M. E. Biglia, M. Cooper, E. Grew, M. Yates, J. Sfragulla, A. Guereschi, M. F. Márquez-Zavalía, M. A. Galliski
Liraite, ideally NaCa2Mn2[Fe3+Fe2+]Mn2(PO4)6(H2O)2, is a new mineral found in the Ceferino Namuncurá pegmatite, Pocho Department, Córdoba province, Argentina. It occurs in ellipsoidal nodules up to 20 cm in diameter in the intermediate zone of a Muscovite-Rare Element class pegmatite. Secondary phosphates, such as varulite, robertsite, fluorapatite, phosphosiderite, and Sr-rich metaswitzerite, together with minor quartz in veinlets, are associated minerals. Liraite is interpreted to have formed by reaction of phosphate minerals with Na-bearing hydrothermal fluids. It is dark brown with greenish hues (nearly black) in massive aggregates and dark olive green in translucent slices with a dark brownish green streak and a vitreous luster. It is brittle with an irregular fracture, one very good cleavage, and a good cleavage orthogonal to the very good cleavage. The Mohs hardness is 5, and the measured and calculated densities are 3.52(1) and 3.529(1) g/cm3, respectively. In transmitted light it is pleochroic X = Y = olive, Z = yellowish brown with X = Y > Z and optical orientation X = 2V(calc.) = 69.2°. The refractive indicies measured with monochromatic light (λ = 589 nm) are α = 1.732 (3), β = 1.739 (3), γ = 1.754 (3). Liraite is orthorhombic (Pcab) and has unit-cell parameters a = 12.608(6) Å, b = 12.918(6) Å, c = 11.737(4) Å, V = 1911.6(14) Å3, Z = 4. The six strongest reflections in the X-ray powder diffraction pattern are as follows: [d in Å, (I), (hkl)] 2.7452, 100, (421); 2.8563, 65, (014); 2.9266, 49, (004); 2.7061, 30, (412); 2.0966, 29, (334); 2.7693, 26, (402). The crystal structure was refined to an R index of 1.94% based on 2910 observed (>4σF) reflections measured with MoKα X-radiation. Chemical analysis by electron microprobe of the structure crystal (holotype specimen) gave Na2O 1.58, FeO 5.29, Fe2O3 11.45, CaO 10.52, MgO 0.77, MnO 24.00, P2O5 41.55, SrO 0.72, ZnO 0.19, H2O (calc.) 3.50, total 99.57 wt.% where water was calculated from the crystal-structure analysis and the Fe3+/Fe2+ ratio was determined by charge balance. The empirical formula calculated on the basis of 26 oxygen atoms is (Na0.53□0.47)Σ1.00(Ca1.93Sr0.07)Σ2.00(Fe3+1.48Fe2+0.76Mn3.48Mg0.20Zn0.02)Σ5.94P6.02O24(H2O)2, ideally NaCa2M(1)Mn2M(2)[Fe3+Fe+2]M(3)Mn2(PO4)6(H2O)2. The Gladstone-Dale relation gives a compatibility index of 1 – (KP/KC) = 0.010 (superior). This new member of the wicksite group is Mn-rich, and, like bederite, has Mn dominant at the M(1) and M(3) sites. However, the Na site in liraite is Na-dominant with M(2)[Fe3+Fe2+], whereas bederite is □-dominant with M(2)Fe3+2. Liraite has a very low MgO content, and even with all available Mg assigned to the M(2) site, Fe2+ > Mg at M(2). Consequently, liraite is the first wicksite-group mineral with endmember M(2) composition [Fe3+Fe2+].
{"title":"Liraite, ideally NaCa2Mn2[Fe3+Fe2+]Mn2(PO4)6(H2O)2, a new phosphate mineral of the wicksite group from the Ceferino Namuncurá pegmatite, Córdoba, Argentina","authors":"M. E. Biglia, M. Cooper, E. Grew, M. Yates, J. Sfragulla, A. Guereschi, M. F. Márquez-Zavalía, M. A. Galliski","doi":"10.3749/canmin.2000110","DOIUrl":"https://doi.org/10.3749/canmin.2000110","url":null,"abstract":"\u0000 Liraite, ideally NaCa2Mn2[Fe3+Fe2+]Mn2(PO4)6(H2O)2, is a new mineral found in the Ceferino Namuncurá pegmatite, Pocho Department, Córdoba province, Argentina. It occurs in ellipsoidal nodules up to 20 cm in diameter in the intermediate zone of a Muscovite-Rare Element class pegmatite. Secondary phosphates, such as varulite, robertsite, fluorapatite, phosphosiderite, and Sr-rich metaswitzerite, together with minor quartz in veinlets, are associated minerals. Liraite is interpreted to have formed by reaction of phosphate minerals with Na-bearing hydrothermal fluids. It is dark brown with greenish hues (nearly black) in massive aggregates and dark olive green in translucent slices with a dark brownish green streak and a vitreous luster. It is brittle with an irregular fracture, one very good cleavage, and a good cleavage orthogonal to the very good cleavage. The Mohs hardness is 5, and the measured and calculated densities are 3.52(1) and 3.529(1) g/cm3, respectively. In