Search

The dike rocks under study are localized in Mesozoic (T3-J2) clastic rocks in the western part of Verkhoyansk-Kolyma fold area. Studying the nature of the dikes and geodynamic setting of their formation is of great interest now in view of the controversy surrounding their assignment to definite magmatic complexes of the VerkhoyanskKolyma fold area and the uncertain origin of mineralization in the Yana-Kolyma gold belt. Major elements were determined using the silicate analysis of magmatic rocks. The mineral compositions of dike rocks were studied using a Tescan MIRA 3 LMU scanning electron microscope. Studies of REE and other trace elements were performed with the use of mass spectrometers – quadrupolar Agilent7500ce (Japan) and highresolution Element2 (Germany). Their petrologic compositions vary widely including basanite, trachybasalt, andesite, trachyandesite, dacite and granodiorite. The rocks are spatially associated with gold mineralization of the Yana-Kolyma gold belt. Intense secondary alteration of the dikes includes carbonatization, chloritization, pelitization, sericitization, saussuritization, and epidotization. The SiO2 content in the sampled rocks varies from 46.8 to 70.5 wt. %, while the total amount of Na2O+K2O ranges from 2.69 to 7.59 wt. %. The dike rocks belong to the low- and high-K calc-alkaline and the shoshonite magmatic series. They exhibit a uniform REE distribution pattern intermediate between those of OIB and E-MORB. The flat HREE trend is close to that of MORB. The Eu anomaly is absent (0.9-1.0). Positive Ba, K and negative Ti, Ta, and Nb anomalies are observed. Trace element trends are much like those established for mafic rocks from dikes at the Malo-Tarynskoe and Tin-Yuryuete gold deposits in the western part of the Verkhoyansk-Kolyma fold area. The dikes could have formed from mixed enriched and depleted mantle sources, possibly with the involvement of a subduction-related component. The dike rocks under study are localized in Mesozoic (T3-J2) clastic rocks in the western part of Verkhoyansk-Kolyma fold area. Studying the nature of the dikes and geodynamic setting of their formation is of great interest now in view of the controversy surrounding their assignment to definite magmatic complexes of the VerkhoyanskKolyma fold area and the uncertain origin of mineralization in the Yana-Kolyma gold belt. Major elements were determined using the silicate analysis of magmatic rocks. The mineral compositions of dike rocks were studied using a Tescan MIRA 3 LMU scanning electron microscope. Studies of REE and other trace elements were performed with the use of mass spectrometers – quadrupolar Agilent7500ce (Japan) and highresolution Element2 (Germany). Their petrologic compositions vary widely including basanite, trachybasalt, andesite, trachyandesite, dacite and granodiorite. The rocks are spatially associated with gold mineralization of the Yana-Kolyma gold belt. Intense secondary alteration of the dikes includes carbonatization, chloritization, pelitization, sericitization, saussuritization, and epidotization. The SiO2 content in the sampled rocks varies from 46.8 to 70.5 wt. %, while the total amount of Na2O+K2O ranges from 2.69 to 7.59 wt. %. The dike rocks belong to the low- and high-K calc-alkaline and the shoshonite magmatic series. They exhibit a uniform REE distribution pattern intermediate between those of OIB and E-MORB. The flat HREE trend is close to that of MORB. The Eu anomaly is absent (0.9-1.0). Positive Ba, K and negative Ti, Ta, and Nb anomalies are observed. Trace element trends are much like those established for mafic rocks from dikes at the Malo-Tarynskoe and Tin-Yuryuete gold deposits in the western part of the Verkhoyansk-Kolyma fold area. The dikes could have formed from mixed enriched and depleted mantle sources, possibly with the involvement of a subduction-related component. [ABSTRACT FROM AUTHOR]

Small samples of native gold from Rosia Montana (Apuseni Mts.) and from Cavnic (Baia-Mare district) were scanned by micro-PIXE method to identify especially minor (between 0.1 and 1%) elements and possible micro-inclusions (micro-areas of different composition from the surrounding material - e.g. rich in tellurium and antimony). The samples were also studied using an AXIO IMAGER - Carl Zeiss polarized light microscope and a Scanning Electron Microscope (SEM) from FEI, model Inspect S with an Energy Dispersive X-Ray Spectroscopy (EDAX) unit. Analyzed samples are from recovery obtained by inhabitants from landfills of former mining plants. For Rosia Montana we detected micrometer areas (5 µm X 5 µm) rich in Ag and Sb and without Au, Sb/Ag ratio being 1/3.5-4.5, polarized light microscopy and SEM-EDAX analysis confirming the presence of pyrargyrite-proustite. For Cavnic-Roata samples, one micro-area revealed at micro-PIXE an important presence of Te (16657 ppm), a significant presence of Sb (2861 ppm) and an increase of Ag content, indicating the presence of a Ag telluride. Polarized light microscopy and SEM-EDAX analysis confirmed the presence of cervelleite and argentite (acanthite). [ABSTRACT FROM AUTHOR]