Titanite is associated with scheelite in altered biotite granite, clinopyroxene skarn, actinolite skarn, clinozoisite skarn, and quartz veins in the Jiepai W-Cu deposit, South China. Textural and geochemical characteristics indicate a hydrothermal origin for the titanite. There is compositional variability with respect to the rare earth element (REE) and high field strength element (HFSE) components in titanite from the different rock types. Interstitial titanite from the clinopyroxene (-garnet-vesuvianite) skarn displays low to moderate concentrations of REE (1212–1693 ppm), Nb (1337–1911 ppm), Ta (16–24 ppm), and W (26–42 ppm); low LREE/HREE (0.36–0.47) yet high Nb/Ta (47–85) ratios; along with weak negative Eu (0.71–0.90) and positive Ce (1.1–1.2) anomalies. By contrast, titanite from the actinolite and clinozoisite skarns shows generally higher concentrations of REE (2721–11,550 ppm), Nb (4350–24,228 ppm), Ta (1346–11,781 ppm), and W (32–337 ppm); highly variable LREE/HREE (0.14–0.70) but lower Nb/Ta (0.61–5.6) ratios; along with stronger yet variable negative Eu (0.02–0.14) and positive Ce (1.2–1.6) anomalies. Furthermore, the quartz vein-hosted titanite differs from those occurring in retrograde skarns in its significantly higher LREE/HREE ratios (0.78–6.3) and distinct Eu anomalies, which vary from negative to positive (0.15–1.2). Accordingly, the shift from relatively oxidizing to reducing conditions, as recorded by δEu and δCe in titanite, together with the different LREE/HREE and Nb/Ta ratios of the mineralizing fluids, as constrained by fluid composition and fractional precipitation, took place during emplacement of the hydrothermal W mineralization. In situ LA-ICP-MS U-Pb dating of hydrothermal titanite from the mineralized clinozoisite skarn, quartz vein, and actinolite skarn, respectively, yielded weighted mean 207Pb-corrected 206Pb/238U ages of 427 ± 5 Ma, 427 ± 4 Ma, and 426 ± 7 Ma (1σ), indicative of the dominant Silurian W skarn mineralization at Jiepai. Our new U-Pb data are consistent with published ages for igneous and ore-forming activities in other major W (-polymetallic) deposits in the Miao'ershan-Yuechengling pluton, highlighting the capability of Early Paleozoic granites to develop W (-polymetallic) deposits in South China. Additionally, hydrothermal titanite carrying considerable concentrations of Nb, Ta, and W along with variable Nb/Ta ratios holds potential for deciphering the fluid chemistry and sources for W-skarn deposits elsewhere.
{"title":"In situ LA-ICP-MS U-Pb geochronology and trace element analysis of hydrothermal titanite from the Jiepai W-Cu deposit, South China: Implications for W mineralization","authors":"Jia Li, Xiaofeng Li, Rong Xiao","doi":"10.3749/canmin.1900027","DOIUrl":"https://doi.org/10.3749/canmin.1900027","url":null,"abstract":"\u0000 Titanite is associated with scheelite in altered biotite granite, clinopyroxene skarn, actinolite skarn, clinozoisite skarn, and quartz veins in the Jiepai W-Cu deposit, South China. Textural and geochemical characteristics indicate a hydrothermal origin for the titanite. There is compositional variability with respect to the rare earth element (REE) and high field strength element (HFSE) components in titanite from the different rock types. Interstitial titanite from the clinopyroxene (-garnet-vesuvianite) skarn displays low to moderate concentrations of REE (1212–1693 ppm), Nb (1337–1911 ppm), Ta (16–24 ppm), and W (26–42 ppm); low LREE/HREE (0.36–0.47) yet high Nb/Ta (47–85) ratios; along with weak negative Eu (0.71–0.90) and positive Ce (1.1–1.2) anomalies. By contrast, titanite from the actinolite and clinozoisite skarns shows generally higher concentrations of REE (2721–11,550 ppm), Nb (4350–24,228 ppm), Ta (1346–11,781 ppm), and W (32–337 ppm); highly variable LREE/HREE (0.14–0.70) but lower Nb/Ta (0.61–5.6) ratios; along with stronger yet variable negative Eu (0.02–0.14) and positive Ce (1.2–1.6) anomalies. Furthermore, the quartz vein-hosted titanite differs from those occurring in retrograde skarns in its significantly higher LREE/HREE ratios (0.78–6.3) and distinct Eu anomalies, which vary from negative to positive (0.15–1.2). Accordingly, the shift from relatively oxidizing to reducing conditions, as recorded by δEu and δCe in titanite, together with the different LREE/HREE and Nb/Ta ratios of the mineralizing fluids, as constrained by fluid composition and fractional precipitation, took place during emplacement of the hydrothermal W mineralization. In situ LA-ICP-MS U-Pb dating of hydrothermal titanite from the mineralized clinozoisite skarn, quartz vein, and actinolite skarn, respectively, yielded weighted mean 207Pb-corrected 206Pb/238U ages of 427 ± 5 Ma, 427 ± 4 Ma, and 426 ± 7 Ma (1σ), indicative of the dominant Silurian W skarn mineralization at Jiepai. Our new U-Pb data are consistent with published ages for igneous and ore-forming activities in other major W (-polymetallic) deposits in the Miao'ershan-Yuechengling pluton, highlighting the capability of Early Paleozoic granites to develop W (-polymetallic) deposits in South China. Additionally, hydrothermal titanite carrying considerable concentrations of Nb, Ta, and W along with variable Nb/Ta ratios holds potential for deciphering the fluid chemistry and sources for W-skarn deposits elsewhere.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"58 1","pages":"45-69"},"PeriodicalIF":0.9,"publicationDate":"2020-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44473481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Coolbaugh, J. McCormack, M. Raudsepp, E. Czech, R. McMillan, A. Kampf
Andymcdonaldite is a new ferric-iron-tellurate mineral that occurs within Au-, Te-, and Bi-rich jasperoid at the Wildcat prospect in the Detroit district, Juab County, Utah. The mineral has a yellow-brown to brownish-black color, occurs as extremely cryptocrystalline (11–25 nm) material in thin films and breccia matrix fillings, and is associated with gold (native), tellurium (native), beyerite, clinobisvanite, and a variety of tellurium oxysalt minerals that include carlfriesite, eckhardite, frankhawthorneite, khinite, mcalpineite, paratellurite, tellurite, tlapallite, and xocolatlite. This is the first known natural occurrence of a phase with an ordered (tetragonal) inverse trirutile structure (A3+2B6+O6) which has many synthetic representatives. The B site in andymcdonaldite is occupied by Te and the A site is dominated by Fe with up to approximately 14 mole% substitution by other cations. An empirical formula of (Fe1.74Cu0.12Mn0.06Al0.05Mg0.05)Σ2.02Te1.01O6 was obtained from electron microprobe analyses. Powder X-ray diffraction data, Raman spectra, and unit-cell dimensions for andymcdonaldite strongly resemble those for the synthetic analogue, Fe3+2Te6+O6. The strongest X-ray diffraction lines are [dobsÅ(Iobs)(hkl)]: 4.14(27)(101), 3.28(100)(110), 2.54(71)(103), 1.71(72)(213), and 1.37(39)(303,116). The strongest Raman bands are at 748, 643, and 417 cm–1. The space group is P42/mnm and the cell dimensions are a 4.622–4.630 Å, c 9.077–9.087 Å, and V = 193.94–194.80 Å3 (Z = 2).
