Palaeoproterozoic to Eoarchaean crustal growth in southern Siberia: a Nd-isotope synthesis

Abstract

Nd-isotope analyses from 114 rock samples are reported from the southern part of the Siberian craton to establish a first-order crustal formation scheme for the region. The Nd-isotope data show considerable variability within and among different cratonic units. In many cases this variability reflects differing degrees of mixing between juvenile and older (up to Eoarchaean) crustal components. The fragments of Palaeoproterozoic juvenile crust within the studied segment of the Siberian craton margin have Nd-model ages of c. 2.0–2.3 Ga. Voluminous Palaeoproterozoic granites (c. 1.85 Ga) were intruded into cratonic fragments and suture zones. These granites mark the stabilization of the southern Siberian craton. The complexity in the Nd data indicate a long history of crustal development, extending from the Eoarchaean to the Palaeoproterozoic eras, which is interpreted to reflect the amalgamation of distinct Archaean crustal fragments, with differing histories, during Palaeoproterozoic accretion at 1.9–2.0 Ga and subsequent cratonic stabilization at 1.85 Ga. Such a model temporally coincides with important orogenic events on nearly every continent and suggests that the Siberian craton participated in the formation of a Palaeoproterozoic supercontinent at around 1.9 Ga.

Metasedimentary rocks of the Angara-Kan granulite-gneiss block (Yenisey Ridge, south-western margin of the Siberian Craton): Provenance characteristics, deposition and age

“…These units were the most likely source provenance of the Archean detrital material for the Kan metasedimentary rocks. Within the Sharyzalgay uplift the metamorphic associations and granitoids older than 1.9 Ga yielded mostly Paleo-Mezoarchaean model Nd ages (T Nd (DM) values range from 3.6 to 2.8 Ga) (Gladkochub et al, 2009;Turkina, 2010). Model Nd ages (2.4-2.8 Ga) of the Kan metasediments as well as the detrital zircons with an age of $1.94 Ga support contribution of a Paleoproterozoic juvenile crust unit in sedimentation.…”

“…1). The late Paleoproterozoic felsic volcanic rocks of the Akitkan Formation and A-granites of the Chuya complex are characterized by T Nd (DM) of 2.4-2.9 and 2.3-2.5 Ga, respectively (Neymark et al, 1998;Gladkochub et al, 2009). Model Nd ages of the Akitkan volcanics were interpreted as mixing of minor young-juvenile and older crustal components, whereas the Chuya unit considered to be relict of the Paleoproterozoic juvenile crust (Neymark et al, 1998).…”

Early Proterozoic Postcollisional Granitoids of the Biryusa Block of the Siberian Craton

“…Связано это с тем, что при таком объединении блоков в единую утол-щенную структуру обеспечивается разнообразие субстратов, подвергающихся плавлению, что является одним из ключевых петрологических факторов, приводящих к формированию гранитов разного состава [Донская и др., 2005, 2013; Туркина и др., 2006]. Мы полагаем, что утолщение коры в данном регионе могло достигаться за счет объединения неоархейского Бирюсинского континентального блока [Туркина и др., 2007], палеопротерозойского Урикско-Ийского террейна [Gladkochub et al, 2009] и архейского Тунгусского супертеррейна [Туркина и др., 2007, 2013Gladkochub et al, 2009;Туркина, 2010; Урман-цева и др., 2013] в единую структуру Сибирского кратона [Rosen et al, 1994;Розен, 2003;Gladkochub et al, 2006]. Высокая температура, фиксируемая для всех гранитоидов, связана, по всей видимости, с пос-туплением мантийного материала к основанию коры (наличие гранитоидов со смешанными мантийно-коровыми характеристиками подтверждение этого факта).…”

Geochemistry of the Paleoproterozoic metaterrigenous rocks of the Biryusa Block, southwestern Siberian Craton

“…In rocks of the Tumanshet Formation, this link is dis turbed owing to recycling during their formation. In the southwest of the Siberian Craton, the metavolcanic and granitoid complexes (T Nd (DM) = 2.1-2.3 Ga), which represent relicts of the Paleoproterozoic juvenile crust, were identified in the Urik-Iya graben that separates the Biryusa and Sharyzhalgai blocks (Gladkochub et al, 2009).…”