Geochronology of the Paleoproterozoic Helanshan ductile shear zones: Insights into temporal framework of polyphase deformation in the Khondalite Belt, North China Craton

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Precambrian Research Pub Date : 2024-06-20 DOI:10.1016/j.precamres.2024.107481

Hengzhong Qiao , Guochun Zhao , Changqing Yin , Jiahui Qian , Shangjing Wu , Peipei Deng , Jiawei Li

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Abstract

The Khondalite Belt has been regarded as a Paleoproterozoic collisional orogen in the northwestern North China Craton, but the geochronological framework of polyphase deformation in the Khondalite Belt still remains unclear, particularly the timing of orogen-parallel ductile shearing. In this study, we conducted field-based structural analysis and LA-ICP-MS zircon U-Pb geochronology on the Helanshan ductile shear zones (HDSZ) in the Khondalite Belt. The results show that three pre-kinematic leucocratic dykes have been reworked by the shear zones and yielded magmatic zircon ages of 1934 ± 13 Ma, 1924 ± 5 Ma and 1920 ± 24 Ma. Two syn-kinematic leucocratic dykes appeared along the mylonitic foliations and were dated at 1887 ± 21 Ma and 1871 ± 28 Ma. A post-kinematic leucocratic dyke cut the mylonitic foliations and gave a crystallization age of 1816 ± 28 Ma. These emplacement ages of shear zone-related dykes constrain the development of the HDSZ at some time between ∼ 1920 Ma and ∼ 1816 Ma. Meanwhile, zircon overgrowth rims from three intrusions that suffered the shear deformation exhibited metamorphic ages of 1904 ± 11 Ma, 1840 ± 13 Ma and 1826 ± 31 Ma. Similar metamorphic ages of 1901 ± 7 Ma, 1888 ± 8 Ma and 1849 ± 29 Ma were also obtained from high-temperature felsic, pelitic and calcitic mylonites. These results further unravel that the HDSZ most likely developed at ca. 1904–1826 Ma. Additionally, we have summarized available deformation-related geochronological data in the Khondalite Belt, and proposed that this belt underwent three major phases of deformation (D₁-D₃) in the Orosirian. D₁ mainly produced overturned to recumbent isoclinal folds F₁, penetrative transposition foliations S₁ and mineral lineations L₁ at ca. 1.97–1.93 Ga. Subsequently, D₂ dominantly resulted in tight to open upright folds F₂ at ca. 1.93–1.90 Ga. Later, D₃ generated a series of NE- to E-trending orogen-parallel ductile shear zones at ca. 1.90–1.82 Ga. Together with multiple high-grade metamorphism and magmatism, the D₁-D₃ deformation recorded a complex protracted orogeny (>100 Myr) in response to the collision between the Yinshan and Ordos blocks.

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古新生代贺兰山韧性剪切带的地质年代学：洞察华北克拉通邝达岩带多相变形的时间框架

孔雀石带一直被认为是华北克拉通西北部的古新生代碰撞造山带，但孔雀石带多相变形的地质年代框架仍不清楚，尤其是造山带平行韧性剪切的时间。在本研究中，我们对崆峒山带贺兰山韧性剪切带（HDSZ）进行了野外构造分析和LA-ICP-MS锆石U-Pb地质年代研究。研究结果表明，三个前激变白云岩堤受到剪切带的再加工，其岩浆锆石年龄分别为 1934 ± 13 Ma、1924 ± 5 Ma 和 1920 ± 24 Ma。两个同步构造的白云岩岩堤出现在绵状构造的叶脉上，年代分别为 1887 ± 21 Ma 和 1871 ± 28 Ma。一个后成因白云岩岩堤切断了麦饭石褶皱，其结晶年代为 1816 ± 28 Ma。这些与剪切带相关的堤坝的形成年代推定，高分断裂带的发育时间介于1920 Ma ∼ 1816 Ma之间。与此同时，遭受剪切变形的三个侵入体的锆石生长边缘的变质年龄分别为 1904 ± 11 Ma、1840 ± 13 Ma 和 1826 ± 31 Ma。高温长英岩、辉绿岩和钙钛矿的变质年龄也类似，分别为 1901 ± 7 Ma、1888 ± 8 Ma 和 1849 ± 29 Ma。这些结果进一步揭示了HDSZ最有可能形成于约1904-1826Ma。1904-1826 Ma。此外，我们还总结了邝达里特岩带现有的与变形相关的地质年代数据，并提出该岩带在奥罗西期经历了三个主要的变形阶段（D1-D3）。D1主要产生了翻转至后退的等轴褶皱F1、穿透性换位褶皱S1和矿线纹L1，时间约为1.97-1.93 Ga。L1。随后，D2 在约 1.93-1.90 Ga 时主要形成了紧密到开放的直立褶皱 F2。F2。之后，D3 在约 1.90-1.82 Ga 时产生了一系列与造山带平行的东北至东向韧性剪切带。1.90-1.82Ga。D1-D3变形与多次高品位变质作用和岩浆作用一起，记录了阴山地块与鄂尔多斯地块碰撞后复杂而漫长的造山运动（100 Myr）。

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来源期刊

Precambrian Research 地学-地球科学综合

CiteScore

7.20

自引率

28.90%

发文量

325

审稿时长

12 months

期刊介绍： Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as: (1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology; (2) Geochronology and isotope and elemental geochemistry; (3) Precambrian mineral deposits; (4) Geophysical aspects of the early Earth and Precambrian terrains; (5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes. In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes. Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.