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首页> 外文期刊>Geodinamica Acta >Origin and evolution of the Havran Unit, Western Sakarya basement (NW Turkey): new LA-ICP-MS U-Pb dating of the metasedimentary-metagranitic rocks and possible affiliation to Avalonian microcontinent
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Origin and evolution of the Havran Unit, Western Sakarya basement (NW Turkey): new LA-ICP-MS U-Pb dating of the metasedimentary-metagranitic rocks and possible affiliation to Avalonian microcontinent

机译：西萨卡里亚地下室（土耳其西北部）Havran单元的起源和演化：准沉积-变质岩的新LA-ICP-MS U-Pb年代测定以及可能与阿瓦隆微大陆的联系

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摘要

One of the pre-Jurassic metamorphic basements of the Western Sakarya Zone (NW Turkey) is the Havran Unit which contains metasedimentary (i.e. the Kalabak formation) and metaintrusive rocks of Devonian age. An LA-ICP-MS U-Pb zircon dating study was conducted on 125 zircon grains obtained from a metasedimentary rock to better understand the origin and evolution of the Kalabak formation. Around 107 of 175 spot analyses are concordant with rates 90–110% and the zircon ages vary between 426 ± 5.2 and 3406.9 ± 195.7 Ma. Zircon populations cluster in ranges: 426 ± 5.2–535 ± 13Ma (8.4%, Palaeozoic), 549 ± 14–999 ± 11Ma (54.21%, Neoproterozoic), 1012 ± 200–1543 ± 50Ma (6.54%, Mesoproterozoic), 1736 ± 123–2414 ± 58Ma (18.7%, Palaeoproterozoic), and 2512 ± 30–3406.9 ± 195.7 Ma (12.15%, Archean). Dominating Neoproterozoic ages notate Cadomian-Avalonian terrains and Mesoproterozoic ages should mainly be related to Avalon terrains. The Karacabey metagranite consists of coarse-grained, equigranular, hypidiomorphic, and rarely foliated monzogranite and granodiorite. It is located to the north of the town of Karacabey in the eastern part of the Biga Peninsula. Main mineral assemblage is quartz, K-feldspar, plagioclase, and biotite. Zircon, apatite, monazite, magnetite, and sphene occur as accessory phases. Aluminum Saturation Index (ASI) values vary between 0.91 and 1.63, indicating the pluton as a metaluminous-peraluminous, I-type granite. The metagranite samples are plotted in the high-K-calcalkaline field on the SiO2 vs. K2O diagram. N-MORB-normalised spidergrams display a profound enrichment in the large-ion lithophile elements (LILE), light rare earth elements (LREE), and depletion in high field strength elements, suggesting that its genesis relates to hydrous melting of a mantle wedge in a subduction zone and/or melting of subduction zone-influenced source areas. Chondrite-normalised rare earth element spidergrams are indicative of the importance of plagioclase and amphibole fractionation. In tectonic discrimination diagrams, all of the metagranite samples fall into the volcanic arc granite and late post-collisional granite fields. U/Pb LA-ICP-MS zircon dating of the metagranite yielded an age of 400.3 ± 1.4 Ma (Early Devonian), interpreted as the age of igneous crystallisation. These age data show that the Karacabey metagranite is a member of the lower to mid Devonian granites, recently described from the Biga Peninsula. In light of these findings, we argue that the Havran Unit was an exotic terrain which possibly was once a part of far-travelled Avalon terrains and was attached to Sakarya Zone.
机译：西萨卡里亚地区（西北土耳其）的侏罗纪前变质基底之一是Havran单元，其中包含变质沉积（即卡拉巴克组）和泥盆纪时代的超侵入岩。进行了LA-ICP-MS U-Pb锆石定年研究，研究了从准沉积岩石中获得的125个锆石晶粒，以更好地了解Kalabak地层的起源和演化。 175个点分析中的约107个与90-110％的比率一致，锆石年龄在426±5.2和3406.9±195.7 Ma之间变化。锆石种群在以下范围内聚集：426±5.2–535±13Ma（8.4％，古生代），549±14–999±11Ma（54.21％，新元古代），1012±200–1543±50Ma（6.54％，中元古代），1736± 123–2414±58Ma（18.7％，古元古代）和2512±30–3406.9±195.7 Ma（12.15％，太古宙）。在新元古代时代占主导地位的是Cadomian-Avalonian地形，中元古代时代应主要与Avalon地形有关。卡拉卡比变质岩由粗粒状，等粒状，亚同形，很少成叶的辉长花岗岩和花岗闪长岩组成。它位于Biga半岛东部的Karacabey镇的北部。主要的矿物组合是石英，钾长石，斜长石和黑云母。锆石，磷灰石，独居石，磁铁矿和蝶粉作为辅助相出现。铝饱和指数（ASI）值在0.91和1.63之间变化，表明该岩心体为金属铝质，I型花岗岩。在SiO2对K2O图上的高K-钙碱性区域中绘制了变花岗岩样品。 N-MORB归一化的蜘蛛图显示出大离子的亲石元素（LILE），轻稀土元素（LREE）和高场强元素的贫化，表明其成因与地幔楔的含水熔融有关。俯冲带和/或俯冲带影响源区的融化。球粒陨石标准化的稀土元素蜘蛛图表明斜长石和闪石分级分离的重要性。在构造判别图中，所有变花岗岩样品均落入火山弧花岗岩和碰撞后后期花岗岩田。变质岩的U / Pb LA-ICP-MS锆石定年年龄为400.3±1.4 Ma（泥盆纪早期），被解释为火成岩结晶年龄。这些年龄数据表明，卡拉卡比变质花岗岩是泥盆纪中下花岗岩的一员，最近在比加半岛有描述。根据这些发现，我们认为哈夫兰部队是一个奇特的地形，可能曾经是远距离旅行的阿瓦隆地形的一部分，并隶属于萨卡里亚地区。

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