Xu Bo, Yin Run-Sheng, Chiaradia Massimo, Miao Zhuang, Griffin William L, Hou Zeng-Qian, Yang Zhi-Ming, O'Reilly Suzanne Y
State Key Laboratory of Geological Processes and Mineral Resources, Frontiers Science Center for Deep-time Digital Earth, China University of Geosciences, Beijing 100083, China.
The Beijing SHRIMP Center, Chinese Academy of Geological Sciences, Beijing 100037, China.
Sci Adv. 2024 Aug 23;10(34):eadp7383. doi: 10.1126/sciadv.adp7383. Epub 2024 Aug 21.
The sources of fluids and metals in porphyry systems of continental-collision settings are poorly constrained. Mercury isotopes display unique mass-independent fractionation (expressed as ΔHg) and may provide important constraints on metal and volatile sources given that Hg is a highly volatile metal. Here, we report Hg isotope data on ore-forming porphyries, barren magmatic rocks, and mantle-derived mafic magmas from southern Tibet. The fertile porphyries and coeval mafic magmas display mainly positive ΔHg values (up to +0.25 per mil), while ΔHg values in barren magmatic rocks and mafic magmas are largely negative (-0.54 to 0.00 per mil). The positive ΔHg values observed here are consistent with seawater and marine sediments, suggesting that the ultimate source of fluids involved in the genesis of post-subduction porphyry copper deposits was the mantle lithosphere metasomatized by previous oceanic plate subduction. Our Hg isotope data provide an alternative view to current metallogenetic models on collisional porphyry systems that focus on melting of the lower continental crust.
大陆碰撞环境斑岩系统中流体和金属的来源受到的限制较少。汞同位素显示出独特的质量无关分馏（以ΔHg表示），鉴于汞是一种高度挥发性金属，它可能为金属和挥发物来源提供重要限制。在此，我们报告了来自藏南的成矿斑岩、无矿岩浆岩和幔源镁铁质岩浆的汞同位素数据。富矿斑岩和同期镁铁质岩浆主要显示正的ΔHg值（高达千分之0.25），而无矿岩浆岩和镁铁质岩浆中的ΔHg值大多为负（千分之 -0.54至0.00）。这里观察到的正ΔHg值与海水和海洋沉积物一致，表明俯冲后斑岩铜矿床成因中涉及的流体的最终来源是先前大洋板块俯冲交代的地幔岩石圈。我们的汞同位素数据为当前聚焦于下地壳熔融的碰撞斑岩系统成矿模型提供了另一种观点。