{"title":"Andymcdonaldite (Fe3+2Te6+O6), a new ferric iron tellurate with inverse trirutile structure from the Detroit district, Juab County, Utah","authors":"M. Coolbaugh, J. McCormack, M. Raudsepp, E. Czech, R. McMillan, A. Kampf","doi":"10.3749/canmin.1900060","DOIUrl":"https://doi.org/10.3749/canmin.1900060","url":null,"abstract":"\u0000 Andymcdonaldite is a new ferric-iron-tellurate mineral that occurs within Au-, Te-, and Bi-rich jasperoid at the Wildcat prospect in the Detroit district, Juab County, Utah. The mineral has a yellow-brown to brownish-black color, occurs as extremely cryptocrystalline (11–25 nm) material in thin films and breccia matrix fillings, and is associated with gold (native), tellurium (native), beyerite, clinobisvanite, and a variety of tellurium oxysalt minerals that include carlfriesite, eckhardite, frankhawthorneite, khinite, mcalpineite, paratellurite, tellurite, tlapallite, and xocolatlite. This is the first known natural occurrence of a phase with an ordered (tetragonal) inverse trirutile structure (A3+2B6+O6) which has many synthetic representatives. The B site in andymcdonaldite is occupied by Te and the A site is dominated by Fe with up to approximately 14 mole% substitution by other cations. An empirical formula of (Fe1.74Cu0.12Mn0.06Al0.05Mg0.05)Σ2.02Te1.01O6 was obtained from electron microprobe analyses.\u0000 Powder X-ray diffraction data, Raman spectra, and unit-cell dimensions for andymcdonaldite strongly resemble those for the synthetic analogue, Fe3+2Te6+O6. The strongest X-ray diffraction lines are [dobsÅ(Iobs)(hkl)]: 4.14(27)(101), 3.28(100)(110), 2.54(71)(103), 1.71(72)(213), and 1.37(39)(303,116). The strongest Raman bands are at 748, 643, and 417 cm–1. The space group is P42/mnm and the cell dimensions are a 4.622–4.630 Å, c 9.077–9.087 Å, and V = 193.94–194.80 Å3 (Z = 2).","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"58 1","pages":"85-97"},"PeriodicalIF":0.9,"publicationDate":"2020-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900060","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49245536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Offset dikes, radial and concentric fractures infilled with quartz diorite, are important hosts of Ni-Cu-PGE mineralization in the Sudbury area. To better understand their emplacement and evolution, the cathodoluminescence (CL) and trace-element chemistry of quartz were examined in quartz diorite from the Foy, Trill, Whistle, Hess, Parkin (North Range), and Copper Cliff (South Range) offsets. Although the potential causes of the CL response in quartz are considered, the primary focus was the qualitative textures and patterns, as these can provide valuable paragenetic information. Quartz from the North Range displays a strong blue luminescence dominated by homogenous and sharply zoned CL patterns, while that from the Copper Cliff offset displays a weak CL response. Locally recrystallized granoblastic quartz shows diffuse concentric zoning and other heterogeneous CL patterns. Trace-element EPMA-WDS analyses indicate that quartz from the Foy, Trill, and Whistle offsets is enriched in Al (30–600 ppm) and Ti (50–520 ppm) as compared to Fe (<25–490 ppm), while quartz from the Parkin and Hess offsets is enriched in Fe (270–700 ppm) as compared to Ti (44–211 ppm) and Al (95–250 ppm). In contrast to the North Range offsets, quartz from Copper Cliff has low Al concentrations (30–85 ppm) and very low Ti concentrations (<25 ppm). Application of the Ti-in-quartz geothermometer indicates that quartz from the North Range offsets crystallized above 600 °C, while that from the Copper Cliff offset crystallized below 600 °C. The CL responses and trace-element compositions of anhedral quartz from the North Range offsets are consistent with primary crystallization of quartz from magmatic quartz diorite, while those of the granoblastic quartz record dynamic recrystallization and Ostwald ripening. Copper Cliff quartz is anomalous in its CL response, trace-element content, and crystallization temperature, which may reflect overprinting during regional metamorphism of the South Range of the Sudbury Igneous Complex. Quartz CL is demonstrated to be an important tool for discerning and discriminating between paragenetic processes related to the formation of the offset dikes and has clear applications to the study of other quartz-bearing igneous rocks in the Sudbury area.
