Geochronology, geochemistry and tectonic setting of the Cadomian (Ediacaran–Cambrian) magmatism in the Istranca (Strandja) Massif: new insights into magmatism along the northern margin of Gondwana in NW Turkey

Cadomian (Ediacaran–Cambrian) magmatic rocks have been reported in the eastern (e.g. the Çatalca and İhsaniye plutons) and western (e.g. the Binkılıç and Safaalan plutons) parts of the Istranca (Strandja) Massif. This paper aims to investigate the tectonic setting and the magma evolution history of the Cadomian magmatic rocks using both new and previously existing geochemical and geochronological data. The meta-granitoid rocks with intermediate to felsic composition are the main magmatic activity in the region. They intrude into metamorphic basement rocks composed of gneiss, schist, amphibolite, calc-schist, and quartzites (the Tekedere group). These plutons show strong foliation and traces of the polyphase metamorphism. All plutons are peraluminous and slightly metaluminous, mostly calc-alkaline and high-K calc-alkaline, and plot into the volcanic arc granites (VAG) field on the tectono-magmatic discrimination diagrams. The zircon U–Pb crystallization ages of the plutons are between 525.3 ± 3.5 Ma and 548.7 ± 2.3 Ma. Initial εNd values vary from −0.02 to 1.86. Nd-T_DM model ages range between 1.08 and 1.24 Ga and indicate that the primitive magmas were originated and/or assimilated by the remelting of Neoproterozoic juvenile crustal rocks. New geochemical and geochronological data suggest a magma generation within a subduction-related magmatic arc setting in response to the southward subduction of the Proto-Tethys Ocean during the Late Precambrian-Early Palaeozoic period in the Istranca Massif.

伊斯特兰贾（斯特兰贾）地块的东部（如恰尔卡贾、伊赫桑耶深成岩体）和西部（如宾克勒奇、萨法拉兰深成岩体）均已发现卡多米（埃迪卡拉纪-寒武纪）岩浆岩。本文旨在利用全新及已有地球化学与地质年代学数据，探究该区域卡多米岩浆岩的构造背景及岩浆演化历史。中-长英质成分的变花岗岩类是该区域主要的岩浆活动产物，它们侵入于由片麻岩、片岩、角闪岩、钙片岩及石英岩构成的变质基底岩系（特凯德莱雷群）之中。这些深成岩体均发育强烈的面理构造，并记录有多期变质作用的痕迹。所有深成岩体均属过铝质-准铝质范畴，整体以钙碱性及高钾钙碱性系列为主，在构造岩浆判别图解中均落入火山弧花岗岩（VAG）区域。各深成岩体的锆石U-Pb结晶年龄介于525.3±3.5 Ma至548.7±2.3 Ma之间。初始εNd值范围为-0.02至1.86，Nd-T_DM模式年龄介于1.08 Ga至1.24 Ga之间，指示原始岩浆起源于新元古代新生地壳岩石的重熔，或受到该类地壳岩石的同化混染作用。全新的地球化学与地质年代学数据表明，伊斯特兰贾地块在晚前寒武纪-早古生代时期，处于原特提斯洋向南俯冲的构造背景下，其岩浆形成于俯冲相关的岩浆弧环境。