Eric E Hiatt | University of Wisconsin Oshkosh (original) (raw)
Papers by Eric E Hiatt
The Canadian Mineralogist, 2018
Canadian Mineralogist, 2018
Chert and iron formation from the Ferriman Group (ca. 1.88 Ga) of the Labrador Trough, Canada, co... more Chert and iron formation from the Ferriman Group (ca. 1.88 Ga) of the Labrador Trough, Canada, contain an exceptional assemblage of fossil bacteria and biofilms. Analysis of lithofacies in a well-defined stratigraphic framework suggests that these microbes were restricted to suboxic, shallow-water environments through three sea level cycles. Microfossils are preserved as chert and sedimentary apatite (francolite) casts in hematite-rich, peritidal facies. Morphologies include sphere-, rod-, and filament-shaped bacteria; however, filamentous forms are the most common. Secondary electron imaging of freshly broken surfaces shows that filaments are similar in size and shape to modern bacteria; filaments vary between 0.5 and 5 μm wide and reach tens of μm in length. They commonly envelop chert and iron oxide grains, which stabilized the seafloor and contributed to firmground development. The filamentous morphology, similar mat-forming behavior, and paleoenvironmental conditions where thes...
The Challenge of Finding New Mineral ResourcesGlobal Metallogeny, Innovative Exploration, and New Discoveries
Sedimentary Geology
Abstract The Ediacaran Nova America and Gabriel members of the Salitre Formation are composed of ... more Abstract The Ediacaran Nova America and Gabriel members of the Salitre Formation are composed of limestone and economic phosphorite that accumulated on an unrimmed epeiric ramp along the margins of the Irece Basin, Brazil. Deposition occurred during a marine transgression punctuated by higher-order fluctuations in relative sea-level that produced m-scale, shallowing-upward peritidal cycles. Cycles consist of six lithofacies rich in microbial sedimentary structures including subtidal, cross-stratified grainstones and hemispheroidal columnar stromatolite reefs overlain by intertidal flat sediments indicative of decreasing accommodation. Phosphorite is restricted to the paleocoast where digitate stromatolite biostromes colonized tidal flats. Phosphorite accumulation is interpreted to have been associated with biostromes because photosynthetic oxygen production created a redox gradient beneath the seafloor that phosphogenic chemosynthetic bacteria exploited. The concentration of francolite or sedimentary apatite in microbial laminae suggests these bacteria actively stored, released, and concentrated phosphate to promote in situ precipitation. The sealing effect of interbedded, fine-grained tidal deposits was also critical for maintaining the high levels of pore water phosphate required. The absence of francolite in subtidal columnar stromatolite reefs implies phosphogenesis was prevented in deeper, more energetic environments because wave pumping of oxygenated seawater through reefs surrounded by constantly moving grainy sediment promoted the recycling of P directly back to the water column. The Salitre Formation has a complex paragenesis, including hydrothermal alteration that produced Mississippi Valley-type Pb-Zn mineralization. δ 18 O values of Nova America member dolomites range from − 10.2‰ to − 0.5‰ (mean = − 3.9‰) and δ 13 C ranges from − 9.2‰ to + 10.0‰ (mean = + 2.8‰). Samples contain varying proportions of low-Mg calcite and saddle dolomite. δ 18 O values of hydrothermal veins range from − 4.7‰ to − 3.0‰ (mean = − 4.2‰) reflecting equilibration with temperatures > 80 °C. δ 13 C values are between − 7.0‰ and + 5.6‰ (mean = − 1.8‰,). Late lateritic weathering produced calcretes with δ 18 O values between − 3.3‰ and − 1.3‰, and δ 13 C values from − 9.2‰ to − 8.0‰ (mean values are − 1.8‰ and − 8.7‰, respectively). Petrographic analysis, generally low δ 18 O, and high δ 13 C values suggest hydrothermal dolomitization and remobilization of P led to secondary phosphate mineralization of intertidal stromatolite biostromes to produce economic phosphorite. Collectively, these results suggest that the benthic P-cycle in the Neoproterozoic was more complex than previously surmised and emphasize the multifaceted significance of microbial, paleoenvironmental, and diagenetic processes that allowed phosphorite to accumulate on the Sao Franciscan craton. Such information further elucidates attributes of the onset of Earth's second major phosphogenic episode, which is roughly coincident with the Neoproterozoic Oxygenation Event (NOE) and the evolution of multicellular animals.