{"title":"Cathodoluminescence and trace-element chemistry of quartz from Sudbury offset dikes: Observations, interpretations, and genetic implications","authors":"E. Wehrle, A. McDonald","doi":"10.3749/canmin.1900049","DOIUrl":"https://doi.org/10.3749/canmin.1900049","url":null,"abstract":"\u0000 Offset dikes, radial and concentric fractures infilled with quartz diorite, are important hosts of Ni-Cu-PGE mineralization in the Sudbury area. To better understand their emplacement and evolution, the cathodoluminescence (CL) and trace-element chemistry of quartz were examined in quartz diorite from the Foy, Trill, Whistle, Hess, Parkin (North Range), and Copper Cliff (South Range) offsets. Although the potential causes of the CL response in quartz are considered, the primary focus was the qualitative textures and patterns, as these can provide valuable paragenetic information. Quartz from the North Range displays a strong blue luminescence dominated by homogenous and sharply zoned CL patterns, while that from the Copper Cliff offset displays a weak CL response. Locally recrystallized granoblastic quartz shows diffuse concentric zoning and other heterogeneous CL patterns. Trace-element EPMA-WDS analyses indicate that quartz from the Foy, Trill, and Whistle offsets is enriched in Al (30–600 ppm) and Ti (50–520 ppm) as compared to Fe (<25–490 ppm), while quartz from the Parkin and Hess offsets is enriched in Fe (270–700 ppm) as compared to Ti (44–211 ppm) and Al (95–250 ppm). In contrast to the North Range offsets, quartz from Copper Cliff has low Al concentrations (30–85 ppm) and very low Ti concentrations (<25 ppm). Application of the Ti-in-quartz geothermometer indicates that quartz from the North Range offsets crystallized above 600 °C, while that from the Copper Cliff offset crystallized below 600 °C. The CL responses and trace-element compositions of anhedral quartz from the North Range offsets are consistent with primary crystallization of quartz from magmatic quartz diorite, while those of the granoblastic quartz record dynamic recrystallization and Ostwald ripening. Copper Cliff quartz is anomalous in its CL response, trace-element content, and crystallization temperature, which may reflect overprinting during regional metamorphism of the South Range of the Sudbury Igneous Complex. Quartz CL is demonstrated to be an important tool for discerning and discriminating between paragenetic processes related to the formation of the offset dikes and has clear applications to the study of other quartz-bearing igneous rocks in the Sudbury area.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"947-963"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900049","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43027470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Practically all aspects of agate genesis generate debate. The time is ripe to clarify the most important enigmas concerning the environments of formation of agates and the related famous amethyst geodes of Brazil and Uruguay. Agates form over a wide range of temperatures, from those of basaltic and andesitic melts (about 1100 °C) down to about 50 °C, and at rather low pressures. Their formation in liquid mafic magmas is indicated by a correlation between (1) the orientation of amygdules and the inclination of onyx banding in them and (2) the attitude of amygdules in the lava flow layers. The correlation arises because lava moves at a different rate close to and far from the upper and lower rims of a flow. The alkaline supercritical fluid fills gas vesicles in lavas and dissolves silica, mainly, from ambient lava or rock to produce a silica sol. If the pressure on the fluid causes percolation of water from amygdules, the sol coagulates on the walls of the vesicle to form a concentric lining. If the pressure in amygdules falls below the maximum osmotic pressure of a sol (about 0.1 MPa for a silica sol), percolation of fluid stops, and coagulation leads to the formation of horizontal onyx banding. Multiple repetitions of precipitation of various gel layers can be caused by overlapping fresh flows upon the cooling older agate-bearing lava flow. In a submarine setting, phase separation of the fluid and the formation of a film of gel between vapor (or diluted solution) and brine stimulate the osmotic processes, which result in growth of hollow membrane tubes and branching moss-like arrays at the bottom of amygdules. Some agates exhibit numerous channels as a result of repeated extrusion of fluid or gel from inner zones to the periphery of amygdules that were compressed under the burden of new flows. Previously, such channels were interpreted to be feeding channels for silica supply in amygdules. Periodic compression of amygdules after percolation of fluid from them requires no additional supply of silica because the volume of the amygdules is reduced in proportion to the loss of fluid. The concentric and horizontal banding and mossy textures of agates from the lithophysae of felsic volcanic rocks were created during active volcanism as well. The agates from dissolution-induced cavities in carbonate rocks and the famous amethyst druses of Brazil and Uruguay formed at the moderate temperatures associated with low-grade burial metamorphism, as indicated by the lack of moss textures and onyx banding.
