What should be observed on the sun

Three problems are emphasized in particular: the preflare magnetic field configuration, velocity fields, and the nature of acceleration processes in flares. It is concluded that what we need most urgently are high-resolution hard X-ray, soft X-ray, and EUV-pictures, coronal spectra, and magnetograms with high resolution both in space and time. A space-shuttle equipped with instrumentation of this kind would contribute significantly to our knowledge of the flare process.     

Preliminary seismic hazard maps of Slovenia

The preparation of the preliminary seismic hazard maps of the territory of Slovenia has been based on an expansion of the basic approach laid out by Cornell in 1968. Three seismic source models were prepared. Two of them are based mainly on the earthquake catalogue using the Poissonian probability model. A map of seismic energy release and a map of earthquake epicenter density are used to delineate seismic sources in these models. The geometry of the third model which is based on a rough estimate of seismotectonic setting is taken from the probabilistic seismic hazard analysis of a nuclear power plant in Slovenia. Published ground motion attenuation models based on strong motion records of recent strong earthquakes in Italy are used. Test maps for variable and uniform b-values are presented. The computer program, Seisrisk III, developed by the U.S. Geological Survey is used.     

The BanskáŠtiavnica ore district: relationship between metallogenetic processes and the geological evolution of a stratovolcano

The Banská?tiavnica ore district is in the central zone of the largest stratovolcano in the Central Slovakia Neogene Volcanic Field, which is situated at the inner side of the Carpathian arc over the Hercynian basement with the Late Paleozoic and Mesozoic sedimentary cover. Volcanic rocks of the High-K orogenic suite are of the Badenian through Pannonian age (16.5–8.5?Ma). Their petrogenesis is closely related to subduction of flysch belt oceanic basement underneath the advancing Carpathian arc and to back-arc extension processes. The stratovolcano includes a large caldera 20?km in diameter and a late-stage resurgent horst in its centre, exposing a basement and extensive subvolcanic intrusive complex. The following stages have been recognized in the evolution of the stratovolcano: (1)?formation of a large pyroxene/hornblende-pyroxene andesite stratovolcano; (2)?denudation, emplacement of a diorite intrusion; (3) emplacement of a large granodiorite bell-jar pluton within the basement; (4) emplacement of granodiorite/quartz-diorite porphyry stocks and dyke clusters around the pluton; (5) caldera subsidence and its filling by biotite-hornblende andesite volcanics, emplacement of quartz-diorite porphyry sills and dykes at the subvolcanic level; (6)?renewed activity of andesites from dispersed centres on slopes of the volcano; (7) uplift of a resurgent horst accompanied by rhyolite volcanics and granite porphyry dykes. The following types of ore deposits (mineralizations) have been identified in the Banská?tiavnica ore district: 1. Quartz-pyrophyllite-pyrite high-sulphidation system at ?obov, related to the diorite intrusion. 2. Magnetite skarn deposits and occurrences?at contacts of the granodiorite pluton with Mesozoic carbonate rocks. Magnetite ores occur as lenses in the calcic skarns. 3.?Stockwork/disseminated base metal deposit along an irregular network of fractures in apical parts of the granodiorite pluton and in remnants of basement rocks. Mineral paragenesis is simple, with leading sphalerite and galena and minor chalcopyrite and pyrite. In overlying andesites the mineralization is accompanied by metasomatic quartzites and argillites with pyrophyllite, kaolinite, illite and pyrite. 4. Porphyry/skarn copper deposits and occurrences related to granodiorite/quartz-diorite porphyry dyke clusters and stocks around the granodiorite intrusion. The mineralized zone is represented by accumulations of chalcopyrite in exo- and endo-skarns, usually of the magnesian type affected by serpentinization. Besides chalcopyrite, pyrhotite, minor bornite, chalcosite, tennantite and magnetite, rare molybdenite and gold are present. The alteration pattern around productive intrusions includes an external zone of propylitization, a zone of argillitic alteration (kaolinite – illite – pyrite) and an internal zone of phyllic alteration (quartz – sericite – pyrite). Biotitization is rare and limited to porphyry intrusions. 5. Intrusion related “mesothermal” gold deposit in an andesitic environment just above the granodiorite intrusion. Gold of high fineness with base metal mineralization is contained in brecciated and/or banded quartz veins of subhorizontal orientation, parallel to the surface of granodiorite pluton. At least the first phase of mineralization is older than quartz-diorite porphyry sills, which separate granodiorite and blocks of mineralized andesite. 6. Hot spring type advanced argillic systems in the caldera filling. Silicites and opalites accompanied by kaolinite, alunite and pyrite grade downward into smectite dominated argillites. 7. Vein type epithermal precious/base metal deposits and occurrences as a result of the long lasting interaction among structural evolution of the resurgent horst and evolving hydrothermal system, extensive intrusive complex and deep seated siliceous magma chamber serving as heat and magmatic fluid source. Three types of epithermal veins occur in a zonal arrangement: (a) base metal veins ± Au with transition to Cu?±?Bi mineralization at depth in the east/central part of the horst, (b)?Ag – Au veins with minor base metal mineralization and (c) Au – Ag veins located at marginal faults of the horst. Isotopic composition of oxygen and hydrogen in hydrothermal fluids indicate mixing of magmatic and meteoric component (with generally increasing proportion of meteoric component towards younger mineralization periods?). Veins are accompanied by zones of silicification, adularization and sericitization, indicating a low sulphidation environment. 8.?Replacement base metal mineralization of a limited extent in the Mesozoic carbonate rocks next to sulphide rich epithermal base metal veins.     

