The Canadian Journal of Mineralogy and Petrology最新文献

{"title":"Trace Element Characteristics of Tourmaline in Porphyry Cu Systems: Development and Application To Discrimination","authors":"C. Beckett-Brown, A. McDonald, M. McClenaghan","doi":"10.3749/2200037","DOIUrl":"https://doi.org/10.3749/2200037","url":null,"abstract":"\u0000 Samples of tourmaline supergroup minerals from seven mineralized porphyry systems (Cu ±Au, ±Mo) that include Casino (Yukon, Canada), Coxheath (Nova Scotia, Canada), Donoso breccia (Chile), Highland Valley Copper (British Columbia, Canada), New Afton (British Columbia, Canada), Schaft Creek (British Columbia, Canada), and Woodjam (British Columbia, Canada) were examined to characterize their trace element signatures and to evaluate discriminating variables that distinguish them from tourmaline supergroup minerals forming in other environments. Trace element analyses, conducted via LA-ICP-MS, reveal striking similarities in trace element character among the mineralized environments examined in contrast to those considered to be barren. Key concentrations of elements (Sr, Pb, Zn, Cu, and Ga) and select element ratios (Sr/Pb and Zn/Cu) are useful discriminators. These discriminators are presented and compared to that of tourmaline supergroup minerals forming in other geologic environments. The tourmaline supergroup minerals from porphyry systems are characterized by high Sr/Pb values (avg: 297) and relatively low Zn/Cu (avg: 4.8) values. A ternary plot of Sr/Pb–Zn/Cu–Ga is effective in distinguishing porphyry-related tourmaline supergroup minerals. Compared to porphyry grains, tourmaline supergroup minerals derived from felsic pegmatites have lower Sr/Pb values (avg: 2.91) and higher Zn/Cu values (avg: 472); those from orogenic Au deposits have high Sr/Pb (avg: 193) similar to porphyries but intermediate Zn/Cu (avg: 223) and lower Ga (avg: 43 ppm); and those considered metamorphic (greenschist to amphibolite) form in the center of the ternary. An effective approach for discrimination was developed utilizing an understanding of both intrinsic and extrinsic controls. More broadly, this work has implications for using tourmaline supergroup minerals recovered from surficial sediments to identify prospective areas for further porphyry exploration.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"188 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115268051","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":"Raydemarkite, the Natural Analogue of Synthetic α-MoO3·H2O, from Cookes Peak, Luna County, New Mexico, USA","authors":"Hexiong Yang, X. Gu, Francis X. Sousa, R. Gibbs, J. McGlasson, R. Downs","doi":"10.3749/2200049","DOIUrl":"https://doi.org/10.3749/2200049","url":null,"abstract":"\u0000 A new mineral species, raydemarkite, ideally MoO3·H2O, was discovered in an unnamed short adit on the Summit group of claims near Cookes Peak, Luna County, New Mexico, USA. It occurs as sprays of acicular or prismatic crystals on a matrix consisting mainly of quartz and pyrite. Individual crystals of raydemarkite are up to 1.00 × 0.10 × 0.06 mm. Associated minerals include sidwillite, ilsemannite, jordisite, powellite, anhydrite, gypsum, bouškaite, pyrite, and quartz. Raydemarkite is colorless in transmitted light and transparent with white streak and vitreous luster. It is flexible and has a Mohs hardness of ∼1½; cleavage is perfect on {100} and {001}. Twinning is common on (010). The measured and calculated densities are 3.44(5) and 3.41 g/cm3, respectively. Raydemarkite is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded an empirical formula, based on 4 O apfu, of MoO3·H2O.\u0000 Raydemarkite is the natural analogue of the α-form of MoO3·H2O, which was first synthesized over a century ago (Rosenheim & Davidsohn 1903). Its crystal structure was solved using single-crystal X-ray diffraction data. It is triclinic, crystallizing in space group and the unit-cell parameters a = 7.3750(2), b = 3.70920(10), c = 6.6833(2) Å, α = 108.1080(10), β = 112.779(2), γ = 91.7420(10)°, V = 157.828(8) Å3, and Z = 2. The crystal structure of raydemarkite is built up from isolated double chains of highly distorted, edge-sharing MoO5(H2O) octahedra parallel to [010] that are linked together through hydrogen bonds, accounting for its acicular/prismatic morphology and the marked flexibility. Synthetic hemihydrate MoO3·1/2H2O (monoclinic, space group P21/m) can be regarded as a combination of molybdite and raydemarkite both structurally and chemically.