John F. Slack
John Slack is a Scientist Emeritus with the USGS Geology, Energy & Minerals (GEM) Science Center in Reston, VA.
Science and Products
Filter Total Items: 69
The F'derik-Zouerate iron district: Mesoarchean and Paleoproterozoic iron formation of the Tiris Complex, Islamic Republic of Mauritania The F'derik-Zouerate iron district: Mesoarchean and Paleoproterozoic iron formation of the Tiris Complex, Islamic Republic of Mauritania
High-grade hematitic iron ores (of HIF, containing 60-65 wt%Fe) have been mined in Mauritania since 1952 from Superior-type iron deposits of the F'derik-Zouerate district. Depletion of the high-grade ores in recent years has resulted in new exploration projects focused on lower-grade magnetite ores occurring in Algoma-type banded iron formation (of BIF, containing ca. 35 wt% Fe)...
Authors
Cliff D. Taylor, Carol A. Finn, Eric D. Anderson, Dwight Bradley, Mohamed Joud, Ahmed Taleb Mohamed, John D. Horton, Craig A. Johnson
U-Pb, Re-Os, and Ar/Ar geochronology of rare earth element (REE)-rich breccia pipes and associated host rocks from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri U-Pb, Re-Os, and Ar/Ar geochronology of rare earth element (REE)-rich breccia pipes and associated host rocks from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri
Rare earth element (REE)-rich breccia pipes (600,000 t @ 12% rare earth oxides) are preserved along the margins of the 136-million metric ton (Mt) Pea Ridge magnetite-apatite deposit, within Mesoproterozoic (~1.47 Ga) volcanic-plutonic rocks of the St. Francois Mountains terrane in southeastern Missouri, United States. The breccia pipes cut the rhyolite-hosted magnetite deposit and...
Authors
John N. Aleinikoff, David Selby, John F. Slack, Warren C. Day, Renee M. Pillers, Michael A. Cosca, Cheryl Seeger, C. Mark Fanning, Iain Samson
Measurement of in situ sulfur isotopes by laser ablation multi-collector ICPMS: opening Pandora’s Box Measurement of in situ sulfur isotopes by laser ablation multi-collector ICPMS: opening Pandora’s Box
Laser ablation multi-collector ICPMS is a modern tool for in situ measurement of S isotopes. Advantages of the technique are speed of analysis and relatively minor matrix effects combined with spatial resolution sufficient for many applications. The main disadvantage is a more destructive sampling mechanism relative to the ion microprobe technique. Recent advances in instrumentation...
Authors
William I. Ridley, Michael Pribil, Alan E. Koenig, John F. Slack
Depositional conditions for the Kuna Formation, Red Dog Zn-PB-Ag-Barite District, Alaska, inferred from isotopic and chemical proxies Depositional conditions for the Kuna Formation, Red Dog Zn-PB-Ag-Barite District, Alaska, inferred from isotopic and chemical proxies
Water column redox conditions, degree of restriction of the depositional basin, and other paleoenvironmental parameters have been determined for the Mississippian Kuna Formation of northwestern Alaska from stratigraphic profiles of Mo, Fe/Al, and S isotopes in pyrite, C isotopes in organic matter, and N isotopes in bulk rock. This unit is important because it hosts the Red Dog and...
Authors
Craig A. Johnson, Julie A. Dumoulin, Robert A. Burruss, John F. Slack
Oxic to anoxic transition in bottom waters during formation of the Citronen Fjord sediment-hosted Zn-Pb deposit, North Greenland Oxic to anoxic transition in bottom waters during formation of the Citronen Fjord sediment-hosted Zn-Pb deposit, North Greenland
Bulk geochemical data acquired for host sedimentary rocks to the Late Ordovician Citronen Fjord sediment-hosted Zn-Pb deposit in North Greenland constrain the redox state of bottom waters prior to and during sulphide mineralization. Downhole profiles for one drill core show trends for redox proxies (MnO, Mo, Ce anomalies) that suggest the local basin bottom waters were initially oxic...
Authors
John F. Slack, Diogo Rosa, Hendrik Falck
Hydrothermal, biogenic, and seawater components in metalliferous black shales of the Brooks Range, Alaska: Synsedimentary metal enrichment in a carbonate ramp setting Hydrothermal, biogenic, and seawater components in metalliferous black shales of the Brooks Range, Alaska: Synsedimentary metal enrichment in a carbonate ramp setting
Trace element and Os isotope data for Lisburne Group metalliferous black shales of Middle Mississippian (early Chesterian) age in the Brooks Range of northern Alaska suggest that metals were sourced chiefly from local seawater (including biogenic detritus) but also from externally derived hydrothermal fluids. These black shales are interbedded with phosphorites and limestones in...
