Designing Optimized Field Programs for the Detection of Mississippi Valley-Type Pb-Zn Deposits of the North American Arctic Paleozoic Platform

Research subject. The Mississippi Valley type deposits make up about a third of the global balance of lead and zinc reserves, resources and production. Additionally, silver, antimony, arsenic, barium, bismuth, cadmium, cobalt, gallium, indium, mercury, molybdenum, nickel and thallium can be present in the ores of these deposits. In the North-East of Russia, the Mississippi Valley type of deposits is poorly represented. In this work, we investigate the deposits of the Sardana ore cluster of the Republic of Sakha (Yakutia) and individual deposits of the Magadan region. Materials and methods. The article discusses the results of previous scientific research and new data on the geochemical features, isotopic composition of ores and geological and structural conditions for the formation of the Sardana cluster deposit. In addition, the potential for identifying stratiform lead-zinc deposits is associated with favourable geodynamic conditions in the region, as well as with the refinement and adaptation of the forecast-search model of MVT deposits for the North-East of Russia. Results. The mineralogical and geochemical features of the rocks and ores of the Sardana cluster deposits, the morphology of ore bodies, their zoning elements, as well as isotopic ratios indicate that the ores are likely to be of the Mississippi Valley type with the onset of ore deposition at early diagenetic and catagenetic stages. The distribution of rare elements indicates a significant role of superimposed metamorphism of the host carbonate-terrigenous strata in the deposition of the ores of producing stages. Conclusion. The potential possibility of increasing the mineral and raw material base of lead and zinc is associated with the identification of sedimentary basins with a stagnant anoxic regime of carbonate accumulation in the immediate vicinity of the development areas of rift complexes, as well as with the presence of other critically important forecast-search signs. In addition to the well-known Killakh metallogenic zone, Tuora-Sis and Orulgan metallogenic taxa located in the north of the Republic of Sakha (Yakutia) with known stratiform manifestations of lead and zinc belong to such areas.

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Trace Mississippi Valley-type lead-zinc mineralization : origins and relationship to midcontinent MVT ore districts

10.32469/10355/61917 ◽

2017 ◽

Author(s):

◽

Joshua D. Field

Keyword(s):

Fluid Inclusions ◽

Minor Element ◽

Mississippi Valley ◽

The North ◽

Seawater Sulfate ◽

Mitigating Factors ◽

Reduced Sulfur ◽

Mississippi Valley Type ◽

Ore District ◽

Valley Type

The North American mid-continent is known for its large Mississippi Valley type (MVT) ore districts. Deposits with the same mineralogy but at much smaller scales, known as trace MVT occurrences, are also widespread throughout the mid-continent, and have been found in Paleozoic strata ranging from the Cambrian to the Pennsylvanian. This research attempts to determine if trace MVT occurrences differ from their ore district counterparts in magnitude of scale only, or if the two types of deposits are formed from fundamentally different processes. Lead isotope compositions of the trace sphalerite matrices indicate that a significant portion of the Pb was derived from igneous basement, but a lack of collinearity with the midcontinent MVT ore districts indicates that the basement-derived Pb was diluted by Pb from other sources. Negative ?34S values of trace sphalerite matrices favor incomplete biological or thermochemical reduction of seawater sulfate reservoirs, and a lack of correlation between Pb and S isotopes shows they were not transported together to the site of mineralization. Primary, sphalerite-hosted fluid inclusions have Th values and salinities that suggest trace MVT occurrences did not form as a result of regional trends of both cooling and dilution. The compositions of these fluid inclusions resemble sphalerite ore-stage mineralization rather than gangue-stage fluids, but the general lack of detectible methane suggests conditions that precluded the presence of abundant reduced sulfur. Similar sphalerite matrix compositions show that any differences between trace and ore district fluids in major and minor element composition did not affect the ability of the trace fluids to transport metals in solution. Forest City basin trace occurrences have Cl/Br ratios which indicate several of them precipitated from brines derived from evaporatively concentrated seawater, but do not constrain seawater age. Reaction path models showed that trace occurrences from the FCB could be evolved from any Paleozoic-aged seawater, but trace fluids from the Greater Upper Mississippi Valley and Illinois basin regions were successfully modeled only by Devonian brines. Collectively, any variations observed do not appear to have been mitigating factors in controlling the scale MVT mineralization, but low to undetectable methane concentrations indicate either that metal-rich fluids did not encounter large quantities of organic matter, or that conditions during trace mineralization were too oxidizing for reduced sulfur to have been abundant.

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Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽

10.3390/geosciences11040172 ◽

2021 ◽

Vol 11 (4) ◽

pp. 172

Author(s):

Jonathan Chick ◽

Sydney E. McKim ◽

Adriana Potra ◽

Walter L. Manger ◽

John R. Samuelsen

Keyword(s):

Linear Trend ◽

Ore Deposits ◽

Source Rocks ◽

Mississippi Valley ◽

Isotopic Signatures ◽

Boone Formation ◽

Tripolitic Chert ◽

Geochemical Studies ◽

Mississippi Valley Type ◽

Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

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