The Canadian Journal of Mineralogy and Petrology最新文献

{"title":"Cesium Fractionation in Miarolitic Pegmatites: A Reevaluation of K-Feldspar Data","authors":"A. J. Anderson, T. S. Ercit, T. Mccarron","doi":"10.3749/2200044","DOIUrl":"https://doi.org/10.3749/2200044","url":null,"abstract":"\u0000 A review of K-feldspar compositions from miarolitic pegmatites shows that in most pegmatites the pocket K-feldspars are enriched in Rb and Cs relative to exopocket K-feldspar within the same body. Rayleigh modeling of simultaneous crystallization of K-feldspar from a melt and coexisting aqueous solution predicts that the Cs content of K-feldspar falls to nil, which implies that rare-alkali enriched (up to 2190 ppm Cs) pocket K-feldspar must have crystallized from a fluid-undersaturated pegmatite melt. However, most petrologists contend that miarolitic cavities develop after exsolution of an aqueous phase from a pegmatite melt. To investigate the process responsible for the high uptake of Cs and Rb in pocket K-feldspar we determined the rare-alkali content of synthetic K-feldspars that crystallized at 500 °C from a supercritical aqueous fluid in a granitic melt + fluid system. The K/Cs ratio of the synthetic K-feldspar was compared to modeled K/Cs ratios for K-feldspars formed from a water-saturated melt in which the initial Cs concentration (Co) of the melt was identical to the starting glass used in experiments. Our results show that the K/Cs ratios of synthetic K-feldspar are orders of magnitude lower than that predicted using the Rayleigh fractionation model. We attribute the high uptake of Rb and Cs in K-feldspar to kinetic effects associated with rapid crystal growth in an undercooled water-saturated melt. Therefore, we propose that Rb- and Cs-rich K-feldspars that line the pockets of natural miarolitic pegmatites are the products rapid growth in an aqueous fluid that coexists with a highly fractionated residual melt.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129601241","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}

{"title":"Vaterite Optical Petrography in Lake Sturgeon Otoliths","authors":"B. Chakoumakos, B. Pracheil","doi":"10.3749/2200031","DOIUrl":"https://doi.org/10.3749/2200031","url":null,"abstract":"\u0000 Vaterite occurring in fish otoliths exhibits plumose and spherulitic habits, the latter being like those grown from aqueous solutions. Vaterite spherulites are known to have sheaf-like texture and can be up to 100 μm in size. In thin section, the spherulites typically show uniaxial positive interference figures between cross-polarizers using a polarizing light microscope but without conoscopic or Bertrand lenses because the spherulites mimic the effect of these lenses. Plumose vaterite can show both uniaxial (+) and biaxial (+) interference figures with a small 2V, which suggests that crystal structural models for vaterite should have the plane of the carbonate group parallel to the optic axis or acute bisectrix. Vaterite spherulites grown from aqueous solution exhibit similar structure and growth habits.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"126 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131626459","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}

{"title":"Geogenic, Anthropogenic, and Authigenic Minerals Hosting Arsenic and Antimony in Yellowknife Bay Sediments","authors":"Katrina A. Paudyn, H. Jamieson, J. Chételat, Christopher E. Schuh, M. Palmer, S. Mchale","doi":"10.3749/2200035","DOIUrl":"https://doi.org/10.3749/2200035","url":null,"abstract":"\u0000 Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada) is a water body valued by surrounding communities for its subsistence, recreational, and cultural use. Located directly downstream of the former Giant Mine and Con Mine, Yellowknife Bay has received inputs from mine waste streams enriched in arsenic (As), antimony (Sb), and metals since the late 1930s. Lake sediments in Yellowknife Bay provide a record of metal(loid) contamination from aerially deposited roaster stack emissions, mine effluent, and Giant Mine tailings. A sediment sampling program was conducted in Yellowknife Bay to characterize As and Sb mineralogy using scanning electron microscopy-mineral liberation analysis. Mineralogical analysis of As- and Sb-hosted minerals in nine sediment cores suggests that arsenic trioxide (As2O3), originally deposited during the period of peak-mining emissions, has since been transformed into authigenic sulfides (interpreted to be realgar) down core from peak-mining emissions. Arsenic has also been attenuated by iron (Fe)-oxyhydroxides and roaster-generated iron oxides up-core from peak-mining emissions, near the sediment–water interface. The Sb-bearing minerals appear to be stable in Yellowknife Bay sediments, with no conclusive evidence of post-depositional mobility having been identified. The observed prevalence of arsenic trioxide in surface sediments proximal to Giant Mine suggests that As and Sb contamination is ongoing, likely from terrestrial weathering of contaminated soils and shoreline outcrops. Arsenic-bearing oxide minerals prevalent in surface sediments may become unstable should redox conditions in the hypolimnion change; prolonged anoxia could destabilize the As hosting minerals and release As to bottom waters. Therefore, long-term monitoring of the water column, including hypolimnion conditions, in Yellowknife Bay is recommended.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122406281","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}