Precambrian Research
ABSTRACT The Paleoproterozoic Roraima Supergroup is a siliciclastic succession exposed in Guyana,... more ABSTRACT The Paleoproterozoic Roraima Supergroup is a siliciclastic succession exposed in Guyana, Venezuela and Brazil that filled the extensive Roraima Basin on the Amazon Craton. Sequence stratigraphy, mineral geochemistry, and geochronology are integrated to understand the evolution of the basin within the tectonic framework of the Amazon Craton, and fluid flow events to evaluate its uranium resource potential. Three depositional sequences comprise the Roraima Supergroup in Guyana. These are bounded by laterally extensive sequence boundaries, marking both fluvial incision and source area uplift, followed by aggradation and basin subsidence. The Roraima Supergroup experienced at least three major fluid events following deposition, associated with: 1) early burial (1820 Ma); 2) metasomatism during intrusion of the Avanavero Suite mafic sills (1799 ±9 Ma to 1779 ±10 Ma); and 3) late burial diagenesis (1756 ±5 Ma to 1723 ±10 Ma). The events are identified based on petrography, 207Pb/206Pb and 40Ar/39Ar ages of fluorapatite and white mica, and the isotopic compositions of H, C, O, and Sr in white mica and calcite. Despite having multiple characteristics indicating that it could host unconformity-related U deposits, the Roraima Basin suffered extensive permeability loss during early burial and then with Avanavero Suite intrusion. As a result, the probability that high-grade unconformity-related U deposits formed in the study area is unlikely.
Sedimentary Geology
ABSTRACT The Paleoproterozoic Sokoman Formation (ca. 1.88 Ga) of the Labrador Trough, eastern Can... more ABSTRACT The Paleoproterozoic Sokoman Formation (ca. 1.88 Ga) of the Labrador Trough, eastern Canada, is a ca. 100-m-thick succession of interbedded iron formation and fine-grained, terrigenous clastic sedimentary rocks. Detailed examination of drill cores and outcrops indicates a dynamic paleoshelf where an oxygen-stratified water column, coastal upwelling of hydrothermally derived Fe and Si, as well as tide- and storm-generated currents controlled lithofacies character. Vertical and lateral facies stacking patterns record deposition through two relative sea-level cycles that produced seven distinct lithofacies comprising two unconformity-bounded sequences. Sequence 1 reflects deposition of hematitic peritidal iron formation as deep as the upper shoreface. Sequence 2 is truncated by later erosion and encompasses the change to deeper-water accumulation of magnetite and Fe silicate-rich iron formation. The character and lateral distribution of redox-sensitive facies indicate that iron formation accumulation was controlled as much by shelf hydraulics as oxygen levels. The development of a suboxic surface ocean is interpreted to reflect photosynthetic oxygen production from a combination of peritidal stromatolites and cyanobacterial phytoplankton that flourished in nutrient-rich, upwelled waters offshore. Deposition of other continental margin iron formations also occurred on Paleoproterozoic shelves that were favourably positioned for coastal upwelling. Variability between iron formations reflects intrinsic factors such as shelf profile, fluvial contribution, eolian input, evaporation rates, and coastal current systems, which influenced upwelling dynamics and the delivery of Fe, Si, and nutrients. Aridity onshore was a primary depositional control since it governed the transport and type of diluting terrigenous clastics as well as evaporative precipitation along the coastline. As in the Phanerozoic, unconformities, and transgressive and maximum flooding surfaces frame iron formation sequences, but with important differences. The absence of trace and body fossils as well as lack of terrestrial vegetation can make the recognition of these surfaces difficult. Transgressive surfaces can also be easily mistaken for Phanerozoic-style maximum flooding surfaces since stratigraphic condensation was restricted to inboard environments during ravinement. Outboard the accumulation of fresh precipitates increased sedimentation to produce a maximum flooding surface not usually marked by a prominent depositional hiatus. Understanding these differences is essential for establishing an accurate sequence stratigraphic framework. Such context is important because it is the backdrop for interpreting the sedimentology, oceanography, microbial ecology, and geochemistry of continental margin iron formations in proper paleoenvironmental, diagenetic, and metamorphic context.
