Chronological and geochemical variations of the late Mesozoic granitoids in the Taihang Mountains and middle-southern Tan-Lu Fault: Implications for lithosphere destruction of the North China Craton
Chronological and geochemical variations of the late Mesozoic granitoids in the Taihang Mountains and middle-southern Tan-Lu Fault: Implications for lithosphere destruction of the North China Craton
复制标题
太行山及郯庐断裂中南部晚中生代花岗岩年代学和地球化学变化对华北克拉通岩石圈破坏的意义
DOI：
10.2475/06.2021.04
复制
发表时间：
2021-06
影响因子：
2.9
通讯作者：
Anderson J. Lawford
中科院分区：
文献类型：
--
作者：
Kang Yue-Lan;Shi Yu-Ruo;Anderson J. Lawford
晚中生代，华北克拉通（NCC）经历了明显的岩石圈减薄和破坏，尤其是东部地区，但与这一过程相关的机制和时间仍然存在争议。太行山（TH）位于华北克拉通东部的西部，郯庐断裂带（TLF）位于东部，是揭示岩浆成因深部过程的两个重要岩浆区。我们研究了这两个地区火成岩的时空分布，以约束构造背景和岩浆来源。 TH北部房山岩体的SHRIMP锆石U-Pb年龄为136~128Ma。它们的εHf(t)值和δ18O值分别显示-27.7至-18.5和6.68至7.26 permil的范围。因此，我们得出结论，岩石是由底板岩浆和下地壳熔体混合形成的。还报告了来自塔吉克斯坦北部云蒙山杂岩的六个花岗岩样品的 O-Hf 同位素组成。结合前人研究，我们认为TH地区岩浆岩地球化学特征在中生代晚期变化不大，而TLF地区岩石地球化学特征变化较大。这两个区域之间的差异可能反映了古太平洋俯冲过程的不同影响。 TLF 地区的高 Mg# 埃达克质岩石 (HMA) 的 Mg# 值高于 TH 地区的 HMA 岩石。我们的结论是，TLF地区的HMA岩石主要是由拆沉的下地壳与地幔物质相互作用形成的，古太平洋俯冲对TH岩浆的影响有限。根据年代学和地球化学特征，我们认识到三个阶段：1）~166~140Ma，多向挤压导致华北克拉通地壳缩短、增厚，伴随着地壳区域部分熔融和镁铁质岩浆底侵；2）140~125Ma，TLF发生左旋走滑运动。随后断层周围的下地壳发生拆沉，华北克拉通演化成伸展构造环境，3）125 Ma后，华北克拉通可能由于拆沉后的应力松弛而发生大规模伸展。 TLF是地幔物质和流体输送的有利通道，说明大规模断裂带是华北克拉通岩石圈破坏的关键因素。
In the Late Mesozoic, the North China Craton (NCC) underwent significant lithospheric thinning and destruction, especially in the eastern part, but the mechanism and timing related to this process are still contentious. The Taihang Mountains (TH) are located in the western part of the eastern NCC and the Tan-Lu Fault (TLF) is in the eastern part, which are two essential magmatic areas that reveal deep processes of magma origin. We investigated the spatial-temporal distribution of igneous rocks from these two areas to constrain the tectonic setting and magmatic sources. SHRIMP zircon U-Pb ages of the granitoids within the Fangshan pluton in northern TH area range from 136 to 128 Ma. Their εHf(t) values and δ18O values show ranges of −27.7 to −18.5 and 6.68 to 7.26 permil, respectively. Hence, we conclude that the rocks were formed by mixing between underplating magma and the melts from the lower crust. The O-Hf isotopic compositions of six granitoid samples from the Yunmengshan complex in northern TH are also reported. In combination with previous studies, we propose that the geochemical characteristics of the magmatic rocks from the TH area had insignificant changes during late Mesozoic time, but the rocks from the TLF area varied greatly. The difference between those two areas may reflect the diverse impact of the Paleo-Pacific subduction process. The high Mg# adakitic rocks (HMA) from TLF area have higher Mg# values than the HMA rocks from TH area. Our conclusion is that the HMA rocks in the TLF area were mainly formed by delaminated lower crust interacting with mantle materials and that the Paleo-Pacific subduction had limited impact on TH magmas. Based on chronology and geochemical characteristics, we recognize three stages: 1) ∼166 to 140 Ma, multi-directional compression resulted in crustal shortening and thickening in the NCC, accompanied by regional partial melting of the crust and underplating of mafic magmas, 2) 140 to 125 Ma, the TLF underwent left-lateral strike-slip movement. Subsequent delamination of the lower crust around the fault and the NCC evolved into an extensional tectonic environment, 3) after 125 Ma, a large-scale extension of the NCC occurred likely due to stress relaxation after delamination. The TLF acted as a favorable channel for transporting mantle material and fluids, which implies that the large-scale fault zone was a key factor of the NCC lithosphere destruction.