Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone
Unravelling metamorphic ages of suture zone rocks from the Sabzevar and Makran areas (Iran): Robust age constraints for the larger Arabia–Eurasian collision zone
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揭开来自萨布泽瓦尔和莫克兰地区（伊朗）缝合带岩石的变质年龄：较大的阿拉伯-欧亚碰撞带的稳健年龄限制
DOI：
10.1111/jmg.12603
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发表时间：
2021
影响因子：
3.4
通讯作者：
Moslempour
中科院分区：
文献类型：
--
作者：
Bröcker;Omrani;Berndt;Moslempour
在本研究中，我们建立了影响伊朗中部微大陆北部（Sabzevar）和南部（Makran）边缘新特提斯缝合带的变质作用的时间框架。为此，我们将Rb-Sr和U-Pb年代学应用于这些矿床的蓝片岩和角闪岩相岩石。到目前为止，还没有来自Sabzevar地区的高磷/低磷岩石的同位素年龄，这些岩石暴露在索尔塔纳巴德附近的Govain和Chili山脉。戈文山3块蓝片岩的Rb-Sr年龄分别为56.52±0.32、57.20±0.32和55.12±0.33 Ma。这些年龄为Sabzevar带晚古新世至早始新世高变质作用提供了第一个明确的证据，并证实了间接得出的早期年龄分配的准确性。古新世晚期-始新世早期戈万山蓝片岩与公里级碎裂HP麻粒岩的年龄差异与早白垩世（阿尔比安）变质年龄明显不同。在Soltanabad以西60公里处进一步证实了这些岩石与同一俯冲带复合体无关的解释。蓝片岩记录了阿尔比世至晚白垩世弧后盆地的闭合，而麻粒岩则是由于更古老的海洋岩石圈的俯冲而形成的。马克兰地区Iranshahr地区角闪岩的铀- pb锆石测年结果显示，其截距年龄为87.8±1.8 Ma，加权平均年龄为88.1±1.7 Ma。来自同一地区的7个蓝片岩和角闪岩相样品的Rb-Sr矿物等时线显示出非常一致的年龄。84 Ma（±< 1-3 Ma），与变质等级无关。记录不同p - t条件的岩石具有相同的变质年龄这一明显的矛盾，要么表明在挖掘过程中，在俯冲系统的不同深度同时形成的岩石发生了构造混合，要么表明非常迅速的挖掘使得封闭温度的差异变得难以区分。新的数据与之相似，但更加精确，与先前报道的K-Ar年龄相比，表明大多数现有数据并未受到外来Ar污染的严重损害。钾- Ar指示更古老的蓝片岩和/或角闪岩相变质作用（bbb80 - 85 Ma）尚未得到证实，但可以与更大的地质框架相协调，这意味着在此之后不久，阿拉伯板块在巴干-德尔坎大陆块体下开始向北俯冲。120 Ma。
In this study we establish a time frame for metamorphic processes affecting Neotethyan suture zones at the northern (Sabzevar) and southern (Makran) margin of the Central Iranian Microcontinent. For this purpose, we have applied Rb–Sr and U–Pb geochronology to blueschist‐ and amphibolite facies rocks from these occurrences. So far, no isotopic ages are available for high‐P/low‐Trocks from the Sabzevar area which are exposed in the Govain and Chili mountains near Soltanabad. Three newly dated blueschists from the Govain mountain yielded Rb–Sr ages of 56.52 ± 0.32, 57.20 ± 0.32, and 55.12 ± 0.33 Ma respectively. These ages provide the first unambiguous evidence for late Palaeocene to early Eocene high‐Pmetamorphism in the Sabzevar zone and confirm the accuracy of earlier age assignments that were derived indirectly. The clearly confirmed age difference between late Palaeocene–early Eocene blueschists of the Govain mountain and kilometre‐scale dismembered HP granulites with Early Cretaceous (Albian) metamorphic ages from outcropsc. 60 km to the west of Soltanabad further corroborates interpretations that these rocks are not related to the same subduction zone complex. The blueschists record closure of an Albian to Late Cretaceous back‐arc basin, whereas the granulites formed due to subduction of older oceanic lithosphere. Uranium–Pb zircon dating of an amphibolite from the Iranshahr region in the Makran Zone yielded an intercept age of 87.8 ± 1.8 Ma and weighted mean age of 88.1 ± 1.7 Ma. Rb–Sr mineral isochrons for seven blueschist‐ and amphibolite facies samples from the same area generated very consistent ages ofc. 84 Ma (± <1–3 Ma), regardless of metamorphic grade. The apparent contradiction that rocks recording differentP–Tconditions have identical metamorphic ages either indicates tectonic mixing of rocks during exhumation that originally had formed at the same time at different depths of the subduction system, or very rapid exhumation so that differences in closure temperatures became indistinguishable. The new data are similar, but much more precise, than previously reported K–Ar ages and suggest that most of the existing data had not been significantly compromised by contamination with extraneous Ar. Potassium–Ar indications for older blueschist‐ and/or amphibolite facies metamorphism (>85 Ma) have not yet been confirmed but can be reconciled with the larger geological frame implying that northward subduction of the Arabian plate beneath the Bajgan–Durkan continental block started shortly afterc. 120 Ma.
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影响因子：
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