The Kinetics of Degassing-Induced Crystallization at Soufriere Hills Volcano, Montserrat

A series of decompression experiments at 875°C, with a 16h anneal period at 160 MPa, and depressurizations to a finalwater pressure (P_f) of 125–30 MPa, were run for between1 and 504 h. Using an experimentally derived plagioclase liquidus,the depressurizations are estimated to impose an undercooling(     

Degassing at the Soufriere Hills Volcano, Montserrat, Recorded in Matrix Glass Compositions

Compositions of matrix glasses from the current eruption ofSoufrière Hills Volcano indicate that decompression-drivencrystallization results in 20–70 wt % groundmass crystallizationduring eruption and variable degassing. Variations in crystallinityand volatile contents (water and chlorine) of matrix glassesare attributed to variations in extrusion rates and residencetimes in the lava dome. Residual water contents in pumice clasts(0·2–0·6 wt %) indicate minimum pressuresof 1·1–3·7 MPa in 1997 Vulcanian explosions.Residual water contents of 1·6 wt % in a ballistic blockejected in sub-Plinian explosive activity on 17 September 1996imply larger pressure drops (     

Crystal Size Distribution of Plagioclase and Amphibole from Soufriere Hills Volcano, Montserrat: Evidence for Dynamic Crystallization-Textural Coarsening Cycles

The crystal size distributions (CSDs) of plagioclase and amphibolewere determined from andesites of the Soufrière Hillsvolcano, Montserrat. Plagioclase occurs as separate crystalsand as chadocrysts in large amphibole oikocrysts. The chadocrystsrepresent an earlier stage of textural development, preservedby growth of the oikocryst. Seventeen rock and eight chadocrystplagioclase CSDs are considered together as a series of samplesof textural development. All are curved, concave up, and coincident,differing only in their maximum crystal size. Three amphiboleCSDs have a similar shape and behaviour, but at a differentposition from the plagioclase CSDs. A dynamic model is proposedfor the origin of textures in these rocks. Crystallization ofplagioclase started following emplacement of andesite magmaat a depth of at least 5 km. A steep, straight CSD developedby nucleation and growth. This process was interrupted by theinjection of mafic magma into the chamber, or convective overturnof hotter magma. The magma temperature rose until it was buffered,initially by plagioclase solution and later by crystallization.During this period textural coarsening (Ostwald ripening) ofplagioclase and amphibole occurred: small crystals dissolvedsimultaneously with the growth of large crystals. The CSD becameless steep and extended to larger crystal sizes. Early stagesof this process are preserved in coarsened amphibole oikocrysts.Repetitions of this cycle generated the observed family of CSDs.Textural coarsening followed the ‘Communicating Neighbours’model. Hence, each crystal has its own, unique growth–solutionhistory, without appealing to mixing of magmas that crystallizedin different environments. KEY WORDS: Ostwald ripening; textural coarsening; oikocryst; CSD; texture     

Geochemical Evolution of the Soufriere Hills Volcano, Montserrat, Lesser Antilles Volcanic Arc

The geochemical evolution of Montserrat provides an importantbackground to understanding the current activity of this islandarc volcano. Here we present major and trace element, and U-,Th- and O-isotope data for rocks generated in the last 300 kyrthat provide constraints on the magmatic processes occurringbeneath the volcano. Samples range from low- to medium-K calc-alkalinebasalts to dacites. Three suites can be distinguished on thebasis of major and trace element compositions: the South SoufrièreHills suite; the Soufrière Hills suite, including thelava from the current eruption; and the mafic inclusions. Magmaticdifferentiation of the magma that crystallized to form the maficinclusions appears to have been governed by closed-system processes,modelled by fractional crystallization (F     

Kinematic Modeling of Pyroclastic Flows Produced by Gravitational Dome Collapse at Soufriere Hills Volcano, Montserrat

