碰撞背景岩浆-热液体系Mo富集机制及出溶过程：以冈底斯荣嘎钼矿为例

The collision-type porphyry Mo deposit is one kind of new porphyry Mo deposit porposed by Chinese scholars based on the study of porphyry Mo deposit in the Qinling–Dabie orogens and many innovative theories and understandings have been put forward. In comparison, the genetic mechanism of porphyry Mo deposit in the young orogens is still poorly studied. The Bangong–Nujiang metallogenic belt is a new discovery with obvious prospecting breakthrough in the last ten years, mainly including porphyry–skarn and porphyry–hypothermal types Cu–Au deposits. The Rongga deposit located at the south of Bangong–Nujiang suture zone, is the first porphyry Mo deposit discovered that has a perspective large scale in the Bangong–Nujiang metallogenic belt. This discovery of Rongga deposit has enriched the mineralization types and a series of metallogenic theory and model are challenged in the Bangong–Nujiang belt. This project, focused on the critical scientific topic of “the Mo enriched mechanism and exsolution process in collisional setting”, we plan to perform in situ analysis on trace elements or isotopic compositions of individual inclusions and sulfides from differerent ore stages. Finally, the magma formation conditions of ore-related magma have been constrained. Moreover, we elucidated the magmatic-hydrothermal evolving processes and Mo enriched mechanism, and revealed the key coupling conditions of porphhyry Mo deposit, together with comparison between porphyry Cu-Au and Mo mineralization, which could provide theoretical support for the metallogenic potential of porphyry Mo deposit and prospecting exploration deployment in the Bangong–Nujiang metallogenic belt.

碰撞型（collision-type）斑岩钼矿床是我国学者新划分的一种斑岩钼矿类型，基于秦岭-大别造山带斑岩钼矿的研究，提出了许多创新性理论和认识。相比较而言，年轻造山带斑岩钼矿成因机制的研究还比较薄弱。西藏班公湖-怒江成矿带为近十年来找矿突破明显的一个矿带，主要发育斑岩-浅成低温热液型和斑岩-矽卡岩型铜金矿床。荣嘎矿床位于班-怒缝合带南缘，为该带新发现的首例具大型远景的斑岩钼矿床。该矿床的发现丰富了班-怒带成矿作用类型，对已有的成矿认识、模型等造成了明显的挑战。本申请围绕“班公湖-怒江成矿带斑岩钼矿成因机制和成矿潜力”这一关键科学问题，拟通过包裹体、原位硫化物微量及同位素分析等，示踪荣嘎岩浆源区特征，阐明岩浆-热液演化过程和Mo富集机制，揭示班-怒成矿带斑岩型钼矿床形成的关键控制因素，并与该带铜成矿作用进行对比，为区域斑岩型钼成矿潜力分析及找矿部署提供理论支撑。

荣嘎矿床位于西藏阿里地区革吉县，是班公湖-怒江成矿带首例斑岩型钼矿床，研究意义重大。本项目系统查明了荣嘎斑岩钼矿床蚀变、矿化特征，脉体类型，划分出石英-硅酸盐、Mo-Fe硫化物、Fe-Cu-Mo硫化物和碳酸盐-表生作用4个阶段，识别出22种脉体类型；开展成岩、成矿年代学研究，厘定岩浆演化序列，鉴别出荣嘎矿区两期岩浆作用，分别为成矿前早白垩世晚期（~104Ma）岩浆作用，成矿期晚白垩世早期岩浆作用（~99Ma），获得辉钼矿年龄为99Ma，成矿与晚白垩世二长花岗斑岩密切相关；提出荣嘎钼矿床形成于碰撞造山背景，与拉萨和羌塘地体的碰撞有关，早期成矿流体具有中高温、中盐度、高氧逸度、富K、富Na、贫CO2、贫F等特征，而后逐渐向低温、低盐度流体演化；建立了荣嘎钼矿成因模式，综合分析认为深部岩浆房的形成可能与大洋板片俯冲时期的壳幔物质有关，而后岩浆经碰撞造山过程上侵成矿，形成具特殊地质特征的碰撞造山背景下的斑岩钼矿床。上述研究丰富了班-怒带成矿理论认识。