Evolution of the Mesozoic Granites in the Xiong'ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications

摘要：基于同位素的年龄和 geochemical 分析的新数据，中生代花岗石的三种类型在西方的河南省为 Xiong'ershan-Waifangshan 区域被识别了省：在早阶段(160 妈) 的 high-Ba-Sr 我类型花岗石 emplaced，在中间的阶段(130 妈) 的我类型花岗石和在迟了的阶段(115 妈) 的 anorogenic A 类型花岗石。high-Ba-Sr 我类型花岗石的 Geochemical 特征建议它可能被与闪石和石榴石的主要残余的部分融化从变厚的更低的外壳产生了。异例和 Sr 内容变化反映的否定 Eu 的渐渐的增加这些花岗石从的来源区域的进步 shallowing 对迟了的舞台早。早阶段的 Wuzhangshan 花岗石的新 40Ar/39 Ar 高原年龄(156.0 摮牵摥愠 ? 敬獡 ? 睴? 瑳条獥 ? 桔 ? 慥汲 ? 瑳条 ? 桳畯摬戠 ? 敲慬整 ? 潴琠敨椠瑮畲楳湯漠 ? 桴 ? 慭湩戠摯 ? 景琠敨圠湡硧慩汮湩 ? 牧湡瑩 ? 眠楨档眠獡攠灭慬散 ? 畤楲杮琠敨 ? 摮獯湩慩? 数楲摯眠瑩 ?? 楤条湥瑥捩愠摮洠湩牥污穩摥愠敧漠 ? 有 ? 0 ?????? ？？

Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong＇ershan-Waifangshan region in western Henan Province： high-Ba-Sr I-type granite emplaced in the early stage （-160 Ma）, I-type granite in the middle stage （-130 Ma） and anorogenic A-type granite in the late stage （-115 Ma）. Geochemical characteristics of the high-Ba-Sr I-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. Gradual increase of negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to late stage. New ^40Ar/^39Ar plateau ages of the early-stage Wuzhangshan granite （156.0±1.1 Ma, amphibole） and middle-stage Heyu granite （131.8±0.7 Ma, biotite） are indistinguishable from their SHRIMP U-Pb ages previous published, indicating a rapid uplift and erosion in this region. The representative anorogenic A- type granite, Taishanmiao pluton, was emplaced at -115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between -160 Ma and -115 Ma. The genesis of the early- and middle-stage I-type granites could be linked to delamination of subducted lithosphere of the Qinling orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic process. In fact, along the Qiniing -Dabie-Sulu belt, the Mesozoic granitoids in western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial ^87Sr/^86Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze cratous.