TY - JOUR

T1 - Adakite-like granitoids of Songkultau: A relic of juvenile Cambrian arc in Kyrgyz Tien Shan

AU - Konopelko, D.

AU - Seltmann, R.

AU - Dolgopolova, A.

AU - Safonova, I.

AU - Glorie, S.

AU - De Grave, J.

AU - Sun, M.

N1 - Funding Information: We are grateful to Anatoly Ilyukhin, Gilby Jepson, Jack Gillespie and Alina Perfilova who were involved in field work and sample preparation. Insightful comments of Tao Wang, Dmitry Alexeiev and an anonymous reviewer helped to improve the manuscript significantly. Dmitry Alexeiev is also acknowledged for his generous support during the first field campaign at Songkultau. The study was supported by the Ministry of Education and Science of the Russian Federation (Project No 14.Y26.31.0018 – I.S ., D.K. ). D. Konopelko acknowledges С0LLАВ travel grant from SPbGU and support through the Natural History Museum , London where part of the study was carried out in the frame of Research Fellowships at the Centre for Russian and Central EurAsian Mineral Studies (CERCAMS). RS acknowledges funding under Natural Environment Research Council Grant NE/P017452/1 “From arc magmas to ores (FAMOS): A mineral systems approach”. This is a contribution to the State Assignment of the Sobolev Institute of Geology and Mineralogy SB RAS (I.S.) and IGCP 662 Project “Orogenic Architecture and Crustal Growth from Accretion to Collision” under the patronage of UNESCO-IUGS. Publisher Copyright: © 2020 China University of Geosciences (Beijing) and Peking University Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2021/1/1

Y1 - 2021/1/1

N2 - The early Paleozoic Terskey Suture zone, located in the southern part of the Northern Tien Shan domain in Kyrgyzstan, comprises tectonic slivers of dismembered ophiolites and associated primitive volcanics and deep-marine sediments. In the Lake Songkul area, early-middle Cambrian pillow basalts are crosscut by the Songkultau intrusion of coarse-grained gneissose quartz diorites and tonalites with geochemical characteristics typical for high-SiO2 adakites (SiO2 ​> ​56 ​wt.%, Al2O3 ​> ​15 ​wt.%, Na2O ​> ​3.5 ​wt.% and high Sr/Y and La/Yb ratios). The Songkultau granitoids have positive initial εNd (+3.8 to +6.4) and εHf (+12.3 to +13.5) values indicating derivation from sources with MORB-like isotopic signature. Volcanic formations, surrounding the Songkultau intrusion, have geochemical affinities varying from ocean floor to island arc series. This rock assemblage is interpreted as a relic of an early-middle Cambrian primitive arc where the adakite-like granitoids were derived from partial melting of young and hot subducted oceanic crust. An age of 505 ​Ma, obtained for the Songkultau intrusion, shows that hot subduction under the Northern Tien Shan continued until middle Cambrian. The primitive arc complexes were obducted onto the Northern Tien Shan domain, where the Andean type continental magmatic arc developed in Cambrian and Ordovician. Formation of the Andean type arc was accompanied by uplift, erosion and deposition of coarse clastic sediments. A depositional age of ca. 470 Ma, obtained for the gravellites in the Lake Songkul area, is in agreement with the timing of deposition for lower Ordovician conglomerates elsewhere in the Northern Tien Shan, and corresponds to the main phase of the Andean type magmatism. The Songkultau adakites in association with surrounding ocean floor and island arc formations constitute a relic of a primitive Cambrian arc and represent a juvenile domain of substantial size identified so far within the predominantly crustal-derived terranes of Tien Shan. On a regional scale this primitive arc can be compared with juvenile Cambrian arcs of Kazakhstan, Gorny Altai and Mongolia.

AB - The early Paleozoic Terskey Suture zone, located in the southern part of the Northern Tien Shan domain in Kyrgyzstan, comprises tectonic slivers of dismembered ophiolites and associated primitive volcanics and deep-marine sediments. In the Lake Songkul area, early-middle Cambrian pillow basalts are crosscut by the Songkultau intrusion of coarse-grained gneissose quartz diorites and tonalites with geochemical characteristics typical for high-SiO2 adakites (SiO2 ​> ​56 ​wt.%, Al2O3 ​> ​15 ​wt.%, Na2O ​> ​3.5 ​wt.% and high Sr/Y and La/Yb ratios). The Songkultau granitoids have positive initial εNd (+3.8 to +6.4) and εHf (+12.3 to +13.5) values indicating derivation from sources with MORB-like isotopic signature. Volcanic formations, surrounding the Songkultau intrusion, have geochemical affinities varying from ocean floor to island arc series. This rock assemblage is interpreted as a relic of an early-middle Cambrian primitive arc where the adakite-like granitoids were derived from partial melting of young and hot subducted oceanic crust. An age of 505 ​Ma, obtained for the Songkultau intrusion, shows that hot subduction under the Northern Tien Shan continued until middle Cambrian. The primitive arc complexes were obducted onto the Northern Tien Shan domain, where the Andean type continental magmatic arc developed in Cambrian and Ordovician. Formation of the Andean type arc was accompanied by uplift, erosion and deposition of coarse clastic sediments. A depositional age of ca. 470 Ma, obtained for the gravellites in the Lake Songkul area, is in agreement with the timing of deposition for lower Ordovician conglomerates elsewhere in the Northern Tien Shan, and corresponds to the main phase of the Andean type magmatism. The Songkultau adakites in association with surrounding ocean floor and island arc formations constitute a relic of a primitive Cambrian arc and represent a juvenile domain of substantial size identified so far within the predominantly crustal-derived terranes of Tien Shan. On a regional scale this primitive arc can be compared with juvenile Cambrian arcs of Kazakhstan, Gorny Altai and Mongolia.

KW - Adakite

KW - Cambrian juvenile arc

KW - Northern Tien Shan (Tianshan)

KW - Terskey suture

KW - PETROGENESIS

KW - COMPLEX

KW - CRUSTAL GROWTH

KW - CONTINENTAL GROWTH

KW - PALEOZOIC TECTONIC EVOLUTION

KW - ZIRCON AGES

KW - ND

KW - TIAN-SHAN

KW - CONSTRAINTS

KW - GEOCHEMISTRY

UR - http://www.scopus.com/inward/record.url?scp=85090884617&partnerID=8YFLogxK

U2 - 10.1016/j.gsf.2020.08.006

DO - 10.1016/j.gsf.2020.08.006

M3 - Article

AN - SCOPUS:85090884617

VL - 12

SP - 147

EP - 160

JO - Geoscience Frontiers

JF - Geoscience Frontiers

SN - 1674-9871

IS - 1

ER -