{"title":"Textural and Mineralogical Evolution of the Little Nahanni Pegmatite Group (NWT, Canada) with Implications for Metasomatism, Rare-Metal Mineralization, and Pegmatite–Wall Rock Interaction","authors":"Jérémie D. Pfister, D. Kontak, L. Groat","doi":"10.3749/2000086","DOIUrl":"https://doi.org/10.3749/2000086","url":null,"abstract":"\u0000 Situated in the Northwest Territories (Canada), the Cretaceous (ca. 85 Ma) Little Nahanni Pegmatite Group is an LCT-type pegmatite swarm enriched in Li, Sn, and Ta. Displaying intensive albitization associated with rare-metal mineralization (i.e., Nb, Ta, Sn), having a notably high surface-area-to-volume ratio (i.e., hundreds of thin dikes), and being particularly well exposed in a suite of thirteen glacial cirques, the Little Nahanni Pegmatite Group provides an ideal opportunity to investigate some unresolved aspects of pegmatite formation and evolution, such as metasomatism, pegmatite–wall rock interaction, and the nature and origin of rare-metal mineralization (i.e., magmatic versus metasomatic).\u0000 Using an integrated approach combining field observations with detailed textural and mineralogical studies, two different stages of pegmatite evolution are documented: primary magmatic followed by intense metasomatism. Preservation of primary magmatic features, such as coarse oriented high aspect-ratio crystals (spodumene, K-feldspar), banded aplites, anisotropic fabrics, and skeletal textures, highlight the importance of undercooling (ΔT) of the melt with consequent disequilibrium crystallization and boundary layer effects. The metasomatic stage is dominated by the formation of domains of secondary albite and is attributed to interaction with a residual highly fluxed sodic melt and is responsible for most of the rare-metal mineralization; less abundant micaceous units and cafemic domains reflect incursion of acidic magmatic-sourced and alkaline wall rock derived fluids.\u0000 Our findings are significant and have widespread application to all pegmatite types. Particularly significant is the finding that the rare-metal mineralization is mostly localized to zones of metasomatism.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114654708","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}

{"title":"Experimental Synthesis of the Rare-Earth Fluoride Gagarinite-(Ce) by Fluid-Induced Alteration of Chevkinite-(Ce)","authors":"B. Bagiński, P. Jokubauskas, Witold Matyszczak, M. Stachowicz, J. Kotowski, R. Macdonald, D. Harlov","doi":"10.3749/2200045","DOIUrl":"https://doi.org/10.3749/2200045","url":null,"abstract":"\u0000 Gagarinite-(Ce) [Na(Ca,Ce)2F6] has been synthesized as a product in experiments designed to examine the fluid-induced alteration of chevkinite-(Ce). The experiments were conducted at 600 °C and 400 MPa for 21 days and at 550 °C and 200 MPa for 63 days. At 600 °C, a rim of gagarinite-(Ce) was seen to develop around chevkinite-(Ce), which was itself enclosed in a glassy, amorphous material containing inclusions of albite. At 550 °C, the chevkinite-(Ce) was observed to be surrounded by a rim of gagarinite-(Ce) and fluorbritholite-(Ce), which in turn was enclosed in massive narsarsukite with inclusions of albite. This assemblage was associated with a sodic pyroxene. In the 550 °C run both rims with gagarinite-(Ce) were subsequently overgrown by both Ce-bearing frankdicksonite and a lamprophyllite group mineral identified as delindeite. Electron probe microanalyses are given of all reactant phases. The stability conditions of gagarinite-(Ce) are in accord with those inferred from the only natural occurrence, Strange Lake, Canada. The formation of gagarinite-(Ce) is ascribed to NaF being the only component added in the experiments, resulting in a very high Na/Ca ratio in the system. New parageneses for narsarsukite, frankdicksonite, and delindeite are reported.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130721587","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}

