The magnetite ocelli preserved in the Chandrapur area of the Assam-Meghalaya Gneissic Complex, eastern India, display viscous coalescence. The viscous coalescence phenomenon generally occurs below a critical capillary number, which is governed by the size of the coalescing droplets. The smaller the size of the coalescing droplets, the greater the possibility that they will exhibit viscous coalescing. From our results we infer that intrusion of younger pegmatitic magma into the much older polyphase deformed quartzofeldspathic gneiss of Chandrapur initiated localized partial melting in the gneissic rocks surrounding the intrusions. This localized partial melting produced small magma pools or leucocratic neosome, which was followed by intermingling between the in situ melt (leucocratic neosome) and external melt (pegmatite), leading to chaotic mixing between the two magmatic phases. Chaotic mixing produced thin veins or filaments of the pegmatitic magma as a result of stretching and folding dynamics. Gradually, the thin filaments underwent capillary instability to produce discrete viscous swirls or ocelli. The ocelli consist of leucocratic minerals like K-feldspar, plagioclase, and quartz, with crystals of magnetite at the center representing magnetite ocelli. The mineralogical assemblage of the ocelli matches that of the pegmatitic rocks. After their formation, some of the smaller magnetite ocelli underwent very gentle collisions due to the effect of capillary and viscous forces. Such collisions produced pairs, clusters, or linear structures that are now preserved in the migmatites of the study area.
{"title":"Significance of Viscous Coalescence in Migmatites of the Assam-Meghalaya Gneissic Complex, Eastern India","authors":"Bibhuti Gogoi, H. Chauhan","doi":"10.3749/canmin.2000042","DOIUrl":"https://doi.org/10.3749/canmin.2000042","url":null,"abstract":"\u0000 The magnetite ocelli preserved in the Chandrapur area of the Assam-Meghalaya Gneissic Complex, eastern India, display viscous coalescence. The viscous coalescence phenomenon generally occurs below a critical capillary number, which is governed by the size of the coalescing droplets. The smaller the size of the coalescing droplets, the greater the possibility that they will exhibit viscous coalescing. From our results we infer that intrusion of younger pegmatitic magma into the much older polyphase deformed quartzofeldspathic gneiss of Chandrapur initiated localized partial melting in the gneissic rocks surrounding the intrusions. This localized partial melting produced small magma pools or leucocratic neosome, which was followed by intermingling between the in situ melt (leucocratic neosome) and external melt (pegmatite), leading to chaotic mixing between the two magmatic phases. Chaotic mixing produced thin veins or filaments of the pegmatitic magma as a result of stretching and folding dynamics. Gradually, the thin filaments underwent capillary instability to produce discrete viscous swirls or ocelli. The ocelli consist of leucocratic minerals like K-feldspar, plagioclase, and quartz, with crystals of magnetite at the center representing magnetite ocelli. The mineralogical assemblage of the ocelli matches that of the pegmatitic rocks. After their formation, some of the smaller magnetite ocelli underwent very gentle collisions due to the effect of capillary and viscous forces. Such collisions produced pairs, clusters, or linear structures that are now preserved in the migmatites of the study area.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"6 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113943041","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}
L. Pautov, M. A. Mirakov, E. Sokolova, Maxwell C. Day, F. Hawthorne, Manuchekhr A. Schodibekov, V. Y. Karpenko, Saimudasir Makhmadsharif, A. R. Faiziev
Shakhdaraite-(Y), ideally ScYNb2O8, is a new mineral from the Leskhozovskaya miarolitic granitic pegmatite at the Shakhdara River, southwestern Pamir (Tajikistan). Shakhdaraite-(Y) occurs mainly as grains from 10 to 150 μm in size in a near-miarolitic pegmatite complex in association with quartz, albite, pyrochlore-microlite, fersmite, and an unnamed Sc-Nb oxide; only one large, single, well-shaped crystal 200 μm long was found in a small cavity with quartz, albite, bertrandite, pyrochlore, and jarosite. Shakhdaraite-(Y) is black to dark-brown, streak is brown. Luster is vitreous semi-metallic. It is brittle with conchoidal fracture. Mohs hardness is 5. VHN100 = 436 kg/mm2. Dcalc. = 5.602 g/cm3. In reflected light, it is light gray and its reflective capacity is moderate to low. Anisotropy is distinct, without color effects. Pleochroism was not observed. Internal reflections are red-brown. Reflectance values were measured in air with SiC as reference material [λ(nm), Rmax, Rmin]: 470, 14.6, 13.9; 546, 14.0, 13.4; 589, 13.9, 13.3; 650, 13.8, 13.1. Electron probe microanalysis (WDS mode, 7 points) gives (wt.%): Nb2O5 50.70; Ta2O5 4.52; TiO2 0.08; WO3 0.79; SnO2 1.54; CaO 1.01; Sc2O3 11.35; MnO 1.38; FeO 0.01; Y2O3 12.00; Ce2O3 0.21; Pr2O3 0.04; Nd2O3 0.27; Sm2O3 0.32; Eu2O3 0.07; Gd2O3 0.86; Tb2O3 0.22; Dy2O3 2.07; Ho2O3 0.29; Er2O3 1.33; Tm2O3 0.35; Yb2O3 2.80; Lu2O3 0.32; PbO 0.24; ThO2 1.90; UO2 3.30, total 97.97. The empirical formula of shakhdaraite-(Y) based on O = 8 apfu (atoms per formula unit) is (Nb1.91Sc0.83Y0.53Ta0.10Mn0.10Ca0.09 Yb0.07U4+0.06Dy0.06Sn0.05Th0.04Er0.03Gd0.02W6+0.02Pb0.01Ce0.01Nd0.01Sm0.01Tb0.01Ho0.01Tm0.01Lu0.01Ti0.01)Σ4.00O8, Z = 2. The simplified formula is Sc(Y,Yb)Nb2O8, where Yb is the dominant lanthanoid. Shakhdaraite-(Y) is monoclinic, space group P2/c, a 9.930(2), b 5.6625(11), c 5.2108(10) Å, β 92.38(3)°, V 292.7(5) Å3, Z = 2. The crystal structure was solved by direct methods [R1 = 0.0269, 878 unique reflections (F > 4σF)]. There are three cation M sites: [6]M(1) = Nb2apfu, [6]M(2) = Sc apfu, and [8]M(3) = Y apfu, ideally M = ScYNb2apfu. The M(1) and M(2) octahedra each form a brookite chain along c. The Y-dominant [8]M(3A) polyhedra form a brookite-like kinked chain, and each M(3A) polyhedron of one brookite-like chain shares two edges with the two M(3A) polyhedra from the adjacent brookite-like chain, thus forming a [Y2O8]10– layer. In the structure of shakhdaraite-(Y), M(1A) and M(2) brookite chains and a layer of [8]-coordinated M(3A) polyhedra alternate along a. Shakhdaraite-(Y) is isostructural with samarskite-(Y), ideally YFe3+Nb2O8. Shakhdaraite-(Y) [Russian Cyrillic: шахдараит-(Y)] is named after its type locality: the valley of the Shakhdara River in the southwest of the Pamir Mountains.
