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Petrogenesis of oligocene plutonic rocks in western Anatolia (NW Turkey): Insights from mineral and rock chemistry, Sr-Nd isotopes, and U-Pb, Ar-Ar and (U-Th)/He geochronology
Geochemistry ( IF 2.6 ) Pub Date : 2021-02-16 , DOI: 10.1016/j.chemer.2021.125747
Şenel Özdamar , Michael F. Roden , Haibo Zou , Mehmet Z. Billor , Willis Hames , Stoyan Georgiev , Istvan Dunkl

Northwestern Anatolia is characterized by voluminous Paleozoic to Cenozoic granitoid bodies with varying compositions. Most of them are composite plutons emplaced into western Anatolia orogenic crust during the Eocene, Oligocene and Miocene along the İzmir-Ankara-Erzincan suture zone. This paper reports systematic good quality mineral and bulk-rock chemistry, Sr-Nd isotope data, honblend Ar-Ar, zircon U-Pb and first apatite (U-Th)/He (AHe) ages to reveal possible source compositions of the Evciler and Eybek granitoids and petrogenetic/geodynamic processes involved during their genesis, and thermochronology of Oligocene magmatism in the NW Anatolia. The Evciler and Eybek granitoids are mainly granodiorite and composed of K-feldspar (usually orthoclase and rarely microcline), plagioclase (albite, oligoclase), hornblende, biotite, quartz and accessory minerals (e.g., titanite, zircon, apatite, opaque), and secondary minerals such as chlorite, sericite and clay minerals. Estimated temperature-pressure conditions are 690–770 ° C at 1.6–2.7 kbar for the Evciler granitoid and 690–760 ° C at 3.2–4.01 kbar for the Eybek granitoid. These two granitoids enriched in LILEs (e.g., U, Th, Rb, and K), LREEs and Pb, and depleted in HREEs (e.g., Nb, Ti) and Sr, Ba and P relative to LILEs, and display small negative Eu anomalies. They belong to calc-alkaline, high-K calc-alkaline and minor shoshonite series, and display metaluminous and I-type character. Their REE patterns show a large fractionation between LREE and HREE ((La/Yb)N = 4.6–21.4) and a small negative Eu anomaly (Eu* = 0.2–0.3). The Evciler granitoid has homogeneous 87Sr/86Sr = 0.7060−0.7063 and 143Nd/144Nd = 0.51259−0.51262, and the Eybek granitoid has 87Sr/86Sr = 0.7060−0.7080 and 143Nd/144Nd = 0.51243−0.51263. New precise 40Ar/39Ar age data of hornblende and 206Pb–238U ages of zircons and (U-Th)/He ages of apatites from the plutons allow a more accurate temporal reconstruction of the Cenozoic magmatism of the western Anatolia. 40Ar/39Ar dating of hornblendes from the Evciler and Eybek granitoids gave plateau ages of between ca. 28 Ma and 25 Ma. Laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) 206Pb-238Pb ages of euhdral magmatic zircons from the samples of these granitoids yield between ca. 28 and 26 Ma. The new high-temperature age constraints indicate Oligocene emplacement ages for the two intrusive bodies. The closeness of the zircon U-Pb and the hornblende Ar-Ar ages show that they experienced quick post-crystallization cooling. However, the significant difference between the apatite (U-Th)/He ages of 19.8 Ma and 7.6 Ma obtained on the Evciler and Eybek granitoids warns that in the post-Oligocene times the two structural blocks had different exhumation histories.



中文翻译:

安纳托利亚西部(土耳其西北部)渐新世深成岩的成因:矿物和岩石化学、Sr-Nd 同位素和 U-Pb、Ar-Ar 和 (U-Th)/He 年代学的见解

安纳托利亚西北部的特征是巨大的古生代至新生代花岗岩体,成分各异。其中大部分是始新世、渐新世和中新世沿伊兹密尔-安卡拉-埃尔津坎缝合带进入安纳托利亚西部造山地壳的复合岩体。本文报告了系统的优质矿物和大块岩石化学、Sr-Nd 同位素数据、混合 Ar-Ar、锆石 U-Pb 和第一磷灰石 (U-Th)/He (AHe) 年龄,以揭示 Evciler 的可能来源组成和 Eybek 花岗岩及其成因过程中涉及的岩石成因/地球动力学过程,以及安纳托利亚西北部渐新世岩浆活动的热年代学。Evciler 和 Eybek 花岗岩主要是花岗闪长岩,由钾长石(通常为正长石,很少为微斜长石)、斜长石(钠长石、寡长石)、角闪石、黑云母、石英和副矿物(如钛铁矿、锆石、磷灰石、不透明),以及次生矿物如绿泥石、绢云母和粘土矿物。对于 Evciler 花岗岩,估计的温度压力条件为 690–770 °C,压力为 1.6–2.7 kbar,Eybek 花岗岩为 690–760 °C,压力为 3.2–4.01 kbar。相对于LILE,这两种花岗岩富含LILEs(如U、Th、Rb和K)、LREEs和Pb,并缺乏HREEs(如Nb、Ti)和Sr、Ba和P,并显示出小的负Eu异常. 它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 次生矿物如绿泥石、绢云母和粘土矿物。对于 Evciler 花岗岩,估计的温度压力条件为 690–770 °C,压力为 1.6–2.7 kbar,Eybek 花岗岩为 690–760 °C,压力为 3.2–4.01 kbar。相对于LILE,这两种花岗岩富含LILEs(如U、Th、Rb和K)、LREEs和Pb,并缺乏HREEs(如Nb、Ti)和Sr、Ba和P,并显示出小的负Eu异常. 它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 次生矿物如绿泥石、绢云母和粘土矿物。对于 Evciler 花岗岩,估计的温度压力条件为 690–770 °C,压力为 1.6–2.7 kbar,Eybek 花岗岩为 690–760 °C,压力为 3.2–4.01 kbar。相对于LILE,这两种花岗岩富含LILEs(如U、Th、Rb和K)、LREEs和Pb,并缺乏HREEs(如Nb、Ti)和Sr、Ba和P,并显示出小的负Eu异常. 它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 Evciler 花岗岩为 7 kbar,Eybek 花岗岩为 690–760 °C,3.2–4.01 kbar。相对于LILE,这两种花岗岩富含LILEs(如U、Th、Rb和K)、LREEs和Pb,并缺乏HREEs(如Nb、Ti)和Sr、Ba和P,并显示出小的负Eu异常. 它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 Evciler 花岗岩为 7 kbar,Eybek 花岗岩为 690–760 °C,3.2–4.01 kbar。相对于LILE,这两种花岗岩富含LILEs(如U、Th、Rb和K)、LREEs和Pb,并缺乏HREEs(如Nb、Ti)和Sr、Ba和P,并显示出小的负Eu异常. 它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 并显示小的负 Eu 异常。它们属于钙碱性、高钾钙碱性和次要钾长石系列,显示出金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性 并显示小的负 Eu 异常。它们属于钙碱性、高钾钙碱性和次要钠长石系列,具有金属铝和I型特征。他们的 REE 模式显示 LREE 和 HREE 之间有很大的分馏((La/Yb)N = 4.6–21.4)和一个小的负 Eu 异常(Eu* = 0.2–0.3)。Evciler 花岗岩具有均质性87 SR / 86 SR = 0.7060-0.7063和143的Nd / 144的Nd = 0.51259-0.51262,并且Eybek花岗岩类具有87 SR / 86 SR = 0.7060-0.7080和143的Nd / 144的Nd = 0.51243-0.51263。新的精确角闪石40 Ar/ 39 Ar 年龄数据和锆石的206 Pb– 238 U 年龄和来自岩体的磷灰石的 (U-Th)/He 年龄可以更准确地重建安纳托利亚西部新生代岩浆活动的时间。40氩/ 39来自 Evciler 和 Eybek 花岗岩的角闪石的 Ar 年代测定给出了大约在 2000 年之间的高原年龄。28 毫安和 25 毫安。激光烧蚀电感耦合等离子体质谱仪 (LA-ICP-MS)来自这些花岗岩样品的206 Pb - 238 Pb 年龄的自相岩浆锆石产量约为 28 和 26 马。新的高温年龄限制表明两个侵入体的渐新世侵位年龄。锆石 U-Pb 和角闪石 Ar-Ar 年龄的接近表明它们经历了快速的后结晶冷却。然而,在 Evciler 和 Eybek 花岗岩上获得的 19.8 Ma 和 7.6 Ma 的磷灰石 (U-Th)/He 年龄之间的显着差异警告说,在后渐新世时期,这两个构造块体具有不同的折返历史。

更新日期:2021-02-16
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