Cathodoluminescent petrography (CL) is a well established technique that can provide a means to e... more Cathodoluminescent petrography (CL) is a well established technique that can provide a means to examine fabrics, diagenetic phases and cement relationships in sedimentary rocks. CL is very useful in the study of carbonate rocks because of the activators and quenchers. Mn is the most important CL activator in carbonate minerals and concentrations of ca. 20 ppm can cause luminescence, although levels of just a few ppm may be enough to cause weak CL depending on the amount of Fe present. Fe begins to quench luminescence at levels of ca. 200 ppm, and effectively quenches luminescence at levels of 103 ppm. Mn and Fe both have divalent reduced forms that readily fit into trigonal carbonate crystal structures and they have different redox potentials, so the concentration of these cations provide a baseline for understanding oxygen levels of the pore fluids from which the carbonate precipitated. Dolomite is an important sedimentary mineral that can be difficult to interpret because many dol...
Special Paper 370: Extreme depositional environments: mega end members in geologic time, 2003
Sedimentary Geology, 2015
ABSTRACT Phosphorus is a nutrient fundamental to life and when it precipitates in modern environm... more ABSTRACT Phosphorus is a nutrient fundamental to life and when it precipitates in modern environments bacteria are intimately involved in its release, concentration, and mineralization. Preserved fossil bacteria in phosphate crusts and grains from the ca. 1850 million-year-old Bijiki Iron Formation Member of the Michigamme Formation, Michigan provide insight into the longevity and nature of this relationship. The Michigamme Formation accumulated near the end of the Earth's initial phosphogenic episode (ca. 2.2 and 1.8 Ga) to produce one of the first granular phosphorites. Phosphatic lithofacies consist of fine- to medium-sand-sized francolite peloids concentrated on bedding surfaces in peritidal facies. Granular beds are up to 2 cm thick and peloids are often partially to completely replaced by dolomite and chert. The grains contain organic matter and pyrite framboids that suggest bacterial breakdown of organic matter and bacterial sulfate reduction.
Sedimentology, 2013
ABSTRACT The Palaeoproterozoic Frere Formation (ca 1.89 Gyr old) of the Earaheedy Basin, Western ... more ABSTRACT The Palaeoproterozoic Frere Formation (ca 1.89 Gyr old) of the Earaheedy Basin, Western Australia, is a ca 600 m thick succession of iron formation and fine- grained, clastic sedimentary rocks that accumulated on an unrimmed continental margin with oceanic upwelling. Lithofacies stacking patterns suggest that depo- sition occurred during a marine transgression punctuated by higher frequency relative sea-level fluctuations that produced five parasequences. Decametre-scale parasequences are defined by flooding surfaces overlain by either laminated mag- netite or magnetite-bearing, hummocky cross-stratified sandstone that grades upward into interbedded hematite-rich mudstone and trough cross-stratified granular iron formation. Each aggradational cycle is interpreted to record progra- dation of intertidal and tidal channel sediments over shallow subtidal and storm-generated deposits of the middle shelf. The presence of aeolian deposits, mud cracks and absence of coarse clastics indicate deposition along an arid coastline with significant wind-blown sediment input. Iron formation in the Fre- re Formation, in contrast to most other Palaeoproterozoic examples, was depos- ited almost exclusively in peritidal environments. These other continental margin iron formations also reflect upwelling of anoxic, Fe-rich sea water, but accumulated in the full spectrum of shelf environments. Dilution by fine- grained, windblown terrigenous clastic sediment probably prevented the Frere iron formation from forming in deeper settings. Lithofacies associations and interpreted paragenetic pathways of Fe-rich lithofacies further suggest precipita- tion in sea water with a prominent oxygen chemocline. Although essentially un- metamorphosed, the complex diagenetic history of the Frere Formation demonstrates that understanding the alteration of iron formation is a prerequisite for any investigation seeking to interpret ocean-atmosphere evolution. Unlike studies that focus exclusively on their chemistry, an approach that also considers palaeoenvironment and oceanography, as well the effects of post-depositional fluid flow and alteration, mitigates the potential for incorrectly interpreting geochemical data.
