Bird River Research Articles

There Is No Cherokee Syllabary at Red Bird River Shelter (15CY52): Reply to Tankersley and Weeks

Despite new arguments by Tankersley and Weeks that we misinterpreted petroglyph engravings and ignored site formation processes at the Red Bird River Shelter in Kentucky (15CY52), we remain convinced that there is no evidence for Cherokee Syllabary writing at the site. The petroglyphs are clearly not symbols present in any version of the Cherokee Syllabary. There is no empirical evidence for any site formation processes that have altered the shelter or its petroglyphs in the ways they suggest. There is still no evidence that Sequoyah ever spent any time in the vicinity of Red Bird River Shelter.

Red Bird and Sequoyah: A Reply to Simek et al.

Red Bird was a Cherokee murdered at the Red Bird River Petroglyph site (15Cy51) and buried at the Red Bird River Rockshelter (15Cy52) during the late eighteenth century, where he left an important record of traditional petroglyphs. His legacy is key to understanding the origins of Sequoyah's Cherokee Syllabary and its relationship to rock art. Personal testimonies of Red Bird's descendants are supported by primary documents and archaeological evidence, including the letters of Sequoyah's maternal uncle, John Watts, and prototypes of Cherokee Syllabary characters engraved at 15Cy52 in 1808, when members of Sequoyah's matrilineal family resided nearby.

Evidence for Neoarchean hydrous arc magmatism, the anorthosite-bearing Mayville Intrusion, western Superior Province, Canada

The Neoarchean (2742.8 ± 0.8 Ma) megacrystic anorthosite-bearing Mayville layered intrusion of the Bird River greenstone belt in the Superior Province of Canada is well preserved and well exposed. Given its good preservation, we studied the Mayville Intrusion through a combination of extensive field and petrographic observations, mineral chemistry, and whole-rock major and trace element and Sm-Nd and U-Th-Pb isotopic analyses to unravel its petrogenesis and geodynamic setting, and determine whether its amphibole is of igneous origin and indicative of hydrous magmatism. The Mayville Intrusion intrudes pillow basalts and gabbros of the Mayville Assemblage, which was erupted onto and emplaced into the Mesoarchean phase of the Maskwa Lake tonalite-trondhjemite-granodiorite (TTG) Batholith. Some of the anorthosites and leucogabbros of the Mayville Intrusion have undergone extensive shearing and hydrothermal alteration and had their Sm-Nd and U-Th-Pb isotope systems reset. Despite metamorphism and deformation affecting the Mayville Intrusion, it has largely retained its primary igneous minerals and textures, and trace element and Sm-Nd and Pb isotope compositions. Abundant interstitial magmatic amphibole oikocrysts in the anorthosites and leucogabbros exhibit whole-grain optical continuity and well-preserved igneous grain boundaries with magmatic plagioclase, indicating that the Mayville Intrusion crystallized from a hydrous magma.The Mayville Intrusion has variably positive εNd (2743 Ma) values (+0.7 to +3.9) that are indicative of its derivation from a depleted mantle source. The anorthosites and leucogabbros of the Mayville Intrusion crystallized from a hydrous Ca- and Al-rich tholeiitic parental magma that fractionated from a hydrous primitive arc tholeiitic parental magma. These lithologies were derived by partial melting of a depleted, shallow hydrous sub-arc mantle wedge source. The parental magmas to the gabbros, leucogabbros and anorthosites of the Anorthosite to Leucogabbro Zone subsequently experienced minor contamination by Mesoarchean TTGs (Maskwa Lake TTG Batholith). The field relationships and trace element geochemistry of the Mayville Intrusion and its proximity to the continental arc Maskwa Lake TTG Batholith indicate that it formed in a Chilean-style continental back-arc geodynamic setting. The findings of this study demonstrate that hydrous arc magmatism and modern-style plate tectonic processes have been operating since at least the Late Archean.

