The Yichun topaz-lepidolite granite is the latest and most evolved unit of the Yichun granitic complex, South China, and is well known by virtue of its unusual Ta-Nb-Li mineralization. A drill hole down to 300 m has intersected the granite from top to bottom, and revealed three petrographic zones: K-feldspar-rich facies in the lower part, albite-rich facies in the middle part, and Ab-and Kfs-rich facies in the upper part. Geochemically, the Yichun granite belongs to the phosphorus-rich type of rare-elementenriched granite. The phosphorus is concentrated in the feldspars, which contain up to 0.93 wt% P 2 O 5 . It is less enriched in feldspars in the middle part, where primary amblygonite is abundant. Principal accessory minerals include columbite-tantalite, cassiterite, zircon, and wodginite in all facies, and microlite in the middle facies. The composition of the columbite-group minerals corresponds to manganocolumbite and manganotantalite. Zircon contains mostly 4 to 8 wt% HfO 2 , but the HfO 2 contents may reach up to 22 wt% at the rim. From the lower part to the middle part of the drill hole, the progressive increases in Ta/(Nb + Ta) of columbite and Ta-rich cassiterite, and in Hf content of zircon, are strongly suggestive of magmatic differentiation. On the other hand, in the upper part of the drill hole, the decrease in Ta/(Nb + Ta) of columbite and cassiterite, in Hf content of zircon, and the increase in Fe of lepidolite, and especially marked enrichment in Fe and W in columbite (5.76% FeO, 7.28% WO 3 ) at the uppermost part of the drill hole, indicate another environment at the final stage of crystallization of the granite, influenced by fluid probably derived from the surrounding mica schist. SOMMAIRELe granite à topaze-lépidolite de Yichun, l'unité la plus tardive et la plus évoluée du complexe granitique de Yichun, du sud de la Chine, est bien connu à cause de son enrichissement inhabituel en Ta-Nb-Li. Un trou de forage de 300 m a intersecté ce granite pour révéler trois zones pétrographiques: faciès riche en feldspath potassique en profondeur, faciès albitique au milieu, et faciès enrichi dans les deux feldpaths vers le haut. En termes géochimiques, le granite de Yichun fait partie des granites enrichis en phosphore et en éléments rares. Le phosphore est concentré dans les feldspaths, qui contiennent jusqu'à 0.93% de P 2 O 5 (poids). La concentration diminue dans le faciès du milieu, qui contient beaucoup d'amblygonite primaire. Parmi les principaux minéraux accessoires se trouvent columbite-tantalite, cassitérite, zircon, et wodginite dans tous les faciès, et microlite dans le faciès du milieu. La composition des minéraux du groupe de la columbite atteint le champ de la manganocolumbite et de la manganotantalite. Le zircon contient en général entre 4 et 8% de HfO 2 (poids), mais peut en contenir jusqu'à 22% en bordure des grains. En passant de la partie inférieure au milieu de l'intervalle échantillonné par le trou de forage, nous documentons une augmentation progressive en Ta/(Nb + Ta) de la columbi...