Volcanic activity commenced 18 July 1995 at SoufriereHills volcano and has led to the creation of a newlava dome, which has repeatedly collapsed between 1996and 1999 resulting in highly mobile pyroclastic flows. The majority of associated pyroclastic flow phenomenaare consistent with initiation by gravitationalcollapse as blocks fall from oversteepened flanks ofthe new dome. If gravity controls the energy transferof such collapses, then areas likely to be affectedcan be predicted on the basis of topography. We focuson `dense' flows initiated by non-explosive,gravitational collapse (`Merapi-type' pyroclasticflows) and employ a graphical computer model (Flow3D)written to simulate this type of volcanic flow. Theprogram constructs a digital terrain model based upona 3D network of (x, y, z) triplets, which serves as thebasis for the numerical computations. A synthetic domewas added to the topographic model to improve theaccuracy of the simulations. After estimating thesmall number of key adjustable parameters, simulatedflow pathways, runout distances, and velocitiesclosely approximated observed Merapi-type pyroclasticflows on Montserrat. These simulations demonstrate thevalidity of a simple kinematic method to model densepyroclastic flow phenomena. While the simulationspresented here do not elucidate additional physics ofpyroclastic flow phenomena, this type of modeling canbe completed easily and without extensivea priori knowledge of volcano-specific parameters otherthan topography. Accordingly, it may serve as a rapidand inexpensive first-order approach for initialhazard assessment.     

Remobilization of Andesite Magma by Intrusion of Mafic Magma at the Soufriere Hills Volcano, Montserrat, West Indies

The 1995–1999 eruption of the Soufriere Hills volcano,Montserrat, has produced a crystal-rich andesite containingquench-textured mafic inclusions, which show evidence of havingbeen molten when incorporated into the host magma. Individualcrystals in the andesite record diverse histories. Amphibolephenocrysts vary from pristine and unaltered to strongly oxidizedand pseudomorphed by anhydrous reaction products. Plagioclasephenocrysts are commonly reverse zoned, often with dusty sievetextures. Reverse zoned rims are also common on orthopyroxenephenocrysts. Pyroxene geothermometry gives an average temperatureof 858 ± 20°C for orthopyroxene phenocryst cores,whereas reverse zoned rims record temperatures from about 880to 1050°C. The heterogeneity in mineral rim compositions,zoning patterns and textures is interpreted as reflecting non-uniformreheating and remobilization of the resident magma body by intrusionof hotter mafic magma. Convective remobilization results inmixing together of phenocrysts that have experienced differentthermal histories, depending on proximity to the intruding maficmagma. The low temperature and high crystallinity are interpretedas reflecting the presence of a cool, highly crystalline magmabody beneath the Soufriere Hills volcano. The petrological observations,in combination with data on seismicity, extrusion rate and SO₂fluxes, indicate that the current eruption was triggered byrecent influx of hot mafic magma. KEY WORDS: Montserrat; eruption; magma mixing; mafic inclusion; sieve texture     

Plagioclase zoning as an indicator of magma processes at Bezymianny Volcano,Kamchatka

Back-scattered electron (BSE)-derived zoning patterns of plagioclase phenocrysts are used to identify magma processes at Bezymianny Volcano, Kamchatka, based on the 2000–2007 sequence of eruptive products. The erupted magmas are two-pyroxene andesites, which last equilibrated at ~915°C temperature, 77–87 MPa pressure, and a water content of ~1.4 wt%. Textural and compositional zoning of individual plagioclase phenocrysts typically includes a repeated core-to-rim sequence of oscillatory zoning (An_50–60) truncated by a dissolution surface followed by an abrupt increase in An content (up to An₈₅), which then gradually decreases rimward. This zoning pattern is interpreted to be the result of frequent replenishments of the magma chamber which cause both thermal and chemical interaction between resident and recharge magmas. The outermost 70- to 150-μm-wide zoning patterns of plagioclase phenocrysts are composed of dissolution surface with a subsequent increase in An and Fe contents. Zoning patterns of the rims exhibit correlation among plagioclase phenocrysts within one eruption. Rims are interpreted as a result of crystallization of a batch of magma in the conduit after recharge event.     

Chlorine variations in the magma of Soufrière Hills Volcano, Montserrat: Insights from Cl in hornblende and melt inclusions

The Soufrière Hills Volcano in Montserrat erupts a Cl-rich, porphyritic andesite. HCl degassing accompanies eruption and is dependent on the growth rate of the lava dome. The magma contains hornblende phenocrysts that show repetitive zoning in most elements, including Cl. On the basis of the zoning data, (Cl/OH) ratios in the melt, calculated from partitioning data, increase rimward through each zone, indicating that the phenocrysts formed under conditions of varying (Cl/OH)_m. An empirical relationship between A-site occupancy in the hornblende and temperature implies that crystallisation of each zone is also accompanied by increasing temperature. Each zone ends at a resorption horizon, and crystallisation recommences at lower temperature and (Cl/OH)_m. Melt inclusion H₂O and Cl contents for the 8th January 2007 explosive eruption can be explained by closed-system degassing with D_Cl^fl-m between 5 and 30, or by open-system degassing accompanied by a small amount of crystallisation. However, neither simple closed-system degassing nor convective circulation of magma can explain the positive correlation of (Cl/OH)_m with temperature. We suggest that the zoning can be caused by accumulation of CO₂-rich vapour in the andesite, probably as a result of mafic magma injection into the chamber. Decreasing H₂O fugacity and/or increasing Cl_m result in increasing (Cl/OH)_m while heat transferred with the volatiles causes the rise in temperature. Intermittently, the accumulated fluid is lost to the surface, possibly as a result of renewed eruptive activity. This model requires the CO₂-rich fluid to be decoupled from the magma, consistent with previous observations of continuous CO₂ emissions at the surface.     

