The Canadian Journal of Mineralogy and Petrology最新文献

{"title":"Discreditation of Borishanskiite as a Mineral Species (= Polarite, PdPb)","authors":"L. Cabri, A. McDonald, T. Evstigneeva","doi":"10.3749/2200050","DOIUrl":"https://doi.org/10.3749/2200050","url":null,"abstract":"\u0000 A re-examination by electron probe microanalysis of the holotype sample of the platinum-group mineral borishanskiite, previously defined as Pd1+x(As,Pb)2 with x = 0–0.2, reveals that the mineral contains no detectable As. The new data also show the mineral to be stoichiometric, i.e., vacancy-free, with the average chemical composition (based on 2 apfu) of Pd0.99(Pb0.72Bi0.28)Σ1.00 (n = 3) or ideally, PdPb. A comparison of the powder X-ray diffraction patterns for borishanskiite (PDF 00-029-0960) and polarite (PDF 00-023; ideally PdPb) show that, within error, the two are same. Further, the refined unit-cell parameters of borishanskiite, a = 7.18(2), b = 8.62(2), c = 10.66(2) Å, agree well with those of polarite, a = 7.140, b = 8.563, c =10.501 Å. Given the new chemical data for borishanskiite, which suggest the ideal chemical formula PdPb, along with its crystallographic similarity to polarite, it is concluded that borishanskiite is equivalent to polarite. Discussion of the extent of the PdBi–PdPb solid-solution series and confusion concerning the ideal formula for polarite is also presented.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126922688","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":"Oscillatory Zoned Liddicoatite from Anjanabonoina, Central Madagascar. III. Trace Elements","authors":"A. Lussier, F. Hawthorne","doi":"10.3749/2200026","DOIUrl":"https://doi.org/10.3749/2200026","url":null,"abstract":"\u0000 Large crystals of liddicoatite (tourmaline) from the Anjanabonoina Pegmatite of Central Madagascar are well-known for their distinct patterns of oscillatory zoning. This study follows two previous investigations, in which the crystal chemistry (Lussier et al. 2011a) and variations of major chemical constituents (Lussier & Hawthorne 2011) were characterized in detail. Here, the variations of elements present only at the trace level are investigated. The measurement by laser ablation inductively coupled plasma mass spectrometry of 26 trace elements, with abundances spanning four orders of magnitude (∼10−1 to 103 ppm) is reported. Trace elements were analyzed along continuous analytical traverses from the core to the rim of the crystal. Abundance profiles for most of the trace elements quantified (21 of 26) show clear oscillations that coincide with optical oscillatory zoning features. Throughout the crystal, the occurrence of compositional oscillation is independent of trace-element abundance; even where mean abundance is low, ∼1 ppm (e.g., V3+, Y3+, Th4+), oscillatory behavior is clear. Conversely, the magnitude of the oscillatory amplitude shows a strong near-linear dependence on element abundance. Within individual oscillatory zones, four unique line-shapes are observed, each differentiated by (1) the direction of a compositional discontinuity at the zone limits and (2) the orientation of the nonlinear curvature across the zone. For any individual zone, the variation in element concentration, C, can be fitted to the equation C = ±Aeλ(x−Φ) + Δ where A is the zone amplitude; Φ is a reference position, and λi and Δi are fitted parameters. Comparison of the fitted equations shows that linear correlation between element pairs is common, occurring between pairs consisting of trace–trace, trace–major, and major–major elements. The oscillatory behavior of constituent elements is related to the location of the trace element in the tourmaline structure, with elements at the X- and Y-sites typically showing increases and decreases in abundance over single oscillatory zones. Throughout each zone, Mg has high abundance (∼104 ppm) at the start of each zone, followed by an extremely abrupt decrease in abundance, typically over a distance of <1 mm, making its behavior different to that of other elements (both trace and major). Finally, there are systematic differences in trace-element abundances between pyramid {201} and prism {100} sectors of the crystal, echoing the differences observed for major elements between these two sectors and consistent with face-dependent differences in element uptake.