The Canadian Mineralogist, 2018
Canadian Mineralogist, 2018
Chert and iron formation from the Ferriman Group (ca. 1.88 Ga) of the Labrador Trough, Canada, co... more Chert and iron formation from the Ferriman Group (ca. 1.88 Ga) of the Labrador Trough, Canada, contain an exceptional assemblage of fossil bacteria and biofilms. Analysis of lithofacies in a well-defined stratigraphic framework suggests that these microbes were restricted to suboxic, shallow-water environments through three sea level cycles. Microfossils are preserved as chert and sedimentary apatite (francolite) casts in hematite-rich, peritidal facies. Morphologies include sphere-, rod-, and filament-shaped bacteria; however, filamentous forms are the most common. Secondary electron imaging of freshly broken surfaces shows that filaments are similar in size and shape to modern bacteria; filaments vary between 0.5 and 5 μm wide and reach tens of μm in length. They commonly envelop chert and iron oxide grains, which stabilized the seafloor and contributed to firmground development. The filamentous morphology, similar mat-forming behavior, and paleoenvironmental conditions where thes...
The Challenge of Finding New Mineral ResourcesGlobal Metallogeny, Innovative Exploration, and New Discoveries
Sedimentary Geology
Abstract The Ediacaran Nova America and Gabriel members of the Salitre Formation are composed of ... more Abstract The Ediacaran Nova America and Gabriel members of the Salitre Formation are composed of limestone and economic phosphorite that accumulated on an unrimmed epeiric ramp along the margins of the Irece Basin, Brazil. Deposition occurred during a marine transgression punctuated by higher-order fluctuations in relative sea-level that produced m-scale, shallowing-upward peritidal cycles. Cycles consist of six lithofacies rich in microbial sedimentary structures including subtidal, cross-stratified grainstones and hemispheroidal columnar stromatolite reefs overlain by intertidal flat sediments indicative of decreasing accommodation. Phosphorite is restricted to the paleocoast where digitate stromatolite biostromes colonized tidal flats. Phosphorite accumulation is interpreted to have been associated with biostromes because photosynthetic oxygen production created a redox gradient beneath the seafloor that phosphogenic chemosynthetic bacteria exploited. The concentration of francolite or sedimentary apatite in microbial laminae suggests these bacteria actively stored, released, and concentrated phosphate to promote in situ precipitation. The sealing effect of interbedded, fine-grained tidal deposits was also critical for maintaining the high levels of pore water phosphate required. The absence of francolite in subtidal columnar stromatolite reefs implies phosphogenesis was prevented in deeper, more energetic environments because wave pumping of oxygenated seawater through reefs surrounded by constantly moving grainy sediment promoted the recycling of P directly back to the water column. The Salitre Formation has a complex paragenesis, including hydrothermal alteration that produced Mississippi Valley-type Pb-Zn mineralization. δ 18 O values of Nova America member dolomites range from − 10.2‰ to − 0.5‰ (mean = − 3.9‰) and δ 13 C ranges from − 9.2‰ to + 10.0‰ (mean = + 2.8‰). Samples contain varying proportions of low-Mg calcite and saddle dolomite. δ 18 O values of hydrothermal veins range from − 4.7‰ to − 3.0‰ (mean = − 4.2‰) reflecting equilibration with temperatures > 80 °C. δ 13 C values are between − 7.0‰ and + 5.6‰ (mean = − 1.8‰,). Late lateritic weathering produced calcretes with δ 18 O values between − 3.3‰ and − 1.3‰, and δ 13 C values from − 9.2‰ to − 8.0‰ (mean values are − 1.8‰ and − 8.7‰, respectively). Petrographic analysis, generally low δ 18 O, and high δ 13 C values suggest hydrothermal dolomitization and remobilization of P led to secondary phosphate mineralization of intertidal stromatolite biostromes to produce economic phosphorite. Collectively, these results suggest that the benthic P-cycle in the Neoproterozoic was more complex than previously surmised and emphasize the multifaceted significance of microbial, paleoenvironmental, and diagenetic processes that allowed phosphorite to accumulate on the Sao Franciscan craton. Such information further elucidates attributes of the onset of Earth's second major phosphogenic episode, which is roughly coincident with the Neoproterozoic Oxygenation Event (NOE) and the evolution of multicellular animals.