{"title":"Shakhdaraite-(Y), ScYNb2O8, from the Leskhozovskaya Granitic Pegmatite, the Valley of the Shakhdara River, Southwestern Pamir, Gorno-Badakhshanskii Autonomous Region, Tajikistan: New Mineral Description and Crystal Structure","authors":"L. Pautov, M. A. Mirakov, E. Sokolova, Maxwell C. Day, F. Hawthorne, Manuchekhr A. Schodibekov, V. Y. Karpenko, Saimudasir Makhmadsharif, A. R. Faiziev","doi":"10.3749/canmin.2000122","DOIUrl":"https://doi.org/10.3749/canmin.2000122","url":null,"abstract":"\u0000 Shakhdaraite-(Y), ideally ScYNb2O8, is a new mineral from the Leskhozovskaya miarolitic granitic pegmatite at the Shakhdara River, southwestern Pamir (Tajikistan). Shakhdaraite-(Y) occurs mainly as grains from 10 to 150 μm in size in a near-miarolitic pegmatite complex in association with quartz, albite, pyrochlore-microlite, fersmite, and an unnamed Sc-Nb oxide; only one large, single, well-shaped crystal 200 μm long was found in a small cavity with quartz, albite, bertrandite, pyrochlore, and jarosite. Shakhdaraite-(Y) is black to dark-brown, streak is brown. Luster is vitreous semi-metallic. It is brittle with conchoidal fracture. Mohs hardness is 5. VHN100 = 436 kg/mm2. Dcalc. = 5.602 g/cm3. In reflected light, it is light gray and its reflective capacity is moderate to low. Anisotropy is distinct, without color effects. Pleochroism was not observed. Internal reflections are red-brown. Reflectance values were measured in air with SiC as reference material [λ(nm), Rmax, Rmin]: 470, 14.6, 13.9; 546, 14.0, 13.4; 589, 13.9, 13.3; 650, 13.8, 13.1. Electron probe microanalysis (WDS mode, 7 points) gives (wt.%): Nb2O5 50.70; Ta2O5 4.52; TiO2 0.08; WO3 0.79; SnO2 1.54; CaO 1.01; Sc2O3 11.35; MnO 1.38; FeO 0.01; Y2O3 12.00; Ce2O3 0.21; Pr2O3 0.04; Nd2O3 0.27; Sm2O3 0.32; Eu2O3 0.07; Gd2O3 0.86; Tb2O3 0.22; Dy2O3 2.07; Ho2O3 0.29; Er2O3 1.33; Tm2O3 0.35; Yb2O3 2.80; Lu2O3 0.32; PbO 0.24; ThO2 1.90; UO2 3.30, total 97.97. The empirical formula of shakhdaraite-(Y) based on O = 8 apfu (atoms per formula unit) is (Nb1.91Sc0.83Y0.53Ta0.10Mn0.10Ca0.09 Yb0.07U4+0.06Dy0.06Sn0.05Th0.04Er0.03Gd0.02W6+0.02Pb0.01Ce0.01Nd0.01Sm0.01Tb0.01Ho0.01Tm0.01Lu0.01Ti0.01)Σ4.00O8, Z = 2. The simplified formula is Sc(Y,Yb)Nb2O8, where Yb is the dominant lanthanoid. Shakhdaraite-(Y) is monoclinic, space group P2/c, a 9.930(2), b 5.6625(11), c 5.2108(10) Å, β 92.38(3)°, V 292.7(5) Å3, Z = 2. The crystal structure was solved by direct methods [R1 = 0.0269, 878 unique reflections (F > 4σF)]. There are three cation M sites: [6]M(1) = Nb2apfu, [6]M(2) = Sc apfu, and [8]M(3) = Y apfu, ideally M = ScYNb2apfu. The M(1) and M(2) octahedra each form a brookite chain along c. The Y-dominant [8]M(3A) polyhedra form a brookite-like kinked chain, and each M(3A) polyhedron of one brookite-like chain shares two edges with the two M(3A) polyhedra from the adjacent brookite-like chain, thus forming a [Y2O8]10– layer. In the structure of shakhdaraite-(Y), M(1A) and M(2) brookite chains and a layer of [8]-coordinated M(3A) polyhedra alternate along a. Shakhdaraite-(Y) is isostructural with samarskite-(Y), ideally YFe3+Nb2O8. Shakhdaraite-(Y) [Russian Cyrillic: шахдараит-(Y)] is named after its type locality: the valley of the Shakhdara River in the southwest of the Pamir Mountains.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132777929","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}
Wenqing Huang, P. Ni, Jungui Zhou, Ting Shui, J. Pan, Mingsen Fan, Yu-Long Yang
The Yuanjiang marble-hosted ruby deposit lies in the central segment of the Ailao Shan metamorphic massif of the Ailao Shan-Red River metamorphic belt. The mineralizing fluid and age were characterized by detailed petrography, Raman spectroscopy, microthermometry, and in situ titanite laser ablation-inductively coupled plasma-mass spectrometry dating. Some fluid inclusions in the corundum show an interesting morphology with a diaspore crystal fully separating the whole inclusion into two smaller inclusions. This morphological feature can be explained by morphological ripening and subsequent reactions between the trapped H2O and the host corundum during the cooling of the inclusion. Fluid inclusions in the ruby belong to the system CO2–H2S–COS–S8–H2S2–CH4–AlO(OH) with various daughter minerals, including diaspore, gibbsite, and native sulfur (S8). The observed seven-component fluid inclusion composition can be explained by two steps: (1) original fluid inclusion capture during deposit formation with compositions including CO2, H2S, COS, CH4, S8, and H2S2, and (2) post-entrapment fluid inclusion modification, such as diaspore and gibbsite. The presence of hydrous minerals in fluid inclusions strongly supports the idea that water was once present in the initial fluids. In the Yuanjiang deposit, petrographic evidence shows that titanite formed simultaneously with ruby, and U-Pb dating of titanite allows us to conclude that the ruby mineralization formed at 23.4 ± 0.3 Ma, in other words during the Himalayan orogeny.
