E. Wm. Heinrich

Relationships between geology and composition of some pegmatitic monazites

Abstract Fourteen monazites from several well-studied pegmatites and pegmatite districts in the western states have been analysed by X-ray fluorescence spectrometry for the cerium subgroup of rare-earth elements, as well as yttrium and thorium. The results have been correlated with the paragenesis, mineralogy and geology of the occurrences. They show several distinct, and in some cases unique, rare-earth element distributions which are characteristic not only of individual pegmatites but also of entire pegmatite districts.

Geologic types of glass-sand deposits and some North American representatives

Although the major glass-sand deposits of the midwestern United States are of the classic blanket marine sandstone type, throughout the United States and Canada a wide variety of geological types of silica deposits is available as glass-sand sources and potential sources. These include: (I) Unconsolidated sands: (A) Littoral — Cohansey Formation, New Jersey; (B) Alluvial plain — Citronelle Formation, Florida; (C) Marine dunes — Pacific Grove, California; (D) Lake dunes — Redcliff, Alberta; (E) Stream channel — Ravensdale, Washington. (11) Arkosic sands: Idaho Formation, Idaho. (III) Consolidated sandstones and orthoquartzites: (A) Marine and littoral — St. Peter Formation, Oriskany Formation, Potsdam Sandstone; (B) Alluvial — Pottsville Formation, Pennsylvania. (IV) Quartzites: Lorrain–north shore Lake Huron, Ontario; Grenville — Baie Comeau, Quebec. (V) Hydrothermal veins: Quartz Mountain, Washington; Carson City, Nevada. (VI) Tectonically crushed rocks: (A) Sandstone — Moberly Mountain, British Columbia; (B) Quartzite — St. Donat and St. Remi, Quebec. (VII) Weathering products — Oriskany Formation, Goshen, Virginia. Another, nongeological category would be waste sands — leftovers from other mining operations, such as the residual sands from the Fort McMurray, Alberta, tar sands operations. The chief deposits of the north-central United States are the St. Peter (Ordovician) and Sylvania (Devonian) sandstones. The St. Peter is believed to have been derived from Precambrian quartzites of the Canadian Shield (which themselves originally may have been second-generation sandstones), and the Sylvania probably was derived from St. Peter outcrops, making it a third- (or fourth-) generation sandstone.

The Diversity of Rare-Earth Mineral Deposits and their Geological Domains

Concentrations of rare-earth (RE) minerals are represented by an unusually great diversity of geological types of deposits, particularly when compared to the variety of deposits of such elements as, for example, Pb, Zn and Cu. In part this diversity stems from the fact that RE elements not only form their own minerals in various groups (oxides, multiple oxides, fluorides, carbonates, phosphates, silicates) but also appear widespread vicariously in numerous minerals of many other elements (oxides, multiple oxides, fluorides, silicates).

Hydrogen-mineral reactions and their application to the removal of iron from spodumene

Pegmatitic deposits contain three distinctly different types of spodumene: 1.(1) Phenocrystic spodumene in unzoned pegmatites. This type is high-iron spodumene, with Fe2O3 = 0.6 − 0.9%.2.(2) Zonal spodumene. Large laths in central zones; it contains 0.01–0.03% Fe2O3.3.(3) Spodumene plus quartz aggregates pseudomorphous after petalite; Fe2O3 = 0.007 − 0.03%. Only Type 1 generally occurs in deposits sufficiently large and uniform to be economically exploitable. Two processes are presently available for iron removal. Both require initial inversion of the (a) spodumene to its β-dimorph: 1.(1) The chlorine process in which the isomorphous iron is converted to bon chloride and2.(2) The hydrogen process in which the Fe3+ ion is reduced to metallic iron.

Dikes of the McClure mountain — Iron mountain alkalic complex, Fremont county, Colorado, U.S.A.

AbstractThe McClure Mountain — Iron Mountain alkalic complex, the largest of three Precambrian alkalic complexes in south-central Colorado, is an irregularly ovoid body about 8×6.5 kilometers in plan. It contains major petrologic units (in age sequence): 1) peridotite and ilmenite-magnetite lenses, 2) gabbro, 3) hornblende syenite, 4) ijolite and 5) nepheline syenite, whose internal arrangement is irregular. Dikes are numerous and varied both within the complex and in the surrounding Precambrian metasediments and meta-volcanics (Idaho Springs formation), granitoids and migmatites to a distance of 27 kilometers from the complex. Fenitization has only locally affected these wall rocks at their contacts with the complex.Dikes within the complex are chiefly light colored and of syenitic or nepheline syenitic composition. Texturally they range from aphanitic, through porphyritic with an aphanitic to fine-grained matrix, to uniformly medium-grained.Most of the intracomplex dikes (save the few carbonatites) are represented by compositionally equivalent major units within the complex. In contrast, the extracomplex dikes are chiefly lamprophyres and carbonatites, none of which has a compositionally similar unit within the complex. The carbonatite dikes are younger than the lamprophyres; where the two types co-occupy the same fracture, the lamprophyre has been carbonatized. The lamprophyres are represented by an extraordinary number of textural varieties, involving phenocrysts and phenocryst combinations of augite, barkevikite, olivine and plagioclase in varying matrix combinations of olivine, augite, barkevikite, biotite, magnetite, apatite, plagioclase and orthoclase. Many of the dikes can be classed as camptonites or olivine camptonites. The Goldie lamprophyres contain local marginal phases spectacularly marked by concentrically zoned ovoids. The Cabin dike is studded by megaphenocrysts of augite.The carbonatites are of three main types:1)Relatively homogeneous calcitic or dolomitic carbonatites with few accessories.2)Composite carbonate — hematitic potash feldspar bodies which, with diminution of carbonate, grade into feldspathic Th-RE veins.3)Carbonatites with abundant barite and/or fluorite, and rarer species. The Goldie carbonatite also contains a complex suite of aluminofluorides. Many carbonatites and Th-RE veins emit, when broken, a fetid gas consisting of a mixture of fluorinated hydrocarbons of the C5 and C6 types along with F2, HF, and F2O. The fluorine has been derived from structurally degraded radioactive fluorite; the hydrocarbon gases appear to represent primary inclusions.Within the dike halo are two small breccia pipes consisting of fenitized, locally derived Precambrian gneiss blocks with minor fragments of transported biotitized lamprophyre in a subordinate calcitic matrix also containing aegirine, crocidolite, potash feldspar and hematite.The abundance of the lamprophyres, the great width of the dike halo, the lack of ring structure within the complex, the restriction of carbonatite to dikes, and the subordinate fenitization effects all combine to suggest that the McClure Mountain — Iron Mountain complex is now exposed at a relatively deep niveau, possibly near the mesozone — catazone boundary.

Hydrothermal Alterations of Conglomeratic Uranium Ores, Pronto Mine, Ontario, Canada

Hydrothermal alteration of the conglomeratic uranium ores is intensive and extensive at the Pronto deposit. The sequence of the main alteration is: (1) albitization, (2) chloritization and (3) carbonatization, resulting in the formation of albitized conglomerates, albitites (usually hematitic), chloritic albitites and conglomerates, chloritites and carbonate rocks. In some of the last, dolomite and/ or calcite form pseudomorphs after quartz pebbles. The alterations have markedly changed both the distribution of the radioactive minerals, generally concentrating them near footwall contacts, and the habit of both brannerite and uraninite. In both unaltered conglomerate and altered ores none of the pyrite displays any detrital characteristics. Indeed, much of it is euhedral. Sulfur isotope ratios indicate a magmatic-hydrothermal origin for the pyrite.