Magma Storage Region Processes Inferred from Geochemistry of Fe-Ti Oxides in Andesitic Magma, Soufriere Hills Volcano, Montserrat, W.I.

Analyses of Fe–Ti oxides help constrain models of magmastorage region processes for the Soufrière Hills Volcano,Montserrat (W.I.), and provide clear evidence of the natureof transient heating events in the magma storage region. Toconstrain timescales of magma heating and remobilization, theTiO₂ zoning patterns in a time series of natural titanomagnetiteswere compared with those produced in controlled phase equilibriumexperiments on the andesite. Most samples of andesite eruptedfrom 1995 to 2002 contain titanomagnetite crystals with uniformcore compositions (TiO₂     

Remobilization of Highly Crystalline Felsic Magma by Injection of Mafic Magma: Constraints from the Middle Sixth Century Eruption at Haruna Volcano, Honshu, Japan

The latest eruption of Haruna volcano at Futatsudake took placein the middle of the sixth century, starting with a Plinianfall, followed by pyroclastic flows, and ending with lava domeformation. Gray pumices found in the first Plinian phase (lowerfall) and the dome lavas are the products of mixing betweenfelsic (andesitic) magma having 50 vol. % phenocrysts and maficmagma. The mafic magma was aphyric in the initial phase, whereasit was relatively phyric during the final phase. The aphyricmagma is chemically equivalent to the melt part of the phyricmafic magma and probably resulted from the separation of phenocrystsat their storage depth of 15 km. The major part of the felsicmagma erupted as white pumice, without mixing and heating priorto the eruption, after the mixed magma (gray pumice) and heatedfelsic magma (white pumice) of the lower fall deposit. Althoughthe mafic magma was injected into the felsic magma reservoir(at 7 km depth), part of the product (lower fall ejecta) precedederuption of the felsic reservoir magma, as a consequence ofupward dragging by the convecting reservoir of felsic magma.The mafic magma injection made the nearly rigid felsic magmaerupt, letting low-viscosity mixed and heated magmas open theconduit and vent. Indeed the lower fall white pumices preservea record of syneruptive slow ascent of magma to 2 km depth,probably associated with conduit formation. KEY WORDS: high-crystallinity felsic magma; magma plumbing system; multistage magma mixing; upward dragging of injected magma; vent opening by low-viscosity magma     

Control on the emplacement of the andesite lava dome of the Soufriere Hills volcano, Montserrat by degassing-induced crystallization

Lava solidification is controlled by two mechanisms: external cooling and gas exsolution, the latter inducing crystallization due to increasing liquidus temperature. The andesite lava dome of the Soufriere Hills Volcano, Montserrat, is an extrusion dominated by crystallization caused by gas exsolution where cooling is unimportant in controlling emplacement. In the magma chamber the magma has an estimated viscosity of 7 × 10⁶ Pa s. During ascent, gas exsolution caused the magma to extrude in a highly crystalline state, with only 5–15% residual melt, viscosities in the range 10¹³–10¹⁴ Pa s and mechanical strength > 1 MPa. Deformation can be heterogeneous with extrusion along shear zones. Rheological stiffening in the upper conduit also causes large overpressures, shallow seismicity, and cyclic patterns of dome extrusion. Gas-rich porphyritic andesites tend to be the least mobile kind of lava, because transition from magma into hot crystalline material was reached during ascent.     