Behaviour of quartz gravity meters under high frequency vertical motion

Summary Tests on the vertical vibrating table in the frequency range of70–110 Hz indicate that quartz gravity meters are10–100 times more sensitive at some frequencies than under low-frequency excitation. At high frequencies, the reading beam is at rest and deflected from the correct position. Slow fluctuations of amplitude and frequency near resonance could cause slow irregular motion of the beam with absence of low-frequency ground motion of sufficient intensity.

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Seismic noise at the international gravity point in Prague-Ruzyně (Czechoslovakia)

Summary The vertical component of ground displacement was measured at the Prague - Ruzyn International Gravity Point in the frequency range of 1–300 Hz. The permanent noise, the vibrations caused by the observers during gravimetric observations and by the wind, as well as those due to normal operations at the airport, display maximum peak-to-peak amplitudes of 0.06 µm in the frequency range of 1–50 Hz; with a CG-2 gravimeter this is not detrimental to the accuracy of the observations. The taxiing of turbo-jet and jet aircraft and engine tests of aircraft generate vibrations in frequency ranges of 75–90 and 190–270 Hz. Their amplitudes, according to the results of laboratory tests published for various types of gravity meters (CG-2, GAK-PT, GVP-3, KVG), are of magnitudes which generate errors in tenths of mgl.     

Post-drilling destabilization of temperature profile in borehole Yaxcopoil-1, Mexico

As part of the International Continental Scientific Drilling Program (ICDP), the 1.5-km-deep borehole Yaxcopoil-1, located in the Chixculub meteor impact structure in Mexico, has undergone further study after drilling operations ceased. Temperature logs were repeated ten times at intervals 0.3–0.8, 15, 24 and 34 months after borehole shut-in. The logs bear a distinct signature of transient heat transfer by groundwater flow manifested by a gradual distortion of the linear temperature profile when a cold wave of 0.8–1.6°C amplitude was detected propagating downward from 145 to 312 m at a rate of 4–6 m/month. To understand the nature of this moving anomaly, a 20-day monitoring of the cold wave was carried out at a depth of 307 m that showed further cooling of 0.6°C during the first 16 days of the passage followed by temperature stabilisation. As an explanation of this unusual phenomenon, a theory is proposed, whereby the drilling mud has accumulated within the overlying and cooler highly porous and permeable karstic rocks during the drilling and migrates downward. The observed migration rate suggests a permeability higher than 10^?11 m². This indicates a high vulnerability to contamination of the only freshwater aquifer in the Yucatan region.