A back-arc origin for the Neoarchean megacrystic anorthosite-bearing Bird River Sill and the associated greenstone belt, Bird River subprovince, Western Superior Province, Manitoba, Canada

This study presents extensive new field, petrographic, and whole-rock major and trace element and Sm–Nd and Pb isotope data for the Neoarchean megacrystic anorthosite-bearing Bird River Sill, spatially associated Neoarchean supracrustal rocks of the Bird River greenstone belt, and the Mesoarchean Maskwa Lake TTG Batholith I, Manitoba, Canada. Field observations indicate that the 2743 Ma Bird River Sill was emplaced into the Northern Lamprey Falls Formation in an oceanic setting and subsequently intruded by the ca. 2725 Ma Maskwa Lake Batholith II. The Northern Lamprey Falls Formation is in fault contact with the overlying Peterson Creek Formation, which in turn is unconformably overlain by the Bird River Formation. The peridotites of the Bird River Sill were subjected to intense alteration and ductile shearing, resulting in the redistribution of many major and trace elements and resetting of their Sm–Nd and U–Th–Pb isotopic systems. The gabbro, leucogabbro, and anorthosite units of the sill largely retain their primary igneous textures and minerals, REE and HFSE compositions, and Sm–Nd and Pb isotope signatures. These geochemical and petrographic data indicate that these units of the Bird River Sill crystallised from a hydrous, Ca- and Al-rich tholeiitic magma that fractionated from a hydrous primitive arc tholeiitic parental magma. The major and trace element geochemistry and initial eNd values of the Bird River Sill (+ 0.53 to + 4.72) and the Northern Lamprey Falls Formation (+ 1.40 to + 2.66) of the Bird River greenstone belt crystallised from parental magma batches that were derived by partial melting of variably-depleted mantle sources. High-magnesian andesites from the Bird River Formation formed by partial melting of subducting oceanic crust and/or slab sediments and subsequent interaction with sub-arc mantle peridotite, whereas the Peterson Creek Formation dacites and Maskwa Lake TTG Batholith I tonalites formed by partial melting of juvenile lower arc crust. The major and trace element geochemistry of the Bird River Sill and greenstone belt and the Maskwa Lake TTG Batholith I, and geological relationships and lithological associations point to a transition from continental arc to continental back-arc magmatism along the southern active margin of the North Caribou terrane at ca. 2743 Ma, resulting in the formation of the Maskwa Lake microcontinent that occurred prior to subsequent continental arc magmatism along the southern margin of this microcontinent. Combined field observations and geochemical data indicate that the Bird River Sill and Bird River greenstone belt are a dismembered Archean subduction-related ophiolite that marks a suture zone between the Winnipeg River subprovince and the Maskwa Lake microcontinent.

The Red Bird River Shelter (15CY52) Revisited: The Archaeology of the Cherokee Syllabary and of Sequoyah in Kentucky

This article reanalyzes petroglyphs from the Red Bird River Shelter (15CY52), a small sandstone shelter in Kentucky. In 2009–2013, it was claimed that some of the carvings at the site represented the earliest known examples of Cherokee Syllabary writing, dating to the first two decades of the nineteenth century. It was also suggested that Sequoyah, the Cherokee artist and intellectual who invented the Cherokee Syllabary in the early nineteenth century, had made these petroglyph versions during a visit to see his white paternal family living in Kentucky. Our reanalysis categorically contests this interpretation. We do not see Cherokee Syllabary writing at Red Bird River Shelter. We do not believe that historical evidence supports the notion that Sequoyah had white relatives in Kentucky whom he visited there at the time required for him to have authored those petroglyphs. We also believe that this account misrepresents Sequoyah's Cherokee identity by tying him to white relatives for whom there is no historical warrant. We argue that the Red Bird River Shelter is a significant precontact petroglyph site with several panels of line-and-groove petroglyphs overlain by numerous examples of modern graffiti, but there is no Sequoyan Syllabary inscription there.

