18 research outputs found
GEOLOGICAL SETTING AND GENESIS OF THE KURMANSKY GABBRO-TRONDHJEMITE MASSIF (MIDDLE URALS)
This paper reports the results of petrogeochemical studies of the Kurmansky gabbro-trondhjemite massif (eastern slope of the Middle Urals), lying in the western part of the large Reftinsky allochthonous block within the accretion East Uralian megazone. The relevance of this study is determined by the uncertainty in geodynamic setting and formation conditions of the rock massif and its role in the evolution of the Ural Mobile belt. We specified the countours of the massif. It is shown that the rocks were resulted from spatiotemporal convergence of partial melting in the mantle and lower crust at the island-arc stage of the Ural Mobile belt evolution. Partial melting of mantle peridotite, under the influence of an aqueous fluid rising from the subduction zone, initiated the occurrence of basite melts. The separation of the melt and its subsequent evolution to the compositions of gabbrodiorite and diorite took place at Ptot=10 kbar. Trondhjemites were formed as a result of partial melting of amphibolites at Ptot≥8 kbar, PH2O=0.1–0.2 kbars. The crystallization of trondhjemites in the crust was accompanied by the wollastonite skarns on contact with carbonate rock and xenoliths culminated at mesoabyssal level, Ptot=PH2O=1 kbar. The comparison between the composition of Kurmansky gabbro-trondhjemite massif and the island-arc- and collision-related magmatic suites in the region allowed us to assume that the Kurmansky massif belongs to the independent Early Devonian (?) gabbro-trondhjemite complex of island arc origin. The rock metamorphism conditions were evaluated, with the transformations supposedly related to the accretion of early island arc complexes at the Murzinsky-Aduysky microcontinent, which took place in the Devonian
ГЕОЛОГИЧЕСКАЯ ПОЗИЦИЯ И ГЕНЕЗИС КУРМАНСКОГО ГАББРО-ТРОНДЬЕМИТОВОГО МАССИВА (СРЕДНИЙ УРАЛ)
This paper reports the results of petrogeochemical studies of the Kurmansky gabbro-trondhjemite massif (eastern slope of the Middle Urals), lying in the western part of the large Reftinsky allochthonous block within the accretion East Uralian megazone. The relevance of this study is determined by the uncertainty in geodynamic setting and formation conditions of the rock massif and its role in the evolution of the Ural Mobile belt. We specified the countours of the massif. It is shown that the rocks were resulted from spatiotemporal convergence of partial melting in the mantle and lower crust at the island-arc stage of the Ural Mobile belt evolution. Partial melting of mantle peridotite, under the influence of an aqueous fluid rising from the subduction zone, initiated the occurrence of basite melts. The separation of the melt and its subsequent evolution to the compositions of gabbrodiorite and diorite took place at Ptot=10 kbar. Trondhjemites were formed as a result of partial melting of amphibolites at Ptot≥8 kbar, PH2O=0.1–0.2 kbars. The crystallization of trondhjemites in the crust was accompanied by the wollastonite skarns on contact with carbonate rock and xenoliths culminated at mesoabyssal level, Ptot=PH2O=1 kbar. The comparison between the composition of Kurmansky gabbro-trondhjemite massif and the island-arc- and collision-related magmatic suites in the region allowed us to assume that the Kurmansky massif belongs to the independent Early Devonian (?) gabbro-trondhjemite complex of island arc origin. The rock metamorphism conditions were evaluated, with the transformations supposedly related to the accretion of early island arc complexes at the Murzinsky-Aduysky microcontinent, which took place in the Devonian.В статье представлены результаты петрогеохимических исследований пород Курманского габбро-трондьемитового массива (восточный склон Среднего Урала), залегающего в западной части крупного Рефтинского аллохтонного блока, локализованного в пределах Восточно-Уральской мегазоны аккреционной природы. Актуальность исследований заключается в установлении геодинамических режимов формирования пород, их позиции в эволюции Уральского подвижного пояса. В ходе исследования уточнены контуры массива. Показано, что данные породы образовались в результате сближенных по времени и в пространстве процессов частичного плавления в мантии и нижней коре на островодужном этапе развития Уральского подвижного пояса. Частичное плавление мантийного перидотита под воздействием восходящего из зоны субдукции водного флюида привело к зарождению базитового расплава. Отделение расплава и его последующая эволюция до составов габбро-диорита, диорита происходили при Pобщ=10 кбар. Трондьемиты, ассоциированные с габброидами, были получены в результате частичного плавления амфиболитов при Pобщ≥8 кбар, PH2O=0.1–0.2 Pобщ. Их становление в коре сопровождалось развитием волластонитовых скарнов на контактах с ксенолитами карбонатных пород и завершилось в мезоабиссальной обстановке при Pобщ=PH2O=1 кбар. Выполнено сопоставление состава слагающих массив пород с развитыми в районе магматическими образованиями островодужной и коллизионной стадий, что позволило высказать предположение о принадлежности Курманского массива к самостоятельному раннедевонскому (?) габбро-трондьемитовому комплексу островодужной природы. Охарактеризованы условия метаморфизма пород массива, высказано предположение о связи этих преобразований с аккрецией раннеостроводужных комплексов на Мурзинско-Адуйский микроконтинент, имеющей место в девоне
The Migmatization and Granite Formation Processes within the Western Exocontact of the Aduyskiy Massif. Middle Urals
The mechanisms and sources of magma generation for the large Permian Aduyskiy granite massif, well known for rare metal, semi-precious stone and molybdenum deposits, are considered. Valuable information was obtained from study of the Kamenskiy and Krutikhinskiy massifs located at the base of Aduyskiy granite body. The migmatites of these two massifs as well as the accompanying partial melting have approximately the same zircon and Rb-Sr age. These processes range about 309-298 Ma in the Kamenskiy and 308-283 Ma in Krutikhinskiy massifs with the main and most intense stage within 296-298 Ma. That time, the main volume of the granite melt for Kamenskiy, Krutikhinskiy, and Aduyskiy massifs was formed. The migmatites of magma generation zone have banded texture in Kamenskiy massif, but, in Krutikhinskiy massif, anatectic melt formed the numerous veins and small intrusive bodies. These magmatic differences were formed mainly due to protolith composition. Камenskiy migmtites are characterized by Devonian – Carboniferous quartz diorites and granodiorites. Predominantly granitic rocks are characteristic for Krutikhinskiy massif. Basic dykes accompanied the migmatization in both massifs