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

作　　者：D.Konopelko R.Seltmann A.Dolgopolova I.Safonova S.Glorie J.De Grave M.Sun 

机构地区：[1]St.Petersburg State University,7/9 University Embankment,St.Petersburg,199034,Russia [2]Novosibirsk State University,1 Pirogova St.,Novosibirsk,630090,Russia [3]Natural History Museum,Centre for Russian and Central EurAsian Mineral Studies(CERCAMS),London,SW75BD,UK [4]Sobolev Institute of Geology and Mineralogy SB RAS,Koptyuga Ave.3,Novosibirsk,630090,Russia [5]Department of Earth Sciences,School of Physical Sciences,The University of Adelaide,SA,5005,Australia [6]Department of Geology,Ghent University,Krijgslaan 281/S8,B-9000,Ghent,Belgium [7]Department of Earth Sciences,The University of Hong Kong,Pokfulam Road,Hong Kong,China

出　　处：《Geoscience Frontiers》2021年第1期147-160,共14页地学前缘（英文版）

基　　金：supported by the Ministry of Education and Science of the Russian Federation(Project No 14.Y26.31.0018-I.S.,D.K.)。

摘　　要：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 deepmarine 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.%,Na2 O>3.5 wt.%and high Sr/Y and La/Yb ratios).The Songkultau granitoids have positive initialεNd(+3.8 to+6.4)andεHf(+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

关 键 词：Northern Tien Shan(Tianshan) Terskey suture ADAKITE Cambrian juvenile arc 

分 类 号：P588.121[天文地球—岩石学] P534.41[天文地球—地质学]