Contrasting textural record of two distinct metamorphic events of similar P-T conditions and different durations

A structural, metamorphic and geochronological study of the StareMesto belt implies the existence of two distinct metamorphic events of similar peak P-T conditions (700-800 � C, 8-10 kbar) during the Cambro-Ordovician and the Carboniferous tectonometamorphic events. The hypothesis of two distinct periods of metamorphism was suggested on the basis of structural discordance between an undoubtedly Carboniferous granodiorite sill intrusion and earlier Cambro-Ordovician fabrics of a banded amphibolite complex. The analysis of crystal size distribution (CSD) shows high nucleation density (N0) and low average growth rate (Gt) for Carboniferous mylonitic metagabbros and mylonitic granodiorites. The…

Neoproterozoic-Early Paleozoic Peri-Pacific Accretionary Evolution of the Mongolian Collage System: Insights From Geochemical and U-Pb Zircon Data From the Ordovician Sedimentary Wedge in the Mongolian Altai

Neoproterozoic to early Paleozoic accretionary processes of the Central Asian Orogenic Belt have been evaluated so far mainly using the geology of ophiolites and/or magmatic arcs. Thus, the knowledge of the nature and evolution of associated sedimentary prisms remains fragmentary. We carried out an integrated geological, geochemical and zircon U–Pb geochronological study on a giant Ordovician metasedimentary succession of the Mongolian Altai Mts. This succession is characterized by dominant terrigenous components mixed with volcanogenic material. It is chemically immature, compositionally analogous to graywacke and marked by significant input of felsic to intermediate arc components, pointi…

Cambrian–Ordovician magmatism of the Ikh-Mongol Arc System exemplified by the Khantaishir Magmatic Complex (Lake Zone, south–central Mongolia)

Abstract The Khantaishir Magmatic Complex (KMC) (south–central Mongolia) exposes a section of a magmatic system consisting of deep crustal, ultramafic cumulates (coarse-grained Amp gabbros and hornblendites; c. 0.35–0.5 GPa) to shallower crustal levels dominated by Amp–Bt tonalites ( c. 0.1–0.2 GPa). The magmatic rocks were emplaced during most of the Cambrian ( c. 538–495 Ma) and are mostly geochemically primitive (Mg# ~ 50), Na-rich and metaluminous. The (normal-) calc-alkaline signature and characteristic trace-element enrichment in hydrous-fluid mobile large-ion lithophile elements (LILE) relative to high-field strength elements (HFSE) suggest an origin within a magmatic arc. Multiple i…

Reply to comments by A. Krohe and A.P. Willner on “Structural evolution of the central part of the Krušné Hory (Erzgebirge) Mountains in the Czech Republic—evidence for changing stress regime during Variscan compression”