Age, petrologic significance and provenance analysis of the Hamedan low-pressure migmatites; Sanandaj-Sirjan Zone, west Iran
Age, petrologic significance and provenance analysis of the Hamedan low-pressure migmatites; Sanandaj-Sirjan Zone, west Iran
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Hamedan低压混合岩的年龄、岩石学意义和物源分析；
DOI：
10.1080/00206814.2018.1517392
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发表时间：
2018
影响因子：
2.6
通讯作者：
Moazzen Mohssen
中科院分区：
文献类型：
--
作者：
Sepahi Ali Asghar;Jafari Seyedeh Razieh;Osanai Yasuhito;Shahbazi Hossein;Moazzen Mohssen
Alvand深成杂岩(伊朗西部Sanandaj-Sirjan带(SaSZ))内部热晕内有变质泥质岩夹层的变质泥质岩发生了部分熔融，产生了各种类型的混合岩。哈马丹混合岩的中生体可分为两类：(1)富堇青石、贫铝硅酸盐的中生体；(2)贫堇青石的、富铝硅酸盐的中介体。白砂体也是多种多样的，从富含斜长石到富含钾长石的白砂体不等。矿物化学研究和温压估算表明，形成中间体的温度和压力分别为640-700℃和3-5kbar。混合岩中粒的214个颗粒的锆石U-Pb年代学研究表明，锆石变质边缘的年龄为160~180 Ma(约170 Ma)，继承碎屑锆石核的年龄为190~2590 Ma。遗传核心年龄显示出不同的年龄种群，但200-600 Ma的年龄种群更频繁。碎屑状锆石的年龄年龄表明，较年轻的锆石颗粒(200-500 Ma)更有可能来自伊朗板块，而较老的颗粒(600 Ma至2.5 Ma)可能既来自冈瓦那北部(如阿拉伯-努比亚盾)，也可能来自邻近的古老克拉通，如非洲。我们认为，岩浆活动，特别是~167 Ma的镁铁质深成作用是变质、部分熔融和混合岩化热源的主要触发因素。与SASZ西北部白垩纪区域变质事件的假设相反，这项研究证明变质作用应该更古老，并可能与侏罗纪岩浆脉冲有关。
Meta-pelitic rocks with interlayers of meta-psammites within the inner thermal aureole of the Alvand plutonic complex (Sanandaj-Sirjan Zone (SaSZ), western Iran) underwent partial melting; generating various types of migmatites. The mesosome of the Hamedan migmatites is classified into two groups: (1) cordierite-rich and Al-silicate-poor mesosomes and (2) cordierite-poor, Al-silicate-rich groups. Leucosomes are also variable, ranging from plagioclase-rich to K-feldspar-rich leucosomes. Mineral-chemical studies and thermobarometric estimations indicate temperature and pressure of 640–700°C and 3–5 kbar, respectively, for the formation of mesosomes. U–Pb zircon geochronology on 214 grains from the mesosome of migmatites indicates ages of 160–180 Ma (ca ~170 Ma) for zircon metamorphic rims and variable ages of 190–2590 Ma for the inherited detrital zircon cores. Inherited core ages show various age populations, but age populations at 200–600 Ma are more frequent. The age populations of the detrital zircons clarify that the provenance of the younger zircon grains (200–500 Ma) was more likely the Iranian plate, whereas the older grains (600 Ma to >2.5 Ga) may be sourced from both northern Gondwana (such as Arabian-Nubian Shield) and the neighbouring, old cratons like as Africa. We suggest that magmatic activities, especially mafic plutonism at ~167 Ma, are the main triggers for the heat source of metamorphism, partial melting, and migmatization. In contrast to a presumed idea for a Cretaceous regional metamorphic event in the NW parts of the SaSZ, this study attests that the metamorphism should be older and can be associated with Jurassic magmatic pulses.