The Occurrence of Forsterite and Highly Oxidizing Conditions in Basaltic Lavas from Stromboli Volcano, Italy

We report the occurrence of unusual, high-magnesium (Fo₉₆) olivinephenocrysts in a basaltic lava and an ejected lithic block fromthe Upper Vancori period (13 ka) and the recent activity (2002–2003)of Stromboli volcano, Italy. The samples that contain this distinctivemineral chemistry are a shoshonitic basalt and a basaltic andesitewith anomalous bulk-rock chemical characteristics in which theiron is highly oxidized (6–8 wt % Fe₂O₃ and <1 wt %FeO). In other respects these samples are similar to the majorityof Stromboli basalts, characterized by the coexistence of olivine,clinopyroxene, plagioclase and Fe–Ti oxides as phenocrysts,and clinopyroxene, plagioclase and Fe–Ti oxides in thegroundmass. In the high-magnesium olivine samples, Fe–Tioxides (pseudobrookite) typically occur as symplectitic intergrowthswith the olivine phenocrysts, indicating simultaneous growthof the two phases. We propose, as a paragenetic model, thatthe Fo₉₆ olivine phenocrysts crystallized from a highly oxidizedbasaltic magma in which most of the iron was in the ferric state;hence, only magnesium was available to form olivine. The highlyoxidized state of the magma reflects sudden degassing of volatilephases associated with instantaneous, irreversible, transientdegassing of the magma chamber; this is postulated to occurduring periods of sudden decompression induced by fracturingof the volcanic edifice associated with paroxysmic activityand edifice collapse. KEY WORDS: Stromboli; Mg-rich olivine; oxygen fugacity; redox state of magmas; irreversible processes     

腾冲火山岩斜长石斑晶的过剩氩兼论火山活动的分期

在腾冲黑空山、打鹰山和马鞍山火山岩的斜长石斑晶里首次发现存在过剩氩,并从基质中得到比以往的全岩年龄更年轻的KAr年龄,论证了以往所发表这一时间段的KAr 年龄结果可能因过剩氩而偏老,结合马鞍山已经取得的10 ka左右的U系年龄结果认为,腾冲最近一期火山活动的终止时间应为全新世。     

Magma Ascent and Crustal Accretion at Ultraslow-Spreading Ridges: Constraints from Plagioclase Ultraphyric Basalts from the Arctic Mid-Ocean Ridge

Plagioclase ultraphyric basalts (PUBs) with up to 54% plagioclasephenocrysts were dredged in the rift valley and adjacent flanksof the ultraslow-spreading Mohns and Knipovich ridges. The PUBsshow large variations in crystal morphologies and zoning. Thelarge variations suggest that single basalt samples containa mixture of plagioclase crystals that aggregated at differentlevels in the magma conduits. Resorbed crystals and repeatedreverse zones suggest that the magma reservoirs were replenishedand heated several times. Thin concentric zones with melt inclusions,and sharp reductions in the anorthite content of 3–7%,are common between the reverse zones. These zones, and skeletalcrystals with distinctly lower anorthite contents than massivecrystals, are interpreted to be the result of rapid crystalliztionduring strong undercooling. The changes between short periodsof cooling and longer periods with reheating are explained bymultiple advances of crystal-rich magma into cool regions followedby longer periods of gradual magma inflow and temperature increase.The porphyritic basalts are characterizd by more depleted andmore fractionated compositions than the aphyric basalts, withlower (La/Sm)_N, K₂O and Mg-numbers. This relationship, and theobservation that PUBs are sampled only close to segment centresalong these ridges, suggests that the PUBs formed by higherdegrees of melting and evolved in more long-lived magma reservoirs.We propose that the zoning patterns of plagioclase crystalsand crystal morphologies of these PUBs reflect the developmentand flow of magma through a stacked sill complex-like conduitsystem, whereas the aphyric equivalents represent later flowof magma through the conduit. The formation of voluminous higher-degreemelts may trigger the development of the magma conduits andexplain the generally depleted compositions of PUB magmas. KEY WORDS: basalt; mineral chemistry; MORB; magma mixing; magma chamber; major element     

Origin of Low-K Intermediate Lavas at Nekoma Volcano, NE Honshu Arc, Japan: Geochemical Constraints for Lower-Crustal Melts

