The Saidengnan deposit, located in the Bangong-Nujiang suture zone, is proposed to be the first intra-oceanic island-arc porphyry Cu (Au) deposit in the Bangong-Nujiang metallogenic belt. The Cu (Au) mineralization is hosted in the quartz diorite porphyry as fine grained disseminated form. Zircon U-Pb ages of the ore-forming quartz diorite porphyry and the post-mineralization granodiorite are 118.1-118.8 Ma and 116.2 Ma, respectively, suggesting that mineralization occurred in the Early Cretaceous. The S isotopes (δ³⁴S = -3.8 to -1.5) of ore sulfides and H-O isotopes (δD = -99 ‰ to -89.9 ‰, δ¹⁸O_H2O = 4.9 ‰ to 9.4 ‰) of ore-bearing quartz veins indicate that the ore-forming fluids was sourced from the ore-forming intrusion. All intrusive rocks are enriched in light REE and LILE (Rb, K) and depleted in HFSE (Ni, Ta, Ti), similar with the island-arc magmas. Whole rock (⁸⁷Sr/⁸⁶Sr)_i values (0.7040 to 0.7056), εNd(t) values (-0.35 to 1.94), and significantly positive zircon ε_Hf(t) values (7.37 to 11.38) and young T_DM2 of zircon Hf (455 to 705 Ma) indicate that the Saidengnan intrusive rocks are dominantly derived from mantle wedge metasomatized by subducted fluids and sediments. This is different from the Duolong continental arc magmas formed by crust-mantle mixing. Combined with stratigraphic data published, we propose that the Saidengnan porphyry Cu (Au) deposit should be formed in the intra-oceanic island-arc setting caused by the oceanic-oceanic subduction of the Bangong-Nujiang Ocean.

赛登南矿床位于班公—怒江缝合带，被认为是班公—怒江成矿带第一个洋内岛弧斑岩铜（金）矿床。Cu (Au) 矿化以细粒浸染形式存在于石英闪长斑岩中。成矿石英闪长斑岩和成矿后花岗闪长岩的锆石U-Pb年龄分别为118.1-118.8 Ma和116.2 Ma，表明成矿发生在早白垩世。矿石硫化物的S同位素( δ ³⁴ S = -3.8 to -1.5)和H2O同位素( δ D = -99 ‰ to -89.9 ‰, δ ¹⁸ O _H2O= 4.9‰～9.4‰)的含矿石英脉表明成矿流体来源于成矿侵入体。所有侵入岩都富含轻稀土元素和 LILE（Rb、K），贫 HFSE（Ni、Ta、Ti），与岛弧岩浆相似。全岩 ( ⁸⁷ Sr/ ⁸⁶ Sr) _i值（0.7040 至 0.7056）、ε Nd(t) 值（-0.35 至 1.94）和显着正锆石ε _Hf (t) 值（7.37 至 11.38）和年轻的 T _DM2锆石Hf(455～705 Ma)的Hf(455～705 Ma)表明赛登南侵入岩主要来源于俯冲流体和沉积物交代的地幔楔。这与壳幔混合形成的多龙大陆弧岩浆不同。结合已发表的地层资料，我们认为赛登南斑岩铜(Au)矿床应形成于班公-怒江洋洋-洋俯冲形成的洋内岛弧环境中。