Structural and geochronological evidence for Early Cretaceous orogen-parallel extension of the ductile lithosphere in the northern Dabie orogenic belt, East China
Structural and geochronological evidence for Early Cretaceous orogen-parallel extension of the ductile lithosphere in the northern Dabie orogenic belt, East China
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中国东部大别造山带北部早白垩世造山带韧性岩石圈平行伸展的构造和年代学证据
DOI：
10.1016/j.jsg.2010.09.002
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发表时间：
2011-03
影响因子：
3.1
通讯作者：
Jiang, Dazhi
中科院分区：
文献类型：
--
作者：
Xiang, Biwei;Wang, Yongsheng;Zhu, Guang;Jiang, Dazhi
北大别造山带的北大别穹隆（NDD），北为小天—磨子坛韧性剪切带（XMSZ），南为渭河—水州剪切带（WSSZ）。XMSZ和WSSZ的织物几何形状和运动学是相似的。它们均表现出由上至北西向或西北西向的剪切作用，显微结构相似，表明变形温度约为600 ~ 650°c。XMSZ糜棱岩中角闪石和黑云母的40ar - 39ar测年表明剪切带发育于142 Ma之前。U-Pb锆石LA-ICPMS定年表明，切割XMSZ的未变形花岗岩岩脉在130 Ma之前发生韧性剪切。WSSZ发育于早白垩世。NDD内部以早白垩世早期的混染岩片麻岩和变形岩体的北西向或北西向剪切为主。我们认为XMSZ、WSSZ和NDD内部参与了相同的早白垩世变形。XMSZ和WSSZ最初是一个连接的，更平坦的区域，我们称之为东大别滑脱带（EDDZ）。它在地壳深度超过18公里处形成。EDDZ运动学表明，早白垩世初期，大别造山带东部的韧性地壳和可能的部分岩石圈地幔经历了普遍的造山带平行伸展和东东向伸展。这种变形之后的大规模岩浆侵入以及由此产生的浮力增加导致了NDD的发掘和EDDZ的翘曲。今天观测到的侵蚀将EDDZ分成两个区域（XMSZ和WSSZ）。华北克拉通东部发育多处早白垩世变质岩心杂岩，多数表现为顶向北西或西北西的剪切作用。我们认为，这种广泛的均匀剪切感反映了中国东部韧性岩石圈的均匀流动方向，这种流动方向在华北克拉通东北部的辽南、夷五庐山和玉门山变质核杂岩中也有记载。
The WNW-trending North Dabie dome (NDD) in the northern Dabie orogenic belt is bounded by the Xiaotian-Mozitan ductile shear zone (XMSZ) in the north and the Wuhe-Shuihou shear zone (WSSZ) in the south. Fabric geometries and kinematics of both the XMSZ and the WSSZ are similar. They both show a top-to-NW or WNW sense of shear and display similar microstructures which indicate that the deformation temperature was about 600–650 °C.40Ar–39Ar dating of hornblende and biotite from the mylonites of the XMSZ suggests that the shear zone was developed prior to 142 Ma. U–Pb zircon LA-ICPMS dating of undeformed granite dikes that cut the XMSZ suggests that the ductile shearing occurred before 130 Ma. The WSSZ was also developed in the Early Cretaceous. The interior of the NDD is dominated by top-to-NW or WNW sense of shear in the migmatitic gneiss and deformed plutons of the earliest Early Cretaceous ages. We suggest that the XMSZ, the WSSZ, and the interior of the NDD were involved in the same Early Cretaceous deformation. The XMSZ and the WSSZ were originally a single connected, more flat-lying zone, which we call the East Dabie Detachment Zone (EDDZ). It developed at a crustal level of over 18 km in depth. Kinematics of the EDDZ suggest that the ductile crust and possibly part of the lithospheric mantle in the eastern Dabie orogen underwent pervasive orogen-parallel and ESE-ward extension at the beginning of the Early Cretaceous. Large-scale magmatic intrusions following this deformation and the resultant increase in buoyancy led to the exhumation of the NDD and the warping of the EDDZ. Erosion separated the EDDZ into two zones (the XMSZ and the WSSZ) as observed today. Many metamorphic core complexes of Early Cretaceous were developed in the eastern North China Craton, most showing top-to-NW or WNW sense of shear. We suggest that such a widespread uniform shear sense reflects a uniform flow direction of the ductile lithosphere in the East China that has also been documented in the Liaonan, Yiwulushan and Yumenshan metamorphic core complexes in the northeastern part of the North China Craton.
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影响因子：
3.4
作者：
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通讯作者：
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影响因子：
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