Heberer Bianca, Anzenbacher Thomas, Neubauer Franz, Genser Johann, Dong Yunpeng, Dunkl István
Dept. Geography and Geology, University of Salzburg, Hellbrunnerstr. 34, A-5020 Salzburg, Austria.
State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Northern Taibai Str. 229, Xi'an 710069, China.
Tectonophysics. 2014 Mar 17;617:31-43. doi: 10.1016/j.tecto.2014.01.011.
The western sector of the Qinling-Dabie orogenic belt plays a key role in both Late Jurassic to Early Cretaceous "Yanshanian" intracontinental tectonics and Cenozoic lateral escape triggered by India-Asia collision. The Taibai granite in the northern Qinling Mountains is located at the westernmost tip of a Yanshanian granite belt. It consists of multiple intrusions, constrained by new Late Jurassic and Early Cretaceous U-Pb zircon ages (156 ± 3 Ma and 124 ± 1 Ma). Applying various geochronometers (Ar/Ar on hornblende, biotite and K-feldspar, apatite fission-track, apatite [U-Th-Sm]/He) along a vertical profile of the Taibai Mountain refines the cooling and exhumation history. The new age constraints record the prolonged pre-Cenozoic intracontinental deformation as well as the cooling history mostly related to India-Asia collision. We detected rapid cooling for the Taibai granite from ca. 800 to 100 °C during Early Cretaceous (ca. 123 to 100 Ma) followed by a period of slow cooling from ca. 100 Ma to ca. 25 Ma, and pulsed exhumation of the low-relief Cretaceous peneplain during Cenozoic times. We interpret the Early Cretaceous rapid cooling and exhumation as a result from activity along the southern sinistral lithospheric scale tear fault of the recently postulated intracontinental subduction of the Archean/Palaeoproterozoic North China Block beneath the Alashan Block. A Late Oligocene to Early Miocene cooling phase might be triggered either by the lateral motion during India-Asia collision and/or the Pacific subduction zone. Late Miocene intensified cooling is ascribed to uplift of the Tibetan Plateau.
秦岭 - 大别造山带西段在晚侏罗世至早白垩世的“燕山期”陆内构造以及印度 - 亚洲碰撞引发的新生代侧向逃逸过程中均起着关键作用。秦岭北部的太白山花岗岩位于燕山期花岗岩带的最西端。它由多个侵入体组成，受到新的晚侏罗世和早白垩世U - Pb锆石年龄（156 ± 3 Ma和124 ± 1 Ma）的限制。沿着太白山的垂直剖面应用各种地质年代计（角闪石、黑云母和钾长石的Ar/Ar法、磷灰石裂变径迹、磷灰石[U - Th - Sm]/He法），细化了冷却和剥露历史。新的年龄限制记录了前新生代长期的陆内变形以及主要与印度 - 亚洲碰撞相关的冷却历史。我们检测到太白山花岗岩在早白垩世（约123至100 Ma）期间从约800℃快速冷却至100℃，随后从约100 Ma至约25 Ma经历了一段缓慢冷却过程，并且在新生代时期低起伏白垩纪准平原发生了脉冲式剥露。我们将早白垩世的快速冷却和剥露解释为近期假定的太古宙/古元古代华北地块向阿拉善地块之下陆内俯冲的南部左旋岩石圈尺度撕裂断层活动的结果。渐新世晚期至中新世早期的冷却阶段可能是由印度 - 亚洲碰撞期间的侧向运动和/或太平洋俯冲带触发的。中新世晚期的强化冷却归因于青藏高原的隆升。