{"title":"The genesis of agates and amethyst geodes","authors":"I. N. Kigai","doi":"10.3749/canmin.1900028","DOIUrl":"https://doi.org/10.3749/canmin.1900028","url":null,"abstract":"\u0000 Practically all aspects of agate genesis generate debate. The time is ripe to clarify the most important enigmas concerning the environments of formation of agates and the related famous amethyst geodes of Brazil and Uruguay. Agates form over a wide range of temperatures, from those of basaltic and andesitic melts (about 1100 °C) down to about 50 °C, and at rather low pressures. Their formation in liquid mafic magmas is indicated by a correlation between (1) the orientation of amygdules and the inclination of onyx banding in them and (2) the attitude of amygdules in the lava flow layers. The correlation arises because lava moves at a different rate close to and far from the upper and lower rims of a flow. The alkaline supercritical fluid fills gas vesicles in lavas and dissolves silica, mainly, from ambient lava or rock to produce a silica sol. If the pressure on the fluid causes percolation of water from amygdules, the sol coagulates on the walls of the vesicle to form a concentric lining. If the pressure in amygdules falls below the maximum osmotic pressure of a sol (about 0.1 MPa for a silica sol), percolation of fluid stops, and coagulation leads to the formation of horizontal onyx banding. Multiple repetitions of precipitation of various gel layers can be caused by overlapping fresh flows upon the cooling older agate-bearing lava flow. In a submarine setting, phase separation of the fluid and the formation of a film of gel between vapor (or diluted solution) and brine stimulate the osmotic processes, which result in growth of hollow membrane tubes and branching moss-like arrays at the bottom of amygdules. Some agates exhibit numerous channels as a result of repeated extrusion of fluid or gel from inner zones to the periphery of amygdules that were compressed under the burden of new flows. Previously, such channels were interpreted to be feeding channels for silica supply in amygdules. Periodic compression of amygdules after percolation of fluid from them requires no additional supply of silica because the volume of the amygdules is reduced in proportion to the loss of fluid. The concentric and horizontal banding and mossy textures of agates from the lithophysae of felsic volcanic rocks were created during active volcanism as well. The agates from dissolution-induced cavities in carbonate rocks and the famous amethyst druses of Brazil and Uruguay formed at the moderate temperatures associated with low-grade burial metamorphism, as indicated by the lack of moss textures and onyx banding.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"867-883"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43613414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bin Wu, H. Wen, Christophe Bonnetti, Rucheng Wang, Jin-Hui Yang, Fu-Yuan Wu
The nepheline syenite pegmatite in the Saima alkaline complex in northeastern China is characterized by REE mineralization, mainly rinkite-(Ce) and associated alteration minerals. As the most abundant REE-bearing mineral in the pegmatite, rinkite-(Ce) closely coexists with microcline, nepheline, natrolite, and calcite. Some rinkite-(Ce) grains show compositional sector-zonation, in which the inner core displays relatively high Ti, Ca, and Sr concentrations, but low Zr, REE, and Na contents. Primary rinkite-(Ce) has undergone multiple episodes of fluid interactions, and accordingly, from weak to strong, three different mineral assemblages of hydrothermal alteration can be summarized: (1) rinkite-(Ce) + secondary natrolite ± K-feldspar ± minor fluorbritholite-(Ce); (2) rinkite-(Ce) relics + secondary natrolite + K-feldspar + fluorbritholite-(Ce) + unidentified Ca-Ti silicate mineral + fluorite and calcite; and (3) pseudomorphs after rinkite-(Ce). The pseudomorphs can be divided into two groups characterized by distinct mineral associations: (1) Ca-bearing strontianite + fluorbritholite-(Ce) + natrolite + fluorite + calcite coexisting with silicate minerals; and (2) calcite + fluorite + fluorbritholite-(Ce) + rinkite-(Ce) relics ± Ca-bearing strontianite ± ancylite-(Ce) associated with a calcite matrix. These alteration mineral assemblages are evidence of magmatic-derived alkali metasomatism due to an alkali-CO2-F-rich fluid and Ca-metasomatism due to a different, externally derived Sr- and Ca-rich fluid. The metasomatic events acted as the potential driving force for the rinkite-(Ce) dissolution and pseudomorph-forming process. The high concentration of rinkite-(Ce) in the nepheline syenite pegmatite results from the fractional crystallization of the Saima CO2-rich alkaline silicate magma, and the successive alterations of rinkite-(Ce) attest to the important role played by hydrothermal fluids in controlling the remobilization of REE and the crystallization of secondary rare earth minerals.
中国东北萨马碱性杂岩中的霞石正长伟晶岩以稀土矿化为特征，主要为滑石(Ce)及伴生蚀变矿物。滑石(Ce)是伟晶岩中含量最丰富的含稀土矿物，与微斜长石、霞石、钠辉石、方解石密切共生。部分冰铁矿(Ce)颗粒呈扇形分带状，其内核Ti、Ca、Sr含量较高，而Zr、REE、Na含量较低。原生冰毒岩-(Ce)经历了多次流体相互作用，因此，热液蚀变的矿物组合由弱到强可归纳为3种不同的矿物组合:(1)冰毒岩-(Ce) +次生钠辉石±钾长石±小萤石-(Ce);(2)滑石-(Ce)遗迹+次生钠硝石+钾长石+萤石-(Ce) +不明Ca-Ti硅酸盐矿物+萤石和方解石;(3)冰晶-(Ce)后的伪晶。伪晶可分为两组，矿物组合特征明显:(1)含钙硅石+萤石-(Ce) +钠硝石+萤石+方解石与硅酸盐矿物共存;(2)方解石+萤石+萤石-(Ce) +滑石-(Ce)遗迹±与方解石基质相关的含钙锶矿±ancyite -(Ce)。这些蚀变矿物组合是岩浆源性碱交代作用(由富碱- co2 - f流体引起)和钙交代作用(由另一种外部源性富锶和富钙流体引起)的证据。交代事件是滑冰石(Ce)溶蚀和伪晶形成过程的潜在驱动力。霞石正长辉晶岩中高含量的滑石矿-(Ce)是萨马富co2碱性硅酸盐岩浆分步结晶的结果，滑石矿-(Ce)的连续蚀变证明了热液流体在控制稀土再活化和次生稀土矿物结晶过程中的重要作用。
