Isotopic dating of the Khoy metamorphic complex (KMC), northwestern Iran: A significant revision of the formation age and magma source
Isotopic dating of the Khoy metamorphic complex (KMC), northwestern Iran: A significant revision of the formation age and magma source
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DOI：
10.1016/j.precamres.2010.12.004
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发表时间：
2011-03
影响因子：
3.8
通讯作者：
H. Azizi;Sun‐Lin Chung;Tsuyoshi Tanaka;Y. Asahara
中科院分区：
文献类型：
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作者：
H. Azizi;Sun‐Lin Chung;Tsuyoshi Tanaka;Y. Asahara
Khoy变质杂岩（KMC）由变质长岩、变质长岩和一些变质沉积岩组成，上覆渐近-中新世Qom组。由于缺乏可靠的地层序列或同位素定年资料，许多研究都提出了不一致的KMC形成年龄和构造背景。例如，各种各样的研究都提出了侏罗纪时代、白垩纪时代或更年轻的时代。基于U-Pb锆石和Rb-Sr矿物等时线测年的新同位素信息揭示了KMC变质作用的成因和时间。这些新的结果并不能证实之前提出的年龄。根据岩心65点U-Pb测年结果和变质岩、变质岩中锆石矿物年轮的测年结果，表明晚元古代（550 ~ 590ma）花岗岩和玄武岩岩浆的固结作用。Rb-Sr矿物等时线测年表明，变质作用发生在146Ma以前。糜棱岩片理覆盖变质花岗岩杂岩，可能发生于前渐新世。此外，143nd /144Nd和87sr /86Sr的初始比值强烈表明，原始基性岩浆形成于俯冲带的衰竭地幔中，并有一些再循环沉积物的污染。
The Khoy metamorphic complex (KMC) consists of metabasite, metagranite and some metasediments, which are overlain by the Oligo-Miocene Qom formation. Because there are no reliable stratigraphic sequences or isotope dating data available, discordant ages for the formation and tectonic setting of the KMC have been proposed by many studies. For example, various studies have suggested a Jurassic age, Cretaceous age or younger age. In the present study, new isotopic information based on U–Pb zircon and Rb–Sr mineral isochron dating has revealed the origin and timing of metamorphism for the KMC. These new results do not confirm the previously proposed ages. The results of U–Pb dating from 65 points in the core and rings of zircon minerals from the metagranite and metabasite rocks suggests a late Proterozoic (550–590Ma) consolidation of granitic and basaltic magma. In addition, Rb–Sr mineral isochron dating indicates that the metamorphism occurred 146Ma ago. Finally, mylonitic foliation overprinted the metamorphic and granitic complex, probably occurring in the pre-Oligocene. Furthermore, initial143Nd/144Nd and87Sr/86Sr ratios strongly suggest that the original basic magma formed in a depleted mantle in the subduction zone, with some contamination from recycled sediments.