TY - JOUR

T1 - Early Devonian volcanics of southeastern Gorny Altai

T2 - Geochemistry, isotope (Sr, Nd, and O) composition, and petrogenesis (Aksai complex)

AU - Krupchatnikov, V. I.

AU - Vrublevskii, V. V.

AU - Kruk, N. N.

PY - 2018/8/1

Y1 - 2018/8/1

N2 - Geological, geochemical, and isotope (Sr, Nd, and O) parameters of Early Devonian (405 Ma) volcanics of southeastern Gorny Altai (Aksai and Kalguty volcanotectonic structures) are discussed. The studied igneous rock association comprises magnesian andesitoids, Nb-enriched andesite basalts, and A-type peraluminous silicic rocks (dacites, rhyolites, granites, and leucogranites). Magnesian andesitoids (mg# > 50) are characterized by a predominance of Na among alkalies (K2O/Na2O ≈ 0.1-0.7), medium contents of TiO2 (~ 0.8-1.3 wt.%) and Al2O3 (~ 12-15 wt.%), enrichment in Cr (up to 216 ppm), and low Sr/Y ratios (4-15). The Nb-enriched (Nb = 10-17 ppm) andesite basalts have high contents of TiO2 (1.7-2.7 wt.%) and P2O5 (0.4-1.4 wt.%). The A-type granitoids are characterized by high contents of K(K2O/Na2O ≤ 60) and alumina (ASI ≤ 2.9) and depletion in Ba, Sr, P, and Ti. The magnesian andesitoids and Nb-enriched andesite basalts are products of melts generated in the metasomatized lithospheric mantle; silicic magmas were formed through the melting of Cambrian-Ordovician metaturbidites of the Gorny Altai Group and, partly, Early-Middle Cambrian island-arc metabasites. The above rock association might have resulted from a plume impact on the lithospheric substrates of the continental paleomargin during the evolution of the Altai-Sayan rift system.

AB - Geological, geochemical, and isotope (Sr, Nd, and O) parameters of Early Devonian (405 Ma) volcanics of southeastern Gorny Altai (Aksai and Kalguty volcanotectonic structures) are discussed. The studied igneous rock association comprises magnesian andesitoids, Nb-enriched andesite basalts, and A-type peraluminous silicic rocks (dacites, rhyolites, granites, and leucogranites). Magnesian andesitoids (mg# > 50) are characterized by a predominance of Na among alkalies (K2O/Na2O ≈ 0.1-0.7), medium contents of TiO2 (~ 0.8-1.3 wt.%) and Al2O3 (~ 12-15 wt.%), enrichment in Cr (up to 216 ppm), and low Sr/Y ratios (4-15). The Nb-enriched (Nb = 10-17 ppm) andesite basalts have high contents of TiO2 (1.7-2.7 wt.%) and P2O5 (0.4-1.4 wt.%). The A-type granitoids are characterized by high contents of K(K2O/Na2O ≤ 60) and alumina (ASI ≤ 2.9) and depletion in Ba, Sr, P, and Ti. The magnesian andesitoids and Nb-enriched andesite basalts are products of melts generated in the metasomatized lithospheric mantle; silicic magmas were formed through the melting of Cambrian-Ordovician metaturbidites of the Gorny Altai Group and, partly, Early-Middle Cambrian island-arc metabasites. The above rock association might have resulted from a plume impact on the lithospheric substrates of the continental paleomargin during the evolution of the Altai-Sayan rift system.

KW - A-type granitoids

KW - Central Asian Orogenic Belt

KW - Early Devonian magmatism

KW - geochemistry

KW - Gorny Altai

KW - magnesian andesitoids

KW - Nb-enriched andesite basalts

KW - A-TYPE GRANITES

KW - MAGNESIAN ANDESITES

KW - CHINA

KW - ROCKS

KW - CLASSIFICATION

KW - MAGMATISM

KW - PERALUMINOUS GRANITES

KW - EVOLUTION

KW - DISCRIMINATION

KW - GENERATION

UR - http://www.scopus.com/inward/record.url?scp=85051115010&partnerID=8YFLogxK

U2 - 10.1016/j.rgg.2018.07.012

DO - 10.1016/j.rgg.2018.07.012

M3 - Article

AN - SCOPUS:85051115010

VL - 59

SP - 905

EP - 924

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 8

ER -