AGE OF THE BIRD RIVER SILL, SOUTHEASTERN MANITOBA, CANADA, WITH IMPLICATIONS FOR THE SECULAR VARIATION OF LAYERED INTRUSION-HOSTED STRATIFORM CHROMITE MINERALIZATION

The Archean Bird River sill, a 20-km-long and up to 800-m-thick mafic-ultramafic layered intrusion in the Bird River greenstone belt of southeastern Manitoba, Canada, contains significant resources of chromium and nickel-copper, and locally anomalous concentrations of platinum group elements. Stratiform chromitite, displaying both remarkable lateral continuity and local irregularities due to synmagmatic disruption, occurs in up to six main intervals over a thickness of ~60 m in the lower ultramafic part of the intrusion. Ni-Cu sulfide mineralization is hosted in ultramafic rocks at the base of, or just below, the sill (e.g., past-producing Maskwa-Dumbarton mines). In this study, we report a U-Pb age (chemical abrasion-thermal ionization mass spectrometry) for a leucogabbro from the Chrome property of 2743.0 ± 0.5 Ma (n = 8 single grains of zircon), which is interpreted as the age of crystallization of the sill and defines the timing of the associated Cr-Ni-Cu ± platinum group element (PGE) mineralization. Other Neoarchean mafic-ultramafic intrusions containing economic concentrations of chromite and/or Ni-Cu-(PGEs) occur in the northwestern part of the Superior province in the Canadian Shield (e.g., McFaulds Lake, Big Trout Lake, Puddy Lake, Shebandowan) and share broadly similar geologic relationships. The age of intrusion-hosted stratiform chromite mineralization worldwide, excluding ophiolite-hosted chromitites, ranges from Archean to Paleoproterozoic, which is comparable to that for komatiite-related Ni deposits. This temporal restriction is consistent with both deposit types requiring the involvement of high-MgO, Cr-rich parent magmas produced during large degrees of mantle melting early in Earth history.

RADIOGENIC ISOTOPE SYSTEMATICS OF THE TANCO AND SILVERLEAF GRANITIC PEGMATITES, WINNIPEG RIVER PEGMATITE DISTRICT, MANITOBA

Isotopic ages for minerals of the Archean lithium–cesium–tantalum (LCT)-family Tanco and Silverleaf granitic pegmatites in southeastern Manitoba range from about 2660 Ma to 2600 Ma. Etched tantalite yields U–Pb ages between ca. 2640 and 2620 Ma, and the six oldest ages form an array indicating 2641 ± 3 Ma, which is interpreted as a major period of crystallization. Fragments of zircon megacrysts give U–Pb ages ranging from ~2660 to 2606 Ma, which may reflect lead loss after crystallization associated with subsolidus fluids from the pegmatite. A Pb–Pb age on megacrystic apatite and associated feldspar gives 2657 ± 18 Ma. Rb–Sr ages on lepidolite from Silverleaf (2620 ± 13 Ma) and Tanco (2631 ± 12 Ma) overlap and agree with the Rb–Sr age of muscovite from Tanco (2620 ± 20 Ma), using a 87 Rb decay constant of 1.395 × 10 −11 yr −1 . Pb–Pb data from K-feldspar and albite show highly evolved unsupported Pb compositions that scatter along or between a single-stage isochron of about 2640 Ma and a mixing line between the composition of common Pb at about 2640 Ma on the Stacey and Kramers growth curve and the composition of radiogenic Pb generated at around 2640 Ma. This indicates that feldspars exchanged Pb with radioactive minerals like tantalite both early, during the period of pegmatite emplacement and cooling, and in geologically recent times. Early exchange is consistent with the observation of progressive structural modification of feldspars, whereas disturbed Rb–Sr systematics indicate late exchange of these elements between feldspar and its environment. The peraluminous composition of late granites and pegmatites in this suite and high initial 87 Sr/ 86 Sr ratio (> 0.8) of the Tanco pegmatite suggest an origin from melting of metasedimentary rocks beneath the Bird River greenstone belt. These rocks are most likely associated with the English River Subprovince exposed to the northeast.