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131331311","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":"Recognizing Tourmaline in Mineralized Porphyry Cu Systems: Textures and Major-Element Chemistry","authors":"C. Beckett-Brown, A. McDonald, M. McClenaghan","doi":"10.3749/2200011","DOIUrl":"https://doi.org/10.3749/2200011","url":null,"abstract":"\u0000 Samples of tourmaline supergroup minerals from seven mineralized porphyry systems (Cu, ±Au, ±Mo), including Casino (Yukon Territory, Canada), Coxheath (Nova Scotia, Canada), Donoso breccia-Los Bronces (Chile), Highland Valley Copper (British Columbia, Canada), New Afton (British Columbia, Canada), Schaft Creek (British Columbia, Canada), and Woodjam (British Columbia, Canada), were examined at a variety of scales to evaluate their relationships with mineralization. Data from paragenetic observations show that tourmaline supergroup minerals are generally early hydrothermal minerals that predate both mineralization and alteration (e.g., overgrown and crosscut by). In general, tourmaline supergroup minerals occur as sub- to euhedral crystals that are black in hand sample and can be found in a variety of mineralized settings (including breccias, veins, and disseminations) and alteration assemblages (including potassic, sodic-calcic, phyllic, propylitic, and argillic). As tourmaline supergroup minerals are physically and chemically resilient and occur throughout a given porphyry system, they are comprehensive recorders of the type and extent of various geochemical processes that exist during the complex genesis of these systems. Data from BSE imaging shows two primary zonation types: concentric and sector. These are interpreted to reflect conditions of rapid crystallization and disequilibrium. Results from SEM-EDS analyses show that most tourmaline supergroup minerals are dravite (∼80% of grains), with the remainder being primarily classified as schorl. Porphyry tourmaline supergroup minerals exhibit remarkably consistent ∼2.0 apfu Mg values (range: 0.69–2.89), with the majority of tourmaline supergroup minerals plotting along the oxy-dravite–povondraite trend, reflecting the predominance of the Al3+ ↔ Fe3+ substitution at constant Mg values. This pattern starts from the povondraite side (reflecting the oxidizing nature of early porphyry mineralizing fluids) and trends toward oxy-dravite as a porphyry system evolves, a feature that can, in turn, be interpreted to reflect relative emplacement depths. In mineralized porphyry systems, tourmaline supergroup minerals exhibit remarkably similar physical and chemical characteristics among the systems examined, suggesting that the source and geological processes must be extraordinarily similar. Unfortunately, these characteristics are not unique to porphyry systems and such observations should be integrated with additional data, such as trace element mineral chemistry, to effectively discriminate tourmaline supergroup minerals that have formed in porphyry systems.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129470239","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":"Polygonal Serpentine and Chrysotile in the Kurosegawa Belt, Kyushu, Japan","authors":"S. Enju, S. Uehara, Teruo Inoo","doi":"10.3749/2200017","DOIUrl":"https://doi.org/10.3749/2200017","url":null,"abstract":"\u0000 The basic crystallographic properties of polygonal serpentine (PS) have been revealed in previous studies, while their variation, occurrence, and formation conditions are poorly understood. This study defines four categories of chrysotile and PS: clinochrysotile (chrysotile 2Mc1), orthochrysotile (chrysotile 2Orc1), clino-type PS, and ortho-type PS. When chrysotile and PS coexist or are indistinguishable, we will call them fibrous serpentine (FS), regardless of their ratios. By researching the occurrence, distribution, microtexture, crystal structure, and chemical composition of PS and chrysotile based on these categories, we reveal the features of each type and discuss their relationships and formation processes. The chrysotile and PS of the Kurosegawa belt in Kyushu are enriched in ortho-type FS (O-FS) compared with other localities. O-FS-enriched samples (group-O) show a linear, wide vein occurrence and splintery texture or irregular veins with space-filling textures, while clino-type FS (C-FS)-enriched samples occur as thin veins in serpentinites or as massive-foliated aggregates. Polygonal serpentine is more frequently seen in group-O compared with group-C. In our observation, the crystal structure of chrysotile and PS is continuous, making it difficult to define a clear border between them. Ortho-type PS is frequently seen, whereas clino-type PS is absent in most localities. Orthochrysotile tends to grow into 15-sectored ortho-type PS, whereas clinochrysotile grows into 30-sectored clino-type PS. These features of the crystal structure and coexistence and proportion of the fibrous serpentines in each group were mostly common in all studied localities in the Kurosegawa belt in Kyushu, indicating similar formation conditions within group-O or -C. Based on the textures and occurrences, group-O formed by crystallization from the fluid in the fracture made by brittle deformation, while group-C formed in the last stage of alteration mainly by replacement by alteration. The serpentines in the Kurosegawa belt in Kyushu seem to have followed a similar process, at least at the late stage of serpentinization where FS forms and the difference in the ratio of C-FS to O-FS may have been derived from the difference in the timing of formation during the emplacement process. A formation model for chrysotile and PS is proposed based on these observations. In this model, C-FS and O-FS form under different conditions, such as differences in pressure. This model still needs verification by further observations at different localities and by synthetic experiments.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126087646","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}