{"title":"Fluid Inclusion and Titanite U-Pb Age Constraints on the Yuanjiang Ruby Mineralization in the Ailao Shan-Red River Metamorphic Belt, Southwest China","authors":"Wenqing Huang, P. Ni, Jungui Zhou, Ting Shui, J. Pan, Mingsen Fan, Yu-Long Yang","doi":"10.3749/canmin.2100009","DOIUrl":"https://doi.org/10.3749/canmin.2100009","url":null,"abstract":"\u0000 The Yuanjiang marble-hosted ruby deposit lies in the central segment of the Ailao Shan metamorphic massif of the Ailao Shan-Red River metamorphic belt. The mineralizing fluid and age were characterized by detailed petrography, Raman spectroscopy, microthermometry, and in situ titanite laser ablation-inductively coupled plasma-mass spectrometry dating. Some fluid inclusions in the corundum show an interesting morphology with a diaspore crystal fully separating the whole inclusion into two smaller inclusions. This morphological feature can be explained by morphological ripening and subsequent reactions between the trapped H2O and the host corundum during the cooling of the inclusion. Fluid inclusions in the ruby belong to the system CO2–H2S–COS–S8–H2S2–CH4–AlO(OH) with various daughter minerals, including diaspore, gibbsite, and native sulfur (S8). The observed seven-component fluid inclusion composition can be explained by two steps: (1) original fluid inclusion capture during deposit formation with compositions including CO2, H2S, COS, CH4, S8, and H2S2, and (2) post-entrapment fluid inclusion modification, such as diaspore and gibbsite. The presence of hydrous minerals in fluid inclusions strongly supports the idea that water was once present in the initial fluids.\u0000 In the Yuanjiang deposit, petrographic evidence shows that titanite formed simultaneously with ruby, and U-Pb dating of titanite allows us to conclude that the ruby mineralization formed at 23.4 ± 0.3 Ma, in other words during the Himalayan orogeny.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122519938","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 duopoly of curling stone sources suitable for international competition (Ailsa Craig, Firth of Clyde, Scotland and Trefor, Llŷn Peninsula, North Wales) has led to a long-held paradigm that the rocks from these localities are geologically unique. To evaluate this paradigm, we provide the first comprehensive, detailed analyses of the geological, mineralogical, and textural properties of curling stones, with a focus on three main areas: (1) the collective features of all curling stone lithologies, (2) the differences among the lithologies used for running bands versus striking bands, and (3) the presence of quartz, whose brittleness was previously considered to be undesirable in curling stones. The four curling stone varieties from the two localities (Ailsa Craig Blue Hone, Ailsa Craig Common Green, Blue Trefor, and Red Trefor) were analyzed using petrography, scanning electron microscopy, digital image analysis, powder X-ray diffraction, and normative mineralogy, with the following results: The curling stone varieties that are suitable for international competition can be broadly characterized as fine- to medium-grained, sparsely porphyritic to glomeroporphyritic, weakly to moderately altered, massive to weakly foliated, Phanerozoic granitoids (sensu lato). All four varieties are composed of feldspar (65–80 mod.%, with albite being the dominant component) and quartz (15–25 mod.%), along with mafic and accessory minerals (5–20 mod.%). The Ailsa Craig suite is classified as alkali feldspar quartz syenite, whereas the Trefor suite ranges from quartz monzogabbro (Blue Trefor) to granodiorite-granite (Red Trefor). None are strictly classified as granite.Predominantly equigranular textures are preferred for running bands (Ailsa Craig Blue Hone), whereas seriate to glomeroporphyritic textures are preferred for striking bands (Ailsa Craig Common Green, Blue Trefor, and Red Trefor). These are consistent with observations of used curling stones: pitting adversely affects larger grains in the running band, whereas a wider grain-size distribution correlates with fewer crescent-shaped fractures in the striking band.The appreciable abundance of unstrained, interstitial quartz (15–25 mod.%) in all curling stone samples challenges the longstanding belief of its absence and undesirability in curling stones. The degree of strain in quartz is likely to be a key criterion for selecting prospective curling stone materials. In conclusion, none of the examined characteristics of curling stones are unique in comparison to granitoids worldwide.
适合国际比赛的冰壶石资源的双寡头垄断(苏格兰克莱德湾的艾尔萨克雷格和北威尔士Llŷn半岛的特雷弗)导致了一个长期存在的模式，即来自这些地方的岩石在地质上是独一无二的。为了评估这一模式，我们对冰壶石的地质、矿物学和质地特性进行了首次全面、详细的分析，重点关注三个主要领域:(1)所有冰壶石岩性的共同特征，(2)用于跑带和冲击带的岩性之间的差异，以及(3)石英的存在，石英的脆性以前被认为是冰壶石中不希望出现的。采用岩石学、扫描电镜、数字图像分析、粉末x射线衍射和规范矿物学等方法，对两个地区的4个冰壶石品种(Ailsa Craig Blue Hone、Ailsa Craig Common Green、Blue Trefor和Red Trefor)进行了分析，结果如下:适合参加国际竞争的冰壶石品种大致可分为细粒到中粒、稀斑状到肾小球斑状、弱蚀变到中等蚀变、块状到弱叶理、显生宙花岗岩类(sensu lato)。这四个品种均由长石(65-80莫德%，钠长石为主要成分)和石英(15-25莫德%)以及镁铁质和辅助矿物(5-20莫德%)组成。alsa Craig套属碱长石石英正长岩，而Trefor套属石英二长辉长岩(蓝长辉长岩)至花岗闪长花岗岩(红长辉长岩)。没有一个被严格归类为花岗岩。主要是等边纹理优先用于跑步带(艾尔萨·克雷格蓝带)，而连续到肾小球状纹理优先用于击打带(艾尔萨·克雷格普通绿带、蓝带和红带)。这与对使用过的冰壶石的观察结果一致:在运行带中，点蚀对较大的颗粒产生不利影响，而在冲击带中，较宽的颗粒尺寸分布与较少的新月形裂缝相关。在所有的冰壶石样品中，未拉伸的间隙石英(15 - 25%)的可观丰度挑战了长期以来认为其在冰壶石中不存在和不受欢迎的观点。石英的应变程度可能是选择有前途的冰壶石材料的关键标准。总之，与世界范围内的花岗岩相比，没有任何一种冰壶石的特征是独一无二的。
{"title":"Taking Rocks for Granite: An Integrated Geological, Mineralogical, and Textural Study of Curling Stones Used in International Competition","authors":"Derek. D. V. Leung, A. McDonald","doi":"10.3749/canmin.2100052","DOIUrl":"https://doi.org/10.3749/canmin.2100052","url":null,"abstract":"The duopoly of curling stone sources suitable for international competition (Ailsa Craig, Firth of Clyde, Scotland and Trefor, Llŷn Peninsula, North Wales) has led to a long-held paradigm that the rocks from these localities are geologically unique. To evaluate this paradigm, we provide the first comprehensive, detailed analyses of the geological, mineralogical, and textural properties of curling stones, with a focus on three main areas: (1) the collective features of all curling stone lithologies, (2) the differences among the lithologies used for running bands versus striking bands, and (3) the presence of quartz, whose brittleness was previously considered to be undesirable in curling stones. The four curling stone varieties from the two localities (Ailsa Craig Blue Hone, Ailsa Craig Common Green, Blue Trefor, and Red Trefor) were analyzed using petrography, scanning electron microscopy, digital image analysis, powder X-ray diffraction, and normative mineralogy, with the following results: The curling stone varieties that are suitable for international competition can be broadly characterized as fine- to medium-grained, sparsely porphyritic to glomeroporphyritic, weakly to moderately altered, massive to weakly foliated, Phanerozoic granitoids (sensu lato). All four varieties are composed of feldspar (65–80 mod.