transmitted light it is pleochroic X = Y = olive, Z = yellowish brown with X = Y > Z and optical orientation X = 2V(calc.) = 69.2°. The refractive indicies measured with monochromatic light (λ = 589 nm) are α = 1.732 (3), β = 1.739 (3), γ = 1.754 (3). Liraite is orthorhombic (Pcab) and has unit-cell parameters a = 12.608(6) Å, b = 12.918(6) Å, c = 11.737(4) Å, V = 1911.6(14) Å3, Z = 4. The six strongest reflections in the X-ray powder diffraction pattern are as follows: [d in Å, (I), (hkl)] 2.7452, 100, (421); 2.8563, 65, (014); 2.9266, 49, (004); 2.7061, 30, (412); 2.0966, 29, (334); 2.7693, 26, (402). The crystal structure was refined to an R index of 1.94% based on 2910 observed (>4σF) reflections measured with MoKα X-radiation. Chemical analysis by electron microprobe of the structure crystal (holotype specimen) gave Na2O 1.58, FeO 5.29, Fe2O3 11.45, CaO 10.52, MgO 0.77, MnO 24.00, P2O5 41.55, SrO 0.72, ZnO 0.19, H2O (calc.) 3.50, total 99.57 wt.% where water was calculated from the crystal-structure analysis and the Fe3+/Fe2+ ratio was determined by charge balance. The empirical formula calculated on the basis of 26 oxygen atoms is (Na0.53□0.47)Σ1.00(Ca1.93Sr0.07)Σ2.00(Fe3+1.48Fe2+0.76Mn3.48Mg0.20Zn0.02)Σ5.94P6.02O24(H2O)2, ideally NaCa2M(1)Mn2M(2)[Fe3+Fe+2]M(3)Mn2(PO4)6(H2O)2. The Gladstone-Dale relation gives a compatibility index of 1 – (KP/KC) = 0.010 (superior). This new member of the wicksite group is Mn-rich, and, like bederite, has Mn dominant at the M(1) and M(3) sites. However, the Na site in liraite is Na-dominant with M(2)[Fe3+Fe2+], whereas bederite is □-dominant with M(2)Fe3+2. Liraite has a very low MgO content, and even with all available Mg assigned to the M(2) site, Fe2+ > Mg at M(2). Consequently, liraite is the first wicksite-group mineral with endmember M(2) composition [Fe3+Fe2+].","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"33 11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132644776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Black sand beach placers from Kodiak, Sitkinak, and Tugidak Islands, Alaska, have been mined intermittently for gold and minor platinum-group alloys for more than 100 years. High-grade platinum-rich magnetic separate and accompanying black sand from the southern beach placer of Tugidak Island were studied using electron microprobe WDS and scanning electron microscope EDS; mineral classification and identification were based on these techniques. The major platinum mineral is isoferroplatinum, followed by minor tetraferroplatinum and tulameenite, and rare ferronickelplatinum. Two types of alteration were identified in about 3–4% of the alloy grains: rim formation involving Pt loss and increased Fe, Ni, and/or Cu, and fracturing and vein filling by Cu-rich alloy. Ruthenium-Ir-Os-Pt alloys occur as inclusions and veins as well as form part of composite grains. Ten percent of the alloy grains contain a large variety of platinum-group minerals (PGM). Inclusions of cuprorhodsite, malanite, cuproiridsite, laurite, erlichmanite, cooperite, braggite, bowieite, kashinite, miassite, hollingworthite, irarsite, sperrylite, stillwaterite, genkinite, stibiopalladinite, keithconnite, zvyagintsevite, and probable palladodymite and vincentite were identified. Two unidentified inclusion phases also occur. Most of the PGM inclusions are primary and were trapped by a growing crystal from a melt; some inclusions exhibit textures that suggest trapping of an As,Te,S-rich immiscible melt. Secondary inclusions and evidence of deformation were observed in a few alloy grains. Associated with PGM inclusions or as separate inclusions are various base-metal sulfides. Two silicate-melt inclusions in one isoferroplatinum grain have an andesite–shoshonite composition. Minor gold and Ag-rich gold in the high-grade magnetic separate contain magnetite, pyrrhotite, and chromite inclusions. The gold composition suggests that their sources are the numerous quartz veins and apophyses related to granitoids on Kodiak Island. The composition of the placer chromite is similar to chromite from the Border Ranges mélange fault system and suggests that the Uyak Complex ultramafic and mafic rocks are part of a supra-subduction-zone ophiolite and are the source of the platinum-group minerals.