{"title":"Rinkite-(Ce) in the nepheline syenite pegmatite from the Saima alkaline complex, northeastern China: Its occurrence, alteration, and implications for REE mineralization","authors":"Bin Wu, H. Wen, Christophe Bonnetti, Rucheng Wang, Jin-Hui Yang, Fu-Yuan Wu","doi":"10.3749/canmin.1900042","DOIUrl":"https://doi.org/10.3749/canmin.1900042","url":null,"abstract":"The nepheline syenite pegmatite in the Saima alkaline complex in northeastern China is characterized by REE mineralization, mainly rinkite-(Ce) and associated alteration minerals. As the most abundant REE-bearing mineral in the pegmatite, rinkite-(Ce) closely coexists with microcline, nepheline, natrolite, and calcite. Some rinkite-(Ce) grains show compositional sector-zonation, in which the inner core displays relatively high Ti, Ca, and Sr concentrations, but low Zr, REE, and Na contents. Primary rinkite-(Ce) has undergone multiple episodes of fluid interactions, and accordingly, from weak to strong, three different mineral assemblages of hydrothermal alteration can be summarized: (1) rinkite-(Ce) + secondary natrolite ± K-feldspar ± minor fluorbritholite-(Ce); (2) rinkite-(Ce) relics + secondary natrolite + K-feldspar + fluorbritholite-(Ce) + unidentified Ca-Ti silicate mineral + fluorite and calcite; and (3) pseudomorphs after rinkite-(Ce). The pseudomorphs can be divided into two groups characterized by distinct mineral associations: (1) Ca-bearing strontianite + fluorbritholite-(Ce) + natrolite + fluorite + calcite coexisting with silicate minerals; and (2) calcite + fluorite + fluorbritholite-(Ce) + rinkite-(Ce) relics ± Ca-bearing strontianite ± ancylite-(Ce) associated with a calcite matrix. These alteration mineral assemblages are evidence of magmatic-derived alkali metasomatism due to an alkali-CO2-F-rich fluid and Ca-metasomatism due to a different, externally derived Sr- and Ca-rich fluid. The metasomatic events acted as the potential driving force for the rinkite-(Ce) dissolution and pseudomorph-forming process. The high concentration of rinkite-(Ce) in the nepheline syenite pegmatite results from the fractional crystallization of the Saima CO2-rich alkaline silicate magma, and the successive alterations of rinkite-(Ce) attest to the important role played by hydrothermal fluids in controlling the remobilization of REE and the crystallization of secondary rare earth minerals.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"903-924"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900042","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42572608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Alexandre, T. Heine, M. Fayek, E. Potter, R. Sharpe
The Chisel Lake deposit, in the Flin Flon – Snow Lake Mineral Belt in northern Manitoba, is characterized by an ore mineral assemblage dominated by pyrite and sphalerite, with minor chalcopyrite, galena, and pyrrhotite and trace amounts of other Cu-, Fe-, Sb-, Sn-, As-, Ni-, and Ag-bearing sulfides. Silver is hosted in a variety of Ag-bearing sulfides (chalcopyrite and freibergite–argentotennantite series) and its own sulfide (acanthite). The major elements chemical compositions of the ore sulfides define two populations of sphalerite (Fe-rich and Fe-poor), three populations of chalcopyrite (pure, Ag-rich, and Ag- and Sb-rich), and a typical galena, in addition to pyrite and pyrrhotite. Trace elements are dominated by Mn and Cd for sphalerite; Sn, Zn, and Ge for chalcopyrite; Se and Ni for pyrrhotite; and As and Co for pyrite. Formation temperature was best estimated, from the Fe and trace elements (Ga, Ge, Mn, and In) concentrations in sphalerite, at approximately 340 °C, with other methods giving less reliable temperature and pressure estimates.
{"title":"Ore mineralogy of the Chisel Lake Zn-Cu-Ag (+Au) VMS deposit in the Flin Flon – Snow Lake Domain, Manitoba, Canada","authors":"P. Alexandre, T. Heine, M. Fayek, E. Potter, R. Sharpe","doi":"10.3749/canmin.1900034","DOIUrl":"https://doi.org/10.3749/canmin.1900034","url":null,"abstract":"\u0000 The Chisel Lake deposit, in the Flin Flon – Snow Lake Mineral Belt in northern Manitoba, is characterized by an ore mineral assemblage dominated by pyrite and sphalerite, with minor chalcopyrite, galena, and pyrrhotite and trace amounts of other Cu-, Fe-, Sb-, Sn-, As-, Ni-, and Ag-bearing sulfides. Silver is hosted in a variety of Ag-bearing sulfides (chalcopyrite and freibergite–argentotennantite series) and its own sulfide (acanthite).\u0000 The major elements chemical compositions of the ore sulfides define two populations of sphalerite (Fe-rich and Fe-poor), three populations of chalcopyrite (pure, Ag-rich, and Ag- and Sb-rich), and a typical galena, in addition to pyrite and pyrrhotite. Trace elements are dominated by Mn and Cd for sphalerite; Sn, Zn, and Ge for chalcopyrite; Se and Ni for pyrrhotite; and As and Co for pyrite. Formation temperature was best estimated, from the Fe and trace elements (Ga, Ge, Mn, and In) concentrations in sphalerite, at approximately 340 °C, with other methods giving less reliable temperature and pressure estimates.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"925-945"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42619193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. C. Peterson, M. Metcalf, A. Kampf, Reynaldo R. Contreira Filho, J. Reid, B. Joy
Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl·2H2O, are very closely related chemically and structurally, but are found in very different environments. Cadwaladerite was found at the edge of a salar in Chile. Lesukite has been described from a volcanic fumarole and from burning coal seams. Both materials have cubic symmetry with a = 19.788 to 19.859Å. The crystal structure, common to both, consists of a rigid three-dimensional framework of edge- and corner-sharing Al(OH,H2O)6 octahedra that contains large interconnected cavities where loosely held Cl, OH, and H2O are located. The fact that Cl is loosely held within the structure is demonstrated by a dramatic reduction in Cl content after washing the material in distilled water, while the structural integrity is maintained. Herein, cadwaladerite is confirmed as a valid mineral species and lesukite is discredited because the only difference between the two materials is the loosely held extra-framework Cl, OH, and H2O. Cadwaladerite, Al2(H2O)(OH)4·n(Cl,OH,H2O) (Z = 48) takes precedence over lesukite based on the date of description. Material similar to cadwaladerite is found as a corrosion product on some types of nuclear fuel elements and is also closely related to the molecular species used in antiperspirant and water filtration.
