Precambrian Fe- and Al-Rich Pelites from the Yenisey Ridge, Siberia: Geochemical Signatures for Protolith Origin and Evolution during Metamorphism

Abstract

In the Trans-Angarian region of the Yenisey Ridge in eastern Siberia (Russia), Fe-and Al-rich low-pressure, andalusite-bearing pelitic schists of the Teya Sequence were subjected to prograde pressure increase in the vicinity of the thrust and were overprinted by medium-pressure, kyaniteand sillimanite-bearing assemblages and microtextures of collisional metamorphism. Major, trace, and rare-earth element contents of rock samples from the different metamorphic zones were determined in order to examine the composition, nature, and evolution of their protolith during metamorphism. Results indicate that these rocks are the redeposited and metamorphosed products of Precambrian kaolinitic weathering crusts. The protolith of the Teya Sequence metapelites was produced by erosion of post-Archean granitoid rocks, which accumulated under humid conditions in shallow-water basins along the continental margin. These results agree with lithofacies data and with the geodynamic reconstruction of the Precambrian evolution of the Yenisey Ridge. Geochemical and petrological data coupled with a mass balance analysis show that the coherent mobility of REEs during collisional metamorphism may be attributed both to mineral reactions responsible for modal changes and to local chemical heterogeneity inherited from the initial protolith, with the prevalence of one or another process at different stages of rock evolution.

Grenville tectonic events and evolution of the Yenisei Ridge at the western margin of the Siberian Craton

“…2c). This is supported by geo physical data [23], as well as by U-Pb and Sm-Nd age estimation of the protolith for pelitic rocks formed at the Siberian Craton 2.0-1.9 Ga ago [39,66]. Late Riphean thermal metamorphism (862 Ma) under con ditions of very high metamorphic gradient (dT/dH > 100°C/km) close to granitoid plutons and dyna mometamorphism of migmatites pertaining to the Garevka Complex in the Cis Yenisei Shear Zone (845 ± 7 Ma) [28] developed almost synchronously with col lision.…”

The ‘triple point’ paradigm of aluminosilicates revisited

“…Erosion of felsic igneous rocks is also inferred by the higher Th/U (6–7.5) and lower La/Th (0.14–0.2) ratios relative to average PAAS compositions (Likhanov & Reverdatto, ). Detailed reconstructions of the composition and nature of their protolith based on whole‐rock major and trace element geochemistry have demonstrated that these rocks represent a re‐deposited and metamorphosed product of Precambrian kaolinite weathering crusts (Likhanov & Reverdatto, ). U‐Pb SHRIMP II and Sm‐Nd isotopic data revealed that these rocks originated from a crustal source comprising mostly crystalline and sedimentary rocks (granite‐gneisses complexes) of the Siberian Craton with an Early Proterozoic model age of 1.9–2.0 Ga accumulated under humid climate conditions in shallow‐water basins along the continental margin (Likhanov & Reverdatto, ).…”

P-T-t RECONSTRUCTIONS OF SOUTH YENISEI RIDGE METAMORPHIC HISTORY (Siberian craton): PETROLOGICAL CONSEQUENCES AND APPLICATION TO THE SUPERCONTINENTAL CYCLES

“…Холодова, И.В. Николаева) по методикам, описанным ранее [Likhanov, Reverdatto, 2007]. Петрохимические данные для изученных метапелитов показывают следующие вариации составов (мас.…”