TY - JOUR

T1 - Geodynamic setting, structure, and composition of continuous trachybasalt-trachyandesite-rhyolite series in the north of Altai-Sayan area

T2 - the role of crust-mantle interaction in continental magma formation

AU - Vorontsov, A. A.

AU - Perfilova, O. Yu

AU - Kruk, N. N.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - The geologic positions and geochemical and isotope parameters of the Ordovician-early Silurian and Early-Middle Devonian continuous volcanic series of the Minusa basin and its mountainous framing are compared. Both series are composed mostly of moderately alkaline rocks with variations in SiO2 contents from 45 to 77 wt.%. The Ordovician-early Silurian series differs from the Early-Middle Devonian one in lower contents of TiO2 (< 1.7 wt.%) and Fe2O3tot and higher contents of Al2O3 in all rock varieties and in the more fractionated REE patterns of trachybasalts. The compositions of both series reflect two simultaneous mechanisms of magma evolution. The main process was fractional crystallization leading to the formation of rocks from trachybasalts to trachyrhyodacites. The accessory mechanism was the contamination of fractionated melts by crustal material, anatectic melting of crust, and mixing of deep-seated magmas with crustal melts. These processes had specifics at each stage and were controlled by the composition of the sources of parental melts. Their geochemical and isotopic parameters (high alkalinity, high contents of lithophile elements, negative anomalies of Nb, Ta, and Ti, and enrichment in radiogenic Sr) point to the interaction of mantle plumes with the lithospheric mantle that was metasomatically transformed during the preceding Vendian-early Cambrian subduction processes.

AB - The geologic positions and geochemical and isotope parameters of the Ordovician-early Silurian and Early-Middle Devonian continuous volcanic series of the Minusa basin and its mountainous framing are compared. Both series are composed mostly of moderately alkaline rocks with variations in SiO2 contents from 45 to 77 wt.%. The Ordovician-early Silurian series differs from the Early-Middle Devonian one in lower contents of TiO2 (< 1.7 wt.%) and Fe2O3tot and higher contents of Al2O3 in all rock varieties and in the more fractionated REE patterns of trachybasalts. The compositions of both series reflect two simultaneous mechanisms of magma evolution. The main process was fractional crystallization leading to the formation of rocks from trachybasalts to trachyrhyodacites. The accessory mechanism was the contamination of fractionated melts by crustal material, anatectic melting of crust, and mixing of deep-seated magmas with crustal melts. These processes had specifics at each stage and were controlled by the composition of the sources of parental melts. Their geochemical and isotopic parameters (high alkalinity, high contents of lithophile elements, negative anomalies of Nb, Ta, and Ti, and enrichment in radiogenic Sr) point to the interaction of mantle plumes with the lithospheric mantle that was metasomatically transformed during the preceding Vendian-early Cambrian subduction processes.

KW - crustal contamination

KW - Devonian

KW - fractionation

KW - isotopic compositions of Sr and Nd

KW - magmatic sources

KW - Minusa basin

KW - Ordovician

KW - rare lithophile elements

KW - rhyolite

KW - Silurian

KW - trachyandesite

KW - trachybasalt

KW - LAKE ZONE

KW - MECHANISMS

KW - U-PB

KW - OZERNAYA ZONE

KW - ORIGIN

KW - CALEDONIDES

KW - EVOLUTION

KW - CENTRAL-ASIA

KW - MINUSA BASIN

KW - AGE

UR - http://www.scopus.com/inward/record.url?scp=85058174604&partnerID=8YFLogxK

U2 - 10.1016/j.rgg.2018.12.009

DO - 10.1016/j.rgg.2018.12.009

M3 - Article

AN - SCOPUS:85058174604

VL - 59

SP - 1640

EP - 1659

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 12

ER -