Authors
John F. Slack, David Selby, Julie A. Dumoulin
Science and Products
Filter Total Items: 69
The F'derik-Zouerate iron district: Mesoarchean and Paleoproterozoic iron formation of the Tiris Complex, Islamic Republic of Mauritania The F'derik-Zouerate iron district: Mesoarchean and Paleoproterozoic iron formation of the Tiris Complex, Islamic Republic of Mauritania
High-grade hematitic iron ores (of HIF, containing 60-65 wt%Fe) have been mined in Mauritania since 1952 from Superior-type iron deposits of the F'derik-Zouerate district. Depletion of the high-grade ores in recent years has resulted in new exploration projects focused on lower-grade magnetite ores occurring in Algoma-type banded iron formation (of BIF, containing ca. 35 wt% Fe)...
Authors
Cliff D. Taylor, Carol A. Finn, Eric D. Anderson, Dwight Bradley, Mohamed Joud, Ahmed Taleb Mohamed, John D. Horton, Craig A. Johnson
U-Pb, Re-Os, and Ar/Ar geochronology of rare earth element (REE)-rich breccia pipes and associated host rocks from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri U-Pb, Re-Os, and Ar/Ar geochronology of rare earth element (REE)-rich breccia pipes and associated host rocks from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri
Rare earth element (REE)-rich breccia pipes (600,000 t @ 12% rare earth oxides) are preserved along the margins of the 136-million metric ton (Mt) Pea Ridge magnetite-apatite deposit, within Mesoproterozoic (~1.47 Ga) volcanic-plutonic rocks of the St. Francois Mountains terrane in southeastern Missouri, United States. The breccia pipes cut the rhyolite-hosted magnetite deposit and...
Authors
John N. Aleinikoff, David Selby, John F. Slack, Warren C. Day, Renee M. Pillers, Michael A. Cosca, Cheryl Seeger, C. Mark Fanning, Iain Samson
Measurement of in situ sulfur isotopes by laser ablation multi-collector ICPMS: opening Pandora’s Box Measurement of in situ sulfur isotopes by laser ablation multi-collector ICPMS: opening Pandora’s Box
Laser ablation multi-collector ICPMS is a modern tool for in situ measurement of S isotopes. Advantages of the technique are speed of analysis and relatively minor matrix effects combined with spatial resolution sufficient for many applications. The main disadvantage is a more destructive sampling mechanism relative to the ion microprobe technique. Recent advances in instrumentation...
Authors
William I. Ridley, Michael Pribil, Alan E. Koenig, John F. Slack
Depositional conditions for the Kuna Formation, Red Dog Zn-PB-Ag-Barite District, Alaska, inferred from isotopic and chemical proxies Depositional conditions for the Kuna Formation, Red Dog Zn-PB-Ag-Barite District, Alaska, inferred from isotopic and chemical proxies
Water column redox conditions, degree of restriction of the depositional basin, and other paleoenvironmental parameters have been determined for the Mississippian Kuna Formation of northwestern Alaska from stratigraphic profiles of Mo, Fe/Al, and S isotopes in pyrite, C isotopes in organic matter, and N isotopes in bulk rock. This unit is important because it hosts the Red Dog and...
Authors
Craig A. Johnson, Julie A. Dumoulin, Robert A. Burruss, John F. Slack
Oxic to anoxic transition in bottom waters during formation of the Citronen Fjord sediment-hosted Zn-Pb deposit, North Greenland Oxic to anoxic transition in bottom waters during formation of the Citronen Fjord sediment-hosted Zn-Pb deposit, North Greenland
Bulk geochemical data acquired for host sedimentary rocks to the Late Ordovician Citronen Fjord sediment-hosted Zn-Pb deposit in North Greenland constrain the redox state of bottom waters prior to and during sulphide mineralization. Downhole profiles for one drill core show trends for redox proxies (MnO, Mo, Ce anomalies) that suggest the local basin bottom waters were initially oxic...
Authors
John F. Slack, Diogo Rosa, Hendrik Falck
Hydrothermal, biogenic, and seawater components in metalliferous black shales of the Brooks Range, Alaska: Synsedimentary metal enrichment in a carbonate ramp setting Hydrothermal, biogenic, and seawater components in metalliferous black shales of the Brooks Range, Alaska: Synsedimentary metal enrichment in a carbonate ramp setting
Trace element and Os isotope data for Lisburne Group metalliferous black shales of Middle Mississippian (early Chesterian) age in the Brooks Range of northern Alaska suggest that metals were sourced chiefly from local seawater (including biogenic detritus) but also from externally derived hydrothermal fluids. These black shales are interbedded with phosphorites and limestones in...
Authors
John F. Slack, David Selby, Julie A. Dumoulin