Age of Granodiorite Porphyry and Beresite from the Darasun Gold Field, Eastern Transbaikal Region, Russiaстатья
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Дата последнего поиска статьи во внешних источниках: 15 июля 2014 г.
Аннотация:The Darasun ore field situated in the southern West Stanovoi Terrane near the Mongolia–Okhotsk Suture comprises the Darasun (>100 t Au), Talatui (~38.2 t Au), and Teremki (3 t Au) lode gold deposits. In the opinion of many researchers, the Darasun deposit is spatially and paragenetically linked to granodiorite porphyry of the Amudzhikan Complex and related metasomatic rocks (beresites). Wholerock samples of granodiorite porphyry, monomineralic fractions of plagioclase, Kfeldspar, and biotite, as well as sericite from beresite (26 samples in total), were analyzed by the Rb–Sr method. Eight biotite and sericite samples were analyzed by the K–Ar method. The Rb–Sr mineral isochrons obtained for individual granodiorite porphyry samples yielded initial 87Sr/86Sr ratios varying from 0.70560 to 0.70591. The consistent results of both meth ods allowed us to accept the ages of granodiorite porphyry and beresite as 160.5 ± 0.4 and 159.6 ± 1.5 Ma, respectively. The age of granodiorite porphyry of the Amudzhikan Complex of 160.5 ± 0.4 Ma corresponds to the boundary between the Early and Middle Jurassic and marks the completion of collision between the East Siberian and Mongolia–China continents and related orogeny. Since that time, the eastern Transbaikal region has been involved in the postorogenic (withinplate) stage of evolution, characterized by the formation of large gold, uranium, and other ore deposits.