Zoisite-(Pb), a New Orthorhombic Epidote-Related Mineral from the Jakobsberg Mine, Värmland, Sweden, and Its Relationships with Hancockite

The new mineral zoisite-(Pb), ideally CaPbAl3(SiO4)(Si2O7)O(OH), was discovered in a sample from the Jakobsberg manganese-iron oxide deposit, Värmland, Sweden. Zoisite-(Pb) is found as pale pink subhedral prisms elongated on [010], up to 0.3 mm in size, associated with calcite, celsian, diopside, grossular, hancockite, hyalophane, native lead, phlogopite, and vesuvianite. Associated feldspars show one of the highest PbO contents (~7–8 wt%) found in nature. Electron-microprobe analysis of zoisite-(Pb) point to the empirical formula (Ca1.09Pb0.86Mn2+0.01Na0.01)∑1.97(Al2.88Fe3+0.10Mn3+0.04)∑3.02Si3.00O12(OH)1.00. The eight strongest diffraction lines [dobs, Iobs, (hkl)] are 8.63 s (101), 8.11 mw (200), 4.895 m (011), 4.210 m (211), 3.660 s (112, 311), 3.097 mw (312), 2.900 s (013), and 2.725 m (511). Zoisite-(Pb) is isostructural with zoisite and its crystal structure was refined up to R1 = 0.0213 for 2013 reflections with Fo > 4σ(Fo). Pb shows a stereochemically active lone pair leading to a lopsided distribution of its coordinating oxygens. A full chemical and Raman characterization of zoisite-(Pb) and of the Pb-bearing epidote hancockite is reported, together with an improved crystal structural model of hancockite, refined up to R1 = 0.0254 for 2041 reflections with Fo > 4σ(Fo). The effects of the incorporation of Pb in the crystal structure of zoisite-(Pb), hancockite, and related synthetic and natural phases are described and discussed.

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

The margarosanite group (now officially confirmed by IMA-CNMNC) consists of triclinic Ca-(Ba, Pb) cyclosilicates with three-membered [Si3O9]6– rings (3R), with the general formula AB2Si3O9, where A = Pb, Ba and Ca and B = Ca. A closest-packed arrangement of O atoms parallel to (101) hosts Si and B cations in interstitial sites in alternating layers. The 3R layer has three independent Si sites in each ring. Divalent cations occupy three independent sites: Ca in B occupies two nonequivalent sites, Ca1 (8-fold coordinated), and Ca2 (6-fold coordinated). A (=Ca3) is occupied by Pb2+ (or Ba2+) in 6+4 coordination, or 6+1 when occupied by Ca; this third site occurs within the 3R-layer in a peripheral position. Three minerals belong to this group: margarosanite (ideally PbCa2Si3O9), walstromite (BaCa2Si3O9) and breyite (CaCa2Si3O9). So far, no solid solutions involving the Ca1 and Ca2 sites have been described. Therefore, root names depend on the composition of the Ca3 site only. Isomorphic replacement at the Ca3 sites has been noted. We here report data on a skarn sample from the Jakobsberg Mn–Fe oxide deposit, in Värmland, Sweden, representing intermediate compositions on the walstromite–margarosanite binary, in the range ca. 50–70% mol.% BaCa2Si3O9. The Pb-rich walstromite is associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite. A crystal-structure refinement (R1 = 4.8%) confirmed the structure type, and showed that the Ca3 (Ba, Pb) site is split into two positions separated by 0.39 Å, with the Ba atoms found slightly more peripheral to the 3R-layers.

Removal of Metal Ions from Water Using Oxygen Plasmas

Zinc ion dissolved in water is attempted to be removed by generating the oxides of zinc using the oxygen gas in DBD plasma system. The removal rate of zinc oxides’ production (ZnO and Zn(OH2)) were measured at different treatment periods by the oxygen plasma penetration in water. The removal rate of the deposit increases initially and then decreases with the treatment period. The maximum removal rate (29%) of zinc from water is achieved at the treatment period of 10 min, where pH is minimum. From FTIR the generation properties of zinc oxide can be recognized. Initially the amount the deposit increases with the ozone treatment period due to production of both ZnO and Zn(OH)2. After that, the production of Zn(OH)42- increases even when the total removal rate of the deposit decreases. Therefore, to remove zinc ion from water forming metal oxide deposit, the penetration amount of the active oxygens to the water must be controlled to keep the pH lower than around 7.5. Because with increasing pH amount of removal rate of ZnO deposit decreases. The pH of the zinc dissolved water treated by ozone depends on both zinc and ozone concentration in water.

Nano-Micron Exsolved Spinels in Titanomagnetite and Their Implications for the Formation of the Panzhihua Fe–Ti–V Oxide Deposit, Southwest China

The nano-micron exsolved spinels with various mineralogical characteristics in titanomagnetite from Fe–Ti oxide gabbros in the Panzhihua Fe–Ti–V oxide deposit, SW China, have been studied by field emission scanning electron microscopy (FE-SEM) and electron probe microanalysis (EPMA) based on comparisons of physical and chemical conditions at different stratigraphic heights to investigate the compositional inheritance between titanomagnetite and exsolved spinel and further explore the relationship between the morphology and growth of exsolved spinels. Restored chemical data for titanomagnetite combined with evidence from petrography and whole-rock geochemistry imply fractional crystallization of the Panzhihua Fe–Ti–V oxide deposit, where the titanomagnetite of thick massive oxides at the bottom of the No. VIII orebody represents the early crystallizing phase characterized by high temperature and oxygen fugacity. The chemical variation in the exsolved spinel, which has the same trend as the restored composition of titanomagnetite, represents inheritance from the parent rock within the Panzhihua deposit. Exsolved spinel continuously adjusts morphology and grain size to decrease the total energy of the manganate-spinel system from fine-grained spinels parallel to the {100} plane of titanomagnetite to spinels with complex stellate morphology to bulky granular spinels with high degrees of idiomorphism. The unusual multiple magma replenishment during the mineralizing process and at different stratigraphic heights in the Panzhihua intrusion had an important influence on the thermal evolution history of the orebody, resulting in the identifiable spatial distribution patterns of spinel morphology and grain size. Using spinel exsolution as a discriminator for the provenance of magmatic ore deposits may provide intuitive and easy mineralogical evidence to qualitatively discuss the evolution of the metallogenetic environment and the ore-forming conditions for similar large mafic intrusions.