Cathodoluminescence,fluid inclusion and stable C–O isotope study of tectonic breccias from thrusting plane of a thin-skinned calcareous nappe

Basal hydraulic breccias of alpine thin-skinned Muráň nappe were investigated by means of cathodoluminescence petrography, stable isotope geochemistry and fluid inclusions analysis. Our study reveals an unusual dynamic fluid regime along basal thrust plane during final episode of the nappe emplacement over its metamorphic substratum. Basal thrusting fluids enriched in ¹⁸O, silica, alumina, alkalies and phosphates were generated in the underlying metamorphosed basement at epizonal conditions corresponding to the temperatures of 400–450°C. The fluids fluxed the tectonized nappe base, leached evaporite-bearing formations in hangingwall, whereby becoming oversaturated with sulphates and chlorides. The fluids further modified their composition by dedolomitization and isotopic exchange with the host carbonatic cataclasites. Newly formed mineral assemblage of quartz, phlogopite, albite, potassium feldspar, apatite, dravite tourmaline and anhydrite precipitated from these fluids on cooling down to 180–200°C. Finally, the cataclastic mush was cemented by calcite at ambient anchizonal conditions. Recurrent fluid injections as described above probably enhanced the final motion of the Muráň nappe.     

Geoelectrical mapping of contamination in the cemeteries: the case study in Piracicaba,São Paulo/Brazil

This paper presents the results of electrical resistivity methods in the area delineation that was potentially contaminated by liquefaction products, which are also called putrefactive liquids in Vila Rezende municipal cemetery, Piracicaba, São Paulo, Brazil. The results indicate a depth of water table between 3.1 and 5.1 m, with two groundwater direction flows, one to the SW and another to the SE. Due to the contamination plumes, which have the same groundwater direction flow, as well the conductive anomalies observed in the geoelectric sections, the contamination suspicions in the area were confirmed. The probable plume to the SE extends beyond the limits of the cemetery. The location of the conductive anomalies and the probable contamination plumes showed that the contamination is linked with the depth of the water table and the burial time. Mapping using the geostatistical method of ordinary kriging applied to the work drew structural characteristics of the regional phenomenon and spatial behavior of the electrical resistivity data, resulting in continued surfaces. Thus, this method has proved to be an important tool for mapping contamination plumes in cemeteries.     

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

Forty-one diamonds sourced from the Juina-5 kimberlite pipe in Southern Brazil, which contain optically identifiable inclusions, have been studied using an integrated approach. The diamonds contain <20 ppm nitrogen (N) that is fully aggregated as B centres. Internal structures in several diamonds revealed using cathodoluminescence (CL) are unlike those normally observed in lithospheric samples. The majority of the diamonds are composed of isotopically light carbon, and the collection has a unimodal distribution heavily skewed towards δ¹³C ~ ?25 ‰. Individual diamonds can display large carbon isotope heterogeneity of up to ~15 ‰ and predominantly have isotopically lighter cores displaying blue CL, and heavier rims with green CL. The light carbon isotopic compositions are interpreted as evidence of diamond growth from abiotic organic carbon added to the oceanic crust during hydrothermal alteration. The bulk isotopic composition of the oceanic crust, carbonates plus organics, is equal to the composition of mantle carbon (?5 ‰), and we suggest that recycling/mixing of subducted material will replenish this reservoir over geological time. Several exposed, syngenetic inclusions have bulk compositions consistent with former eclogitic magnesium silicate perovskite, calcium silicate perovskite and NAL or CF phases that have re-equilibrated during their exhumation to the surface. There are multiple occurrences of majoritic garnet with pyroxene exsolution, coesite with and without kyanite exsolution, clinopyroxene, Fe or Fe-carbide and sulphide minerals alongside single occurrences of olivine and ferropericlase. As a group, the inclusions have eclogitic affinity and provide evidence for diamond formation at pressures extending to Earth’s deep transition zone and possibly the lower mantle. It is observed that the major element composition of inclusions and isotopic compositions of host Juina-5 diamonds are not correlated. The diamond and inclusion compositions are intimately related to subducted material and record a polybaric growth history across a depth interval stretching from the lower mantle to the base of the lithosphere. It is suggested that the interaction of slab-derived melts and mantle material combined with subsequent upward transport in channelised networks or a buoyant diapir explains the formation of Juina-5 diamonds. We conclude that these samples, despite originating at great mantle depths, do not provide direct information about the ambient mantle, instead, providing a snapshot of the Earth’s deep carbon cycle.     