100多年来，阿拉斯加科迪亚克岛、锡特基纳克岛和图吉达克岛的黑沙滩砂矿一直在断断续续地开采黄金和少量铂族合金。采用电子探针WDS和扫描电镜EDS对图吉达克岛南部滩涂砂矿的高品位富铂磁分选及其伴生黑砂进行了研究;矿物分类和鉴定是基于这些技术进行的。铂矿物以异铁铂为主，其次为次要的四铁铂和土拉铁矿，稀有的镍铁铂。在3-4%的合金晶粒中发现了两种类型的蚀变:一种是Pt损失和Fe、Ni和/或Cu增加的边缘形成，另一种是富Cu合金的破裂和脉状充填。钌- ir - os - pt合金以夹杂体和脉体的形式存在，并形成复合晶粒的一部分。10%的合金晶粒中含有多种铂族矿物(PGM)。包裹体包括铜长石、马拉云母、铜长石、钾长石、铜长石、布喇辉石、硼长石、钾长石、黄褐石、hollingworthite、铁长石、铁长石、静水长石、genkinite、stibiopalladinite、keithconnite、zyagaginite，以及可能的钯长石和钒长石。还会出现两个未确定的夹杂相。大多数PGM夹杂物是原生的，被熔体中生长的晶体所捕获;一些包裹体显示出富含As、Te、s的非混溶熔体的结构。在少数合金晶粒中观察到次生夹杂物和变形迹象。与PGM夹杂物伴生或作为单独夹杂物的是各种贱金属硫化物。一个异硫铂颗粒中的两个硅酸盐熔体包裹体具有安山岩-舒顺岩组成。高品位磁分选中的次金和富银金含有磁铁矿、磁黄铁矿和铬铁矿包裹体。金的组成表明，它们的来源是科迪亚克岛上与花岗岩类有关的众多石英脉和斑体。砂矿铬铁矿的组成与边界山脉msamuange断裂系统的铬铁矿相似，表明乌亚克杂岩超基性和基性岩是超俯冲带蛇绿岩的一部分，是铂族矿物的来源。
{"title":"Platinum and gold placer from Tugidak Island, Alaska: Platinum-group minerals and their inclusions, gold, and chromite mineralogy","authors":"H. Belkin, A. E. Grosz","doi":"10.3749/canmin.2000016","DOIUrl":"https://doi.org/10.3749/canmin.2000016","url":null,"abstract":"\u0000 Black sand beach placers from Kodiak, Sitkinak, and Tugidak Islands, Alaska, have been mined intermittently for gold and minor platinum-group alloys for more than 100 years. High-grade platinum-rich magnetic separate and accompanying black sand from the southern beach placer of Tugidak Island were studied using electron microprobe WDS and scanning electron microscope EDS; mineral classification and identification were based on these techniques. The major platinum mineral is isoferroplatinum, followed by minor tetraferroplatinum and tulameenite, and rare ferronickelplatinum. Two types of alteration were identified in about 3–4% of the alloy grains: rim formation involving Pt loss and increased Fe, Ni, and/or Cu, and fracturing and vein filling by Cu-rich alloy. Ruthenium-Ir-Os-Pt alloys occur as inclusions and veins as well as form part of composite grains. Ten percent of the alloy grains contain a large variety of platinum-group minerals (PGM). Inclusions of cuprorhodsite, malanite, cuproiridsite, laurite, erlichmanite, cooperite, braggite, bowieite, kashinite, miassite, hollingworthite, irarsite, sperrylite, stillwaterite, genkinite, stibiopalladinite, keithconnite, zvyagintsevite, and probable palladodymite and vincentite were identified. Two unidentified inclusion phases also occur. Most of the PGM inclusions are primary and were trapped by a growing crystal from a melt; some inclusions exhibit textures that suggest trapping of an As,Te,S-rich immiscible melt. Secondary inclusions and evidence of deformation were observed in a few alloy grains. Associated with PGM inclusions or as separate inclusions are various base-metal sulfides. Two silicate-melt inclusions in one isoferroplatinum grain have an andesite–shoshonite composition. Minor gold and Ag-rich gold in the high-grade magnetic separate contain magnetite, pyrrhotite, and chromite inclusions. The gold composition suggests that their sources are the numerous quartz veins and apophyses related to granitoids on Kodiak Island. The composition of the placer chromite is similar to chromite from the Border Ranges mélange fault system and suggests that the Uyak Complex ultramafic and mafic rocks are part of a supra-subduction-zone ophiolite and are the source of the platinum-group minerals.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116091190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Hatert, E. Grew, P. Vignola, N. Rotiroti, F. Nestola, P. Keller, M. Baijot, Yannick Bruni, A. Fransolet, F. D. Bo, Martin Depret
The crystal chemistries of five samples of minerals belonging to the fillowite group were structurally investigated: (A) fillowite from the Buranga pegmatite, Rwanda; (B) fillowite from the Kabira pegmatite, Uganda; (C) johnsomervilleite from Loch Quoich, Scotland; (D) johnsomervilleite from the Malpensata pegmatite, Italy; and (E) chladniite from the Sapucaia pegmatite, Minas Gerais, Brazil. Their crystal structures were refined in space group R (No. 148), using single-crystal X-ray diffraction data, to R1 values of (A) 3.79%, (B) 3.52%, (C) 4.14%, (D) 4.04%, and (E) 5.59%. Unit-cell parameters are: (A) a = 15.122(1), c = 43.258(4) Å; (B) a = 15.125(1), c = 43.198(3) Å; (C) a = 15.036(2), c = 42.972(9) Å; (D) a = 15.090(2), c = 43.050(9) Å; and (E) a = 15.1416(6), c = 43.123(2) Å. The asymmetric unit contains 15 cation sites with coordinations ranging from V to IX, as well as six P sites. The complex structure can be split into three types of chains running parallel to the c axis. These chains are composed of edge- and face-sharing polyhedra. Detailed cation distributions were determined for all five samples, and their comparison allowed us to establish the general formula A3BC11(PO4)9 for fillowite-type phosphates, where A represents the group of sites mainly occupied by Na, B the Ca sites, and C the sites containing the divalent cations Fe2+, Mn, and Mg. This formula was accepted by the CNMNC, and the four valid mineral species occurring in the fillowite group are fillowite (C = Mn), johnsomervilleite (C = Fe2+), chladniite (C = Mg), and galileiite (B and C = Fe2+). Stornesite-(Y) is discredited, since this mineral corresponds to Y-bearing chladniite.
