富挥发分岩浆补给对斑岩型铜-钼矿床形成的关键作用: 以西藏尼木岗讲矿床为例

西藏冈底斯带中段的岗讲斑岩铜-钼矿床发育多期次侵入体，而成矿作用主要与其中一期岩体（流纹英安斑岩）密切相关。为探究其原因，本文对岗讲斑岩铜-钼矿床中发育的各期次侵入体进行了全岩主、微量元素分析，并重点研究各期次侵入体内部新鲜斑晶（黑云母、斜长石）和副矿物（锆石、磷灰石）的化学成分和结构特征。结果表明，矿区各期次侵入岩均属于高钾钙碱性系列，具有相近的锆石饱和温度，都来自较为氧化的岩浆。此外，相比其他期次侵入岩，主成矿期的流纹英安斑岩中的磷灰石具有较高的SO₃、Cl含量，较低的F含量；黑云母含有较高的Cl含量和较低的F含量；同时，斜长石发育反环带。这些证据表明，在主成矿期岩浆就位之前，存在富S、Cl的偏基性岩浆注入了深部岩浆房，并发生岩浆混合作用，这不仅导致了主成矿期斑岩体的就位，同时还诱发流体出溶进入浅部岩浆房，并最终形成岗讲斑岩铜-钼矿床。

The key role of volatile-rich magma replenishment in the formation of porphyry Cu-Mo deposits: A case study of Gangjiang porphyry Cu-Mo deposit, Tibet

The Gangjiang porphyry Cu-Mo deposit in the middle part of the Gangdese belt is composed of multiple phases of porphyry stocks, however, mineralization in them is closely related to the specific porphyry phase (rhyodacite porphyry, RDP). In order to understand this process, this study carried out a comprehensive study on the whole-rock major and trace element compositions of all intrusive rocks from the Gangjiang porphyry Cu-Mo deposit. In addition, the compositions and structures of the fresh minerals (zircon, apatite, biotite, plagioclase) in different intrusive rocks are specially focused on. All samples show high-K calc-alkaline series characteristics with similar zircon saturation temperatures, indicating that they are sourced from a moderate oxidized magma. Compared with other intrusive rocks, apatites in the syn-mineral RDP have higher SO₃ and Cl contents and lower F contents, while biotites have higher Cl contents and lower F contents. Meanwhile, the plagioclases develop a reverse ring zone. All these show that a pulse of S-Cl-rich magma was injected into the mid-crustal magma reservoir prior to the emplacement of the RDP, leading to a pulse of fluid exsolution and injection of RDP magma into the shallower magma chamber, which resulted in the formation of the Gangjiang porphyry Cu-Mo deposit finally.