Extremely low-K basaltic andesite to andesite lavas at Nekomavolcano, situated in the frontal volcanic zone of the NE Honshuarc, were produced from melts that originated in the lower crust.Multiple incompatible trace element model calculations suggestthat extremely low-K basalt found in the same arc is a naturalanalog for the source composition. However, fractional crystallization,magma mixing, and crustal contamination models of primary low-Kbasalt cannot reproduce the Nekoma chemical composition. Derivationof melts from an extremely low-K amphibolitic lower-crustalrock with the residual mineral phases hornblende, olivine, pyroxenes,plagioclase, and magnetite is plausible. Major element compositionsof Nekoma lavas are very similar to those of experimental meltsof amphibolite dehydration melting, which further support theproposal. Light rare earth elements are slightly enriched, buttotal rare earth element abundances are relatively low, suggestinga high degree of partial melting of the source. Ba/Th ratiosare low for frontal arc lavas, reflecting modification of theratio during partial melting. Zr/Hf and Nb/Ta ratios are significantlygreater than is usual for arc lavas, suggesting an anomaloussource composition. Markedly low K, Rb, Cs contents in the extremelylow-K lavas are attributed to an extremely low-K source. Underplatingof an extremely low-K basalt originating from a hydrous depletedmantle wedge could form such an amphibolite. In contrast, Ndand Sr isotope ratios fall close to Bulk Earth values, indicatingan isotopically enriched source. Hornblende-bearing rocks maypredominate in the lower crust of the NE Honshu arc, based onthe observation of crustal xenoliths. The presence of largelow-V_p regions at lower-crustal depths beneath the frontal arcis suggested by geophysical observations. These observationsfurther support lower-crustal melting beneath Nekoma as theorigin of the intermediate low-K lavas. KEY WORDS: amphibolite source; crustal melting; low-K andesite; Sr–Nd isotopes; trace element     

Composition,Structure, and Conditions of Formation of Fluorine-Bearing Sodalite: Experimental Evidence

Fluoro-sodalite was synthesized for the first time at temperatures of 400–800°C and H₂O pressures of 1–2 kbar in the Si–Al–Na–H–O–F system. X-ray diffraction and infrared spectroscopic investigations showed that fluorine is incorporated in the sodalite structure as anionic octahedral groups, [AlF₆]^3–, the number of which can vary from 0 to 1. Correspondingly, the end-members of the F-sodalite series are Na₇(H₂O)₈[Si₅Al₇O₂₄] and Na₈(AlF₆)(H₂O)₄[Si₇Al₅O₂₄]. Depending on the composition of the system, F-sodalite associates at 500–650°C with nepheline, albite, cryolite, and villiaumite, which are joined by analcime below 500°C and aluminosilicate melt above 650°C. Fluorine-bearing sulfate–chlorine-sodalite was found for the first time in a pegmatite sample from the Lovozero massif. The highest fraction of the fluorine end-member in natural sodalite is 0.2. The incorporation of F into the sodalite structure requires much more energy compared with Cl^– and SO ₄ ^2- , because it is accompanied by a structural rearrangement and a transition from tetrahedral Al to octahedral Al.     

Experimental Study on Formation Conditions of Ammoniojarosite and Its Environmental Significance

Formation conditions of ammoniojarosite in system Fe2（SO4）3-（NH4）2SO4-H2O are investigated in this paper. The results show that ammoniojarosite can be formed rapidly under normal temperature and pressure by controlling suitable pH value and Fe2（SO4）3 and （NH4）2SO4 concentrations. The pH value, temperature and concentration of Fe2（SO4）3 medium are key factors influencing the formation of ammoniojarosite. Under normal temperature, precipitation of ammoniojarosite can be seen within 24 hours at pH values between 2.6-3.1, and a great quantity of ammoniojarosite is formed within 48 hours. At about 90℃, the pH value range forming ammoniojarosite extends to 1.2-3.1, and within this range the rise of pH value is advantageous to the formation of ammoniojarosite and high Fe2（SO4）3 concentration is also advantageous. Relative pure ammoniojarosite is synthesized under high Fe2（SO4）3 concentration （≥0.05 M） and ammoniojarosite containing melanterite and colloid amorphous hydroxide vitriol iron is formed at low Fe2（SO4）3 concentration. The deposition process of ammoniojarosite can be used to harness wastewater from mines and other industries and remove S, Fe and other toxic and harmful elements, such as As, Cr, Hg, Pb in water. Rapid formation of ammoniojarosite and other jarosite analogs under normal temperature and pressure has a good potential prospect for harnessing acid wastewater by means of precipitation of jarosite and its analogs.     