Talking leaves and rocks that teach: the archaeological discovery of Sequoyah's oldest written record

The authors investigate the origins of the earliest script of the Cherokees, using inscriptions in the Red Bird River Shelter. Their analysis suggests that the engravings in the cave show the experimental creation of a syllabary (alphabet of signs). This in turn offers support for the historical notion that this writing system was not an ancestral practice preserved through missionaries, but an invention of the early nineteenth century; one that should be credited to the Native American pioneer scholar, Sequoyah.

Long-lived transpression in the Archean Bird River greenstone belt, western Superior Province, Southeastern Manitoba

The Archean Bird River greenstone belt (BRGB) is located on the southwestern edge of the Superior Province between the 3.2 Ga old Winnipeg River subprovince to the south and the metasedimentary belt of the English River subprovince (ERSP) to the north. This position between two major subprovinces makes the BRGB a primary target for investigating the geodynamic and kinematic evolution of a major structural boundary. New structural and geochronological data have allowed us to present an evolutionary framework for the southern boundary of the North Caribou superterrane. The BRGB underwent 3 main deformation phases. The D1 event took place ca. 2698 Ma and displays a north-side-up shearing. The D2 event, occurring at ca. 2684 Ma in a transpressive context, presents a complex structural pattern mixing vertical tectonics in the BRGB and strike-slip tectonics along the boundaries of the greenstone belt with other subprovinces. Between the BRGB and the ERSP, the 2832–2858 Ma old Maskwa batholith acted as a rigid passive block during the collision and marks the boundary between pure dextral strike-slip tectonics along his northern boundary with the ERSP and vertical south-side-up motion in the BRGB. The BRGB can be considered as a pop-up structure with anastomosed shear zones displaying different horizontal offset according to the orientation of the shear zones. The southern boundary with the Winnipeg River subprovince is represented by a sinistral south-side-up shear zone. The same pattern is found at the regional scale where major shear zones acted as a conjugate set in the horizontal plane. At ca. 2640 Ma, the D3 event occurred in a general dextral transpressive tectonic regime coeval with the emplacement of rare-elements pegmatitic plutons in a still hot (400–500 °C) country rock. The geodynamical and mechanical significance of the partitioning between pure strike-slip tectonics in the English River subprovince and vertical motion in the BRGB can be explained by the rheological behaviour of a hot and weak lithosphere undergoing transpressive strain. The structural framework of the BRGB is the result of strong interactions between hot and weak domains, coeval with widespread plutonism, and a rigid older domain (Maskwa batholith) during the D2 transpressive event.

Geology of the Ore Fault Ni-Cu Deposit, Bird River Sill Complex, Manitoba

The geology of the Ore Fault Ni-Cu deposit has been reinterpreted in the light of recent studies of the geology of the Neoarchean Bird River Sill Complex and the occurrence of economic Ni-Cu and Zn-Cu-Ag mineralization. The Ni-Cu sulfides are hosted by the lower of two parallel NNW-trending and moderately W-dipping mafic–ultramafic intrusions related to the Bird River Sill Complex. The bodies intruded a bimodal volcanic suite consisting of weakly deformed mafic flows and felsic pyroclastic rocks. The mafic volcanic rocks are geochemically related to the MORB-type rocks of the Lamprey Falls Formation, and the felsic volcanic rocks are related to arc-type rocks of the Peterson Creek Formation. The original pyroxene- and olivine-dominated mineralogy of the sills has been replaced by variable serpentine-amphibole-talc-carbonate assemblages. The Ni-Cu sulfide assemblage exhibits textures and geochemical signatures typical of orthomagmatic sulfide mineralization. The sulfide minerals are associated with cumulate layers of magnetic ferrochromite that range in thickness from a few to tens of centimeters. A later event of Zn-Cu-Ag sulfide mineralization associated with quartz veining and garnet-chlorite alteration along a fault that strikes north, dips vertically, and cuts all rock types. The mineralized fault is cut by the NE-trending Peterson Creek shear zone. Where the Ni-Cu and Zn-Cu-Ag mineralized zones intersect, remnant magmatic features such as amphibolite or cumulate ferrochromite bands occur within quartz veins or local chlorite alteration. The mixed zones contain a very unusual polymetallic assemblage of Ni, Cu, Zn, Ag, and platinum group elements (PGE).