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126566378","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":"Predicting the Crystal Structure of Beryl from the Chemical Composition","authors":"Rhiana E. Henry, L. Groat, J. Cempírek, R. Škoda, M. Holá","doi":"10.3749/2200034","DOIUrl":"https://doi.org/10.3749/2200034","url":null,"abstract":"\u0000 Crystal-structure prediction is a challenging topic. Few models have been developed that use the chemical composition of a known compound to determine a complete crystal structure. A complete structural model should include all major bond lengths and angles, atomic coordinates, polyhedral volumes and distortions, and unit-cell parameters. The mineral beryl is used here to develop such a model.\u0000 Beryl (Be3Al2Si6O18) is an ideal mineral to show that predicting the crystal structure using chemistry is possible: the framework structure is known, this structure has only two cation sites that experience substitutions, and these substitutions only minimally occur simultaneously. Vacant channel sites are involved in coupled substitutions, allowing alkali cations (typically Na+) to enter the structure, and the channel regularly contains molecular H2O correlated to Na content (Henry et al. 2022). The research employed single-crystal X-ray diffraction and electron probe microanalyses of 80 samples to create a model which was subsequently tested using 33 samples.\u0000 Results show that the complete crystal structure of beryl can be accurately calculated using the Al-site average ionic radius (Al-SAIR) for octahedrally trending beryl, or the Be-site average ionic radius (Be-SAIR) for tetrahedrally trending beryl. Beryl for which Al-SAIR > (0.45 × Be-SAIR) + 0.414 is considered octahedrally trending and that for which Al-SAIR ≤ (0.45 × Be-SAIR) + 0.414 is considered tetrahedrally trending. Red beryl (differentiated by high Fe and Mn) exhibits a different trend, forming a subset of the octahedrally trending beryl. There is an upper limit to the predictable range of beryl structures of 0.604 Å Al-SAIR or 0.326 Å Be-SAIR. This model makes it possible to explore limitations on the crystal structure of beryl and the potential for unusual cation substitutions, or conversely, to compute the structure of a hypothetical pure endmember beryl. It is robust for true beryl (beryl for which Be and Al are the dominant non-Si cations) up to a high limit of cation substitutions, but not for other beryl-group minerals, including stoppaniite, bazzite, avdeevite, and johnkoivulaite.\u0000 Future studies on beryl will be able to estimate basic crystal-structure features arising from standard chemical analyses as used in this research. It enables the creation of an extensive beryl database, aids comparisons of natural beryl to synthetics, and helps provide further guidance on provenance studies. It also invites future crystal-structure prediction research. This approach is applicable to broader fields, as crystal structures are linked to the physical characteristics of minerals and rocks in which they form.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133084646","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":"Cation Ordering in Spinel from Calcium-Aluminum-Rich Inclusions in Carbonaceous Chondrites NWA 2364 and NWA 6991 to Quantify Temperature in the Early Solar System","authors":"V. Houde, R. Flemming, A. Bouvier, V. Terskikh","doi":"10.3749/2200051","DOIUrl":"https://doi.org/10.3749/2200051","url":null,"abstract":"\u0000 Minerals extracted from two calcium-aluminum-rich inclusions, one each from NWA 2364 and NWA 6991 CV3 chondrite meteorites, were examined using micro X-ray diffraction, 27Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and Triple Quantum (3Q) MAS NMR. In situ examination by micro X-ray diffraction was used to confirm the presence of spinel (MgAl2O4) and to identify co-existing minerals. Aluminum-27 3Q MAS NMR was used to confirm the identity of co-existing minerals by their NMR signature in this two-dimensional experiment and to ensure that their NMR peaks did not overlap with those attributed to spinel. Aluminum-27 MAS NMR was used to quantitatively measure cation ordering between the tetrahedral ([4]Al) and octahedral ([6]Al) sites in the spinel. The measured