Origin of the Okrouhlá Radouň episyenite-hosted uranium deposit,Bohemian Massif,Czech Republic: fluid inclusion and stable isotope constraints

The Okrouhlá Radouň shear zone hosted uranium deposit is developed along the contact of Variscan granites and high-grade metasedimentary rocks of the Moldanubian Zone of the Bohemian Massif. The pre-ore pervasive alteration of wall rocks is characterized by chloritization of mafic minerals, followed by albitization of feldspars and dissolution of quartz giving rise to episyenites. The subsequent fluid circulation led to precipitation of disseminated uraninite and coffinite, and later on, post-ore quartz and carbonate mineralization containing base metal sulfides. The fluid inclusion and stable isotope data suggest low homogenization temperatures (～50–140 °C during pre-ore albitization and post-ore carbonatization, up to 230 °C during pre-ore chloritization), variable fluid salinities (0–25 wt.% NaCl eq.), low fluid δ¹⁸O values (?10 to +2 ‰ V-SMOW), low fluid δ¹³C values (?9 to ?15 ‰ V-PDB), and highly variable ionic composition of the aqueous fluids (especially Na/Ca, Br/Cl, I/Cl, SO₄/Cl, NO₃/Cl ratios). The available data suggest participation of three fluid endmembers of primarily surficial origin during alteration and mineralization at the deposit: (1) local meteoric water, (2) Na–Ca–Cl basinal brines or shield brines, (3) SO₄–NO₃–Cl–(H)CO₃ playa-like fluids. Pre-ore albitization was caused by circulation of alkaline, oxidized, and Na-rich playa fluids, whereas basinal/shield brines and meteoric water were more important during the post-ore stage of alteration.     

Field evidence of hydraulic connections between bedrock aquifers and overlying granular aquifers: examples from the Grenville Province of the Canadian Shield

Field evidence of hydraulic connections between a bedrock aquifer and an overlying granular aquifer in the Canadian Shield (Grenville Province) is presented. This issue is rarely considered and investigated despite its important hydraulic and chemical consequences and its widespread occurrence worldwide. The methodology employed is based on complementary field tests conducted at specific experimental sites instrumented both in the rock and in the overlying deposits. One of the bedrock sites revealed a natural hydraulic connection with the overlying granular aquifer caused by the weathered surface of the uppermost bedrock. Another site revealed an artificial hydraulic connection between the bedrock and the granular aquifer created by an improperly sealed casing. A regional study showed that hydraulic connections yield an erroneous interpretation of the true hydraulic properties of the tested aquifer. The detection of hydraulic connections is therefore essential to properly define well-capture areas and contamination conditions. It is recommended to practitioners that pumping tests be performed as well as hydrochemical comparisons of each existing aquifer unit. Falling-head permeability tests are also helpful in verifying the quality of the seal at the bedrock–casing contact. More effective procedural controls and better well-construction practices are necessary to reduce the risks of cross-contamination induced by defective seals.     

Angular momentum and gyroscope in flat space-time theory of gravitation

The study of a previously proposed theory of gravitation in flat space-time (Petry, 1981a) is continued. A conservation law for the angular momentum is derived. Additional to the usual form, there must be added a term coming from the spin of the gravitational field. The equations of motion and of spin angular momentum for a spinning test particle in a gravitational field are given. An approximation of the equations of the spin angular momentum in the rest frame of the test particle is studied. For a gyroscope in an orbit of a rotating massive body (e.g., the Earth) the precession of the spin axis agrees with the result of Einstein's general theory of relativity.     

Further eötvös correction error reduction through the utilization of baseline radio navigation systems

The current accuracy of sea‐going and airborne gravity measurements is not bounded by the precision of the gravimeter but by the precision with which external parameters such as vehicle velocity (speed), azimuthal heading, and geographic position can be determined. Uncertainties in these parameters are summed up in the Eötvös correction in the reduction of the measured data. This work investigates the suitability of baseline navigation systems, in particular Loran‐C and Omega, to further reduce the uncertainty of the Eötvös correction. Emphasis is placed on the velocity measurement error. A new algorithm is developed which derives velocity based upon the change in hyperbolic (or circular) grid readings, as opposed to the standard change in geographic position technique. A comparative analysis shows the new algorithm to be as precise as the currently used conventional calculation. Further, this simplified technique is accompanied with a 20‐fold reduction in computational complexity. Application of the results presented in this paper to the Loran‐C and Omega systems shows a velocity determination capability of 0.1 knot over a six minute integration time, and 0.05 knot for a 15 minute integration time for Loran‐C. The minimum error attainable in Omega is 0.1 knot when determined over a 17 minute measurement time. Further precision can be gleaned by applying the calculated error as a correction to subsequent velocity calculations.     

