西北大学/大陆动力学国家重点实验室秦江锋团队近日揭示了秦岭造山带三叠纪闪长岩：大陆碰撞造山带中金成矿作用被低估。2025年7月10日，《地球化学学报》杂志发表了该成果。

秦岭造山带三叠纪花岗岩体及其伴生闪长岩是华北地块与扬子地块末期碰撞时红幔相互作用的重要证据。研究组从锆石U-Pb年龄、Lu-Hf同位素、角闪石-斜长石-磷灰石地球化学等方面对佛坪茅二梁闪长岩进行了研究。锆石U-Pb定年得到结晶年龄为212±2.8 Ma, εHf(t)值为8.6 ~ +3.0，对应的两阶段Hf模式年龄（T_DM2）为886 ~ 1479 Ma，表明其来源于演化的岩石圈地幔。

岩石成因指标显示出地幔亲和力：角闪石具有高MgO （9.8 ~ 11.2 wt%）和高Nb/Ta比值（14.3 ~ 18.1），而磷灰石具有富F（2.1 ~ 2.8 wt%）和贫Cl （0.08 ~ 0.15 wt%）的特征。基于角闪洞化学的热气压计算约束了805 ~ 866℃和211 ~ 383 MPa的结晶条件，对应于中晶位深度（8 ~ 14 km）。闪孔和锆石均显示氧逸度升高（ΔNNO=）4.08 - 3.71；ΔFMQ = - 1.14 ~ +3.96)和水合物岩浆条件（H₂O = - 4.22 ~ 4.94 wt%）。

晚期斜长石结晶（An21-26.5）反映了水合闪长质岩浆的长时间分馏结晶。这些诊断特征（幔源特征、高fO₂特征、水合物特征）与东秦岭金矿化花岗岩具有显著的收敛性。研究结果表明，三叠纪闪长岩岩浆作用在南秦岭成矿带的金富集过程中可能发挥了未被充分认识的作用。

附：英文原文

Title: Triassic diorites in the Qinling orogen: Underappreciated role for gold metallogeny in continental collision orogenic belt

Author: Zhang, Hua, Zhang, Kai, Zhu, Xi, Qin, Jiangfeng, Mao, Shaohua, Bi, Lisha

Issue&Volume: 2025-07-10

Abstract: The Triassic granitoids and associated diorites in the Qinling orogenic belt reveal critical evidence of crust–mantle interaction during the terminal collision between the North China and Yangtze Blocks. This study presents new constraints from zircon U–Pb age, Lu–Hf isotopes, and amphibole-plagioclase-apatite geochemistry for the Maoerliang diorite in the Foping area. Zircon U–Pb dating yields a crystallization age of 212±2.8 Ma, with εHf(t) values ranging from 8.6 to +3.0 and corresponding two-stage Hf model ages (TDM2) of 886–1479 Ma, indicative of derivation from an evolved lithospheric mantle source. Petrogenetic indicators reveal a mantle affinity: amphiboles exhibit high MgO (9.8–11.2 wt%) and elevated Nb/Ta ratios (14.3–18.1), while apatites display F-rich (2.1–2.8 wt%) and Cl-poor (0.08–0.15 wt%) characteristics. Thermobarometric calculations based on amphibole chemistry constrain crystallization conditions of 805–866 °C and 211–383 MPa, corresponding to mid-crustal emplacement depths (8–14 km). Both amphibole and zircon indicate elevated oxygen fugacity (ΔNNO=4.08 to 3.71; FMQ=1.14 to +3.96) and hydrous magma conditions (H2O=4.22–4.94 wt%). Late-stage plagioclase crystallization (An21–26.5) reflects prolonged fractional crystallization in a hydrous dioritic magma. These diagnostic features—mantle-derived signatures, high fO2, and hydrous nature—exhibit remarkable convergence with gold-mineralized granites in the East Qinling. Our findings suggest that Triassic dioritic magmatism may have played an underappreciated role in facilitating gold enrichment processes within the South Qinling metallogenic belt.

DOI: 10.1007/s11631-025-00786-7

Source: https://link.springer.com/article/10.1007/s11631-025-00786-7