cation distribution was used to calculate the inversion parameter, x, for each sample: x = 0.077 ± 0.007 for NWA 2364, x = 0.027 ± 0.001 for NWA 6991 (gehlenite-rich fraction), and x = 0.052 ± 0.003 for NWA 6991 (Al-bearing diopside-rich fraction). The measured cation-ordering data were input into six literature calibration curves to estimate the temperature of formation or the most recent equilibration temperature of the spinel. The NWA 2364 sample yielded temperatures between 420 and 707 K and the NWA 6991 sample yielded temperatures between 153 and 615 K, depending on the calibration curve used. These temperatures are lower than expected for nebular condensation temperatures, however, reordering may have occurred during cooling from high temperatures, so these values may be taken to represent temperature minima. The calculated spinel-related temperatures may thus represent equilibration temperatures related to subsequent nebular or CV chondrite parent body processes.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115049870","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":"Varicolored Marble in the Central Metasedimentary Belt, Grenville Supergroup. I. Circumstantial Evidence of Melting","authors":"R. Martin, D. Schumann, Jeffrey de Fourestier, Sebastian Fuchs","doi":"10.3749/2200042","DOIUrl":"https://doi.org/10.3749/2200042","url":null,"abstract":"\u0000 Large expanses of granulite-facies white marble occur in the Central Metasedimentary Belt of the Grenville orogen in western Quebec and in contiguous areas of eastern Ontario and New York. Locally, the white rock is transformed into “varicolored” marble, ranging from pink, orange, yellow, green, gray to blue marble, in some cases closely juxtaposed. We have dissected specimens from three target areas in western Quebec. A powerful analytical workflow including high-resolution ZEISS Atlas 5 large-area imaging was employed in combination with detailed energy-dispersive spectroscopy analyses to create digital map-like online datasets of entire samples to display the textures and characteristics in their entirety. We describe in detail the texture and mineralogy of marble specimens collected from exposures created during the construction of Autoroute 5 near Wakefield and of Autoroute 50 near Grenville-sur-la-Rouge and two specimens collected near Bryson, Quebec. At the inferred pressure and temperature and in the presence of H2O, the white marble seems to have melted. A carbonate melt, a powerful flux, can dissolve silicate wallrocks along a mutual contact. In this way, a marble-derived melt has assimilated wallrocks ranging from peridotite to granite. This melting event may have occurred more than once in the 350-million-year lifespan of the Grenville event; the thermal event associated with the Rigolet stage, during gravitational collapse of the orogen approximately one billion years ago, was the most intense. The marble samples contain no vestiges of older deformed assemblages. Whereas the varicolored marble undoubtedly is metasedimentary, a coeval influx of mantle-derived carbonatitic melt and related fluids from a subjacent complex may have caused localized metasomatism of the marble prior to and after melting.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":" 18","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134500814","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":"Minerals from Mines to Mountaintops from Earth to Mars and BeyondPreface","authors":"R. Flemming, L. Groat, B. Chakoumakos, H. Jamieson","doi":"10.3749/int014","DOIUrl":"https://doi.org/10.3749/int014","url":null,"abstract":"","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132144594","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":"Revisiting the Chemistry and Crystal Structure of Sveite","authors":"D. Knaack, R. C. Peterson, J. Reid, M. Leybourne, D. Layton-Matthews","doi":"10.3749/2300009","DOIUrl":"https://doi.org/10.3749/2300009","url":null,"abstract":"\u0000 Sveite, KAl7(NO3)4(OH)16Cl2·8H2O, is a rare, water-soluble mineral with an undetermined atomic structure. New major, minor, and trace element data for sveite from three localities (Cerro Autana Cave, Venezuela; San Joaquin Valley, USA; Ponta Grossa, Brazil) are reported using modern analytical techniques (inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography). Powder X-ray diffraction, micro-X-ray diffraction, and scanning electron microscopy-energy dispersive X-ray spectroscopy are used to characterize the identity of residues following digestions of different strengths, i.e., ultrapure H2O, 2%, 20%, and concentrated HCl acid. Sveite from Venezuela has approximately 3 wt.