Continental collision and accretion recorded in the deep lithosphere of central China (2010)

西秦岭和松潘-甘孜构造域位于青藏高原东北角、扬子西北角和华北西南角这一关键的块体接合部位，然而对其构造归属性的模糊认识一直限制着我们对东亚大地构造演化的探索。在青海省多福屯地区，即松潘-甘孜带最北部的西秦岭地体中，出露一套玄武质火山岩。其中的部分岩浆锆石给出该玄武岩的喷发年龄是~14 Ma。更有意义的是，玄武岩中携带的来自深部地壳的捕虏晶锆石记录了未暴露的新太古代（2.7-2.5 Ga）基底物质的存在。这些捕虏晶锆石的U-Pb和Hf同位素数据，不仅揭示这一未暴露的基底经历2.7-2.4 Ga和1.1-0.8 Ga的新生幔源物质加入以及~1.8 Ga和1.4 Ga的古老地壳再造事件的复杂演化，而且记录了其显生宙（320-300 Ma、230 Ma、160 Ma）热事件的改造。基于这些数据，我们认为至少西秦岭造山带的西部作为一个微陆块，最初分离于华北块体，中-新元古代时接近扬子块体，并在显生宙（如早古生代）重新拼贴于华北的南部。随后，西秦岭地体才经历古生代和早中生代的扬子块体北向俯冲、碰撞，以及后期侏罗纪的岩石圈伸展事件。

The West Qinling and Songpan-Ganzi tectonic domains are located at the critical junction zone among the northeastern Tibetan Plateau, northwestern Yangtze Block, and southwestern North China Block. However, ambiguous understanding of their tectonic affinity has long restricted our exploration of the tectonic evolution of East Asia. A suite of basaltic volcanic rocks is exposed in the Duofutun area of Qinghai Province, which is the northernmost West Qinling terrane within the Songpan-Ganzi belt. Some magmatic zircons from these rocks yield an eruption age of ~14 Ma for the basalts. More importantly, xenocrystic zircons derived from the deep crust hosted in the basalts record the presence of unexposed Neoarchean (2.7–2.5 Ga) basement materials. The U-Pb and Hf isotopic data of these xenocrystic zircons not only reveal that this unexposed basement underwent complex evolutionary processes marked by the addition of juvenile mantle-derived materials during 2.7–2.4 Ga and 1.1–0.8 Ga, as well as ancient crustal reworking events at ~1.8 Ga and ~1.4 Ga, but also record its modification by Phanerozoic thermal events occurring at 320–300 Ma, 230 Ma and 160 Ma. Based on these data, we propose that at least the western segment of the West Qinling orogenic belt, as a microcontinent, initially rifted away from the North China Block, approached the Yangtze Block during the Meso-Neoproterozoic, and was re-amalgamated to the southern margin of the North China Block during the Phanerozoic (e.g., Early Paleozoic. Subsequently, the West Qinling terrane underwent northward subduction and collision of the Yangtze Block during the Paleozoic and Early Mesozoic, as well as late Jurassic lithospheric extension events.