从结构上研究了五种属于长尾辉石组的矿物样品的晶体化学性质:(A)来自卢旺达布兰加伟晶岩的长尾辉石;(B)来自乌干达Kabira伟晶岩的长柳;(C)来自苏格兰Quoich湖的johnsomervilleite;(D)来自意大利Malpensata伟晶岩的johnsomervilleite;(E)来自巴西米纳斯吉拉斯州Sapucaia伟晶岩的晶晶石。利用单晶x射线衍射数据对空间群R (No. 148)的晶体结构进行细化，得到R1值为(A) 3.79%， (B) 3.52%， (C) 4.14%， (D) 4.04%， (E) 5.59%。单元格参数为:(A) A = 15.122(1)， c = 43.258(4) Å;(B) a = 15.125(1)， c = 43.198(3) Å;(C) a = 15.036(2)， C = 42.972(9) Å;(D) a = 15.090(2)， c = 43.050(9) Å;(E) a = 15.1416(6)， c = 43.123(2) Å。不对称单元包含15个配位从V到IX的阳离子位点，以及6个P位点。这种复杂的结构可以被分成三种平行于c轴的链。这些链由边共享和面共享多面体组成。我们确定了所有5个样品的详细阳离子分布，并通过它们的比较，我们建立了填料型磷酸盐的通式A3BC11(PO4)9，其中A表示主要由Na占据的位点群，B表示Ca位点群，C表示含有二价阳离子Fe2+、Mn和Mg的位点群。该公式为CNMNC所接受，长辉石组中存在的4种有效矿物分别为长辉石(C = Mn)、约翰萨默维勒石(C = Fe2+)、软橄榄石(C = Mg)和加利利石(B和C = Fe2+)。Stornesite-(Y)是不可信的，因为这种矿物对应于含Y的绿泥石。
{"title":"Crystal chemistry and nomenclature of fillowite-type phosphates","authors":"F. Hatert, E. Grew, P. Vignola, N. Rotiroti, F. Nestola, P. Keller, M. Baijot, Yannick Bruni, A. Fransolet, F. D. Bo, Martin Depret","doi":"10.3749/canmin.2000043","DOIUrl":"https://doi.org/10.3749/canmin.2000043","url":null,"abstract":"\u0000 The crystal chemistries of five samples of minerals belonging to the fillowite group were structurally investigated: (A) fillowite from the Buranga pegmatite, Rwanda; (B) fillowite from the Kabira pegmatite, Uganda; (C) johnsomervilleite from Loch Quoich, Scotland; (D) johnsomervilleite from the Malpensata pegmatite, Italy; and (E) chladniite from the Sapucaia pegmatite, Minas Gerais, Brazil. Their crystal structures were refined in space group R (No. 148), using single-crystal X-ray diffraction data, to R1 values of (A) 3.79%, (B) 3.52%, (C) 4.14%, (D) 4.04%, and (E) 5.59%. Unit-cell parameters are: (A) a = 15.122(1), c = 43.258(4) Å; (B) a = 15.125(1), c = 43.198(3) Å; (C) a = 15.036(2), c = 42.972(9) Å; (D) a = 15.090(2), c = 43.050(9) Å; and (E) a = 15.1416(6), c = 43.123(2) Å. The asymmetric unit contains 15 cation sites with coordinations ranging from V to IX, as well as six P sites. The complex structure can be split into three types of chains running parallel to the c axis. These chains are composed of edge- and face-sharing polyhedra. Detailed cation distributions were determined for all five samples, and their comparison allowed us to establish the general formula A3BC11(PO4)9 for fillowite-type phosphates, where A represents the group of sites mainly occupied by Na, B the Ca sites, and C the sites containing the divalent cations Fe2+, Mn, and Mg. This formula was accepted by the CNMNC, and the four valid mineral species occurring in the fillowite group are fillowite (C = Mn), johnsomervilleite (C = Fe2+), chladniite (C = Mg), and galileiite (B and C = Fe2+). Stornesite-(Y) is discredited, since this mineral corresponds to Y-bearing chladniite.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132603137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Franck Gouedji, C. Picard, M. Audet, T. Augé, J. Spangenberg
The mafic-ultramafic Samapleu deposits of the Yacouba complex, which host nickel, copper sulfides, and platinum-group minerals, are located in the Biankouma-Silipou region, western Ivory Coast. These intrusions originate from the mantle and would have been established during the Proterozoic (2.09 Ga) around 22 km deep within the Archean granulites (3.6–2.7 Ga) which at least partially contaminated them. Platinum-group and sulfide minerals from the Samapleu deposits were studied using optical microscopy, scanning electron microscopy, the electronic microprobe, X-ray fluorescence, fire assay, and a Thermo Fisher Scientific Delta S isotope ratio mass spectrometer system. The sulfide mineralization (mainly pyrrhotite, pentlandite, chalcopyrite ± pyrite) is mainly disseminated with, in places, semi-massive to massive sulfide veins. It is especially abundant in pyroxenite horizons with net or breccia textures. The isotopic ratios of sulfur measured from the sulfides (an average of 0.1‰), the R factor (between 1500 and 10,000), and the Cu/Pd ratios indicate a mantle source. Thus, the sulfides would have formed from sulfide liquids produced by immiscibility from the silicate mantle magma under mafic-ultramafic intrusion emplacement conditions and with possible geochemical modification of the magmas by assimilation of the surrounding continental crust. The platinum-group minerals (michenerite, merenskyite, moncheite, Co-rich gersdorffite, irarsite, and hollingworthite) are mainly associated with the sulfide phases. The nature of the platinum-group minerals is indicative of the probable role of late-magmatic hydrothermal fluids during the mineralizing process.
