TY - JOUR

T1 - Whole-rock geochemistry and U-Pb ages of Devonian bimodal-type rhyolites from the Rudny Altai, Russia: Petrogenesis and tectonic settings

AU - Kuibida, M. L.

AU - Murzin, O. V.

AU - Kruk, N. N.

AU - Safonova, I. Y.

AU - Sun, M.

AU - Komiya, T.

AU - Wong, J.

AU - Aoki, S.

AU - Murzina, N. M.

AU - Nikolaeva, I.

AU - Semenova, D. V.

AU - Khlestov, M.

AU - Shelepaev, R. A.

AU - Kotler, P. D.

AU - Yakovlev, V. A.

AU - Naryzhnova, A. V.

N1 - Funding Information: Writing this paper would be impossible without years of the hard field and laboratory work of skillful geologists from Russia, China and Kazakhstan. We are sincerely grateful to the reviewers who have enabled us to make this paper better. The study was carried out as part of a basic research program at the Ministry of Science and Education of the Russian Federation (Projects Nos. 14.Y26.31.0018), the Russian Foundation for Basic Research (project no. 16-05-01021), Hong Kong RGC grants 17302317 and 17303415; and according to the plan of the State Assignment of the Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/5

Y1 - 2020/5

N2 - The paper presents new original data on the Devonian felsic volcanism of the NW Rudny Altai (Russia) in the west of Central Asian Orogenic Belt (CAOB) – the front part of the Altai convergent margin of the Siberian continent. Two geochemical types of subvolcanic rhyolites were emplaced synchronously with the bimodal rhyolite-basalt association, which began to form in the end-Emsian, and clearly manifested on the border of the Givetian and the Frasnian. The rhyolites yield zircon U-Pb ages of ca. 390 Ma (R1-type) and 380 Ma (R2- and R3-types), reflecting two peaks of the volcanic activity. Most of these rocks have extreme petrochemical characteristics of high SiO2 contents and have contrast Na/K ratios. Their compositions are transition between calc-alkaline and tholeiite series: (La/Yb)n ~ 2–7, Zr/Y ~ 4 (Zr < 350 ppm) and La/Sm ~ 0.55–1. Rhyolites bear the distinctive geochemical signature of A-type felsic magma, such as enrichments in Zr, Nb, Y and Ce (>350 ppm), Zr (>250 ppm), and high Ga/Al (>2.6) values. The island-arc-like R1-rhyolite formed immediately after the beginning of rifting due to widespread crustal melting under reduced conditions. The generation of rift-like R2- and R3-rhyolites took place under non-equilibrium conditions, synchronously with the rise in the upper crust of Givetian-Frasnian basic magmas, as a result of the active lithospheric extension and high thermal input from the underlying hot mantle. We propose an extension regime in the transition area between the island-arc and back-arc basin for the origin of rhyolites. The study of the Devonian volcanism of the Rudny Altai gives important information about the processes that occurred at the initial stage of the formation of the Altai convergent margin.

AB - The paper presents new original data on the Devonian felsic volcanism of the NW Rudny Altai (Russia) in the west of Central Asian Orogenic Belt (CAOB) – the front part of the Altai convergent margin of the Siberian continent. Two geochemical types of subvolcanic rhyolites were emplaced synchronously with the bimodal rhyolite-basalt association, which began to form in the end-Emsian, and clearly manifested on the border of the Givetian and the Frasnian. The rhyolites yield zircon U-Pb ages of ca. 390 Ma (R1-type) and 380 Ma (R2- and R3-types), reflecting two peaks of the volcanic activity. Most of these rocks have extreme petrochemical characteristics of high SiO2 contents and have contrast Na/K ratios. Their compositions are transition between calc-alkaline and tholeiite series: (La/Yb)n ~ 2–7, Zr/Y ~ 4 (Zr < 350 ppm) and La/Sm ~ 0.55–1. Rhyolites bear the distinctive geochemical signature of A-type felsic magma, such as enrichments in Zr, Nb, Y and Ce (>350 ppm), Zr (>250 ppm), and high Ga/Al (>2.6) values. The island-arc-like R1-rhyolite formed immediately after the beginning of rifting due to widespread crustal melting under reduced conditions. The generation of rift-like R2- and R3-rhyolites took place under non-equilibrium conditions, synchronously with the rise in the upper crust of Givetian-Frasnian basic magmas, as a result of the active lithospheric extension and high thermal input from the underlying hot mantle. We propose an extension regime in the transition area between the island-arc and back-arc basin for the origin of rhyolites. The study of the Devonian volcanism of the Rudny Altai gives important information about the processes that occurred at the initial stage of the formation of the Altai convergent margin.

KW - Back-arc basin

KW - Bimodal basalt-rhyolite association

KW - Central Asian Orogenic Belt

KW - Melnichno-Sosnovsky volcanic complex

KW - Rifted-arc

KW - Rifled-arc

KW - NW CHINA PETROGENESIS

KW - EXPERIMENTAL CONSTRAINTS

KW - A-TYPE GRANITES

KW - MASSIVE SULFIDE DEPOSITS

KW - SILICIC MAGMAS

KW - CRUSTAL GROWTH

KW - TAUPO VOLCANIC ZONE

KW - LACHLAN FOLD BELT

KW - ICP-MS

KW - ASIAN OROGENIC BELT

UR - http://www.scopus.com/inward/record.url?scp=85077931594&partnerID=8YFLogxK

U2 - 10.1016/j.gr.2019.12.002

DO - 10.1016/j.gr.2019.12.002

M3 - Article

AN - SCOPUS:85077931594

VL - 81

SP - 312

EP - 338

JO - Gondwana Research

JF - Gondwana Research

SN - 1342-937X

ER -