The late Paleoproterozoic A-type granitoids are important for constraining of the lithotectonic and geodynamic processed involved in the creation of continental crust. The newly identified late Paleoproterozoic felsic extrusive rocks from the southwestern margin of the North China Craton (NCC) consist of rhyolites which show melting corrosion structure, autoclastic texture and fiber structure of mineral grains and have weighted mean SIMS zircon UPb ages of 1794.7 ± 3.6 Ma to 1780.3 ± 5.6 Ma. The rhyolite samples show high SiO₂ (67.59–74.38 wt%) and K₂O + Na₂O (3.68–11.10 wt%), and low MgO (0.05–1.17 wt%), CaO (0.19–2.58 wt%) and P₂O₅ (0.08–0.16 wt%). They display aluminous A-type granite/rhyolite geochemical compositions, such as high A/CNK (0.78–1.23), FeO^T/(FeO^T + MgO) (0.81–0.99) and 10000Ga/Al (2.32–4.03) ratios, and high Zr + Nb + Ce + Y (824–1272 ppm) concentrations, as well as high zirconium saturation temperatures (T_Zr = 873–964 °C). These signatures, along with their low ε_Hf(t) (−3.6 to −1.5) and ε_Nd(t) values (−4.31 to −3.31) and old two-stage Hf model ages (T_DM^C = 2.70–2.57 Ga), indicate that the rhyolites were derived from partial melting of the Neoarchean felsic basement rocks. These volcanic rocks also have low zircon δ¹⁸O values ranging from 1.5‰ to 6.8‰, which were inherited from the Neoarchean ¹⁸O-depleted basement rocks that underwent high-T hydrothermal alteration, rather than resulted from contamination or later high-T water/rock interaction. The rhyolite rocks in this study, the earliest igneous rocks in the southwestern NCC after the Paleoproterozoic consolidation of the crystalline basement, were formed in a rift setting, marking the initial breakup of the Guyuan Rift in the southwestern NCC. The rhyolite rocks in combination with the Xiong'er volcanic rocks in the southern NCC mark the initial rifting of the NCC (Xiong'er Rift and Guyuan Rift) after cratonization (~1.85–1.8 Ga). The youngest retrograde metamorphism (1.80–1.79 Ga) in the NCC indicates that the transition from post-orogenic to intracontinental rift setting occurred at ca. 1.79 Ga.

晚古元古代A型花岗岩对限制大陆壳形成过程中的岩石构造和地球动力学过程很重要。新发现的来自华北克拉通西南缘的晚古元古代长英质挤压岩由流纹岩组成，流纹岩显示出熔融的腐蚀结构，矿粒的自碎质地和纤维结构，加权平均SIMS锆石的U Pb年龄为1794.7±3.6 Ma至1780.3±5.6 Ma。流纹岩样品显示出高SiO ₂（67.59–74.38 wt％）和K ₂ O + Na ₂ O（3.68–11.10 wt％），低MgO（0.05–1.17 wt％），CaO（0.19–2.58 wt％）和P ₂ O ₅（0.08–0.16 wt％）。它们显示出铝质A型花岗岩/流纹岩地球化学成分，例如高的A / CNK（0.78–1.23），FeO ^T /（FeO ^T  + MgO）（0.81–0.99）和10000Ga / Al（2.32–4.03）的比例，以及较高的Zr + Nb + Ce + Y（824–1272 ppm）浓度，以及较高的锆饱和温度（T _Zr  = 873–964°C）。这些签名，以及它们的低ε_的Hf（吨）（-3.6至-1.5）和ε_的Nd（吨）的值（-4.31至-3.31）和老两阶段Hf模式年龄（Ť _DM ^Ç = 2.70–2.57 Ga），表明流纹岩是由新初古时代的长英质基底岩石的部分融化产生的。这些火山岩也具有低的锆石δ ^18个O值范围从1.5‰至6.8‰，这是从太古代继承¹⁸富含O的地下岩石经历了高T水热变化，而不是由于污染或后来的高T水/岩石相互作用所致。在这项研究中，流纹岩岩石是在古元古代对晶体基底的古元古代固结之后西南NCC最早的火成岩，形成了裂谷环境，标志着西南NCC固原裂谷的初始破裂。NCC南部流纹岩与熊耳火山岩的结合标志着克拉通化（〜1.85-1.8 Ga）后，NCC（雄格裂谷和固原裂谷）的初始裂谷。NCC中最年轻的逆行变质作用（1.80–1.79 Ga）表明，造山带从造山后到陆内裂谷的转变发生在ca左右。1.79 Ga。