% more K and 5 wt.% less Al than reported by Martini (1980), and that from California has 20 wt.% less Al than was reported by Graham et al. (1988). Sveite from California has higher N (∼8 wt.%) and lower K (4.5 wt.%), Al (∼12 wt.%), and Cl (∼0.5 wt.%) contents compared to that from Venezuela (∼6 wt.% N, ∼7 wt.% K, ∼15 wt.% Al, and ∼10 wt.% Cl contents). Sveite from Brazil has extremely low K (<0.1 wt.%) and high N (∼24 wt.%) contents with respect to those from the other localities. To inhibit formation of aluminum chloride on dissolution, which can subsequently impact results from geochemical analyses, it is recommended that ultrapure H2O be used to digest sveite. Geochemical and spectroscopic evidence suggests that sveite from different localities may represent distinct mineral species within a potentially larger group of sveite-type minerals. A revised chemical formula for sveite from Venezuela is K2.73Al7.97(NO3)6O8.27Cl4.1·35H2O, Z = 2, leading to a more general formula of (K3−x□x) Al8(NO3)6O8Cl4·nH2O, Z = 2. The lack of K and Cl in material from other localities that shows similar powder diffraction patterns would require a more general formula.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131867128","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 Platinum-Group Minerals of the River Ko Watershed, Sisim Placer Zone, Eastern Sayans, Russia, and the Differentiation of Multicomponent Melts","authors":"A. Barkov, N. Tolstykh, A. A. Nikiforov, R. Martin","doi":"10.3749/2200020","DOIUrl":"https://doi.org/10.3749/2200020","url":null,"abstract":"\u0000 The textures and chemical compositions (based on the results of over 1000 analyses) of a suite of platinum-group minerals obtained from concentrates collected along the River Ko watershed in the Sisim placer zone, Eastern Sayans, Russia, have been analyzed and described. Detrital grains of Ir–Os alloy, considered to have been derived from the Lysanskiy layered ultrabasic complex, are interpreted to be domains of melt in the interstices of olivine–chromian spinel cumulates. This melt fractionated before crystallization of the alloys; some domains show a core-to-rim enrichment in Ir. The incompatible behavior of lithophile elements, base metals, S, semimetals, and H2O in the melt now represented by the alloy led to the crystallization of a broad range of ore minerals in multicomponent globules of residual melt. In this way, laurite and cuproiridsite developed in the melt and now are in a symplectitic intergrowth with the alloy. A spherule of laurite with a core of anthophyllite-rich amphibole and a mantle of irarsite shows that H2O and lithophile components were also present in the PGE-rich melt. Rhodium-rich pentlandite-related minerals, likely including oberthürite, postdate the crystallization of laurite; these may be Ru-enriched and may contain lamellar grains of torryweiserite or ferrotorryweiserite, both of which may represent exsolution products. These two species, and the related kuvaevite, which locally replace the Rh-rich pentlandite-related minerals, appear to be paragenetically later. The new data provide valuable insight on the evolution of late, multicomponent melts in basic–ultrabasic complexes.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128112252","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":"On the Attributes of Mineral Paragenetic Modes","authors":"R. Hazen, S. Morrison, A. Prabhu, Jason R. Williams, M. Wong, S. Krivovichev, Marko Bermanec","doi":"10.3749/2200022","DOIUrl":"https://doi.org/10.3749/2200022","url":null,"abstract":"\u0000 The mineral kingdom has experienced dramatic increases in diversity and complexity through billions of years of planetary evolution as a consequence of a sequence of physical, chemical, and biological processes. Each new formational environment, or “mineral paragenetic mode,” has its own characteristic attributes, including the stage of mineral evolution and geological age, ranges of