Автор(ы):Greg B.Arehart
Издание:Department of Geology Science, Reno, 4 стр.
Isotopic signature of hydrothermal sulfares from Carlin-type ore deposit

Stable isotopes from sulfates of three origins in Carlin-type deposits (CTDs) from western North America fall into distinct clusters and can be utilized to discriminate between barite of Paleozoic (sedimentary exhalative) origin, barite of hydrothermal origin related to gold mineralization, and supergene alunite and jarosite of weathering origin. Although the latter are obvious from field relations, the distinction between hydrothermal and sedex barite is not always so clear. Sedex sulfate sulfur was probably reduced and mobilized during gold mineralization, equilibrated with hydrothermal fluids, and then precipitated as sulfate during the late stages of mineralization, with a distinctly different sulfur and oxygen isotope signature. Isotopic signatures of sulfates may, therefore, be utilized as a mineral exploration tool for CTDs.

ТематикаМинералогия, Полезные ископаемые
Выпуск 4
Автор(ы):Коваленко Д.В., Колосков В.А., Флеров Г.Б.
Издание:Russian journal of Pacific geology, 2009 г., 19 стр.
Late cretaceous–paleocene magmatic complexes of Central Kamchatka: geological settings and compositional features

A comparative analysis of the Late Cretaceous–Paleocene volcanism was conducted for four areas of Kamchatka: the Pravyi Tolbachik–Levaya Shchapina–Adrianovka interlfuve (the northern part of the Tum-rok Range), the area south of the Ipuin River and Mt. Khrebtovaya (the northern Valaginsky Range), the area of Mt. Savul’ch (the upper reaches of the Kitil’gina River, northern Valaginsky Range), and the Kirganik– Levaya Kolpakova interfluve (the Sredinny Range). New petrochemical, geochemical, and isotopic data on the volcanic rocks from these areas are reported. The examination of this material, together with already published data on volcanic and plutonic rocks of similar composition and age, made it possible to establish the following: (1) the considered basaltoids are ascribed to the subalkali basalt–trachyandesite series with transition toward a meymechite–picrite rock association; (2) the alkali content in the rocks of the Valaginsky–Tumrok–Sredinny ranges increases simultaneously with the increase of the Rb content, while the contents of HFSE and radioactive elements decrease and then again increase. Two trends are identified in the Ybn–Cen diagram: a positive trend spanning most of the volcanic and plutonic rocks and a negative trend defined by the data points of the meyme-chite–picrite association. The first trend reflects the rock evolution during crystallization differentiation, while the second trend was produced by different degrees of melting of initial protolith. The possible geodynamic reconstructions of this volcanism are discussed as well

ТематикаПетрология, Региональная геология
МеткиBasalt, Geochemistry, Isotopy, Kamchatka Peninsula, Meymechite, Petrochemistry, Picrite, Volcanics, Камчатка
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