Experimental evidence for a protracted enrichment of tungsten in evolving granitic melts: implications for scheelite min
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ARTICLE
Experimental evidence for a protracted enrichment of tungsten in evolving granitic melts: implications for scheelite mineralization Meng Wang 1,2 & Jun Deng 1 & Tong Hou 1,2 & Insa T. Derrey 2 & Roman E. Botcharnikov 2,3 & Xi Liu 4 & Chao Zhang 2 & Dong-Mei Qi 2 & Zhaochong Zhang 1 & François Holtz 2 Received: 15 March 2019 / Accepted: 28 October 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract The solubility of scheelite in evolved granitic magmas (Qz-Ab-Or-An system with minor FeOtotal, TiO2, and CaO added) was studied experimentally at 200 MPa, 750–850 °C and relatively oxidizing condition (logfO2 = NNO + 2.3, where NNO is Ni-NiO oxygen buffer). Water-saturated granitic melts have been equilibrated with seeds of scheelite crystals. The resulted WO3 contents in the melts vary only slightly from 0.21 to 0.32 wt.% WO3 over the investigated temperature and compositional range (0.7 to 1.4 wt.% CaO) but tends to increase with increasing temperature and decreasing CaO concentration. One important message conveyed from the study is that WO3 concentrations at scheelite saturation are more dependent on temperature in evolved Capoor melts than in Ca-rich melts. Natural granitic rocks associated with scheelite mineralization and associated melt inclusions hosted in quartz have much lower W contents than the experimental melts equilibrated with scheelite. This implies that enrichment of tungsten (W) at magmatic stages is not sufficient to produce significant scheelite mineralization and confirms the important role of W mobilization by magmatic-hydrothermal fluids in the formation of scheelite deposits. Keywords Tungsten . Scheelite . Solubility . Experiment . Protracted enrichment . Mineralization
Introduction Tungsten deposits worldwide typically occur in close proximity to highly evolved granitic intrusions. Scheelite [CaWO4] mineralization typically occurs as veins or stockworks in peribatholitic systems and skarn deposits, which are usually interpreted to be formed by magmatic-hydrothermal processes (Manning and Henderson 1984; Newberry and Swanson 1986; Baker et al. 2005). However, whether the source of W Editorial handling: R. Linnen * Jun Deng [email protected] 1
State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Beijing 100083, China
2
Institut für Mineralogie, Leibniz Universität Hannover, Callinstr. 3, 30167 Hannover, Germany
3
Institut für Geowissenschaften, Gutenberg Universität Mainz, J.-J.-Becher Weg 21, 55128 Mainz, Germany
4
The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education of China, Beijing 100871, China
is provided directly via an magmatic fluid exsolved from evolved granitic magmas or leached from the granitic pluton and/or its host rocks during fluid-rock interaction processes is still debated (e.g., Wood and Samson 2000; Hulsbosch et al. 2016; Harlaux et al. 2018). Thus, determining if scheelite crystals or other W-enriched phases could crystallize during magmatic differentiation is
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