (because of thinner overburden of basalt). The calculations are an indication that the processes operative in the altered basalts led to the opening of giant cavities by ballooning. [ABSTRACT FROM AUTHOR]

The opening and filling of cavities in rocks are the major processes related to the generation and sealing of porosity in ore deposits. This study documents three stages of opening and filling of vesicles and geodes in the basalts and rhyodacites of the southern Paraná volcanic province. Each step detailed here is actually part of a sequence of minor hydrothermal events. First, lava degassing at high temperature (1150°C) formed small (<4  cm) vesicles in the crusts of flow units. In sequence, these vesicles were partly to fully filled at low temperature (30–150°C) by hydrothermal minerals, particularly clays and zeolites; this process also sealed the porosity of the lava. Second, the injection of fluidized sand generated new cavities, which were partly filled with sand; the newly formed porosity was sealed by the low-temperature fluid. Third, intense alteration of the basalt or rhyodacite core into a claystone favoured the opening of small to giant protogeodes (0.1  mm to 4  m) by dissolution; cooling of the fluid led to the precipitation of hydrothermal minerals, particularly the spectacular amethyst, calcite, and gypsum-bearing geodes. [ABSTRACT FROM AUTHOR]

Stable isotopes (C, O, S) and mineralogical studies of the world-class amethyst-geode deposits of the Los Catalanes gemological district, Uruguay, constrain processes operative during mineral deposition. The mineralized basaltic andesites from the Cretaceous Paraná volcanic province are intensely altered to zeolites (clinoptilolite) and clay minerals. Variations in the δO values of silica minerals in geodes (chalcedony, quartz, and amethyst) are much larger and the values generally somewhat lower (21.2-31.5‰) in the Uruguayan deposits than in the Ametista do Sul area of southern Brazil. The range of δS values (−15.0 to −0.3‰) of altered basaltic rocks requires (in addition to sulfur of magmatic origin) the involvement of S-depleted sedimentary sulfur from bacterial sulfate reduction. The results delimit the mineralizing processes to a post-eruption environment characterized by low temperature and strong interaction of the lava flows with meteoric water. [ABSTRACT FROM AUTHOR]

The amethyst-bearing geodes found in the flood basalts of the Arapey formation at Artigas (Uruguay) were formed as protogeodes by bubbles of CO2-rich basalt-derived fluids. The formation of the celadonite rim and the lining of the geodes by agate followed by quartz and amethyst were driven by the artesian water of the Guaraní aquifer percolating the basalts from below. The temperature of the amethyst formation is estimated from fluid inclusion data to be between 50° and 120°C. Oxygen stable isotope data suggest a crystallization temperature of calcite of about only 24°C. The actual wellhead temperature of the water produced from the Guaraní aquifer in the study area is around 29°C. [ABSTRACT FROM AUTHOR]

The article offers information on the different types of minerals found in Illinois localities. It describes the mineral specimens produced across the regions including the Paleozoic sedimentary rocks in southern part, fluorspars in southeast corner, and geodes in west-central area. It mentions that there are deposits of glacial drift minerals including calcite, gold, and quartz across the state.

A personal narrative is presented which explores the author's experience of visiting the Las Choyas geode deposit at the Carillo mining camp, together with his family, in Chihuahua, Mexico.

In a previous work, we showed that massive test particles exhibit a nongeodesic acceleration in a modified theory of gravity obtained by a noncommutative deformation of General Relativity (so-called Matrix Gravity). We propose that this nongeodesic acceleration might be the origin of the anomalous acceleration experienced by the Pioneer 10 and Pioneer 11 spacecrafts. [ABSTRACT FROM AUTHOR]

Abstract: Giant geodes (up to 4 m long) in the massive central portions of altered basalt lavas from the Paraná Magmatic Province, southern Brazil and Uruguay, form a world-class source of amethyst and agate. Although the origin of the cavities has been ascribed to degassing of the lava at >1150 °C, field evidence is conclusive that the giant amethyst-agate-filled geodes were formed by hydrothermal processes at low temperatures. We propose an epigenetic and hydrothermal model for the origin of giant geodes. This model includes hydrothermal brecciation during an early brittle stage and the late formation of the cavities (geodes). In the brittle stage an overpressured aqueous fluid affected the basalt in a P, T field delimited by temperatures between 100 and 150 °C and vapor pressures between 1.2 and 5.5 bar. The fluids were capable of lifting the roof and fracturing the host rock along new subhorizontal and subvertical fractures and breccias in the massive lava. The formation of these structures occurred at shallow depths, unit-by-unit. To open the cavities, dissolution of the now altered basalt to clay minerals is necessary. The process is closely linked to the highest alteration grade of mineralized lavas in Los Catalanes gemological district. Dissolution processes are observed in micrometer-scale in the studied basalts. The primary mineralogy, consisting of labradorite (±andesine)+augite+pigeonite+mesostasis (K-rich), was altered during the interaction of large volumes of hot aqueous fluid with the rock. The alteration of pigeonite and its replacement by smectite is observed around the cavities, followed by the precipitation of amorphous silica and microcrystalline quartz in clay-rich sites. Associated zeolites (heulandite+clinoptilolite) fill the newly formed cavities in progressive stages of hydrothermal alteration. Our data indicate that the temperatures were less than 200 °C and probably less than 150 °C; cavity formation occurred after alteration of the basalt to more than 60 vol.% clay minerals. We thus suggest that cavities related to geode formation are of epigenetic origin. [Copyright &y& Elsevier]