Geology of the Ore Fault Ni-Cu Deposit, Bird River Sill Complex, Manitoba

Geology of the Ore Fault Ni-Cu Deposit, Bird River Sill Complex, Manitoba

The Greer Lake leucogranite, Manitoba, and the origin of lepidolite-subtype granitic pegmatites

The Archean Greer Lake leucogranite intruded metabasalts of the Bird River Greenstone Belt in the southwestern part of the Superior Province of southeastern Manitoba. The considerably evolved, multiphase, peraluminous, B-, P-, and S-poor leucogranite (K/Rb 132 to 24) was probably generated by fault-friction-assisted anatexis of dominantly metatonalitic rocks and subsequent differentiation. The leucogranite produced interior, transitional, non-crosscutting pods of barren, beryl-columbite- and lepidolite-subtype pegmatites that solidified from local segregations of highly fractionated residual melt. Steep fractionation gradients characterize the granite-to-pegmatite transition, most conspicuously so in the case of the most evolved, Li, Rb, Cs, Be, Mn, Sn, Nb-Ta, F-rich, lepidolite-subtype pod AC #3 (with K/Rb ≥ 16 and Cs 330 ppmwt in accessory K-feldspar, ≥2.5 and ≤11,200 ppmwt, respectively, in lepidolite, Cs ≤28,000 ppmwt in beryl, and Ta/(Ta+Nb) at. ≤ 0.95 in manganotantalite). The Greer Lake example documents beyond any doubt the igneous derivation of lepidolite-subtype pegmatites from a plutonic parent. Most cases of generally very scarce lepidolite-subtype pegmatites obscure this relationship, as the volatile-rich, highly fluid melts stable to relatively low temperatures commonly migrate to great distances from their plutonic sources.

MONAZITE-(Sm), A NEW MEMBER OF THE MONAZITE GROUP FROM THE ANNIE CLAIM #3 GRANITIC PEGMATITE, SOUTHEASTERN MANITOBA

Monazite-(Sm) was found in the Annie Claim #3 pod of lepidolite-subtype granitic pegmatite within the Greer Lake intrusion of pegmatitic leucogranite, in the Archean Bird River Subprovince of the Superior Province, in southeastern Manitoba. It occurs as tabular crystals ≤0.4 mm in diameter, associated with manganocolumbite, quartz, albite and lithian muscovite. Monazite-(Sm) is yellowish, translucent, with a white streak, vitreous to greasy luster, and no observed fluorescence. One good cleavage is present, tenacity is brittle, and the fracture is uneven. Monazite-(Sm) has no observable pleochroism; α 1.768 (5), β 1.771(3), γ > 1.808(3); 2 V meas 29(8)°, X = b , Z ∧ c = 9° (β obtuse). It is monoclinic, space group P 2 1 / n ; a refinement from single-crystal and powder (Gandolfi) X-ray-diffraction data gave a 6.725(1), 6.739 ( 3 ), b 6.936(1), 6.951 ( 3 ), c 6.448(1), 6.462 ( 3 ) A, β 104.02(1)°, 104.03 ( 4 )°, V 291.8(1), 293.6 ( 2 ) A 3 , Z = 4; D calc derived from average chemical composition is 5.512 and 5.478 g/cm 3 . The strongest six lines of the (Gandolfi) X-ray-diffraction pattern [ d in A( I )( hkl )] are: 4.647(5)(011), 4.164(8)(111), 3.492(4)(111,020), 3.264(7)(200), 3.065(10)(120), and 2.857(9)(112,012). The monazite-(Sm) contains, in wt.%, up to 14.29 Sm 2 O 3 , 13.48 Gd 2 O 3 and 6.28 Nd 2 O 3 , and moderate percentages of the huttonite and brabantite components. The most Sm-rich composition gives (Sm 0.197 Gd 0.179 Ce 0.148 Th 0.125 Ca 0.107 Nd 0.090 La 0.030 Y 0.030 Pr 0.023 Tb 0.017 Zr 0.017 Dy 0.016 Pb 0.016 U 0.002 ) ∑0.997 (P 0.963 Si 0.044 ) ∑1.007 O 4 . Adjustment of U and Th of the monazite-(Sm) to their original contents 2.64 Ga ago slightly improves the stoichiometry and proves that all the Pb present is radiogenic. The middle- REE- dominant signature of the Annie Claim #3 monazite-(Sm) is shared with the broadly associated Y(Ta,Nb)O 4 mineral (formanite?) and dysprosian xenotime-(Y); this exotic pattern of REE abundances is possibly generated by selective and differential complexing of REE in the granite-to-pegmatite sequence of solidification.