T, P, duration of formation events, and other environmental influences on mineral formation. Furthermore, the minerals associated with each paragenetic mode have a wide range of average properties, including hardness, density, and chemical and structural complexity. A survey of attributes of 57 mineral paragenetic modes representing the full range of mineral-forming processes reveals systematic trends, including: (1) minerals documented from older paragenetic processes are systematically harder on average than those from more recent processes; (2) minerals from paragenetic modes formed at lower T (notably <500 K) display greater average structural complexity than those formed at high T (especially >1000 K); and (3) minerals from paragenetic modes that display greater average chemical complexity are systematically less dense than those from modes with lesser average chemical complexity. In addition, minerals formed in anhydrous environments and/or by abiotic processes are, on average, significantly denser and harder than those formed in hydrous environments and/or by biotic processes.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"99 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":"132717974","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":"Characterizing Zinc-Rich Chromite Cores and Uvarovite-Grossular Garnet Mantles from the Pikoo Property, Central Eastern Saskatchewan, Canada","authors":"Song Gao, K.M. Campbell, R. Flemming, K. Armstrong, B. Kupsch","doi":"10.3749/2200052","DOIUrl":"https://doi.org/10.3749/2200052","url":null,"abstract":"Zinc-rich chromite, (Fe,Zn)Cr2O4, is an important repository for chromium (Cr) that has been observed sporadically worldwide. As another source for Cr, green uvarovite garnet, ideally Ca3Cr2(SiO4)3, is the rarest variety among anhydrous garnets. Here, we present a detailed petrographic, mineralogical, and geochemical characterization of 71 uvarovite garnets with zinc-bearing chromite cores recovered from the Pikoo Property (central eastern Saskatchewan), which also hosts recently discovered kimberlites proven to be diamondiferous. In this work, euhedral to anhedral unzoned chromite occurs as cores or irregular inclusions enclosed by uvarovite–grossular mantles. They contain moderate to high Cr (41.63–66.70 wt.% Cr2O3; Cr/(Cr+Al) = 0.64–0.99), Fe2+ (16.71–28.67 wt.% FeO), and Zn (1.64–15.52 wt.% ZnO) contents, accompanied by an appreciable amount of Mn (0.63–2.32 wt.% MnO). The chromite core with the highest Zn content gave the structural formula (Zn0.409Fe2+0.555Mg0.018Mn0.019)Σ1.00(Cr1.174Al0.674Fe3+0.152)Σ2.00O4, which corresponds to Zn-rich chromite with a minor proportion of other endmembers (e.g., hercynite, FeAl2O4). Zinc enrichment in chromite is most likely the result of metasomatic replacement of primary chromite involving the action of Zn-rich fluids. The Zn-rich chromite cores are commonly porous and demonstrate streaking in the 2D diffraction pattern that is attributable to non-uniform strain. The strain measurements suggest the involvement of fluid-present plastic deformation during metasomatic alteration. The garnets are compositionally zoned aggregates and commonly contain inclusions. Chemical formulae indicate that they are mainly members of the uvarovite–grossular series (up to 93% mol.% Uv) enriched in Ca (22.99–35.57 wt.% CaO) and Cr (up to 28.10 wt.% Cr2O3), but consistently depleted in Mg (mean = 0.10 wt.% MgO) and Ti (mean = 0.26 wt.% TiO2). Most garnet aggregates consist of uvarovite and grossular that exhibit a core-rim zoning pattern characterized by an increase in grossular proportion at the expense of the uvarovite component. Morphological characteristics, textural relations, and compositional trends suggest that uvarovite garnet formed through interaction of Zn-rich chromite with grossular. This mineral assemblage is not genetically related to the Pikoo kimberlite and represents an independent evolutionary event. The use of Zn-bearing chromite as a new kimberlite indicator mineral therefore should be carefully evaluated prior to exploration practices.","PeriodicalId":218967,"journal":{"name":"The Canadian Journal of Mineralogy and Petrology","volume":"7 7 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":"132324318","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}