内蒙古东乌珠穆沁旗西山巴润特花组孢型化石及其时代

本文首次报道内蒙古东乌珠穆沁旗西山下泥盆统巴润特花组底部所发现的丰富的孢型石。共发现孢子１８属，３９种，其中新种２个；凝类４属５种，通过孢型化石的研究，确定巴润特花组为早泥盆世早期，相当西欧吉丁阶，并可与中国云南东部，四川龙门山，西秦岭和新疆西准噶尔同时期孢带比较。     

Dolomitization of the Devonian Swan Hills Formation, Rosevear Field, Alberta, Canada

The Swan Hills Formation (Middle-Upper Devonian) of the Western Canada Basin is host to several NW-SE-trending gas fields developed in massive replacement dolostone. One of these, the Rosevear Field, contains two major dolostone trends along opposing margins of a marine channel that penetrates into a platform-reef complex. Dolostones consist predominantly of branching and bulbous strdmatoporoid floatstones and rudstones with well-developed moldic and vuggy porosity. Replacement dolomite is coarsely crystalline (100-600 μm), inclusion-rich, composed of euhedral through anhedral crystals and has a blotchy to homogeneous red cathodoluminescence. Geochemically, replacement dolomite is characterized by (i) nearly stoichiometric composition (50.1-51.1 mol% CaCO₃), (ii) negative δ¹⁸O values (mean=-7.5‰, PDB) and (iii) variable ⁸⁷Sr/⁸⁶Sr ratios ranging from values similar to Late Devonian-Early Mississippian seawater (～0.7082) to radiogenic compositions comparable to saddle dolomite cements (>0.7100). Dolomitization began after widespread precipitation of early, equant calcite spar and after the onset of pressure solution, implying that replacement dolomite formed in a burial environment. Oxygen isotope data suggest that dolomite formed at 35-75°C, temperatures reached during burial in Late Devonian through Jurassic time, at minimum depths of 450 m. The linear NW-SE orientation of most dolomite fields in the Swan Hills Formation is suggestive of fault control on fluid circulation. Two models are proposed for fault-controlled circulation of dolomitizing fluids at the Rosevear Field. In the first, compaction-driven, updip fluid migration occurred in response to basin tilting commencing in the Late Palaeozoic. Deep basinal fluids migrating updip were focused into channel-margin sediments along fault conduits. The second model calls upon fault-controlled convective circulation of (i) warm Devonian-Mississippian seawater or (ii) Middle Devonian residual evaporitic brines. The overlap in ⁸⁷Sr/⁸⁶Sr and δ¹⁸O compositions, and similar cathodoluminescence properties between replacement and saddle dolomites provide evidence for neomorphism of some replacement dolomite. Quantitative modelling of Sr and O isotopes and Sr abundances suggests partial equilibration of some replacement dolomite with hot radiogenic brines derived during deep burial of the Swan Hills Formation in the Late Cretaceous-Palaeocene. Interaction of replacement dolomite with deep brines led to enrichment in ⁸⁷Sr while leaving δ¹⁸O similar to pre-neomorphism values.     

Calcic hydrosilicate metasomatic rocks at the Gumeshevsk skarn-porphyry copper deposit in the central Urals,Russia

The body of hydroxylellestadite metasomatic rock penetrated by a borehole drilled at the Gumeshevsk deposit at depths of 530–534 m includes a thin interval of younger lower temperature tobermorite-plombierite metasomatic rock with subordinate amounts of Ca-Si gel, tacherenite, cubic lime, and thaumasite. Hydroxylellestadite has never before been found in calc skarns. The hydroxylellestadite metasomatic rock is cut by gypsum and fukalite veinlets, and the tobermorite-plombierite metasomatic rock is intersected by thaumasite veinlets. The pristine rock of the metasomatics was marble, and the metasomatic rock replaced andradite-bearing wollastonite skarn (with wollastonite replaced by foshagite). The ore minerals (chalcopyrite, valleriite, sphalerite, and others) were formed after the hydroxylellestadite metasomatite but most probably before the tobermorite-plombierite metasomatic rock and the veinlets of calcic minerals. The metasomatic rock was produced at significant variations in the oxygen, sulfur, and carbon dioxide fugacities. The composition of the hydroxylellestadite is, according to its microprobe analysis, as follows (wt %): SiO₂ 17.10, TiO₂ 0.01, Al₂O₃ 0.02, FeO 0.20, MnO 0.00, MgO 0.04, CaO 55.40, Na₂O 0.14, K₂O 0.09, P₂O₅ 0.12, CO₂ 1.90 (chemical analysis), SO₃ 21.60, F 0.16, Cl 0.14, total 96.92. The plombierite (SiO₂ 43.8–44.1 wt %, CaO 30.5–31.1 wt %) in the metasomatic rock notably differs from rare plombierite (SiO₂ 48.18 wt %, CaO 39.19 wt %) contained in the veinlets of thaumasite (SiO₂ 12.70 wt %, CaO 30.69 wt %, SO₃ 17.78 wt %).