Neotethys closure history of Anatolia: insights from 40Ar–39Ar geochronology and P–T estimation in high‐pressure metasedimentary rocks
Neotethys closure history of Anatolia: insights from 40Ar–39Ar geochronology and P–T estimation in high‐pressure metasedimentary rocks
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DOI：
10.1111/jmg.12034
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发表时间：
2013-08
影响因子：
3.4
通讯作者：
A. Pourteau;M. Sudo;O. Candan;P. Lanari;Olivier Vidal;R. Oberhänsli
中科院分区：
文献类型：
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作者：
A. Pourteau;M. Sudo;O. Candan;P. Lanari;Olivier Vidal;R. Oberhänsli
安纳托利亚西部和中部的多个高压（HP）、低温（LT）变质单元为研究长期存在的爱琴海俯冲系统东部分支的俯冲和大陆增生相关演化提供了很好的机会。最近关于冈瓦纳衍生的Anatolide-Tauride大陆块体（即Afyon带、Ören单元和Menderes地块南部）的三个变质沉积单元中HP-LT指数矿物Fe - Mg - carphoite的报道表明，这比以往研究中普遍提出的单大陆吸积模式更为复杂。本研究提出了来自这三个HP-LT变质沉积单元的含碳岩岩石的第一个同位素日期（白云母40Ar-39Ar地质年代学），并在可能的情况下结合P-T估计（绿泥石测温、云母气压计、多平衡温度气压计）。结果表明，Afyon带在约67 ~ 62 Ma的绿片岩相条件下发生了含碳绿岩组合的退退。Ören单元的早期逆行阶段可追溯到63-59 Ma。在kuudere - nebiler单元（Menderes地块南部中生代的高压盖层），高压逆行期可追溯到c. 45 Ma，碰撞后冷却期可追溯到c. 26 Ma。这些新结果支持Ören单元代表Afyon带的最西端延续，而Kurudere-Nebiler单元与爱琴海域的基克拉迪蓝片岩单元相关。在安纳托利亚西部，形成了三个连续的HP-LT变质带：最北端的tav<s:1> anlyi带（约88-82 Ma）、Ören-Afyon带（约70 - 65 Ma）和Kurudere-Nebiler单元（约52-45 Ma）。HP-LT变质作用从上部和内部向更深层和更外部的构造单元（如爱琴海地区）的南向年轻趋势表明，在93-90和c. 35 Ma之间，安纳托利亚西部的俯冲作用持续存在。始新世，门德雷斯-陶夫里德地体增生后，俯冲作用停止，导致大陆碰撞和相关的巴罗维亚型变质作用。相比之下，由于板块回滚和海沟迁移，爱琴海俯冲仍然活跃，希腊板块的东部分支（安纳托利亚西南部以下）剧烈弯曲，因此被撕裂。因此，我们认为，在浮力（如大陆）地体增生之后，俯冲继续的可能性可能在很大程度上取决于古地理。
The multiple high‐pressure (HP), low‐temperature (LT) metamorphic units of Western and Central Anatolia offer a great opportunity to investigate the subduction‐ and continental accretion‐related evolution of the eastern limb of the long‐lived Aegean subduction system. Recent reports of the HP–LT index mineral Fe‐Mg‐carpholite in three metasedimentary units of the Gondwana‐derived Anatolide–Tauride continental block (namely the Afyon Zone, the Ören Unit and the southern Menderes Massif) suggest a more complicated scenario than the single‐continental accretion model generally put forward in previous studies. This study presents the first isotopic dates (white mica 40Ar–39Ar geochronology), and where possible are combined with P–T estimates (chlorite thermometry, phengite barometry, multi‐equilibrium thermobarometry), on carpholite‐bearing rocks from these three HP–LT metasedimentary units. It is shown that, in the Afyon Zone, carpholite‐bearing assemblages were retrogressed through greenschist‐facies conditions at c. 67–62 Ma. Early retrograde stages in the Ören Unit are dated to 63–59 Ma. In the Kurudere–Nebiler Unit (HP Mesozoic cover of the southern Menderes Massif), HP retrograde stages are dated to c. 45 Ma, and post‐collisional cooling to c. 26 Ma. These new results support that the Ören Unit represents the westernmost continuation of the Afyon Zone, whereas the Kurudere–Nebiler Unit correlates with the Cycladic Blueschist Unit of the Aegean Domain. In Western Anatolia, three successive HP–LT metamorphic belts thus formed: the northernmost Tavşanlı Zone (c. 88–82 Ma), the Ören–Afyon Zone (between 70 and 65 Ma), and the Kurudere–Nebiler Unit (c. 52–45 Ma). The southward younging trend of the HP–LT metamorphism from the upper and internal to the deeper and more external structural units, as in the Aegean Domain, points to the persistence of subduction in Western Anatolia between 93–90 and c. 35 Ma. After the accretion of the Menderes–Tauride terrane, in Eocene times, subduction stopped, leading to continental collision and associated Barrovian‐type metamorphism. Because, by contrast, the Aegean subduction did remain active due to slab roll‐back and trench migration, the eastern limb (below Southwestern Anatolia) of the Hellenic slab was dramatically curved and consequently teared. It therefore is suggested that the possibility for subduction to continue after the accretion of buoyant (e.g. continental) terranes probably depends much on palaeogeography.