The Xihuashan granitic complex (southern China) is mainly composed of coarse-grained porphyritic biotite granite (G-a), medium-grained porphyritic biotite granite (G-b), and medium-to fine-grained porphyritic biotite granite (G-c). The G-a granite is characterized by monazite-(Ce) and xenotime-(Y), in addition to commonly observed zircon and uranoan thorite. In the G-b and G-c intrusive units, monazite-(Ce) becomes very scarce, whereas Y-bearing minerals, including Y-bearing spessartine, xenotime-(Y), gadolinite-(Y), fergusonite-(Y), and yttrian fluorite (up to 15 wt% Y 2 O 3 ), are concentrated to various extents. Spessartine exhibits chemical zoning, which is displayed, in the core, by elevated contents of Y and heavy REE (HREE) (up to 2.32 wt% Y 2 O 3 and 1.51% HREE 2 O 3 ) and micrometric inclusions of Y-bearing minerals. Similarly, zircon from the G-b and Gc granites contains polymineralic micro-inclusions in the core. Overall, the accessory minerals point to a magmatic environment of crystallization for the G-a granite. In contrast, the crystallization of the G-b and G-c granites involved magmatic and hydrothermal stages. The late-to postmagmatic fluid is enriched in F and CO 2 , and appeared as a result of the final oversaturation of the granitic melt in a fluid phase.Keywords: yttrian fluorite, yttrium-bearing spessartine-almandine, xenotime-(Y), zircon, electron-microprobe data, granite, Xihuashan, China. in the endo-and exocontact zones of the Xihuashan granitic complex (Hsu 1943). Mining of quartz-ferberitetype ores started in 1935. The metallogeny of the deposits and the petrology of associated granites were described by Hsu
The Nanping No. 31 granitic pegmatite, a highly evolved spodumene-type pegmatite in the Nanping pegmatite district, southeastern China, can be divided into five internal zones from the border inward: zones I-III as the outer zones and zones IV-V as the inner zones. It is strongly mineralized with Nb-Ta-Sn oxide minerals. We investigated these minerals by using back-scattered electron (BSE) imaging and quantitative electron-microprobe analyses (EMPA) to characterize their complex internal textures. The primary Nb-Ta oxide minerals show a sequence from columbite-(Fe) (zone I) through tantalite-(Fe) (zone II) to tantalite-(Mn) (zone III), but distinctly become columbite + wodginite in zone IV and, rarely, columbite in the zone V. Microscopic tapiolite-(Fe) is identified as a product of exsolution in cassiterite from the zones II-III, whereas complex associations of wodginite, columbite-tantalite and tapiolite-(Fe) are characteristic of cassiterite in zone IV. The classic variation of the columbite-group minerals from the zones I to III seems to result from the greater stability of tantalite than columbite components during fractional crystallization of the melt. However, decreasing values of Ta/(Nb + Ta) in columbite-group minerals in the inner zones are more probably compensated by crystallization of abundant primary wodginite-group minerals, controlled by the f(O 2 ) of the magma. Columbite-group minerals commonly exhibit zoning, but complex and multiple-generation phenomena are notable in columbite-tantalite crystals from zones IV-V. In the latter case, later generations of columbite-tantalite overgrow or crosscut the earlier ones. Irregular patterns of zoning are linked to the activity of hydrothermal fluids at the late stages of pegmatite evolution. The high mobility of Ta in such fluids is supported by the development of veinlets of tantalite. They cross-cut first the earlier-formed columbite + wodginite aggregates, and later fill brittle-deformation-induced fissures in the columbite, forming a network texture. The complex internal textures of Nb-Ta-Sn oxide minerals from the zones IV-V indicate a distinctly fluid-rich environment at the late stage of crystallization of the Nanping No. 31 pegmatite.Keywords: Nb-Ta oxide minerals, cassiterite, columbite-tantalite, tapiolite-(Fe), wodginite, Ta-rich fluid, the Nanping No. 31 pegmatite, China.sOmmaiRe La pegmatite granititique dite Nanping No. 31, fortement évoluée et cristallisant le spodumène, affleure dans le district pegmatitique de Nanping, dans le sud-est de la Chine; nous distinguons cinq zones internes allant de la bordure vers le centre: les zones I-III sont externes, et les zones IV-V sont internes. La pegmatite est fortement minéralisée en oxydes de Nb-Ta-Sn. Nous avons étudié ces minéraux et leurs textures internes complexes au moyen d'images générées par les électrons rétrodiffusés et par analyses quantitatives effectuées avec une microsonde électronique. Les oxydes de Nb-Ta primaires définissent une séquence allant de columbite-(Fe) (zone I...
Two species of X-site-vacant tourmalines, foitite and rossmanite, occur in the Koktokay No. 3 granitic pegmatite dyke, Altai, northwestern China, a spodumene-subtype pegmatite. Foitite-schorl crystals develop as fillings in the interstices among Fe-rich dravite crystals in the endocontact zone between the pegmatite dyke and the metagabbro country-rock. The evolution of the tourmaline crystals in the endocontact zone occurred in two stages. The first stage is typified by the formation of Fe-rich dravite with variable compositions described by substitutions
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