{"title":"Cadwaladerite, Al2(H2O)(OH)4·n(Cl,OH–,H2O), from Cerros Pintados, Chile, defined as a valid mineral species and the discreditation of lesukite","authors":"R. C. Peterson, M. Metcalf, A. Kampf, Reynaldo R. Contreira Filho, J. Reid, B. Joy","doi":"10.3749/canmin.1900040","DOIUrl":"https://doi.org/10.3749/canmin.1900040","url":null,"abstract":"\u0000 Cadwaladerite, described in 1941 as Al(OH)2Cl·4H2O, and lesukite, described in 1997 as Al2(OH)5Cl·2H2O, are very closely related chemically and structurally, but are found in very different environments. Cadwaladerite was found at the edge of a salar in Chile. Lesukite has been described from a volcanic fumarole and from burning coal seams. Both materials have cubic symmetry with a = 19.788 to 19.859Å. The crystal structure, common to both, consists of a rigid three-dimensional framework of edge- and corner-sharing Al(OH,H2O)6 octahedra that contains large interconnected cavities where loosely held Cl, OH, and H2O are located. The fact that Cl is loosely held within the structure is demonstrated by a dramatic reduction in Cl content after washing the material in distilled water, while the structural integrity is maintained. Herein, cadwaladerite is confirmed as a valid mineral species and lesukite is discredited because the only difference between the two materials is the loosely held extra-framework Cl, OH, and H2O. Cadwaladerite, Al2(H2O)(OH)4·n(Cl,OH,H2O) (Z = 48) takes precedence over lesukite based on the date of description. Material similar to cadwaladerite is found as a corrosion product on some types of nuclear fuel elements and is also closely related to the molecular species used in antiperspirant and water filtration.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"827-841"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900040","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47956804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The local structure of Ta(V) in high-temperature fluoride- and chloride-bearing acidic solutions was investigated using in situ X-ray absorption spectroscopy (XAS). All XAS spectra were collected from two solutions, designated A and B, at beamline ID-20-C at the Advanced Photon Source, Argonne National Laboratory. Spectra were collected from solution A at 350 and 400 °C and from solution B at 25, 360, and 400 °C after the solutions were sealed in a hydrothermal diamond anvil cell. Solution A was prepared by dissolving Ta2O5 powder in 5% HF solution; solution B consisted of TaCl5 dissolved in 2% HF. The dominant tantalum species in solution A at elevated temperatures was TaF83–. In contrast, TaCl6–, which was the dominant complex in solution B at room temperature, disappeared as hydroxide complexes with an average ligand number between 5 and 7 became the dominant species at 350 and 400 °C. The XAS results confirm the previously recognized effect of fluoride activity on Ta speciation in hydrothermal fluids and suggest that both fluoride and hydroxide complexes play an important role in the transport of Ta in acidic fluoride-bearing solutions involved in the formation of mineralized mica-rich replacement units in granitic pegmatites.
{"title":"The local structure of Ta(v) aqua ions in high temperature fluoride- and chloride-bearing solutions: Implications for Ta transport in granite-related postmagmatic fluids","authors":"A. J. Anderson, R. Mayanovic, Thomas Lee","doi":"10.3749/canmin.1900022","DOIUrl":"https://doi.org/10.3749/canmin.1900022","url":null,"abstract":"\u0000 The local structure of Ta(V) in high-temperature fluoride- and chloride-bearing acidic solutions was investigated using in situ X-ray absorption spectroscopy (XAS). All XAS spectra were collected from two solutions, designated A and B, at beamline ID-20-C at the Advanced Photon Source, Argonne National Laboratory. Spectra were collected from solution A at 350 and 400 °C and from solution B at 25, 360, and 400 °C after the solutions were sealed in a hydrothermal diamond anvil cell. Solution A was prepared by dissolving Ta2O5 powder in 5% HF solution; solution B consisted of TaCl5 dissolved in 2% HF. The dominant tantalum species in solution A at elevated temperatures was TaF83–. In contrast, TaCl6–, which was the dominant complex in solution B at room temperature, disappeared as hydroxide complexes with an average ligand number between 5 and 7 became the dominant species at 350 and 400 °C. The XAS results confirm the previously recognized effect of fluoride activity on Ta speciation in hydrothermal fluids and suggest that both fluoride and hydroxide complexes play an important role in the transport of Ta in acidic fluoride-bearing solutions involved in the formation of mineralized mica-rich replacement units in granitic pegmatites.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"843-851"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48714279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Pekov, N. V. Shchipalkina, N. Zubkova, V. Gurzhiy, A. Agakhanov, D. I. Belakovskiy, N. Chukanov, I. Lykova, M. Vigasina, N. Koshlyakova, E. Sidorov, G. Giester
A new mineral, metathénardite, ideally Na2SO4, the high-temperature hexagonal dimorph of thénardite, a natural analogue of the synthetic phase Na2SO4(I), was found in the sublimates of active fumaroles at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The holotype originates from the Glavnaya Tenoritovaya fumarole in which metathénardite is associated with hematite, tenorite, fluorophlogopite, sanidine, anhydrite, krasheninnikovite, vanthoffite, glauberite, johillerite, and lammerite. The cotypes 1 and 2 are from the Arsenarnaya (with hematite, tenorite, fluorophlogopite, sanidine, euchlorine, wulffite, anhydrite, fluoborite, johillerite, nickenichite, calciojohillerite, badalovite, tilasite, cassiterite, and pseudobrookite) and the Yadovitaya (with tenorite, euchlorine, fedotovite, dolerophanite, langbeinite, krasheninnikovite, anhydrite, and hematite) fumaroles, respectively. All specimens with metathénardite were collected from areas with temperatures of 350–400 °C. Metathénardite forms hexagonal tabular, lamellar, or dipyramidal crystals (forms: {001}, {100}, {102}, and {201}) up to 3 mm combined in crusts up to several hundred cm2 in area. The mineral is transparent to semitransparent, colorless, white, light-blue, greenish, yellowish, grayish or brownish, with vitreous luster. Dmeas. = 2.72(1), Dcalc. = 2.717 g/cm3. Metathénardite is optically uniaxial (–), ω = 1.489(2), ε = 1.486(2). The empirical formulae are (Na1.92K0.05Ca0.02Zn0.01)[S0.99O4] (holotype), (Na1.54K0.22Ca0.09Cu0.01Mg0.01)[S1.00O4] (cotype 1), and Na1.65K0.11Ca0.05Cu0.04Mg0.01)[S1.01O4] (cotype 2). Admixed K and bivalent cations probably stabilize the hexagonal aphthitalite-like structure of metathénardite at room temperature. The crystal structure was solved using single crystals of all three samples, R1 = 0.0852, 0.0452, and 0.0449 for holotype and cotypes 1 and 2, respectively. The space group is P63/mmc, and the unit-cell parameters of the holotype are a = 5.3467(9), c = 7.0876(16) Å, V = 157.47(6) Å3, and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.667(27)(100), 3.904(89)(101), 3.565(33)(002), 2.824(94)(102), 2.686(100)(110), and 1.939(35)(202). Metathénardite and thénardite clearly differ from one another in X-ray diffraction data and infrared and Raman spectra.