This paper makes new contributions in motion detection, object segmentation and trajectory estimation to create a successful object tracking system. A new efficient motion detection algorithm referred to as the flux tensor is used to detect moving objects in infrared video without requiring background modeling or contour extraction. The flux tensor-based motion detector when applied to infrared video is more accurate than thresholding "hot-spots", and is insensitive to shadows as well as illumination changes in the visible channel. In real world monitoring tasks fusing scene information from multiple sensors and sources is a useful core mechanism to deal with complex scenes, lighting conditions and environmental variables. The object segmentation algorithm uses level set-based geodesic active contour evolution that incorporates the fusion of visible color and infrared edge informations in a novel manner. Touching or overlapping objects are further refined during the segmentation process using an appropriate shapebased model. Multiple object tracking using correspondence graphs is extended to handle groups of objects and occlusion events by Kalman filter-based cluster trajectory analysis and watershed segmentation. The proposed object tracking algorithm was successfully tested on several difficult outdoor multispectral videos from stationary sensors and is not confounded by shadows or illumination variations. [ABSTRACT FROM AUTHOR]

The amethyst geodes observed in the tholeiitic basaltic flow from the Triz quarry at Ametista do Sul (Rio Grande do Sul, Brazil) show particular wall-layering infillings with, from the outside inwards, celadonite, chalcedony, fine-grained quartz and large-sized amethyst crystals. The primary fluid inclusions analysed in the amethyst crystals yield a 152 to 238 °C crystallization temperature range. The amethyst geodes are always located in the massive, fracture-free, basaltic part of the lava flows and surrounded by a limited wall-lining alteration halo, the thickness of which depends on the geode radius. The geochemical balances calculated from fresh to altered basalt in the geode environment indicate that the amount of SiO2 released from the alteration halo is always sufficient to produce the siliceous rims in the geodes without requirement for extraneous silica supply. The results point to a volcanic origin for the amethyst geode infillings through basalt 'autoalteration' by authigenic high temperature hydrothermal fluids. These fluids can originate from (1) unmixing of volatile coumpounds from melt through pressure release, (2) cooling to supercritical hydrous fluids with 'autoalteration' of the surrounding basalt and (3) migration of the residual hot fluids from the basalt to the geodic cavities through the pressure gradient between the geodic cavity and the rock. [ABSTRACT FROM AUTHOR]

The article presents a summary of a geologist's 30 years of collecting of geodes in Heltonville Lawrence County in Indiana. According to the article, the deposits around Heltonville is a significant locality for geodes and fossils. Studies on the geology of the geode's habitat, the theories on its formation from lime deposits, its mineral contents and morphology are presented.

We investigate the geodesic motion in D-dimensional Majumdar–Papapetrou multi-black hole spacetimes and find that the qualitative features of the D = 4 case are shared by the higher dimensional configurations. The motion of timelike and null particles is chaotic, the phase space being divided into basins of attraction which are separated by a fractal boundary, with a fractal dimension dB. The mapping of the geodesic trajectories on a screen placed in the asymptotic region is also investigated. We find that the fractal properties of the phase space induces a fractal structure on the holographic screen, with a fractal dimension dB - 1. [ABSTRACT FROM AUTHOR]

Size distribution data obtained from detailed field study of bubbles and amethyst-geodes in the basaltic lava flows of the Serra Geral Formation (Ametista do Sul, Rio Grande do Sul, Brazil) are used in cooling and vesiculation models to infer the origin and the formation processes of the geodic cavities. Coupled field observations and modelling results emphasize that (1) the formation of geodes in the studied lava flow can be explained, qualitatively and quantitatively, by the exsolution of magmatic gas from the supersaturated melt with no need for external surface water supply; (2) the vertically elongated habits of the geodes result from higher cooling rate of the magma in contact with the accumulating bubbles; and (3) the abnormal metre-sized geodes with their branching habits result not only from the diffusive/decompressive bubble growth but also from the coalescence of inwards-progressing tubular cavities. [ABSTRACT FROM AUTHOR]