{"title":"Germanium Enrichment Mechanism: An Example from the Maoping Carbonate-Hosted Zn-Pb-(Ge) Deposit, SW China","authors":"Lei Wang, Yan Zhang, Run-sheng Han","doi":"10.3749/2200061","DOIUrl":"https://doi.org/10.3749/2200061","url":null,"abstract":"\u0000 Germanium (Ge), as a critical metal, is in high demand due to its growing usage in emerging industries and green technologies. The Sichuan-Yunnan-Guizhou Zn-Pb metallogenic region, located on the southwestern margin of the Yangtze block, is one of the most important producers of Ge in China. The Maoping Zn-Pb deposit in the Sichuan-Yunnan-Guizhou region contains Ge-bearing sphalerite, whose crystal chemistry and process of Ge incorporation are poorly resolved. Sphalerite occurring in two hydrothermal stages (Sp-II and Sp-III) is recognized in this deposit. Laser ablation inductively coupled plasma mass spectrometry was used to map the concentrations of key elements (including Mn, Fe, Cu, Ga, Ge, As, Ag, Cd, In, Sn, Sb, Hg, and Pb) in Sp-II and Sp-III, and their distributions were qualitatively compared, followed by a quantitative assessment through application of the structural similarity index. The results suggest that Ge positively correlates with Cu in Sp-II, but with Ag in Sp-III, differences that may be related to the temperature of formation. The metamorphic basement is the main source of Ge in the Maoping deposit. Additionally, coal seams in this deposit could potentially be important contributors to Ge enrichment. A model for Ge mineralization was proposed in which the mixing of the Ge-bearing metamorphic fluids with the Ge-bearing basin brines precipitated sphalerite, and the Ge was incorporated into Sp-II and Sp-III via 2Cu+ + Ge4+ ↔ 3Zn2+ and 2Ag+ + Ge4+ ↔ 3Zn2+, respectively, under medium sulfur fugacity and low oxygen fugacity conditions.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123612820","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}

{"title":"The Mooihoek Platinum Pipe, Eastern Bushveld Complex, South Africa – Geochemistry and Mineralization","authors":"T. Oberthür, S. Goldmann, F. Melcher","doi":"10.3749/2200066","DOIUrl":"https://doi.org/10.3749/2200066","url":null,"abstract":"\u0000 The Mooihoek pipe is one of several platiniferous dunite pipes in the eastern Bushveld Complex that were discovered in 1924 and mined until 1930. It has a diameter of about 180 by 400 m and consists of magnesian dunite that crosscuts a sequence of layered leucocratic wall rocks of the lower part of the upper Critical Zone of the Bushveld Complex. The Mg-dunite pipe at Mooihoek hosts a smaller, carrot-shaped inner pipe, 13–16 m in diameter and cylindrical in shape near surface, consisting of mainly iron-rich dunite/wehrlite pegmatite, comprising the platinum-bearing orebody. Specific characteristics of the mineralization are the near absence of sulfides and Pt being the predominant platinum-group element (PGE).\u0000 The present work comprises whole rock analyses, ore microscopy, scanning electron microscopy, and electron probe microanalysis. The main findings are as follows: Chondrite-normalized distribution patterns of the PGE in the Mooihoek samples demonstrate that mainly Pt is strongly enriched relative to the other PGE and Au. The shapes of the patterns are subparallel to each other and also to those of the Onverwacht pipe, indicating a similar mode of origin. Olivine of the ore zone is iron-rich and is frequently accompanied by coarse Ti-magnetite and ilmenite, whereas chromite is rare. Two major generations of platinum-group minerals (PGM) are present at Mooihoek, namely: (1) Early inclusions of mainly ferroan platinum in (magmatic) olivine, Ti-magnetite, and ilmenite, and (2) a later, more complex PGM assemblage, commonly associated with thin veinlets of magnetite, mainly found along grain boundaries of silicates and oxides. This assemblage consists of various Pt-Fe alloys and PGE-antimonides, -sulfarsenides, -arsenides, and -sulfides. Overall, and in line with the geochemical data of the mineralization, Pt-dominated PGM predominate (~70%), followed by Rh, Pd, and Ru species. Pt-Fe alloys are the most frequent PGM (∼44% by number of grains).\u0000 Our hypothesis on the genesis of the Mooihoek pipe and its mineralization largely corresponds to that proposed for the Onverwacht pipe (Oberthür et al. 2021): The magnesian dunite pipe was formed by upward penetration of magmas which replaced the existing cumulates. Fractional crystallization of olivine within a deeper magma chamber and/or during ascent of the melt resulted in the formation of a consanguineous residual, more iron-rich, and PGE-enriched melt. This melt also contained highly mobile, supercritical fluids and was continuously enriched in PGE and other incompatible elements. The PGE-enriched residual melts formed and sealed the inner ore pipe. Apparently, the PGE mineralization is not related to the well-established mechanism of sulfide collection. Instead, it was introduced in the form of nanoparticles and small droplets of PGM, which coagulated to form larger grains during evolution of the mineralizing system. Concomitant supercritical magmatic to hydrothermal fluids were continuously acti","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"595 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131691692","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}

