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[en] Metamorphic rock of Darab is surrounded and intruded by granitic rocks, which is composed of medium to fine grained, it identified as phylite interbedded with quartzite. Milimetric to decimetric vein structures which detreminated as biotite, quartz-biotite, andalusite, quartz-apatite, biotite-apatite, gypsum, tour-maline, quartz-orthoclase, and quartz have been found within the metamorphic rock. Metamorphic grade of the rock is medium at near contact zone, while low grade metamorphism has been identified away from the contact, it may indicate retrogade process has exist. Uranium mineralizations occured in granite and metamorphic rock as well, as brecia fillings or veins at the contact vicinities. Radioactives minerals have been identified as uraninite and monazite, they are mostly associated with magnetic, ilmenite, molybdenite, ilmenorutile, sphalerite, pyrite, arsenophyrite, biotite,tourmaline, apatite, and quartz. Formation of the mineralization were interpreted to be mesothermal at 300 celcius centrigate to 600 celcius centrigate with granite as the bearer. (authors). 4 figs, 7 tabs
[en] In Gol-e-Gohar metamorphic Complex from south-eastern Sanandaj-Sirjan metamorphic zone (Kerman province, Iran), there are two types of metabasites contain layered metamorphosed lava flows and the younger meta-gabbros. The protoliths formed in the Paleozoic era and were metamorphosed during the early Cimmerian orogenic phase in the late Triassic, under temperatures of 640–680ºC and pressures of ~7–10.5kbar (amphibolite facies). These rocks are garnet-bearing amphibolites, garnet free amphibolites and metamorphosed gabbros. Many mineralogical and chemical aspects of these metabasites are similar, although the layered metabasites show tholeiitic and the meta-gabbros depict alkaline affinities. Evidences such as whole rock geochemical characteristics, Sr and Nd isotopic data, (143Nd/144Ndinitial=0.511913–0.512067; εNd550Ma=-0.31–2.68), relatively flat patterns of chondritenormalized Rare Earth Elements and multi-elemental diagrams, the enrichment in TiO2 (average content ~2.16) and high Zr/Y ratios (3–8), indicate that all of Gol-e-Gohar metabasites are formed in an extentional intracontinental rift zone from tholeiitic to alkaline magmas. The data suggest that the paren magmas could derived by low degrees of partial melting of spinel-lherzolite sources in subcontinental lithospheric mantle. These evidences confirm the existence of extentional environments in southern part of the Sanandaj-Sirjan metamorphic zone in the Paleozoic era, when large extensional depressions developed in the Sanandaj-Sirjan metamorphic zone and underlying asthenosphere ascent and partially melted during this time. Gradually, thick sequences of continental detritic sediments and tholeiitic lava flows accumulated in these troughs. Subsequent magmatic event in the area characterizes by emplacement of alkaline gabbro intrusions. At the early Cimmerian orogeny, these sedimentaryigneous rocks associations metamorphosed and the Gol-e Gohar metabasites formed.
[en] The Archean era and Archean formations (highly-metamorphin and granite-greenstone) are characterized. Geochronological methods for dating of Archean formations, among them Rb-Sr isochronous method, U-Pb method, Sm-Nd method, lead-isochronous one (207Pb/204Pb-206Pb/204Pb) are considered. Data on age estimation of the most acient Archean rocks, as well as Archean formations younger than 3000 million years are given
[en] New results are reported of geochronologic dating by the K/Ar method. These prove the Variscan age of the metamorphosis of rocks in the surroundings of Rudnany and Dobsina and a considerable distribution of granitoid rocks of the Cretaceous age in the region of southern Veporides. This zone extends to the west up to Jasenova and Budina. It was established that some samples of gabbroic amphibolic rocks, according to the K/Ar method are of the Upper Proterozoic age. Histograms were used to summarize the results of the datings of different rocks from the crystalline of the West Carpathians and to give their interpretation. The main time of the intrusive phases of the Variscan granitoids is assumed, according to these results, between 280 to 320 M.Y., that of the younger Variscan ones 260 to 280 M.Y. and that of Mesozoic granites aound 90 to 120 M.Y. To these age intervals also fall the metamorphic processes of schists. (author)
[en] The Colorado School of Mines (CSM), under sponsorship of the Department of Energy through the Office of Nuclear Waste Isolation (ONWI), has established a hard-rock research facility at its experimental mine. Even through this site will not become a nuclear waste repository, the CSM has established and maintains an underground test room for use by its own personnel and ONWI and its contractors to conduct in situ investigations. Furthermore, CSM is designing, conducting, and reporting on a series of field research programs to develop site evaluation procedures, excavation techniques, and instrumentation required for nuclear waste repository siting, construction, and monitoring (Hustrulid, 1981). This facility is presently being used to: evaluate and develop techniques for careful excavation of hard rock; develop the mapping techniques required to describe adequately the structural geology; evaluate the structural continuity in the granitic gneiss at the CSM site; evaluate the structural damage done to the rock mass by blasting; develop techniques for evaluating fracture permeability; evaluate permeability changes in the rock mass as a result of blasting. Although specifically oriented toward nuclear waste storage and disposal, the techniques and procedures being developed and evaluated have wide applicability to all underground excavations in hard rock
[en] Using the K-Ar isotope dating method of muscovites it was found that many retrogradely metamorphosed rocks are the results of Variscan retrograde metamorphism and are not pre-Cambrian or Alpine metamorphites (diaphthorites). Samples for dating were taken from the Western Carpathian crystalline formation. The content of radiogenic argon was determined by mass spectrometry using the method of isotope dilution. (M.D.)
[en] Complete text of publication follows. Paleomagnetic study in southern Tibet and the Higher Himalayan Crystalline (HHC) was twofold: (1) the recognition of vertical and horizontal block rotations and (2) the examination of the high grade metamorphic rocks (gneisses) from the HHC for their suitability for paleomagnetic investigations. Toward the separation of local and regional tectonic effects, the results from southern Tibet reflect a regional trend in agreement with oroclinal bending and rotational under-thrusting. On the other hand, measured 'anomalous inclinations' are interpreted as a consequence of extensional tectonic, and the circular distribution of magnetic remanences is attributed to long wavelength folding within the study area as well as doming in the crust. The examination of the high grade metamorphic rocks was successful: The high quota of isolated stable and well grouping secondary magnetic remanences, demonstrate their suitability for paleomagnetic investigations. A high potential source is therefore established which enable considerable contributions within the thermo-tectonic evolution of an orogen. Data suggest no significant vertical rotation on a regional scale versus India. A regional trend comparable to that obtained for south Tibet, and expressed as a dispersion of remanence vector directions on a small circle is observed. The new findings are in disagreement with the hypothesis of a uniform clockwise rotation increasing to the east of the Himalayan arc. A major effect, inferred from paleomagnetic data, attributed to long wavelength folding, doming and associated low/high normal faults/thrust system became more evident. In summary, paleomagnetism is a potential applied method in deciphering deformation processes on local-, meso- and regional scale.