{"title":"Ni-Cu sulfide mineralization and PGM from the Samapleu mafic-ultramafic intrusion, Yacouba complex, western Ivory Coast","authors":"Franck Gouedji, C. Picard, M. Audet, T. Augé, J. Spangenberg","doi":"10.3749/canmin.1900030","DOIUrl":"https://doi.org/10.3749/canmin.1900030","url":null,"abstract":"\u0000 The mafic-ultramafic Samapleu deposits of the Yacouba complex, which host nickel, copper sulfides, and platinum-group minerals, are located in the Biankouma-Silipou region, western Ivory Coast. These intrusions originate from the mantle and would have been established during the Proterozoic (2.09 Ga) around 22 km deep within the Archean granulites (3.6–2.7 Ga) which at least partially contaminated them.\u0000 Platinum-group and sulfide minerals from the Samapleu deposits were studied using optical microscopy, scanning electron microscopy, the electronic microprobe, X-ray fluorescence, fire assay, and a Thermo Fisher Scientific Delta S isotope ratio mass spectrometer system.\u0000 The sulfide mineralization (mainly pyrrhotite, pentlandite, chalcopyrite ± pyrite) is mainly disseminated with, in places, semi-massive to massive sulfide veins. It is especially abundant in pyroxenite horizons with net or breccia textures.\u0000 The isotopic ratios of sulfur measured from the sulfides (an average of 0.1‰), the R factor (between 1500 and 10,000), and the Cu/Pd ratios indicate a mantle source.\u0000 Thus, the sulfides would have formed from sulfide liquids produced by immiscibility from the silicate mantle magma under mafic-ultramafic intrusion emplacement conditions and with possible geochemical modification of the magmas by assimilation of the surrounding continental crust.\u0000 The platinum-group minerals (michenerite, merenskyite, moncheite, Co-rich gersdorffite, irarsite, and hollingworthite) are mainly associated with the sulfide phases. The nature of the platinum-group minerals is indicative of the probable role of late-magmatic hydrothermal fluids during the mineralizing process.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"38 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133572942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. V. Shchipalkina, I. Pekov, S. Britvin, N. Koshlyakova, E. Sidorov
Six different exsolution types are found in crystals of aphthitalite-group alkali sulfates from exhalations of the active Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. The coexisting minerals in these exsolutions are metathénardite, ideally Na2SO4 (P63/mmc), and vanthoffite, Na6Mg(SO4)4 (P21/c) (Type I); metathénardite and belomarinaite, KNaSO4 (P3m1) (Type II); thénardite, Na2SO4 (Fddd), and aphthitalite, K3Na(SO4)2 (Pm1) (Type III); aphthitalite and arcanite, K2SO4 (Pnma) (Type IV); metathénardite and natroaphthitalite, KNa3(SO4)2 (Pm1) (Type V); and two chemical varieties of metathénardite (Type VI). The exsolution processes occur in crystals belonging to the high-temperature, hexagonal Na2SO4(I) (= metathénardite, P63/mmc) structure type with different K:Na ratios formed at temperatures higher than 500 °C. The similarity and hexagonal close-packed nature of the crystal structures of the coexisting phases, all representatives of aphthitalite-like structure types, cause the coherent conjugation of domains during diffusion and cation ordering in the parent phase. The breakdown of solid solution can be facilitated by the mosaic character of crystals of a parent phase (incoherent grain boundaries) and the presence of coherent twin boundaries. The heating of samples with exsolution Types II and V up to 700 °C over 24 h shows that diffusion of K and Na through the domain borders does not result in the complete disorder of these cations and the extinction of domains with different crystal structures.
{"title":"Alkali sulfates with aphthitalite-like structures from fumaroles of the Tolbachik volcano, Kamchatka, Russia. III. Solid solutions and exsolutions","authors":"N. V. Shchipalkina, I. Pekov, S. Britvin, N. Koshlyakova, E. Sidorov","doi":"10.3749/canmin.2000105","DOIUrl":"https://doi.org/10.3749/canmin.2000105","url":null,"abstract":"\u0000 Six different exsolution types are found in crystals of aphthitalite-group alkali sulfates from exhalations of the active Arsenatnaya fumarole, Tolbachik volcano, Kamchatka, Russia. The coexisting minerals in these exsolutions are metathénardite, ideally Na2SO4 (P63/mmc), and vanthoffite, Na6Mg(SO4)4 (P21/c) (Type I); metathénardite and belomarinaite, KNaSO4 (P3m1) (Type II); thénardite, Na2SO4 (Fddd), and aphthitalite, K3Na(SO4)2 (Pm1) (Type III); aphthitalite and arcanite, K2SO4 (Pnma) (Type IV); metathénardite and natroaphthitalite, KNa3(SO4)2 (Pm1) (Type V); and two chemical varieties of metathénardite (Type VI). The exsolution processes occur in crystals belonging to the high-temperature, hexagonal Na2SO4(I) (= metathénardite, P63/mmc) structure type with different K:Na ratios formed at temperatures higher than 500 °C. The similarity and hexagonal close-packed nature of the crystal structures of the coexisting phases, all representatives of aphthitalite-like structure types, cause the coherent conjugation of domains during diffusion and cation ordering in the parent phase. The breakdown of solid solution can be facilitated by the mosaic character of crystals of a parent phase (incoherent grain boundaries) and the presence of coherent twin boundaries. The heating of samples with exsolution Types II and V up to 700 °C over 24 h shows that diffusion of K and Na through the domain borders does not result in the complete disorder of these cations and the extinction of domains with different crystal structures.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125974127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions. The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.