{"title":"New Minerals from the Redmond Mine, North Carolina, USA: II. Cubothioplumbite and Hexathioplumbite, Two New Minerals Containing the Cubane-Like [Pb4(OH)4]4+ Structural Unit","authors":"A. R. Kampf, Jason B. Smith, John M. Hughes, Chiu‐Shun Ma, Christopher R. Emproto","doi":"10.3749/2200070","DOIUrl":"https://doi.org/10.3749/2200070","url":null,"abstract":"\u0000 The new minerals cubothioplumbite (IMA2021-091) and hexathioplumbite (IMA2021-092), both with the ideal formula [Pb4(OH)4]Pb(S2O3)3, were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur together in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Cubothioplumbite has the following properties: yellow equant crystals to about 0.5 mm; white streak; adamantine luster; brittle; Mohs hardness 3; conchoidal fracture; no cleavage; 5.748 g/cm3 calculated density; isotropic with n > 2.00. Hexathioplumbite has the following properties: colorless hexagonal prisms to about 1 mm; white streak; adamantine luster; brittle; Mohs hardness 2½; curved fracture; no cleavage; 5.531 g/cm3 calculated density; uniaxial (−) with ω = 2.005(5) and ε = 1.995(5). Electron probe microanalyses provided the empirical formulae [Pb4(OH)4]Pb(S2O3)2.72(SO4)0.28 and [Pb4(OH)4]Pb(S2O3)2.68(SO4)0.32 for cubothioplumbite and hexathioplumbite, respectively. Cubothioplumbite is cubic, Pa, a = 14.9179(13) Å, V = 3319.9(9) Å3, and Z = 8. Hexathioplumbite is hexagonal, P63, a = 10.7213(10), c = 8.6541(6) Å, V = 861.49(17) Å3, and Z = 2. The structures of cubothioplumbite (R1 = 0.0354 for 1090 I > 2σI) and hexathioplumbite (R1 = 0.0791 for 1062 I > 2σI) both contain cubane-like [Pb4(OH)4]4+ structural units.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127849544","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}