%, with albite being the dominant component) and quartz (15–25 mod.%), along with mafic and accessory minerals (5–20 mod.%). The Ailsa Craig suite is classified as alkali feldspar quartz syenite, whereas the Trefor suite ranges from quartz monzogabbro (Blue Trefor) to granodiorite-granite (Red Trefor). None are strictly classified as granite.Predominantly equigranular textures are preferred for running bands (Ailsa Craig Blue Hone), whereas seriate to glomeroporphyritic textures are preferred for striking bands (Ailsa Craig Common Green, Blue Trefor, and Red Trefor). These are consistent with observations of used curling stones: pitting adversely affects larger grains in the running band, whereas a wider grain-size distribution correlates with fewer crescent-shaped fractures in the striking band.The appreciable abundance of unstrained, interstitial quartz (15–25 mod.%) in all curling stone samples challenges the longstanding belief of its absence and undesirability in curling stones. The degree of strain in quartz is likely to be a key criterion for selecting prospective curling stone materials.\u0000 In conclusion, none of the examined characteristics of curling stones are unique in comparison to granitoids worldwide.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127702958","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}
Silica-rich garronite-Na was found together with epistilbite in Miocene basaltic rock from Shiratobana, Hirado Island, Nagasaki Prefecture in Japan for the first time. Garronite-Na occurs as an anhedral crystal that covers the center of a small cavity in altered basaltic rock, whereas the epistilbite covers the inside of the cavity. Electron probe microanalysis of the garronite-Na gives an empirical formula of (Na1.99K0.27)Σ2.26Ca1.61(Fe0.01Al5.31Si10.64)Σ15.96O32·14.3H2O on the basis of O = 32. Its Na/Ca molar ratio varies from 1.00 to 1.53, and its unit-cell parameters (space group I2) calculated from X-ray powder diffraction data are a = 9.983(11) Å, b = 10.089(14) Å, c = 10.070(10) Å, and β = 90.223(3)° with a calculated density of 2.183 g/cm3. Garronite-Na from Hirado Island formed from an alkaline high-silica solution in the later stages of hydrothermal zeolitization associated with volcanic activity.
在日本长崎县平户岛白坂中新世玄武岩中首次发现了富硅榴辉石钠和长辉石。在蚀变玄武岩中，榴辉石钠以一种倒面体晶体的形式出现，覆盖在一个小洞的中心，而榴辉石则覆盖在洞的内部。电子探针显微分析表明，在O = 32的基础上，经验公式为(Na1.99K0.27)Σ2.26Ca1.61(Fe0.01Al5.31Si10.64)Σ15.96O32·14.3H2O。其Na/Ca摩尔比为1.00 ~ 1.53,x射线粉末衍射数据计算得到的单位胞参数(空间群I2)为a = 9.983(11) Å， b = 10.089(14) Å， c = 10.070(10) Å， β = 90.223(3)°，计算得到的密度为2.183 g/cm3。平户岛的榴辉石钠形成于火山活动引起的热液沸石作用后期的碱性高硅溶液。
{"title":"Silica-Rich Garronite-Na From Hirado Island, Nagasaki Prefecture, Japan","authors":"Yutaro Hirahata, S. Kobayashi, H. Nishido","doi":"10.3749/canmin.2000078","DOIUrl":"https://doi.org/10.3749/canmin.2000078","url":null,"abstract":"\u0000 Silica-rich garronite-Na was found together with epistilbite in Miocene basaltic rock from Shiratobana, Hirado Island, Nagasaki Prefecture in Japan for the first time. Garronite-Na occurs as an anhedral crystal that covers the center of a small cavity in altered basaltic rock, whereas the epistilbite covers the inside of the cavity. Electron probe microanalysis of the garronite-Na gives an empirical formula of (Na1.99K0.27)Σ2.26Ca1.61(Fe0.01Al5.31Si10.64)Σ15.96O32·14.3H2O on the basis of O = 32. Its Na/Ca molar ratio varies from 1.00 to 1.53, and its unit-cell parameters (space group I2) calculated from X-ray powder diffraction data are a = 9.983(11) Å, b = 10.089(14) Å, c = 10.070(10) Å, and β = 90.223(3)° with a calculated density of 2.183 g/cm3. Garronite-Na from Hirado Island formed from an alkaline high-silica solution in the later stages of hydrothermal zeolitization associated with volcanic activity.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121035997","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 mudflats of saline lakes are amenable to authigenic clay formation due to the high ionic strength of the solutions driven by evaporative concentration and due to the fluctuating wet/dry cycles. However, the mudflats of saline lakes have received relatively little study given the challenges in sampling unstable sediments coupled with post-depositional alterations that make direct relationships to the climate difficult. In an effort to gain a better understanding of the authigenic phyllosilicates present, the mudflats of 17 sulfate-rich saline lake basins across southern Saskatchewan were sampled. The <2 μm fraction was separated from the sediments and analyzed utilizing X-ray diffraction (XRD), scanning electron microscopy, bulk chemical analysis via digestion and inductively coupled optical emission spectroscopy, and visible and near-infrared reflectance spectroscopy. The mudflat sediments were characterized as highly variable and were classified based on particle size into sediment classes A (clay-rich), B (unsorted till), and C (sand). Despite the high variability in sorting and thickness of the sedimentary layers, the phyllosilicates were distinctive within each class independent of the basin. Phyllosilicates in sediment class A were characterized by well-crystalline dioctahedral (Al) clays similar to the surrounding soils with smectite > illite > kaolinite > chlorite. Phyllosilicates from sediment class B displayed highly variable characteristics ranging between classes A and C. Clays from sediment class C were dominated by illite with decreasing proportions of smectite, kaolinite, and chlorite. The illite in the sand lenses was poorly formed, with broad reflections in the XRD patterns indicative of small crystallite size or high disorder, which is consistent with an authigenic nature. The clays in class C were rich in iron (Fe) and magnesium (Mg) and displayed lath-like morphologies common with authigenic illite forming in sandy porous sediments. The sand lenses of mudflats represent viable targets for finding authigenic clay minerals in detrital-rich sediments to use in understanding past climates on Earth and Mars.