Precambrian Research
ABSTRACT The Paleoproterozoic Roraima Supergroup is a siliciclastic succession exposed in Guyana,... more ABSTRACT The Paleoproterozoic Roraima Supergroup is a siliciclastic succession exposed in Guyana, Venezuela and Brazil that filled the extensive Roraima Basin on the Amazon Craton. Sequence stratigraphy, mineral geochemistry, and geochronology are integrated to understand the evolution of the basin within the tectonic framework of the Amazon Craton, and fluid flow events to evaluate its uranium resource potential. Three depositional sequences comprise the Roraima Supergroup in Guyana. These are bounded by laterally extensive sequence boundaries, marking both fluvial incision and source area uplift, followed by aggradation and basin subsidence. The Roraima Supergroup experienced at least three major fluid events following deposition, associated with: 1) early burial (1820 Ma); 2) metasomatism during intrusion of the Avanavero Suite mafic sills (1799 ±9 Ma to 1779 ±10 Ma); and 3) late burial diagenesis (1756 ±5 Ma to 1723 ±10 Ma). The events are identified based on petrography, 207Pb/206Pb and 40Ar/39Ar ages of fluorapatite and white mica, and the isotopic compositions of H, C, O, and Sr in white mica and calcite. Despite having multiple characteristics indicating that it could host unconformity-related U deposits, the Roraima Basin suffered extensive permeability loss during early burial and then with Avanavero Suite intrusion. As a result, the probability that high-grade unconformity-related U deposits formed in the study area is unlikely.
Sedimentary Geology
ABSTRACT The Paleoproterozoic Sokoman Formation (ca. 1.88 Ga) of the Labrador Trough, eastern Can... more ABSTRACT The Paleoproterozoic Sokoman Formation (ca. 1.88 Ga) of the Labrador Trough, eastern Canada, is a ca. 100-m-thick succession of interbedded iron formation and fine-grained, terrigenous clastic sedimentary rocks. Detailed examination of drill cores and outcrops indicates a dynamic paleoshelf where an oxygen-stratified water column, coastal upwelling of hydrothermally derived Fe and Si, as well as tide- and storm-generated currents controlled lithofacies character. Vertical and lateral facies stacking patterns record deposition through two relative sea-level cycles that produced seven distinct lithofacies comprising two unconformity-bounded sequences. Sequence 1 reflects deposition of hematitic peritidal iron formation as deep as the upper shoreface. Sequence 2 is truncated by later erosion and encompasses the change to deeper-water accumulation of magnetite and Fe silicate-rich iron formation. The character and lateral distribution of redox-sensitive facies indicate that iron formation accumulation was controlled as much by shelf hydraulics as oxygen levels. The development of a suboxic surface ocean is interpreted to reflect photosynthetic oxygen production from a combination of peritidal stromatolites and cyanobacterial phytoplankton that flourished in nutrient-rich, upwelled waters offshore. Deposition of other continental margin iron formations also occurred on Paleoproterozoic shelves that were favourably positioned for coastal upwelling. Variability between iron formations reflects intrinsic factors such as shelf profile, fluvial contribution, eolian input, evaporation rates, and coastal current systems, which influenced upwelling dynamics and the delivery of Fe, Si, and nutrients. Aridity onshore was a primary depositional control since it governed the transport and type of diluting terrigenous clastics as well as evaporative precipitation along the coastline. As in the Phanerozoic, unconformities, and transgressive and maximum flooding surfaces frame iron formation sequences, but with important differences. The absence of trace and body fossils as well as lack of terrestrial vegetation can make the recognition of these surfaces difficult. Transgressive surfaces can also be easily mistaken for Phanerozoic-style maximum flooding surfaces since stratigraphic condensation was restricted to inboard environments during ravinement. Outboard the accumulation of fresh precipitates increased sedimentation to produce a maximum flooding surface not usually marked by a prominent depositional hiatus. Understanding these differences is essential for establishing an accurate sequence stratigraphic framework. Such context is important because it is the backdrop for interpreting the sedimentology, oceanography, microbial ecology, and geochemistry of continental margin iron formations in proper paleoenvironmental, diagenetic, and metamorphic context.