{"title":"New Minerals from the Redmond Mine, North Carolina, USA: III. Cherokeeite and Cuprocherokeeite, Two New Minerals Containing [Pb2(Zn,Cu2+)(OH)4]2+ Chains","authors":"A. R. Kampf, Jason B. Smith, John M. Hughes, Chiu‐Shun Ma, Christopher R. Emproto","doi":"10.3749/2300001","DOIUrl":"https://doi.org/10.3749/2300001","url":null,"abstract":"\u0000 The new minerals cherokeeite, [Pb2Zn(OH)4](SO4)·H2O (IMA2022-016), and cuprocherokeeite, [Pb8Zn3Cu2+(OH)16](SO4)4·4H2O (IMA2022-086), were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur together in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Cherokeeite has the following properties: colorless to pale pink prisms or blades to about 1 mm; white streak; vitreous luster; brittle; Mohs hardness 2½; splintery fracture; at least two perfect cleavages; 5.011 g/cm3 calculated density; biaxial (+) with α = 1.745(5), β = 1.770(5), γ = 1.805(5), and 2V = 85(2)°. Cuprocherokeeite has the following properties: light blue prisms or blades to about 1 mm; very pale bluish-white streak; vitreous luster; brittle; Mohs hardness 2½; irregular, curved fracture; probably two good cleavages; 5.032 g/cm3 calculated density; biaxial (+) with α = 1.760(5), β = 1.770(5), γ = 1.800(5), and 2V (meas.) = 65(3)°. Electron probe microanalyses provided the empirical formulae [Pb2.00Zn1.00(OH)4](SO4)0.85(S2O3)0.15·H2O and [Pb8.14(Zn2.52Cu2+1.34)(OH)16][(SO4)3.07(S2O3)0.93]·4H2O for cherokeeite and cuprocherokeeite, respectively. Cherokeeite is monoclinic, P21/n, a = 17.1697(7), b = 6.47173(19), c = 17.5304(12) Å, β = 115.440(8)°, V = 1759.06(19) Å3, and Z = 8. Cuprocherokeeite is monoclinic, P21/n, a = 12.6828(5), b = 9.4629(5), c = 14.7876(8) Å, β = 94.798(4)°, V = 1768.53(15) Å3, and Z = 2. The structures of cherokeeite (R1 = 0.0425 for 2681 I > 2σI) and cuprocherokeeite (R1 = 0.0741 for 2411 I > 2σI) both contain edge-sharing chains of octahedra decorated by Pb2+ cations, which are strongly bonded to the chains via short Pb–O bonds. In cherokeeite, the octahedral cations are all Zn, whereas in cuprocherokeeite, one in every four cations is Cu2+.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127119834","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}

{"title":"The Chemical Composition of Helvine-Group Minerals and Implications for Ore Genesis: Case Studies from the Dawan, Qidushan, and Taoxikeng Deposits","authors":"Yiting Zhu, Xiaofeng Li, Xingling Wei","doi":"10.3749/2200067","DOIUrl":"https://doi.org/10.3749/2200067","url":null,"abstract":"\u0000 Helvine-group minerals have characteristic chemical compositions and textures and occur in different environments within magmatic–hydrothermal deposits. However, their origin is still unclear. There are several quartz-vein beryllium deposits with different element assemblages existing in southeastern China; these include the Dawan Be-Mo, Qidushan Be-Zn-Sn, and Taoxikeng Be-W deposits. We present the chemical composition of helvine-group minerals analyzed by electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry, in addition to zircon sensitive high-mass-resolution ion microprobe U-Pb and cassiterite laser ablation inductively coupled plasma mass spectrometry U-Pb ages. The zircon and cassiterite U-Pb data indicate that the Qidushan deposit formed during the Late Cretaceous (127–132 Ma). The electron probe microanalysis data show that the helvine-group minerals from the three deposits are helvine and/or danalite. A wide variety of different trace elements display high concentrations in the different deposits [e.g., helvine-group minerals from the Dawan deposit are rich in Li, B, Sc, V, Ga, Y, Sn, Cs, Th, and U; those from the Qidushan deposit are rich in Sc, Cd, and Sn; whereas those from the Taoxikeng deposit are rich in Y, Cd, Sn, Ta, and total rare-earth elements (ΣREE). The material analyzed from the Dawan deposit has the highest concentrations of Li (28.03–134.96 ppm), Sn (126.01–709.24 ppm), Sc (108.10–287.64 ppm), Cs (0–37.24 ppm), Th (4.78–112.63 ppm), and U (0.79–4.13 ppm). The material analyzed from the Taoxikeng deposit has the highest concentrations of Y (594.95–899.95 ppm), Cd (22.63–25.21 ppm), Ta (0.41–0.86 ppm), and ΣREE (281.69–451.79 ppm). However, those from the Qidushan deposit have the lowest concentrations of Y (10.21–37.70 ppm), Sn (0–26.88 ppm), U (0–19.06 ppm), Eu (0–0.14 ppm), and Cs (being below the detection limit). All of them are rich in heavy REEs but poor in light REEs, with distinctive REE patterns. Our results reveal that both crystallographic substitution and fluid composition control the enrichment of trace elements in helvine-group minerals. The textures and trace element compositions of helvine-group minerals can represent various parageneses and ore-forming fluid compositions. We propose that the δEu values and (La/Yb)N ratios can be used as markers to discriminate the genesis of helvine-group mineral precipitated from different environments based on the chemical compositions and the origin of ore-forming fluids.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114665622","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}