Riding on the Moon

FICTION Riding on the Moon Sidney Saylor Farr ANNIE, WHERE'S ANDREW? I told him we'd hoe that new-ground corn soon's I got in from work. Where'd he go?" Papa walked through the door, having worked a shift in the mine, then thumped down his lunch pail. "The cows broke out, Papa. He went to put 'em back in the pasture." "And now he's laying around in the shade somewhere reading a book! Go find him. We've got work to do." Annie ran up the road towards the pasture. Fine dry dust puffed up between her toes, coating her feet and legs. It was hot for early May. This side of the pasture, she saw Andrew sitting beside Gum Spring, a handkerchief up to his face. "Oh,Andrew, not again! Did you run too hard after the cows? Granny Brock says iff'n a body gets too hot, sometimes it'll cause a nosebleed." "What're you doing here?" Andrew interrupted. "Papa's ready to hoe the new-ground. He said to come help him." "Soon's this stops." "Come on home. Mama will help you." Annie looked as her brother got shakily to his feet. At fourteen he was big, like Papa. Except Andrew had sandy hair and freckles, and Papa had black curly hair and blue eyes. She took after her Papa in looks, having blue eyes and black hair. Andrew, who had their Mama's coloring, had been puny for weeks. His nose had bled the first time in March and several times since. Mama came to the front porch carrying a washpan of water. "Sit down, Andrew. Let's see if I can stop this blood." "I'll go help Papa," Annie said, thinking that if she worked fast Papa wouldn't yell at Andrew for not coming to help. By the time she and Papa had finished hoeing, the sun was headed for a gap in the trees. Papa put their hoes in the shed, and they walked home. Andrew was stretched out on the porch, holding a wet towel to his face. Mama sat nearby, her lips forming the words of Ezekiel 16:6, handed down to her from far-back generations as a remedy to any unnatural bleeding. "When I passed by thee and saw thee polluted in thine own blood, I said unto thee, live. Yea, I said unto thee when thou wast in thy blood, 41 live." Then "Lloyd, it's not working this time; it's never failed me before." She looked anxiously at her husband, who turned away, walked to the end of the porch and looked out across the valley. "I've heard Pap talk about a remedy—said it would work if done in the spring or early summer, when the sap's up in the trees. Your Bible verses ain't working this time." He explained the procedure, then sent the two children to find a poplar tree. "I can't see why Papa won't take you to the mission doctor at Red Bird. The doctor'd help you quicker than any old poplar tree is going to." "Papa's just set in his ways, Annie. Nobody on Stoney Fork believes those mission people are anything but a bunch of furriners." Then, "Annie do you reckon I might die?" Andrew's voice was weak. "Your nose has bled before, and you ain't dead yet. We'd better hurry, it's getting dark." Andrew stumbled, almost fell. Annie took hold of his arm. He looked white and sick, and she was frightened. "Annie, if I was to die you can have my books. Beg Papa to let you go to school. You have to go to school if you're ever going to amount to anything." "Why, I can't take your books, Andrew. You'll need them when you get to be a teacher.""Annie, just in case this don't work and I die before I get through school, you'll have to be a teacher in my place." The Red Bird Mission School had existed in the mountains, near the Red Bird River, for more than...