The trigonometric parallax of the neutron star Geminga

We obtained a series of four observations of the isolated neutron star Geminga over an 18 month period using the Advanced Camera for Surveys (ACS) Wide Field Camera (WFC) on the Hubble Space Telescope in order to determine its trigonometric parallax. We find the parallax π=4.0±1.3 mas, corresponding to a distance to Geminga of 250 _?62 ⁺¹²⁰  pc, a result 60% larger than the previously published value. The proper motion is 178.2±1.8 mas/year. In this paper, we describe the analysis techniques in detail since the amplitude of the parallactic shift is smaller than the camera’s pixel size. We fit each star in the images with an appropriate effective PSF and applied a distortion correction to generate stellar positions accurate to 0.01 pixels (～0.5 mas). The 134 stars common to all images serve to establish a reference frame for alignment of the image series. Our observations were made around the times of maximum parallactic shift. We discuss the implications of this new distance measurement for the inferred radius of Geminga, and the neutron star equation of state.     

Radar observations and the shape of near-Earth asteroid 2008 EV5

We observed the near-Earth ASTEROID 2008 EV5 with the Arecibo and Goldstone planetary radars and the Very Long Baseline Array during December 2008. EV5 rotates retrograde and its overall shape is a 400 ± 50 m oblate spheroid. The most prominent surface feature is a ridge parallel to the asteroid’s equator that is broken by a concavity about 150 m in diameter. Otherwise the asteroid’s surface is notably smooth on decameter scales. EV5’s radar and optical albedos are consistent with either rocky or stony-iron composition. The equatorial ridge is similar to structure seen on the rubble-pile near-Earth asteroid (66391) 1999 KW4 and is consistent with YORP spin-up reconfiguring the asteroid in the past. We interpret the concavity as an impact crater. Shaking during the impact and later regolith redistribution may have erased smaller features, explaining the general lack of decameter-scale surface structure.     

Mineral inclusions in sublithospheric diamonds from Collier 4 kimberlite pipe, Juina, Brazil: subducted protoliths, carbonated melts and primary kimberlite magmatism

We report on a suite of diamonds from the Cretaceous Collier 4 kimberlite pipe, Juina, Brazil, that are predominantly nitrogen-free type II crystals showing complex internal growth structures. Syngenetic mineral inclusions comprise calcium- and titanium-rich phases with perovskite stoichiometry, Ca-rich majoritic-garnet, clinopyroxene, olivine, TAPP phase, minerals with stoichiometries of CAS and K-hollandite phases, SiO₂, FeO, native iron, low-Ni sulfides, and Ca–Mg-carbonate. We divide the diamonds into three groups on the basis of the carbon isotope compositions (δ¹³C) of diamond core zones. Group 1 diamonds have heavy, mantle-like δ¹³C (−5 to −10‰) with mineral inclusions indicating a transition zone origin from mafic protoliths. Group 2 diamonds have intermediate δ¹³C (−12 to −15‰), with inclusion compositions indicating crystallization from near-primary and differentiated carbonated melts derived from oceanic crust in the deep upper mantle or transition zone. A ²⁰⁶Pb/²³⁸U age of 101 ± 7 Ma on a CaTiSi-perovskite inclusion (Group 2) is close to the kimberlite emplacement time (93.1 ± 1.5 Ma). Group 3 diamonds have extremely light δ¹³C (−25‰), and host inclusions have compositions akin to high-pressure–temperature phases expected to be stable in pelagic sediments subducted to transition zone depths. Collectively, the Collier 4 diamonds and their inclusions indicate multi-stage, polybaric growth histories in dynamically changing chemical environments. The young inclusion age, the ubiquitous chemical and isotopic characteristics indicative of subducted materials, and the regional tectonic history, suggest a model in which generation of sublithospheric diamonds and their inclusions, and the proto-kimberlite magmas, are related genetically, temporally and geographically to the interaction of subducted lithosphere and a Cretaceous plume.