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Michael L. Zientek

Publications and source records attributed to Michael L. Zientek.

65 records · Page 4Linked to original sources

Mineral production and mining trends for selected non-fuel commodities in Idaho and Montana, 1905-2001

Idaho and Montana state mining statistics were obtained from historical mineral production records and compiled into a continuous record from 1905 through 2001. To facilitate comparisons, the mineral production data were normalized by converting the units of measure to metric tons for all included commodities. These standardized statistical data include production rates for principal non-fuel mineral commodities from both Idaho and Montana, as well as the production rates of similar commodities for the U.S. and the world for contrast. Data are presented here in both tabular and bar chart format. Moreover, the tables of standardized mineral production data are also provided in digital format as, commodity_production.xls. Some significant historical events pertaining to the mining industry are described as well. When taken into account with the historical production data, this combined information may to help explain both specific fluctuations and general tendencies in the overall trends in the rates of mineral resource production over time.

Open-File Report↗

Rhenium-osmium and samarium-neodymium isotopic systematics of the Stillwater Complex

Isotopic data for the Stillwater Complex, Montana, which formed about 2700 Ma (million years ago), were obtained to evaluate the role of magma mixing in the formation of strategic platinum-group element (PGE) ore deposits. Neodymium and osmium isotopic data indicate that the intrusion formed from at least two geochemically distinct magmas. Ultramafic affinity (U-type) magmas had initial ε Nd of -0.8 to -3.2 and a chondritic initial 187 Os/ 186 Os ratio of ∼0.88, whereas anorthositic affinity (A-type) magmas had ε Nd of -0.7 to +1.7 and an initial 187 Os/ 186 Os ratio of ∼1.13. These data suggest that U-type magmas were derived from a lithospheric mantle source containing recycled crustal materials whereas A-type magmas originated either by crustal contamination of basaltic magmas or by partial melting of basalt in the lower crust. The Nd and Os isotopic data also suggest that Os, and probably the other PGEs in ore horizons such as the J-M Reef, was derived from A-type magmas. The Nd and Os isotopic heterogeneity observed in rocks below the J-M Reef also suggests that A-type magmas were injected into the Stillwater U-type magma chamber at several stages during the development of the Ultramafic series.

Montana↗