{"title":"Telluride Mineralogy of the Deer Horn Au-Ag-Te-(Bi-Pb-W) Deposit, British Columbia: Implications for the Generation of Tellurides","authors":"J. A. Roberts, L. Groat, P. Spry, J. Cempírek","doi":"10.3749/canmin.1900103","DOIUrl":"https://doi.org/10.3749/canmin.1900103","url":null,"abstract":"\u0000 The Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions.\u0000 The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"193 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124305361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Piilonen, G. Poirier, W. Lechner, R. Rowe, R. Richards
Located in the southwest corner of the Ratanakiri Volcanic Province, the Wat Ocheng basalt is the first known zeolite locality in Cambodia. The basalt is a fine-grained, vesicular to amygdaloidal, subalkaline to transitional alkaline intraplate tholeiite comprised of 30% lath-like plagioclase (average: Ab51An45Or4), 35% interstitial augite (average: Wo44En35Fs21), 25–30% zeolites after plagioclase and volcanic glass, and minor skeletal ulvöspinel. It contains mineralized amygdales ranging in size from 0.5 × 0.5 cm to 5 × 9 cm. Nine zeolite species occur at Wat Ocheng, including analcime, chabazite-Ca, gonnardite, natrolite, phillipsite-Ca, and thomsonite-Ca, along with clays, aragonite, calcite, and pyrite. All the zeolite species are being described from Cambodia for the first time. The zeolite and secondary mineral assemblages observed at Wat Ocheng are similar to those reported from other alkaline basalt localities, including those in neighboring Vietnam, and are a product of alteration of the primary Ca-Na minerals and volcanic glass as a result of burial metamorphism and infiltration of heated meteoric waters. The mineral assemblage is not homogeneous across amygdales within the exposed lava flow, suggesting localized closed systems, likely the result of early precipitation of clay minerals and fine-grained zeolites. Decreased porosity and differences in fluid geochemistry would account for the diversity in the observed assemblages. Four stages of hydrothermal alteration and zeolitization have been defined based on mineral textures and chemistry. Zeolite formation began with fine-grained Ca- (chabazite-Ca and phillipsite-Ca) and Na- (analcime) dominant, high TSi (Si/Si+Al) species in Stage II following deposition of clay minerals in Stage I. Stage III is characterized by increasing Na+K contents and decreasing TSi. Crystallization of coarse-grained chabazite-Ca and phillipsite-Ca with increasing Na+K contents in the rims of the crystals followed the development of natrolite with a later-stage epitaxial overgrowth of thomsonite-Ca. The final stage of mineralization (Stage IV) included late-stage calcite, pyrite, and termination of growth of acicular sprays of thomsonite-Ca. Post-magmatic cooling and circulation of meteoric water and fluids derived from alluvial sediments overlying the basalts were involved in zeolitization. Thermal sources include an underlying basaltic andesite flow as well as regional deep-seated, extensional pull-apart structures, the result of a thinned lithosphere and injection of fertile mantle following the collision of the Eurasian and Indochina plates during the Himalayan Orogeny.