DYSPROSIAN XENOTIME-(Y) FROM THE ANNIE CLAIM #3 GRANITIC PEGMATITE, SOUTHEASTERN MANITOBA, CANADA: EVIDENCE OF THE TETRAD EFFECT?

Dysprosian xenotime-(Y) was found in the Annie Claim #3 pod of lepidolite-subtype granitic pegmatite within the Greer Lake intrusion of pegmatitic granite, in the Archean Bird River Subprovince of the Superior Province, in southeastern Manitoba. It occurs as microscopic inclusions in spessartine and as discrete crystals, both enclosed in ferroan muscovite, also associated with manganocolumbite – manganotantalite, microlite, zircon and apatite. The xenotime-(Y) contains up to 14.88 wt.% Dy 2 O 3 (and 7.59 wt.% Gd 2 O 3 , 3.31 wt.% Tb 2 O 3 ), the highest concentration of Dy so far observed in this mineral. In chondrite-normalized REE patterns, the positive Tb anomaly is even higher than that of Dy. Along with xenotime-(Y) and xenotime-(Yb) from other granitic pegmatites, altered granites and alpine veins, the Annie Claim #3 xenotime-(Y) shows prominent double segmenting of the Gd to Lu sequence, ascribed by some authors to the tetrad effect in geological materials generated from, or affected, by aqueous media. Analytical problems could not produce this effect in the xenotime samples.

Age and isotopic composition of late Archean leucogranites: implications for continental collision in the western Superior Province

U-Pb and Sm-Nd isotopic data are presented for leucogranites and pegmatites from the boundary zones of the English River, Winnipeg River, and Wabigoon subprovinces in the late Archean Superior Province of northwestern Ontario. The Ghost Lake batholith and the Separation Rapids pluton are posttectonic, rare-metal-bearing, S-type leucogranites that were generated during the final stages of the amalgamation of the Superior Province. U-Pb dating of monazites yields ages of 2650 ± 3 Ma for a pegmatite from the Dryden area and 2646 ± 2 Ma for the Separation Rapids pluton. Sm-Nd data from these granitoids are compared with similar data from late Archean intrusions and adjacent rocks from the same regions. Values of εNd range from 0 to +2 for pretectonic tonalites, from -2 to +2 for both the Ghost Lake batholith and the Separation Rapids pluton, from +1 to +3.5 for metavolcanic rocks, and from -0.5 to -1.5 for metasedimentary rocks. There is an overall trend of decreasing εNd values from pretectonic tonalites to the latest leucocratic pegmatites. This reflects the origin of more and more granitoids as a result of anatexis as the crust grew and thickened through accretion. The ranges of εNd values found among leucogranites from the two regions overlap with the isotopic values of the basalts and sediments. This suggests that the leucogranites were generated by similar processes involving both a crustal and a juvenile mantle component. Furthermore, the ages from this study and from pegmatites (2652-2643 Ma) in the Bird River greenstone belt provide the best estimate of the age of rare metal mineralization in the western Superior Province. Similar ages (2651-2639 Ma) for rare-metal-bearing leucogranites in southern Abitibi subprovince suggest a specific period of emplacement over a wide area.