{"title":"Authigenic Phyllosilicates in Sand Layers from the Mudflats of Saline Lakes in the Northern Great Prairies, Saskatchewan","authors":"J. Bentz, R. C. Peterson","doi":"10.3749/canmin.1900065","DOIUrl":"https://doi.org/10.3749/canmin.1900065","url":null,"abstract":"\u0000 The mudflats of saline lakes are amenable to authigenic clay formation due to the high ionic strength of the solutions driven by evaporative concentration and due to the fluctuating wet/dry cycles. However, the mudflats of saline lakes have received relatively little study given the challenges in sampling unstable sediments coupled with post-depositional alterations that make direct relationships to the climate difficult. In an effort to gain a better understanding of the authigenic phyllosilicates present, the mudflats of 17 sulfate-rich saline lake basins across southern Saskatchewan were sampled. The <2 μm fraction was separated from the sediments and analyzed utilizing X-ray diffraction (XRD), scanning electron microscopy, bulk chemical analysis via digestion and inductively coupled optical emission spectroscopy, and visible and near-infrared reflectance spectroscopy. The mudflat sediments were characterized as highly variable and were classified based on particle size into sediment classes A (clay-rich), B (unsorted till), and C (sand). Despite the high variability in sorting and thickness of the sedimentary layers, the phyllosilicates were distinctive within each class independent of the basin. Phyllosilicates in sediment class A were characterized by well-crystalline dioctahedral (Al) clays similar to the surrounding soils with smectite > illite > kaolinite > chlorite. Phyllosilicates from sediment class B displayed highly variable characteristics ranging between classes A and C. Clays from sediment class C were dominated by illite with decreasing proportions of smectite, kaolinite, and chlorite. The illite in the sand lenses was poorly formed, with broad reflections in the XRD patterns indicative of small crystallite size or high disorder, which is consistent with an authigenic nature. The clays in class C were rich in iron (Fe) and magnesium (Mg) and displayed lath-like morphologies common with authigenic illite forming in sandy porous sediments. The sand lenses of mudflats represent viable targets for finding authigenic clay minerals in detrital-rich sediments to use in understanding past climates on Earth and Mars.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"674 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133322412","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. Akizawa, A. Yamaguchi, K. Tani, A. Ishikawa, Ryo Fujita, S. Choi
The continental margin is of profound importance as it records continental growth by accretion of orogenic magmas and following continental rifting. A high degree of mantle melting due to hydrous fluid input is expected to simultaneously stimulate continental growth and lower the intrinsic density of the mantle than more fertile mantle, which in turn isolates the continental lithosphere from the convective mantle. The mantle peridotites from Gibbs Island (South Shetland Islands) and Bruce Bank in the Drake Passage provide us an insight into the tectonic history in the circum-Antarctic region. To elucidate the continental growth of Antarctica, we present geochemical data of eight dunites from Gibbs Island and one dunite from Bruce Bank, including Re–Os isotope and highly siderophile element compositions. The dunites are severely affected by serpentinization as evidenced by antigorite + brucite or lizardite (loss on ignition = LOI ranging from 3 to 34 wt.%) but contain primary euhedral to subhedral chromites with or without spherical inclusions. The chromites rarely form lens-shaped aggregates. A dunite from Gibbs Island contains fresh olivine grains filling a fracture in the chromite with low LOI (3 wt.%), indicating a deserpentinization origin from a precursor serpentinized dunite. The dunites show highly depleted bulk-rock major element compositions (Mg/Si = 1.4–1.6 and Al/Si = 0.004–0.01 for Gibbs Island dunites, Mg/Si = 0.66 and Al/Si = 0.008 for Bruce Bank dunite), overlapping a compositional field defined by forearc peridotites. The positive correlation in Re/Ir–LOI space corroborates Re input during the later serpentinization process. The 187Os/188Os ratios of the dunites range from 0.11907 to 0.14493. Phanerozoic Re-depletion (melt depletion) ages of ca. 535–129 Ma are recorded in the Gibbs Island dunites, except for one with a Mesoproterozoic Re-depletion age of ca. 1.2 Ga. Since there exists serpentinization-related perturbation of Re, the ages provide minimum time estimates for melt depletion events. The early Paleozoic melt depletion is inferred to have occurred at a very early stage of Antarctic Peninsula formation in response to plate convergence along the margin of Gondwana, whereas the Mesoproterozoic Re-depletion age reflects convecting mantle heterogeneity unrelated to any nearby crust-forming events. The petrographic characteristics of the chromites and highly depleted nature of the dunites are attributed to melt–peridotite reaction in a subduction zone setting. A feasible interpretation for the dunite formation is that the mantle had experienced two stages of melting with the final stage occurring along the Gondwana continental margin in the subduction zone setting. Resultant highly refractory lithospheric mantle was later displaced and dispersed during the Gondwana breakup. Widespread existence of the dunite may be attributed to multi-stage melt depletion along the continental margin.