{"title":"Zeolite Minerals from Wat Ocheng, Ta Ang, Ratanakiri Province, Cambodia – Occurrence, Composition, and Paragenesis","authors":"P. Piilonen, G. Poirier, W. Lechner, R. Rowe, R. Richards","doi":"10.3749/canmin.2000113","DOIUrl":"https://doi.org/10.3749/canmin.2000113","url":null,"abstract":"\u0000 Located in the southwest corner of the Ratanakiri Volcanic Province, the Wat Ocheng basalt is the first known zeolite locality in Cambodia. The basalt is a fine-grained, vesicular to amygdaloidal, subalkaline to transitional alkaline intraplate tholeiite comprised of 30% lath-like plagioclase (average: Ab51An45Or4), 35% interstitial augite (average: Wo44En35Fs21), 25–30% zeolites after plagioclase and volcanic glass, and minor skeletal ulvöspinel. It contains mineralized amygdales ranging in size from 0.5 × 0.5 cm to 5 × 9 cm. Nine zeolite species occur at Wat Ocheng, including analcime, chabazite-Ca, gonnardite, natrolite, phillipsite-Ca, and thomsonite-Ca, along with clays, aragonite, calcite, and pyrite. All the zeolite species are being described from Cambodia for the first time.\u0000 The zeolite and secondary mineral assemblages observed at Wat Ocheng are similar to those reported from other alkaline basalt localities, including those in neighboring Vietnam, and are a product of alteration of the primary Ca-Na minerals and volcanic glass as a result of burial metamorphism and infiltration of heated meteoric waters. The mineral assemblage is not homogeneous across amygdales within the exposed lava flow, suggesting localized closed systems, likely the result of early precipitation of clay minerals and fine-grained zeolites. Decreased porosity and differences in fluid geochemistry would account for the diversity in the observed assemblages. Four stages of hydrothermal alteration and zeolitization have been defined based on mineral textures and chemistry. Zeolite formation began with fine-grained Ca- (chabazite-Ca and phillipsite-Ca) and Na- (analcime) dominant, high TSi (Si/Si+Al) species in Stage II following deposition of clay minerals in Stage I. Stage III is characterized by increasing Na+K contents and decreasing TSi. Crystallization of coarse-grained chabazite-Ca and phillipsite-Ca with increasing Na+K contents in the rims of the crystals followed the development of natrolite with a later-stage epitaxial overgrowth of thomsonite-Ca. The final stage of mineralization (Stage IV) included late-stage calcite, pyrite, and termination of growth of acicular sprays of thomsonite-Ca. Post-magmatic cooling and circulation of meteoric water and fluids derived from alluvial sediments overlying the basalts were involved in zeolitization. Thermal sources include an underlying basaltic andesite flow as well as regional deep-seated, extensional pull-apart structures, the result of a thinned lithosphere and injection of fertile mantle following the collision of the Eurasian and Indochina plates during the Himalayan Orogeny.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"949 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133044457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Shaw, K. Goodenough, É. Deady, P. Nex, Brian Ruzvidzo, J. Rushton, I. Mounteney
Lithium is a critical metal, vital for electrification of transport. Currently, around half the world's lithium is extracted from rare-metal pegmatites and understanding the genesis and evolution of these igneous rocks is therefore essential. This paper focuses on the pegmatites in the Kamativi region of Zimbabwe. A group of early pegmatites is distinguished from a late pegmatite suite which includes the ca. 1030 Ma Main Kamativi Pegmatite. Previously mined for tin, the mine tailings are now being investigated for lithium. Mineral-scale investigation of samples from the Main Kamativi Pegmatite has allowed recognition of a four-stage paragenesis: (1) an early magmatic assemblage dominated by quartz, alkali feldspar, spodumene (LiAlSi2O6) and montebrasite [LiAl(PO4)(OH, F)]; (2) partial alteration by widespread albitization, associated with growth of cassiterite and columbite group minerals; (3) irregular development of a quartz, muscovite, columbite group mineral assemblage; and (4) widespread low-temperature fluid-induced alteration of earlier phases to cookeite, sericite, analcime, and apatite. Whole-rock geochemistry indicates that the late pegmatites are enriched in Li, Cs, Ta, Sn, and Rb but depleted in Nb, Zr, Ba, Sr, and the rare earth elements relative to early pegmatites and country rock granitoids. A combination of field relationships and published dating indicates that the granitoids, and probably the early pegmatites, were emplaced toward the end of the ca. 2000 Ma Magondi Orogeny, whereas the late pegmatites are almost 1000 million years younger. The late pegmatites thus cannot be genetically related to the granitoids and are instead likely to have formed by partial melting of metasedimentary source rocks. The drivers for this melting may be related to crustal thickening along the northern margin of the Kalahari Craton during the assembly of Rodinia.
{"title":"The Magmatic–Hydrothermal Transition in Lithium Pegmatites: Petrographic and Geochemical Characteristics of Pegmatites from the Kamativi Area, Zimbabwe","authors":"R. Shaw, K. Goodenough, É. Deady, P. Nex, Brian Ruzvidzo, J. Rushton, I. Mounteney","doi":"10.3749/canmin.2100032","DOIUrl":"https://doi.org/10.3749/canmin.2100032","url":null,"abstract":"\u0000 Lithium is a critical metal, vital for electrification of transport. Currently, around half the world's lithium is extracted from rare-metal pegmatites and understanding the genesis and evolution of these igneous rocks is therefore essential. This paper focuses on the pegmatites in the Kamativi region of Zimbabwe. A group of early pegmatites is distinguished from a late pegmatite suite which includes the ca. 1030 Ma Main Kamativi Pegmatite. Previously mined for tin, the mine tailings are now being investigated for lithium. Mineral-scale investigation of samples from the Main Kamativi Pegmatite has allowed recognition of a four-stage paragenesis: (1) an early magmatic assemblage dominated by quartz, alkali feldspar, spodumene (LiAlSi2O6) and montebrasite [LiAl(PO4)(OH, F)]; (2) partial alteration by widespread albitization, associated with growth of cassiterite and columbite group minerals; (3) irregular development of a quartz, muscovite, columbite group mineral assemblage; and (4) widespread low-temperature fluid-induced alteration of earlier phases to cookeite, sericite, analcime, and apatite. Whole-rock geochemistry indicates that the late pegmatites are enriched in Li, Cs, Ta, Sn, and Rb but depleted in Nb, Zr, Ba, Sr, and the rare earth elements relative to early pegmatites and country rock granitoids. A combination of field relationships and published dating indicates that the granitoids, and probably the early pegmatites, were emplaced toward the end of the ca. 2000 Ma Magondi Orogeny, whereas the late pegmatites are almost 1000 million years younger. The late pegmatites thus cannot be genetically related to the granitoids and are instead likely to have formed by partial melting of metasedimentary source rocks. The drivers for this melting may be related to crustal thickening along the northern margin of the Kalahari Craton during the assembly of Rodinia.