Geology topics
A. V. Heyl
Publications and source records attributed to A. V. Heyl.
Evaluation of proposed precipitation mechanisms for Mississippi Valley-type deposits
The mechanism of precipitation is an important aspect of any genetic model for Mississippi Valley-type deposits. Yet most of the precipitation mechanisms for minerals in the Mississippi Valley-type association have serious flaws. Solution mixing would require an unlikely series of solutions to account for the various minerals in the ores, and it does not account for the universal occurrence of organic matter in the ores nor for the oxidation state of sulfur in pyrite in the ores. Sulfate reduction addresses some of these problems, but is inconsistent with kinetic data and could not be reversed to account for the oscillations between precipitation and dissolution of sulfide minerals in the ores. Carbon dioxide effervescence does not address the precipitation of most minerals in the ores, and all of the evidence for effervescence may be explained in other ways. Cooling of the mineralizing solution could precipitate many minerals, but fluid inclusion data suggest that, in many deposits, the solution did not cool significantly as any particular stage formed. A credible genetic model also must explain why all of the minerals precipitated at the same sites; any combination of the above mechanisms which suggests that unrelated mechanisms occurred at the same sites by coincidence is unlikely. The most reasonable scenario is that a hot, thiosulfate-bearing mineralizing solution reacted in various ways with organic matter at the sites of mineralization to precipitate the ore minerals. The organic matter acted as a reductant, source of carbon dioxide, source of organic acids, and a substrate for bacterial metabolism of thiosulfate in various stages of mineralization. Thus organic matter links all stages of the mineralization to the same sites.
Geology and mineral deposits of the Priest Tank Quadrangle, Sierra County, New Mexico
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Preliminary seismotectonic map of the central Mississippi Valley and environs
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Geology and resources of fluorine in the United States
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Minor epigenetic, diagenetic, and syngenetic sulfide, fluorite, and barite occurrences in the central United States
Metallic sulfides, fluorite , barite , and celestite are widespread in the sedimentary rocks of the central United States . Many occurrences are epigenetic concentrations either in known major mineral districts or in clusters of deposits that warrant further exploration for potential ore. Evaluation of trace-element composition, of fluid inclusions, of depositional temperature, and of isotopic composition of sulfur may help discriminate potentially economic deposits from even more widespread, probably noneconomic, syngeneic occurrences . Known major mineral districts and many promising sulfide occurrences are located along complex major fault systems and particularly over structural domes at intersections of fault systems. Economically promising sulfide deposits occur along a west-trending fault system crossing Kentucky and Missouri near the 38th parallel, particularly at associated cryptoexplosion structures along it, at the intersection of the fault system with the Cincinnati arch. Elsewhere in the central United States , promising sulfide occurrences are located along the crest of the Findlay arch, near Serpent Mound, Ohio, along the northwest-trending Mount Carmel fault in southwestern Indiana, and buried at depth in oil fields of west- central Kansas.Other types of deposits that are productive or may have some future economic interest are locally economic and possibly syngenetic red-bed copper occurrences in Oklahoma, Texas, Kansas, and Pennsylvania. Most widespread are the black shale and pyritic sandstone beds, some of which have been a source of pyrite for sulfur and sulfuric acid in conjunction with coal mining. Bedded barite deposits of possibly diagenetic origin have been mined in Arkansas. Diagenetic siderite concretions containing sulfides and barite were widespread sources of iron in the 19th century.
Environment of ore deposition at the Mex-Tex deposits, Hansonburg District, New Mexico, from studies of fluid inclusions
These deposits , in Pennsylvanian limestone and shale, contain barite, fluorite, low-silver galena with "J-type" lead, and quartz, and only minor amounts of other minerals. Mineralization occurs in veins, in blankets of bedded, rhythmically banded "coontail" ore , and in vuggy, coarsely crystalline open-space fillings in tectonic and solution channels in limestone adjacent to faults. Except for widespread silicification, the mineralization is very similar to that of the southern Illinois deposits . The main stages of hypogene mineralization are: 1) sphalerite, pyrite, galena and chalcopyrite; 2) five easily recognizable substages of fluorite with intermittent quartz and barite; and 3) late calcite.More than 500 primary and 2,500 pseudosecondary inclusions , mainly from fluorite, were studied on the freezing and heating microscope stages. Some primary inclusions contain organic matter. Gross supercooling indicates slow ore - fluid movement. Recognizable planes of pseudo-secondaries (each containing 20-200 inclusions ) yield data essentially identical with coeval primaries, but the few planes of presumed secondaries do not.The first three substages of fluorite formed from fluids that were essentially constant in temperature at 186°-205° C (assumed pressure correction +10° C), but increased in salinity from aproximately 10 up to 15 weight percent salts. Succeeding substages formed at gradually decreasing temperatures (to about 140° C) and increasing salinity (maximum 17%), with breaks marking several individual substages. A few inclusions in an early barite have anomalously low homogenization temperatures. Coarse selenite has primary inclusions full of fresh water and hence is presumed to be supergene.These data do not prove any given theory or origin for the fluids or the deposits , but they do place some limits on possible mechanisms of origin.