{"title":"Highly refractory dunite formation at Gibbs Island and Bruce Bank, and its role in the evolution of the circum-Antarctic continent","authors":"N. Akizawa, A. Yamaguchi, K. Tani, A. Ishikawa, Ryo Fujita, S. Choi","doi":"10.3749/canmin.2100030","DOIUrl":"https://doi.org/10.3749/canmin.2100030","url":null,"abstract":"\u0000 The continental margin is of profound importance as it records continental growth by accretion of orogenic magmas and following continental rifting. A high degree of mantle melting due to hydrous fluid input is expected to simultaneously stimulate continental growth and lower the intrinsic density of the mantle than more fertile mantle, which in turn isolates the continental lithosphere from the convective mantle. The mantle peridotites from Gibbs Island (South Shetland Islands) and Bruce Bank in the Drake Passage provide us an insight into the tectonic history in the circum-Antarctic region. To elucidate the continental growth of Antarctica, we present geochemical data of eight dunites from Gibbs Island and one dunite from Bruce Bank, including Re–Os isotope and highly siderophile element compositions.\u0000 The dunites are severely affected by serpentinization as evidenced by antigorite + brucite or lizardite (loss on ignition = LOI ranging from 3 to 34 wt.%) but contain primary euhedral to subhedral chromites with or without spherical inclusions. The chromites rarely form lens-shaped aggregates. A dunite from Gibbs Island contains fresh olivine grains filling a fracture in the chromite with low LOI (3 wt.%), indicating a deserpentinization origin from a precursor serpentinized dunite. The dunites show highly depleted bulk-rock major element compositions (Mg/Si = 1.4–1.6 and Al/Si = 0.004–0.01 for Gibbs Island dunites, Mg/Si = 0.66 and Al/Si = 0.008 for Bruce Bank dunite), overlapping a compositional field defined by forearc peridotites. The positive correlation in Re/Ir–LOI space corroborates Re input during the later serpentinization process. The 187Os/188Os ratios of the dunites range from 0.11907 to 0.14493.\u0000 Phanerozoic Re-depletion (melt depletion) ages of ca. 535–129 Ma are recorded in the Gibbs Island dunites, except for one with a Mesoproterozoic Re-depletion age of ca. 1.2 Ga. Since there exists serpentinization-related perturbation of Re, the ages provide minimum time estimates for melt depletion events. The early Paleozoic melt depletion is inferred to have occurred at a very early stage of Antarctic Peninsula formation in response to plate convergence along the margin of Gondwana, whereas the Mesoproterozoic Re-depletion age reflects convecting mantle heterogeneity unrelated to any nearby crust-forming events. The petrographic characteristics of the chromites and highly depleted nature of the dunites are attributed to melt–peridotite reaction in a subduction zone setting. A feasible interpretation for the dunite formation is that the mantle had experienced two stages of melting with the final stage occurring along the Gondwana continental margin in the subduction zone setting. Resultant highly refractory lithospheric mantle was later displaced and dispersed during the Gondwana breakup. Widespread existence of the dunite may be attributed to multi-stage melt depletion along the continental margin.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129878249","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}
A. Barkov, A. A. Nikiforov, V. Korolyuk, L. P. Barkova, R. Martin
The maximum value of Mg# [= 100Mg/(Mg + Fe2+ + Mn)] in chromium-bearing spinel-group minerals (Chr) in the Ultrabasic Core Zone (UCZ) of the Lyavaraka orthopyroxenite – harzburgite – dunite complex of the Serpentinite Belt in the Kola Peninsula is 54.5–67.5. Such highly magnesian compositions of spinel are associated with notable enrichments of ferric iron (Fe3+# 58–63). There are two generations of accessory Chr in the UCZ unit. The first generation occurs as inclusions in olivine that is not unusually magnesian (Mg# 90.3), and the second is closely associated with serpentine. The compositional series of Chr at Lyavaraka attains more aluminous compositions than was observed in nearby intrusive bodies. The anomalously high level of Mg in Chr, also manifest in ilmenite, is mainly a result of the high intrinsic fugacity of oxygen attained locally in the melt. A progressive buildup in H2O and increase in fO2 likely resulted from efficient vesiculation and selective loss of H2 from the Al-undepleted komatiitic magma crystallizing in a shallow setting. The chromian spinel forming in such a modified magma is virtually unzoned in Mn, and a minor quantity of Mn is also present in olivine and orthopyroxene. In contrast, zinc is strongly partitioned in the core of Chr, as it is relatively incompatible in the coexisting olivine and orthopyroxene at that stage. Zinc efficiently partitioned into the H2O-enriched melt, which crystallized as the pegmatitic orthopyroxenite near the contacts at Lyavaraka. A high potential of oxidation appears to be characteristic of all orthopyroxenite – harzburgite – dunite suites of the Serpentinite Belt formed from a primitive melt of komatiitic composition.
{"title":"The chromian spinels of the Lyavaraka ultrabasic complex, Serpentinite Belt, Kola Peninsula, Russia: Patterns of zoning, hypermagnesian compositions, and early oxidation","authors":"A. Barkov, A. A. Nikiforov, V. Korolyuk, L. P. Barkova, R. Martin","doi":"10.3749/canmin.2100019","DOIUrl":"https://doi.org/10.3749/canmin.2100019","url":null,"abstract":"\u0000 The maximum value of Mg# [= 100Mg/(Mg + Fe2+ + Mn)] in chromium-bearing spinel-group minerals (Chr) in the Ultrabasic Core Zone (UCZ) of the Lyavaraka orthopyroxenite – harzburgite – dunite complex of the Serpentinite Belt in the Kola Peninsula is 54.5–67.5. Such highly magnesian compositions of spinel are associated with notable enrichments of ferric iron (Fe3+# 58–63). There are two generations of accessory Chr in the UCZ unit. The first generation occurs as inclusions in olivine that is not unusually magnesian (Mg# 90.3), and the second is closely associated with serpentine. The compositional series of Chr at Lyavaraka attains more aluminous compositions than was observed in nearby intrusive bodies. The anomalously high level of Mg in Chr, also manifest in ilmenite, is mainly a result of the high intrinsic fugacity of oxygen attained locally in the melt. A progressive buildup in H2O and increase in fO2 likely resulted from efficient vesiculation and selective loss of H2 from the Al-undepleted komatiitic magma crystallizing in a shallow setting. The chromian spinel forming in such a modified magma is virtually unzoned in Mn, and a minor quantity of Mn is also present in olivine and orthopyroxene. In contrast, zinc is strongly partitioned in the core of Chr, as it is relatively incompatible in the coexisting olivine and orthopyroxene at that stage. Zinc efficiently partitioned into the H2O-enriched melt, which crystallized as the pegmatitic orthopyroxenite near the contacts at Lyavaraka. A high potential of oxidation appears to be characteristic of all orthopyroxenite – harzburgite – dunite suites of the Serpentinite Belt formed from a primitive melt of komatiitic composition.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121539680","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}
A. McDonald, I. Kjarsgaard, L. Cabri, K. C. Ross, D. Ames, L. Bindi, D. Good
