Isotopes originated with the emergence of elements in the Universe during the first infinitesimal fraction of a second following the postulated Big Bang now generally accepted as having started the dynamic expansion observed today.l Some remarks concerning this seminal event are in order.

The results of experimental and theoretical studies of isotopic composition of natural waters of the Earth’s hydrosphere are analyzed and summarized in this book. These studies represent a modern direction of science of the natural waters actively developed in hydrology, hydrogeology, oceanography, and climatology starting from the middle of last century. The book is a further development and improvement of the earlier published author’s works: Cosmogenic Isotopes of the Hydrosphere, Nauka, Moscow, 1984; Isotopy of the Hydrosphere, Nauka, Moscow, 1983; Environmental Isotopes in the Hydrosphere, Nedra, Moscow, 1975 and Environmental Isotopes in the Hydrosphere, Wiley, Chichester–New York, 1982.

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.

A granodiorite stock intrudes complexly folded and thrust-faulted Paleozoic sedimentary rocks in the Osgood Mountains of eastern Humboldt County, Nevada. Within the metamorphic aureole surrounding the pluton, the sedimentary rocks are converted to cordierite hornfels and marble; tungsten-bearing tactites developed along the contacts of the granodiorite. Cutting the granodiorite and sedimentary rocks is the Getchell fault, along which the disseminated gold ore bodies of the Getchell mine are localized. K-Ar ages of the granodiorite, andesite porphyry, tungsten-bearing tactites, and altered granodiorite from the Getchell mine indicate that emplacement, alteration, and mineralization are all part of a magmatic-thermal episode which took place approximately 90 m.y. ago.