The Buck and Pegli lithium deposits, southeastern Manitoba; the problem of updip fractionation in subhorizontal pegmatite sheets

Two sheets of complex rare element pegmatites of the petalite subtype crop out in the eastern part of the Bernic Lake pegmatite group, Cat Lake-Winnipeg River field (Bird River subprovince, western Superior province of southeastern Manitoba. They dip west at 7 degrees to 12 degrees ; drilling reveals a downdip extent of 2,400 to 3,000 m, a north-south width of more than 250 m, and thickness varying from 2 to 16 m. Zoning, largely symmetrical, grades from primitive border-wall-core units updip into a complex border-wall-intermediate core-margin core sequence. Mineral assemblages diversify in this direction from K feldspar + albite + quartz + muscovite (+ or - Bi) to suites carrying beryl, petalite, spodumene, triphylite, cassiterite, columbite-tantalite, pollucite, traces of sulfosalts, and multigenerational sequences of amblygonite-montebrasite, tourmaline, Al to Li,Al micas and apatite. Besides extensive enrichment in Li, Be, Sn, Nb < Ta and Cs evident from the mineral assemblages of both pegmatites, strong updip gradients also are shown by fractionation of K feldspar and micas (K/Rb = 32.8-7.2, 27.3-3.6; Rb/Cs = 48.5-13.8, 31.2-7.3, respectively), beryl (Na/Li = 7.5-2.5, Cs = 0.18-1.2 wt %), and columbite-tantalite (Mn/(Mn + Fe) at. = 0.4-0.99, Ta/(Ta + Nb) at. = 0.22-0.60). In contrast, compositional gradients across the more or less concentric zoning of the pegmatite sheets are largely moderate, and relatively best expressed in the topmost parts. The strong compositional gradient along the extensive subhorizontal dip of the thin pegmatite sheets could not originate by thermogravitational convection, gravity-driven transport through the melt, or metasomatism in the solidified pegmatite. The geometry, attitude, and rapid consolidation of the pegmatite sheets provide strong arguments against internal diversification of a homogeneous melt alone. A trainlike intrusion from a layered magma chamber, or a flow differentiation during the intrusion of heterogeneous melt induced by internal differences in fluidity and density, or a combination of both seem to be a required component of the overall fractionation process.

The Extraction of Ferrochromium in the Presence of Nickel From Bird River Chromite Ores

The Extraction of Ferrochromium in the Presence of Nickel From Bird River Chromite Ores

The Extraction of Ferrochromium in the Presence of Nickel From Bird River Chromite Ores

AbstractLaboratory experiments on ore beneficiation and subsequent carbothermic reduction of Bird River chromites were conducted at 1550 and 1650°C. High-carbon ferrochromium alloys with chromium concentrations between 46 and 50% were obtained. When metallic nickel or nickel oxide was added to the charge materials at chromium to nickel ratios close to two, the carbon content of the alloy product was decreased by approximately 20%, although the chromium to carbon ratio did not change substantially. Under optimized conditions with respect to ore beneficiation, chromium recoveries and electric energy consumption, and chromite concentrate suitable for a smelting-reduction process, would only require upgrading to approximately 27% Cr2O3. The ferrochromium-nickel alloy obtained could be utilized as a master alloy for stainless steel production.

Petrography, chemistry and distribution of platinum and palladium in ultramafic rocks of the Bird River Sill, SE Manitoba, Canada

The ultramafic portion of the Archean Bird River Sill, a mafic-ultramafic stratiform intrusion in southeastern Manitoba, is divided into a “lower” and an “upper” series. These series may be the product of two separate magmatic injection pulses that differ in their chemistry, mode of crystallization and petrography. The lower series consists of 80 m of ultramafic rocks and 10 m of mafic rocks. The ultramafic rocks are subdivided into ten periodic units that exhibit gradational variations in major element, sulfur, platinum and palladium concentrations concurrent with systematically evolved changes of the olivine crystal habits. The upper series is divided into a “crackle zone” and a “massive zone”. The 27 m thick crackle zone, consists of a homogeneous olivine cumulate disrupted by a network of conduits containing a fine grained groundmass and olivine crystals that exhibit hopper olivine morphology (Donaldson, 1976). The 38 m thick massive zone comprises mainly subhedral to euhedral olivine crystals hosting PGE enriched layers and chromitite layers near its stratigraphic top. The contrasting petrography, major element, sulfur, platinum and palladium distribution of the lower and the upper series are attributed to different a) parental magmas and b) emplacement mechanisms and crystallization histories.