The First Evidence of Cambrian Granitoid Magmatism during the Formation History of the Bureya Continental Massif of the
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The First Evidence of Cambrian Granitoid Magmatism during the Formation History of the Bureya Continental Massif of the Central Asian Fold Belt R. O. Ovchinnikova,*, Corresponding Member of the RAS A. A. Sorokina, and N. M. Kudryashovb Received March 19, 2020; revised March 19, 2020; accepted April 9, 2020
Abstract—The results of U–Pb geochronological studies of Early Paleozoic granitoids from the northern part of the Bureya continental massif are presented. It has been established that porphyroblastic hornblende–biotite granites of the Kivili massif referring to the complex of the same name are of 502+6 Ma in age, while weakly gneissic biotite granites of the Kivity massif, Sularin complex, are of 492+6 Ma in age. Thus, granitoids of both complexes are of Cambrian rather than Ordovician age, as was previously assumed. In combination with materials already obtained, these data indicate that intensive granitoid magmatism manifested itself in the Middle Cambrian–Early Ordovician within the Bureya continental massif. It is noteworthy that, in the structure of the Jiamusi–Khanka continental massif, which is adjacent to the Bureya one, Early Paleozoic magmatism manifested itself in a broader range, which is from the Early Cambrian to the Silurian. This may indicate both differences in the formation history of these continental massifs and insufficient knowledge of the Bureya massif. DOI: 10.1134/S1028334X20070120
Determination of the chronology of magmatic events that occurred through the history of formation and evolution of the continental massifs in the eastern Central Asian fold belt is a necessary condition for developing an integrated model describing the formation of this orogenic belt, the largest in Eurasia. Note that the study of the Late Precambrian and Early Paleozoic complexes is of key importance ([1, 2] and others). The Bureya massif is one of the largest continental massifs within this belt. However, the history of its formation has not been studied sufficiently, and this refers primarily to the Early Paleozoic time. According to existing ideas, two episodes of magmatic activity took place in the Early Paleozoic and were expressed in the Kivili gabbro-granite (earlier) and Sularin granite (late) complexes. Despite the fact that this idea is supported by most geologists [3, 4], the exact age of these complexes remains uncertain. At present, both complexes are conditionally believed to be of Ordovician age [3]. a Institute
of Geology and Nature Management, Far East Branch, Russian Academy of Sciences, Blagoveshchensk, 675000 Russia b Geological Institute, Kola Science Center, Russian Academy of Sciences, Apatity, Murmansk oblast, 184209 Russia *e-mail: [email protected]
To clarify the problem of the stages of Early Paleozoic magmatism, we performed geochronological studies of granitoids from the Kivili and Sularin complexes, which are located in the northern part of the Bureya continental massif (Fig. 1). The Kivili massif is the largest and, additionally, petrotypical for the Kivili complex. This
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