Oberthürite, Rh3(Ni,Fe)32S32, and torryweiserite, Rh5Ni10S16, are two new platinum-group minerals discovered in a heavy-mineral concentrate from the Marathon deposit, Coldwell Complex, Ontario, Canada. Oberthürite is cubic, space group , with a 10.066(5) Å, V 1019.9(1) Å3, Z = 1. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 3.06(100)(311), 2.929(18)(222), 1.9518(39)(115,333), 1.7921(74)(440), 1.3184(15)(137,355) and 1.0312(30)(448). Associated minerals include: vysotskite, Au-Ag alloy, isoferroplatinum, Ge-bearing keithconnite, majakite, coldwellite, ferhodsite-series minerals (cuprorhodsite–ferhodsite), kotulskite, and mertieite-II, and the base-metal sulfides, chalcopyrite, bornite, millerite, and Rh-bearing pentlandite. Grains of oberthürite are up to 100 × 100 μm and the mineral commonly develops in larger composites with coldwellite, isoferroplatinum, zvyagintsevite, Rh-bearing pentlandite, and torryweiserite. The mineral is creamy brown compared to coldwellite and bornite, white when compared to torryweiserite, and gray when compared chalcopyrite and millerite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 36.2 (470 nm), 39.1 (546 nm), 40.5 (589 nm), and 42.3 (650 nm). The calculated density is 5.195 g/cm3, determined using the empirical formula and the unit-cell parameter from the refined crystal structure. The average result (n = 11) using energy-dispersive spectrometry is: Rh 10.22, Ni 38.83, Fe 16.54, Co 4.12, Cu 0.23 S 32.36, total 100.30 wt.%, which corresponds to (Rh2Ni0.67Fe0.33)Σ3.00(Ni19.30Fe9.09Co2.22Rh1.16Cu0.12)∑31.89S32.11, based on 67 apfu and crystallochemical considerations, or ideally, Rh3Ni32S32. The name is for Dr. Thomas Oberthür, a well-known researcher on alluvial platinum-group minerals, notably those found in deposits related to the Great Dyke (Zimbabwe) and the Bushveld complex (Republic of South Africa). Torryweiserite is rhombohedral, space group , with a 7.060(1), c 34.271(7) Å, V 1479.3(1), Z = 3. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 3.080(33)(021), 3.029(58)(116,0110), 1.9329(30)(036,1115,1210), 1.7797(100)(220,0216), 1.2512(49)(0416), and 1.0226(35)(060,2416,0232). Associated minerals are the same as for oberthürite. The mineral is slightly bluish compared to oberthürite, gray when compared to chalcopyrite, zvyagintsevite, and keithconnite, and pale creamy brown when compared to bornite and coldwellite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 34.7 (470 nm), 34.4 (546 nm), 33.8 (589 nm), and 33.8 (650 nm). The calculated density is 5.555 g/cm3, determined using the empirical formula and the unit-cell parameters from the
oberth rite (Rh3(Ni,Fe)32S32)和torryweiserite (Rh5Ni10S16)是在加拿大安大略省Coldwell Complex Marathon矿床的重矿物精矿中发现的两种新铂族矿物。oberth是立方的，空间群，具有一个10.066(5)Å， v1019.9 (1) Å3, Z = 1。在Å (I)(hkl)中，x射线粉末衍射图的6条最强谱线为:3.06(100)(311)、2.929(18)(222)、1.9518(39)(115,333)、1.7921(74)(440)、1.3184(15)(137,355)和1.0312(30)(448)。伴生矿物包括:钒钙钛矿、金银合金、异铁铂、含锗钾辉石、马辉石、铁长石、铁长石系列矿物(铜长石-铁长石)、钾长石、银长石、镍长石等，以及贱金属硫化物、黄铜矿、斑铜矿、针长石、含铑镍长石等。oberth的晶粒可达100 × 100 μm，矿物通常与colcolite、异铁铂、zvyaginsevite、含铑镍黄铁矿和torryweiserite形成较大的复合材料。与coldwell和bornite相比，这种矿物是奶油棕色的，与torryweiserite相比是白色的，与黄铜矿和millerite相比是灰色的。无法测量条纹或显微硬度。这种矿物没有明显的多色性、双反射性或各向异性。标准COM波长在空气中的反射率值(%)分别为:36.2 (470 nm)、39.1 (546 nm)、40.5 (589 nm)和42.3 (650 nm)。计算密度为5.195 g/cm3，由经验公式和精细化晶体结构的单胞参数确定。能量色散光谱平均结果(n = 11)为:Rh 10.22, Ni 38.83, Fe 16.54, Co 4.12, Cu 0.23 S 32.36，总wt.%为100.30，对应于(Rh2Ni0.67Fe0.33)Σ3.00(Ni19.30Fe9.09Co2.22Rh1.16Cu0.12)∑31.89S32.11，基于67 apfu和晶体化学考虑，理想情况下为Rh3Ni32S32。这个名字是Thomas oberthr博士的名字，他是一位著名的冲积铂族矿物研究人员，特别是在与Great Dyke(津巴布韦)和Bushveld复合体(南非共和国)相关的矿床中发现的那些矿物。Torryweiserite为菱形体，空间群，a = 7.060(1)， c = 34.271(7) Å， V = 1479.3(1)， Z = 3。在Å (I)(hkl)中，x射线粉末衍射图的6条最强谱线为:3.080(33)(021)、3.029(58)(116,0110)、1.9329(30)(036,1115,1210)、1.7797(100)(220,0216)、1.2512(49)(0416)和1.0226(35)(060,2416,0232)。伴生矿物与oberth相同。这种矿物与黄铜矿、黄铜矿、黄铁矿相比略呈蓝色，与黄铜矿、黄铁矿和黄铁矿相比呈灰色，与斑铜矿和coldwell矿相比呈淡奶油棕色。无法测量条纹或显微硬度。这种矿物没有明显的多色性、双反射性或各向异性。标准COM波长在空气中的反射率值(%)分别为:34.7 (470 nm)、34.4 (546 nm)、33.8 (589 nm)和33.8 (650 nm)。利用经验公式和精细化晶体结构的单胞参数，计算得到密度为5.555 g/cm3。波长色散光谱平均结果(n = 10)为:Rh 28.02, Pt 2.56, Ir 1.98, Ru 0.10, Os 0.10, Ni 17.09, Fe 9.76, Cu 7.38, Co 1.77 S 30.97，总计99.73 wt.%，基于31 apfu和晶体化学考虑，对应于(rh4.50 pt0.22 ir0.17 ni0.08 ru0.020 os0.01)∑5.00(Ni4.73Fe2.89Cu1.92Co0.50)Σ10.04S15.96，理想情况下为Rh5Ni10S16。这个名字是为了纪念Thorolf (' tory ') W. Weiser博士，他是一位著名的铂族矿物研究人员，特别是在与Great Dyke(津巴布韦)和Bushveld complex(南非共和国)相关的矿床中发现的铂族矿物。这两种矿物的晶体结构都与镍黄铁矿及其相关矿物相似:oberth rite有两个金属位点，相对于镍黄铁矿中的金属位点是分裂的，torryweiserite具有层状结构，与沿镍黄铁矿发育的结构相似，但又不同[111]。oberthrite和torryweiserite被认为是在~ 500°C的中等fS2条件下，通过在冷却过程中前驱体含铑镍黄铁矿中的Rh-Ni-S纳米颗粒的排序而形成的。伴生的含Rh矿物共生顺序为:含Rh镍黄铁矿→奥氏辉石→托利辉石→铁长石系列矿物，随时间的推移Rh浓度相对增加。最后一步是由Fe2+→Fe3+的氧化和随后的Fe3+的优先去除所驱动的菱铁矿系列矿物的形成，类似于镍黄铁矿转化为紫黄铁矿的过程。对Rh的赋存和分布、已知具有Rh优势化学性质的矿物、Rh3+和Rh2+的潜在存在以及影响Rh在矿物中容纳的晶体化学因素进行了总结评述。
{"title":"Oberthürite, Rh3(Ni,Fe)32S32 and torryweiserite, Rh5Ni10S16, two new platinum-group minerals from the Marathon deposit, Coldwell Complex, Ontario, Canada: Descriptions, crystal-chemical considerations, and comments on the geochemistry of rhodium","authors":"A. McDonald, I. Kjarsgaard, L. Cabri, K. C. Ross, D. Ames, L. Bindi, D. Good","doi":"10.3749/canmin.2100014","DOIUrl":"https://doi.org/10.3749/canmin.2100014","url":null,"abstract":"\u0000 Oberthürite, Rh3(Ni,Fe)32S32, and torryweiserite, Rh5Ni10S16, are two new platinum-group minerals discovered in a heavy-mineral concentrate from the Marathon deposit, Coldwell Complex, Ontario, Canada. Oberthürite is cubic, space group , with a 10.066(5) Å, V 1019.9(1) Å3, Z = 1. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 3.06(100)(311), 2.929(18)(222), 1.9518(39)(115,333), 1.7921(74)(440), 1.3184(15)(137,355) and 1.0312(30)(448). Associated minerals include: vysotskite, Au-Ag alloy, isoferroplatinum, Ge-bearing keithconnite, majakite, coldwellite, ferhodsite-series minerals (cuprorhodsite–ferhodsite), kotulskite, and mertieite-II, and the base-metal sulfides, chalcopyrite, bornite, millerite, and Rh-bearing pentlandite. Grains of oberthürite are up to 100 × 100 μm and the mineral commonly develops in larger composites with coldwellite, isoferroplatinum, zvyagintsevite, Rh-bearing pentlandite, and torryweiserite. The mineral is creamy brown compared to coldwellite and bornite, white when compared to torryweiserite, and gray when compared chalcopyrite and millerite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 36.2 (470 nm), 39.1 (546 nm), 40.5 (589 nm), and 42.3 (650 nm). The calculated density is 5.195 g/cm3, determined using the empirical formula and the unit-cell parameter from the refined crystal structure. The average result (n = 11) using energy-dispersive spectrometry is: Rh 10.22, Ni 38.83, Fe 16.54, Co 4.12, Cu 0.23 S 32.36, total 100.30 wt.