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Scheelite from the Tongshankou porphyry-skarn Cu-Mo(-W) deposit occurs mainly as disseminated grains in the altered granodiorite porphyries at depth (Sch A), in the skarn coeval with retrograde alteration (Sch B) and in distal quartz veins crosscutting marbles (Sch C). Cathodoluminescence (CL) responses within a single Sch A grain reveal two subtypes: CL-clear Sch A-I and CL-turbid, densely veined Sch A-II. The CL contrast, coupled with geochemical data, suggest Sch A-I was metasomatized to form Sch A-II. CL images reveal that Sch A-I, Sch B and Sch C are all homogenous, with blue luminescence and are depleted in heavy rare earth elements (HREE), indicating a primary origin. However, Sch A-II is characterized by higher contents of light REE and heavy REE as well as higher Sr isotopes (0.7080–0.7100) than the primary scheelite (<0.7080). These differences indicate that Sch A-II formed through dissolution-reprecipitation. The Sr isotopes of the primary scheelite (0.7073–0.7078) are generally consistent with those of the mineralized granodiorite porphyries (0.7061–0.7063) and mafic enclaves (0.7058–0.7073). The granodiorite porphyries contain low tungsten contents (3–11 ppm), whereas high tungsten contents were detected in mafic enclaves (48–75 ppm). The coexistence of mafic enclaves and tungsten mineralization at depth, and their consistent Sr isotopes, indicates that the interaction of mafic enclaves and exsolved magmatic fluids from the granodiorite porphyries may have played an important role in the extraction of tungsten from the mafic enclaves and formation of scheelite mineralization. Our work shows that scheelite geochemistry can be used to trace the mineralizing conditions but the compositions may be significantly modified during the ore-forming process. Thus, detailed textural relationships should be investigated before using scheelite geochemistry to constrain the hydrothermal fluids and ore genesis.

The de-r-butylation of some r-butyl-derivatives has been carried out in the liquid phase using amorphous silica alumina and HY type zeolite. The deactivation coefficients obtained in liquid phase were about 10 to 100 times as large as those in the vapor phase de-r-butylation of r-butylbenzene. The activation energies for the reaction of the phenolic derivatives were nearly the same as that for the vapor phase de-r-butylation. However, the activation energies for the di-t-butyl derivatives were almost doubled. The activity of HY type zeolite was lower than that of the silica alumina, but the shape selectivity of the former was observed in the reaction of p-t-butyl-o-phenol.On a procCdC 1 la d6-r-butylation de quelques dCrivCs r-butyliques, en phase liquide, en employant une silice-alumine amorphe et une zBolithe du type HY. Les coefficients de dksactivation obtenus en phase liquide ont 6tC a peu pres 10 a 100 fois plus grands que ceux de la db-t-butylation, en phase gazeuse du r-butyl-benzene. Les energies d'activation pour la rkaction des dBrivCs phCnoliques ont Ct6 presque les m&mes que pour la dC-t-butylation en phase gazeuse; toutefois, les Bnergies d'activation pour les dBrivCs di-r-butyliques ont presque doublC. L'activit6 de la zColithe de type HY a 6t6 plus faible que celle de la silice-alumine amorphe, mais on a observ6 une sClectivitC de forme de la premiere dans la &action du p-r-butyl-ortho-phCnol.

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