Cathodoluminescent petrography (CL) is a well established technique that can provide a means to e... more Cathodoluminescent petrography (CL) is a well established technique that can provide a means to examine fabrics, diagenetic phases and cement relationships in sedimentary rocks. CL is very useful in the study of carbonate rocks because of the activators and quenchers. Mn is the most important CL activator in carbonate minerals and concentrations of ca. 20 ppm can cause luminescence, although levels of just a few ppm may be enough to cause weak CL depending on the amount of Fe present. Fe begins to quench luminescence at levels of ca. 200 ppm, and effectively quenches luminescence at levels of 103 ppm. Mn and Fe both have divalent reduced forms that readily fit into trigonal carbonate crystal structures and they have different redox potentials, so the concentration of these cations provide a baseline for understanding oxygen levels of the pore fluids from which the carbonate precipitated. Dolomite is an important sedimentary mineral that can be difficult to interpret because many dol...
Special Paper 370: Extreme depositional environments: mega end members in geologic time, 2003
Sedimentary Geology, 2015
ABSTRACT Phosphorus is a nutrient fundamental to life and when it precipitates in modern environm... more ABSTRACT Phosphorus is a nutrient fundamental to life and when it precipitates in modern environments bacteria are intimately involved in its release, concentration, and mineralization. Preserved fossil bacteria in phosphate crusts and grains from the ca. 1850 million-year-old Bijiki Iron Formation Member of the Michigamme Formation, Michigan provide insight into the longevity and nature of this relationship. The Michigamme Formation accumulated near the end of the Earth's initial phosphogenic episode (ca. 2.2 and 1.8 Ga) to produce one of the first granular phosphorites. Phosphatic lithofacies consist of fine- to medium-sand-sized francolite peloids concentrated on bedding surfaces in peritidal facies. Granular beds are up to 2 cm thick and peloids are often partially to completely replaced by dolomite and chert. The grains contain organic matter and pyrite framboids that suggest bacterial breakdown of organic matter and bacterial sulfate reduction.
Sedimentology, 2013
ABSTRACT The Palaeoproterozoic Frere Formation (ca 1.89 Gyr old) of the Earaheedy Basin, Western ... more ABSTRACT The Palaeoproterozoic Frere Formation (ca 1.89 Gyr old) of the Earaheedy Basin, Western Australia, is a ca 600 m thick succession of iron formation and fine- grained, clastic sedimentary rocks that accumulated on an unrimmed continental margin with oceanic upwelling. Lithofacies stacking patterns suggest that depo- sition occurred during a marine transgression punctuated by higher frequency relative sea-level fluctuations that produced five parasequences. Decametre-scale parasequences are defined by flooding surfaces overlain by either laminated mag- netite or magnetite-bearing, hummocky cross-stratified sandstone that grades upward into interbedded hematite-rich mudstone and trough cross-stratified granular iron formation. Each aggradational cycle is interpreted to record progra- dation of intertidal and tidal channel sediments over shallow subtidal and storm-generated deposits of the middle shelf. The presence of aeolian deposits, mud cracks and absence of coarse clastics indicate deposition along an arid coastline with significant wind-blown sediment input. Iron formation in the Fre- re Formation, in contrast to most other Palaeoproterozoic examples, was depos- ited almost exclusively in peritidal environments. These other continental margin iron formations also reflect upwelling of anoxic, Fe-rich sea water, but accumulated in the full spectrum of shelf environments. Dilution by fine- grained, windblown terrigenous clastic sediment probably prevented the Frere iron formation from forming in deeper settings. Lithofacies associations and interpreted paragenetic pathways of Fe-rich lithofacies further suggest precipita- tion in sea water with a prominent oxygen chemocline. Although essentially un- metamorphosed, the complex diagenetic history of the Frere Formation demonstrates that understanding the alteration of iron formation is a prerequisite for any investigation seeking to interpret ocean-atmosphere evolution. Unlike studies that focus exclusively on their chemistry, an approach that also considers palaeoenvironment and oceanography, as well the effects of post-depositional fluid flow and alteration, mitigates the potential for incorrectly interpreting geochemical data.