Isotopic study of galenas from the upper Mississippi Valley, the Illinois-Kentucky, and some Appalachian Valley mineral districts
Analyses of lead isotopes in galena in carbonate rock ore deposits collected from several mineralized districts in the Central and Eastern Interior of the United States support previous studies in establishing that the galena is anomalously radiogenic ("J"type")- This study , using care-fully selected samples to test some géologie relationships, shows region-wide and distrietwide systematic variations in isotope ratios. The genetic implications of thèse variations are discussed. Two mechanisms of origin are considered to explain thèse variations in isotopic ratios. One involves mixing of leads from multiple sources, the other calls for variable lead-isotope ratios originating from a single source. Several source materials for the lead ores have been suggested; whether a single source has predominated, or two or more main sources have predominated is still unresolved. Slopes from Pb206/Pb204 versus Pb207/Pb204 plot are compatible with a contribution of lead by the 1300 ± 300 m.y. basement rocks that underlie the deposits. The spatial relationships of alkaline igneous rocks to several of the minerai districts in the Mississippi Valley région suggest a possible mag-matic source for the lead. Isotopic analyses of galenas closely associated with several of the intrusive rocks are similar in isotopic composition to adjacent ore leads, but genetic implications are ambiguous. Galena oc-curring in shales in the Mississippi Valley région outside mineralized districts contains ordinary lead. Théories that call upon such shales to be the major source of the lead in the depoaits of the Mississippi Valley type must explain this distinct différence in isotopic compositions. Galena collected from districts within the Appalachian Ridge and Valley Province contains notably less radiogenic lead than that from the Mississippi Valley minerai districts , and the lead is of the ordinary type.
Mineral paragenesis and zoning in the central Kentucky mineral district
The Central Kentucky mineral district occupies the greater part of the Blue Grass lowland of Kentucky , which lies astride the Lexington dome and the Cincinnati arch. The oldest exposed rocks of the mineralized area are limestones of Middle Ordovician age. The paragenesis throughout the district is constant and traceable, although the relative abundance of minerals varies from vein to vein. The mineral association, areal distribution of the ore minerals, and comparison with other epithermal deposits indicate that the Central Kentucky veins are epithermal. The ore deposits have a district -wide lateral zoning in a concentric pattern. Near the middle of the district , and within the Lexington dome, are two centers of fluorite-calcite-dark sphalerite veins that form Zone 1. Surrounding these centers is a much larger Zone 2 in which nearly all the veins contain fluorite, barite, calcite, and two-colored (yellow-black) sphalerite. Galena is absent or present in very minute quantities in Zones 1 and 2. In Zone 3, which surrounds Zone 2, barite, galena, and bright-colored sphalerite are the principal minerals. Fluorite is absent, or present only in traces. Textures of the mineral veins change from bands of coarse comb crystals in Zone 1 to mostly colloform bands in the outer zones. Structural control of the ore is related to faults and fractures transecting the collapsed Lexington dome and is an important factor in the distribution of mineral veins. The district has many of the mineralogic, zonal, and structural features of the Central Tennessee, Kentucky -Illinois, and Pennine, England, mineral districts, which suggest that the origins of these districts were similar. The ores in the Central Kentucky district were probably deposited from ascending thermal solutions of slightly lower temperatures than those that formed the deposits in the Kentucky -Illinois district . The solutions are believed to have been derived from a deepseated magmatic source centered beneath the Lexington dome, but they may have been greatly diluted by ground waters within the dome. The innermost zone probably is nearest to the emanative centers.
Silver in the United States, exclusive of Alaska and Hawaii
The productive silver districts in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. Only those districts known or believed to have contained 100,000 troy ounces or more silver are shown. Three size categories, based on production and estimated reserves, are distinguished and indicated by size of symbols: districts containing 100,000 to 5 million ounces, those containing 5 million to 50 million ounces, and those containing more than 50 million ounces. Symbols show the approximate centers of the districts. Some of the more prominent districts are identified by name on the map, and all are numbered to correspond to the index. Because a name established through common usage may not be the legal name of the mining district, several names are given in the index for some localities. The index, arranged alphabetically by States, includes a brief description of major geologic features for most districts. Both published and unpublished data were used, and at least one reference is given for each locality if reports on it have been published.
Zinc in the United States
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Radioactive rare-earth deposit at the Scrub Oaks Mine, Morris County, New Jersey
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Stratigraphy of Middle Ordovician rocks in the zinc-lead district of Wisconsin, Illinois, and Iowa
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