TY - GEN

T1 - HISTORY OF DEVELOPMENT OF INTRUSIVE MAGMATISM IN THE URALIAN PLATINUM-BEARING BELT ON THE GROUNDS OF TO U-PB DATING OF ZIRCONS FROM ROCKS, FORMING DIKES IN THE DUNITES OF KAMENUSHESKI MASSIF (MIDDLE URAL, RUSSIA)

AU - Stepanov , S.Yu.

AU - Kutyrev , A.V

AU - Lepekhina , E.N.

PY - 2019/4/25

Y1 - 2019/4/25

N2 - The completion of intrusive magmatism within the Tagil volcanic arc is associated with the introduction of the gabbro-diorite-granite Auerbach complex (Krasnobayev, Fershter, 2013). The age of 400–405 Ma is set for them (Fershter, 2013). A more ancient age is inherent in granites and other rocks of the leucogabbro-anorthosite-plagiogranite series, associated with the partial melting of previously formed gabbroids. Their formation fits into the time interval from 425 to 415 million years (Fershtater, 2013). By their geochemical parameters, the granites composing dikes in the dunites of the Kamenushensky massif are like the anatectic granites of the Uralian Platinum Belt. According to zircon dating, they have an age of 384 ± 0.5 Ma. Thus, the processes of partial melting of gabbro and the formation of anatectic granites within the Uralian Platinum Belt did not end at 415 million years, as was assumed earlier, but continued throughout the entire period of the formation of the Tagil volcanic zone. These processes accompanied the transition from calc-alkaline island-arc magmatism to tholeiitic basaltic magmatism under back-arc spreading conditions, which culminated in the formation of riftogenic fine-grained amphibolite gabbro about 350 million years ago (Fershter, 2013). However, it is necessary to emphasize that zircons from granites, by the characteristics of their structure and composition and due to extremely high uranium contents and low uranium-thorium ratio can have a metasomatic nature (Zircon, 2003). The enrichment of zircons from granites with uranium can be associated with the influence of residual fluid accumulated during the differentiation of melts or the redistribution of a substance as a result of regional or contact metamorphism. The regularities of the structure of granitoid bodies in dunites, petrochemical and petrographic features of the studied granites (metasomatic transformations are not manifested), as well as the history of the geological development of the region, excludes the possibility of significant transformation processes of granites that could disturb the U-Pb system in zircons.

AB - The completion of intrusive magmatism within the Tagil volcanic arc is associated with the introduction of the gabbro-diorite-granite Auerbach complex (Krasnobayev, Fershter, 2013). The age of 400–405 Ma is set for them (Fershter, 2013). A more ancient age is inherent in granites and other rocks of the leucogabbro-anorthosite-plagiogranite series, associated with the partial melting of previously formed gabbroids. Their formation fits into the time interval from 425 to 415 million years (Fershtater, 2013). By their geochemical parameters, the granites composing dikes in the dunites of the Kamenushensky massif are like the anatectic granites of the Uralian Platinum Belt. According to zircon dating, they have an age of 384 ± 0.5 Ma. Thus, the processes of partial melting of gabbro and the formation of anatectic granites within the Uralian Platinum Belt did not end at 415 million years, as was assumed earlier, but continued throughout the entire period of the formation of the Tagil volcanic zone. These processes accompanied the transition from calc-alkaline island-arc magmatism to tholeiitic basaltic magmatism under back-arc spreading conditions, which culminated in the formation of riftogenic fine-grained amphibolite gabbro about 350 million years ago (Fershter, 2013). However, it is necessary to emphasize that zircons from granites, by the characteristics of their structure and composition and due to extremely high uranium contents and low uranium-thorium ratio can have a metasomatic nature (Zircon, 2003). The enrichment of zircons from granites with uranium can be associated with the influence of residual fluid accumulated during the differentiation of melts or the redistribution of a substance as a result of regional or contact metamorphism. The regularities of the structure of granitoid bodies in dunites, petrochemical and petrographic features of the studied granites (metasomatic transformations are not manifested), as well as the history of the geological development of the region, excludes the possibility of significant transformation processes of granites that could disturb the U-Pb system in zircons.

UR - https://www.elibrary.ru/item.asp?id=39112229

M3 - Conference contribution

VL - 36

SP - 288

EP - 292

BT - Magmatism of the Earth and related strategic metal deposits - 2019

PB - ГЕОХИ РАН

T2 - Magmatism of the Earth and related strategic metal deposits

Y2 - 23 May 2019 through 26 May 2019

ER -