{"title":"Alkali sulfates with aphthitalite-like structures from fumaroles of the Tolbachik Volcano, Kamchatka, Russia. I. MetathÉnardite, a natural high-temperature modification of Na2SO4","authors":"I. Pekov, N. V. Shchipalkina, N. Zubkova, V. Gurzhiy, A. Agakhanov, D. I. Belakovskiy, N. Chukanov, I. Lykova, M. Vigasina, N. Koshlyakova, E. Sidorov, G. Giester","doi":"10.3749/canmin.1900050","DOIUrl":"https://doi.org/10.3749/canmin.1900050","url":null,"abstract":"\u0000 A new mineral, metathénardite, ideally Na2SO4, the high-temperature hexagonal dimorph of thénardite, a natural analogue of the synthetic phase Na2SO4(I), was found in the sublimates of active fumaroles at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure eruption, Tolbachik volcano, Kamchatka, Russia. The holotype originates from the Glavnaya Tenoritovaya fumarole in which metathénardite is associated with hematite, tenorite, fluorophlogopite, sanidine, anhydrite, krasheninnikovite, vanthoffite, glauberite, johillerite, and lammerite. The cotypes 1 and 2 are from the Arsenarnaya (with hematite, tenorite, fluorophlogopite, sanidine, euchlorine, wulffite, anhydrite, fluoborite, johillerite, nickenichite, calciojohillerite, badalovite, tilasite, cassiterite, and pseudobrookite) and the Yadovitaya (with tenorite, euchlorine, fedotovite, dolerophanite, langbeinite, krasheninnikovite, anhydrite, and hematite) fumaroles, respectively. All specimens with metathénardite were collected from areas with temperatures of 350–400 °C. Metathénardite forms hexagonal tabular, lamellar, or dipyramidal crystals (forms: {001}, {100}, {102}, and {201}) up to 3 mm combined in crusts up to several hundred cm2 in area. The mineral is transparent to semitransparent, colorless, white, light-blue, greenish, yellowish, grayish or brownish, with vitreous luster. Dmeas. = 2.72(1), Dcalc. = 2.717 g/cm3. Metathénardite is optically uniaxial (–), ω = 1.489(2), ε = 1.486(2). The empirical formulae are (Na1.92K0.05Ca0.02Zn0.01)[S0.99O4] (holotype), (Na1.54K0.22Ca0.09Cu0.01Mg0.01)[S1.00O4] (cotype 1), and Na1.65K0.11Ca0.05Cu0.04Mg0.01)[S1.01O4] (cotype 2). Admixed K and bivalent cations probably stabilize the hexagonal aphthitalite-like structure of metathénardite at room temperature. The crystal structure was solved using single crystals of all three samples, R1 = 0.0852, 0.0452, and 0.0449 for holotype and cotypes 1 and 2, respectively. The space group is P63/mmc, and the unit-cell parameters of the holotype are a = 5.3467(9), c = 7.0876(16) Å, V = 157.47(6) Å3, and Z = 2. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are: 4.667(27)(100), 3.904(89)(101), 3.565(33)(002), 2.824(94)(102), 2.686(100)(110), and 1.939(35)(202). Metathénardite and thénardite clearly differ from one another in X-ray diffraction data and infrared and Raman spectra.","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"885-901"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43680788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Agakhanov, L. Pautov, A. Kasatkin, V. Y. Karpenko, E. Sokolova, Maxwell C. Day, F. Hawthorne, V. A. Muftakhov, I. Pekov, F. Cámara, S. Britvin
Abstract: Fluorapophyllite-(Cs) (IMA 2018-108a), ideally CsCa4(Si8O20)F(H2O)8, is an apophyllite-group mineral from the moraine of the Darai‐Pioz glacier, Tien‐Shan, Northern Tajikistan. Associated minerals are quartz, pectolite, baratovite, aegirine, leucosphenite, pyrochlore, neptunite, fluorapophyllite-(K), reedmergnerite. Fluorapophyllite-(Cs) is a hydrothermal mineral. It is colourless, it has a vitreous luster and a white streak. Cleavage is perfect, it is brittle and has a stepped fracture. Mohs hardness is 4.5–5. Dmeas. = 2.54(2) g/cm3, Dcalc. = 2.513 g/cm3. Fluorapophyllite(Cs) is unixial (+) with refractive indices (λ = 589 nm) ω = 1.540(2), ε = 1.544(2). It is non-pleochroic. Chemical analysis by electron microprobe gave SiO2 48.78, Al2O3 0.05, CaO 22.69, Cs2O 10.71, K2O 1.13, Na2O 0.04, F 1.86, H2Ocalc. 14.61, –O=F2 –0.78, sum 99.09 wt.