%, which corresponds to (Rh2Ni0.67Fe0.33)Σ3.00(Ni19.30Fe9.09Co2.22Rh1.16Cu0.12)∑31.89S32.11, based on 67 apfu and crystallochemical considerations, or ideally, Rh3Ni32S32. The name is for Dr. Thomas Oberthür, a well-known researcher on alluvial platinum-group minerals, notably those found in deposits related to the Great Dyke (Zimbabwe) and the Bushveld complex (Republic of South Africa).\u0000 Torryweiserite is rhombohedral, space group , with a 7.060(1), c 34.271(7) Å, V 1479.3(1), Z = 3. The six strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 3.080(33)(021), 3.029(58)(116,0110), 1.9329(30)(036,1115,1210), 1.7797(100)(220,0216), 1.2512(49)(0416), and 1.0226(35)(060,2416,0232). Associated minerals are the same as for oberthürite. The mineral is slightly bluish compared to oberthürite, gray when compared to chalcopyrite, zvyagintsevite, and keithconnite, and pale creamy brown when compared to bornite and coldwellite. No streak or microhardness could be measured. The mineral shows no discernible pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 34.7 (470 nm), 34.4 (546 nm), 33.8 (589 nm), and 33.8 (650 nm). The calculated density is 5.555 g/cm3, determined using the empirical formula and the unit-cell parameters from the ","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126194534","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}
Naldrettite (Pd2Sb) is a PGM discovered in 2005 in Mesamax Northwest deposit, Ungava region, Quebec, Canada. Before and after its approval, PGM with the naldrettite type composition have been reported from a number of localities worldwide. Most frequently, naldrettite has been documented in magmatic Ni–Cu–PGE sulfide deposits, hydrothermal veins in porphyry coppers of the Cu–Au type, and PGE deposits of Alaskan-type zoned intrusions. Naldrettite has been occasionally found in metasomatic Sb–As sulfide ore, metamorphic Ni–oxide ore, and podiform chromitites, although these occurrences have not been fully constrained by solid chemical analyses or paragenetic reconstruction. In this paper we report the first discovery of naldrettite in Brazil. This new finding occurs in a chromitite sample collected in the Luanga Complex, a Neo-archaean layered intrusion in the Carajás Mineral Province. Paragenetic association with alteration assemblages (ferrianchromite, Fe-hydroxides, chlorite) suggests precipitation of naldrettite from metamorphic hydrothermal fluids. The average composition of the Luanga sample (Pd1.76Pt0.24)Σ2.00(Sb0.57As0.43)Σ1.00 shows major substitution of Pt and As. These elements were derived from the breakdown of primary sperrylite, and were incorporated in naldrettite deposited by percolating fluids, at temperature below 350 °C (maximum temperature registered by the crystallization of associated chlorite). An overview of documented occurrences indicates that naldrettite can form in a variety of igneous rocks (ultramafic, mafic, felsic), even involving minimal concentrations of Pd and Sb. Crystallization of naldrettite generally occurs in the post-magmatic stage due to the activity of hydrothermal fluids containing volatile species Sb, As, Bi, Te, and Pd due to its higher mobility compared with the other PGE. A major issue concerns the origin of fluids that can be: (1) “residual”, after the main crystallization of the host magma, (2) “metamorphic”, during regional metamorphism or serpentinization, and (3) “metasomatic”, emanating from an exotic magma intrusion. The combination of two or three of these factors is the most likely process observed in the naldrettite-bearing complexes.
{"title":"Naldrettite (Pd2Sb): A new find in Brazil and comparison with worldwide occurrences","authors":"G. Garuti, F. Zaccarini","doi":"10.3749/canmin.2000121","DOIUrl":"https://doi.org/10.3749/canmin.2000121","url":null,"abstract":"\u0000 Naldrettite (Pd2Sb) is a PGM discovered in 2005 in Mesamax Northwest deposit, Ungava region, Quebec, Canada. Before and after its approval, PGM with the naldrettite type composition have been reported from a number of localities worldwide. Most frequently, naldrettite has been documented in magmatic Ni–Cu–PGE sulfide deposits, hydrothermal veins in porphyry coppers of the Cu–Au type, and PGE deposits of Alaskan-type zoned intrusions. Naldrettite has been occasionally found in metasomatic Sb–As sulfide ore, metamorphic Ni–oxide ore, and podiform chromitites, although these occurrences have not been fully constrained by solid chemical analyses or paragenetic reconstruction. In this paper we report the first discovery of naldrettite in Brazil. This new finding occurs in a chromitite sample collected in the Luanga Complex, a Neo-archaean layered intrusion in the Carajás Mineral Province. Paragenetic association with alteration assemblages (ferrianchromite, Fe-hydroxides, chlorite) suggests precipitation of naldrettite from metamorphic hydrothermal fluids. The average composition of the Luanga sample (Pd1.76Pt0.24)Σ2.00(Sb0.57As0.43)Σ1.00 shows major substitution of Pt and As. These elements were derived from the breakdown of primary sperrylite, and were incorporated in naldrettite deposited by percolating fluids, at temperature below 350 °C (maximum temperature registered by the crystallization of associated chlorite). An overview of documented occurrences indicates that naldrettite can form in a variety of igneous rocks (ultramafic, mafic, felsic), even involving minimal concentrations of Pd and Sb. Crystallization of naldrettite generally occurs in the post-magmatic stage due to the activity of hydrothermal fluids containing volatile species Sb, As, Bi, Te, and Pd due to its higher mobility compared with the other PGE. A major issue concerns the origin of fluids that can be: (1) “residual”, after the main crystallization of the host magma, (2) “metamorphic”, during regional metamorphism or serpentinization, and (3) “metasomatic”, emanating from an exotic magma intrusion. The combination of two or three of these factors is the most likely process observed in the naldrettite-bearing complexes.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128260397","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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