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"127 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121033241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gunshot residue is emitted as fine particulate matter upon the ignition of percussion-sensitive explosives among other additives in a firearm barrel. The particulates condense from a vapor phase and contain material from the Pb-Sb-Ba-bearing primer, S-bearing gunpowder, and the Pb-bearing bullet fragments. Shooters can inhale or ingest the fine particulates which also attach to their hands, clothing, and other surfaces. Estimation of the bioavailability of the emitted toxic Pb- and Sb-bearing particulates requires detailed knowledge of their mineralogical composition and those of their weathering products. For this purpose, gunshot residue particulates have been collected from soils in front of a firing line of a shooting range in Ontario, Canada. Bulk mineralogical and chemical features of the soils have been characterized using X-ray powder diffraction, inductively coupled plasma-mass spectrometry, and scanning electron microscopy. The focused ion-beam technique has been used to extract a section containing numerous altered gunshot residue particulates from a soil grain. Subsequent transmission electron microscopy shows for the first time that gunshot residue particulates are composed of metallic δ-Pb, α-Sb, galena (PbS), and an unidentified Ba-bearing phase. Weathering of the gunshot residue particulates results in the formation of incidental nanoparticles (i.e., not purposely engineered to occur at the nanometer scale) in the form of δ-Pb, massicot, PbO, and galena. The formation and mobilization of some of these nanoparticles within the soil grain suggest that their release during the weathering of bullets and gunshot residue contributes to the release of Pb into the environment. Hydrocerussite, Pb3(CO3)2(OH)2, cerussite, PbCO3, and massicot and anglesite, PbSO4, are the major secondary Pb-phases in and around altered GSR particulates. These phases form during the weathering of metallic Pb, massicot, and galena nanoparticles in a Ca-carbonate rich environment. Secondary Sb-bearing phases are valentinite, Sb2O3, and amorphous Sb-Pb phases (Sb:Pb ratio = 2:1–4:1). The latter phases have partially replaced large proportions of the Ca-carbonates surrounding the gunshot residue particulates. The larger abundance of the amorphous Sb-Pb phases relative to valentinite suggests that their solubility most likely controls the release of Sb into the bulk soil. The SEM and TEM characterizations and chemical analyses of mineral surface coatings and the colloidal fraction of a leachate from the collected surficial soils indicate that Pb occurs predominantly in the colloidal fraction, is often associated with sulfate-bearing colloids, and is sequestered in sulfate and carbonate/hydroxide coatings.
{"title":"The Release of Incidental Nanoparticles During the Weathering of Gunshot Residue in Soils of a Shooting Range in Ontario, Canada","authors":"Michael Schindler, Haley Mantha","doi":"10.3749/CANMIN.1900092","DOIUrl":"https://doi.org/10.3749/CANMIN.1900092","url":null,"abstract":"\u0000 Gunshot residue is emitted as fine particulate matter upon the ignition of percussion-sensitive explosives among other additives in a firearm barrel. The particulates condense from a vapor phase and contain material from the Pb-Sb-Ba-bearing primer, S-bearing gunpowder, and the Pb-bearing bullet fragments. Shooters can inhale or ingest the fine particulates which also attach to their hands, clothing, and other surfaces. Estimation of the bioavailability of the emitted toxic Pb- and Sb-bearing particulates requires detailed knowledge of their mineralogical composition and those of their weathering products. For this purpose, gunshot residue particulates have been collected from soils in front of a firing line of a shooting range in Ontario, Canada. Bulk mineralogical and chemical features of the soils have been characterized using X-ray powder diffraction, inductively coupled plasma-mass spectrometry, and scanning electron microscopy. The focused ion-beam technique has been used to extract a section containing numerous altered gunshot residue particulates from a soil grain. Subsequent transmission electron microscopy shows for the first time that gunshot residue particulates are composed of metallic δ-Pb, α-Sb, galena (PbS), and an unidentified Ba-bearing phase. Weathering of the gunshot residue particulates results in the formation of incidental nanoparticles (i.e., not purposely engineered to occur at the nanometer scale) in the form of δ-Pb, massicot, PbO, and galena. The formation and mobilization of some of these nanoparticles within the soil grain suggest that their release during the weathering of bullets and gunshot residue contributes to the release of Pb into the environment. Hydrocerussite, Pb3(CO3)2(OH)2, cerussite, PbCO3, and massicot and anglesite, PbSO4, are the major secondary Pb-phases in and around altered GSR particulates. These phases form during the weathering of metallic Pb, massicot, and galena nanoparticles in a Ca-carbonate rich environment. Secondary Sb-bearing phases are valentinite, Sb2O3, and amorphous Sb-Pb phases (Sb:Pb ratio = 2:1–4:1). The latter phases have partially replaced large proportions of the Ca-carbonates surrounding the gunshot residue particulates. The larger abundance of the amorphous Sb-Pb phases relative to valentinite suggests that their solubility most likely controls the release of Sb into the bulk soil. The SEM and TEM characterizations and chemical analyses of mineral surface coatings and the colloidal fraction of a leachate from the collected surficial soils indicate that Pb occurs predominantly in the colloidal fraction, is often associated with sulfate-bearing colloids, and is sequestered in sulfate and carbonate/hydroxide coatings.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"8 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131520620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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