%, H2O was calculated from crystal-structure analysis. The empirical formula based on 29 (O + F) apfu, H2O = 8 pfu, is (Cs0.75K0.24)Σ0.99(Ca3.99Na0.01)Σ4(Si8.01Al0.01)Σ8.02 O20.03F0.97(H2O)8, Z = 2. The simplified formula is (Cs,K)(Ca,Na)4(Si,Al)8O20F(H2O)8. Fluorapophyllite-(Cs) is tetragonal, space group P4/mnc, a 9.060(6), c 15.741(11) Å, V 1292.10(19) Å3. The crystal structure has been refined to R1 = 4.31% based on 498 unique (Fo > 4σF) reflections. In the crystal structure of fluorapophyllite-(Cs), there is one [4]T site occupied solely by Si, = 1.615 Å. SiO4 tetrahedra link to form a (Si8O20)8– sheet perpendicular to [001]. Between the Si–O sheets, there are two cation sites: A and B. The A site is coordinated by eight H2O groups [O(4) site], A–O(4) = 3.152(4) Å; the A site contains Cs0.75K0.24o0.01, ideally Cs apfu. The Cs–O bondlength of 3.152 Å is definitely larger than the K–O bondlength of 2.966–2.971 Å in fluorapophyllite-(K), KCa4(Si8O20)F(H2O)8. The [7]B site contains Ca3.99Na0.01, ideally Ca4 apfu; = 2.420 Å (φ = O, F, H2O). The Si–O sheets connect via A and B polyhedra and hydrogen bonding; two H atoms have been included in the refinement. Fluorapophyllite-(Cs) is isostructural with fluorapophyllite-(K). Fluorapophyllite-(Cs) is a
{"title":"Fluorapophyllite-(Cs), CsCa4(Si8O20)F(H2O)8, a new apophyllite-group mineral from the Darai-Pioz Massif, Tien-Shan, northern Tajikistan","authors":"A. Agakhanov, L. Pautov, A. Kasatkin, V. Y. Karpenko, E. Sokolova, Maxwell C. Day, F. Hawthorne, V. A. Muftakhov, I. Pekov, F. Cámara, S. Britvin","doi":"10.3749/canmin.1900038","DOIUrl":"https://doi.org/10.3749/canmin.1900038","url":null,"abstract":"Abstract: Fluorapophyllite-(Cs) (IMA 2018-108a), ideally CsCa4(Si8O20)F(H2O)8, is an apophyllite-group mineral from the moraine of the Darai‐Pioz glacier, Tien‐Shan, Northern Tajikistan. Associated minerals are quartz, pectolite, baratovite, aegirine, leucosphenite, pyrochlore, neptunite, fluorapophyllite-(K), reedmergnerite. Fluorapophyllite-(Cs) is a hydrothermal mineral. It is colourless, it has a vitreous luster and a white streak. Cleavage is perfect, it is brittle and has a stepped fracture. Mohs hardness is 4.5–5. Dmeas. = 2.54(2) g/cm3, Dcalc. = 2.513 g/cm3. Fluorapophyllite(Cs) is unixial (+) with refractive indices (λ = 589 nm) ω = 1.540(2), ε = 1.544(2). It is non-pleochroic. Chemical analysis by electron microprobe gave SiO2 48.78, Al2O3 0.05, CaO 22.69, Cs2O 10.71, K2O 1.13, Na2O 0.04, F 1.86, H2Ocalc. 14.61, –O=F2 –0.78, sum 99.09 wt.%, H2O was calculated from crystal-structure analysis. The empirical formula based on 29 (O + F) apfu, H2O = 8 pfu, is (Cs0.75K0.24)Σ0.99(Ca3.99Na0.01)Σ4(Si8.01Al0.01)Σ8.02 O20.03F0.97(H2O)8, Z = 2. The simplified formula is (Cs,K)(Ca,Na)4(Si,Al)8O20F(H2O)8. Fluorapophyllite-(Cs) is tetragonal, space group P4/mnc, a 9.060(6), c 15.741(11) Å, V 1292.10(19) Å3. The crystal structure has been refined to R1 = 4.31% based on 498 unique (Fo > 4σF) reflections. In the crystal structure of fluorapophyllite-(Cs), there is one [4]T site occupied solely by Si, <T–O > = 1.615 Å. SiO4 tetrahedra link to form a (Si8O20)8– sheet perpendicular to [001]. Between the Si–O sheets, there are two cation sites: A and B. The A site is coordinated by eight H2O groups [O(4) site], A–O(4) = 3.152(4) Å; the A site contains Cs0.75K0.24o0.01, ideally Cs apfu. The Cs–O bondlength of 3.152 Å is definitely larger than the K–O bondlength of 2.966–2.971 Å in fluorapophyllite-(K), KCa4(Si8O20)F(H2O)8. The [7]B site contains Ca3.99Na0.01, ideally Ca4 apfu; <B–φ> = 2.420 Å (φ = O, F, H2O). The Si–O sheets connect via A and B polyhedra and hydrogen bonding; two H atoms have been included in the refinement. Fluorapophyllite-(Cs) is isostructural with fluorapophyllite-(K). Fluorapophyllite-(Cs) is a","PeriodicalId":9455,"journal":{"name":"Canadian Mineralogist","volume":"57 1","pages":"965-971"},"PeriodicalIF":0.9,"publicationDate":"2019-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3749/canmin.1900038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45997258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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