Marquette Range Supergroup Research Articles

U–Pb geochronology of baddeleyite from the Belleview metadiabase: Age and geotectonic implications for the Negaunee Iron Formation, Michigan

The Belleview metadiabase sill crosscuts the Siamo Slate and the Negaunee Iron Formation of the Marquette Range Supergroup, Michigan. It is one of a series of metamorphosed diabase sills that intrudes the Menominee Group and possibly the Baraga Group. Chloritic sills within the Marquette Range Supergroup have yet to be officially grouped as one or more series or swarms and therefore stratigraphic correlations and temporal relationships between these sills remain speculative. The recovery of the first sensitive high-resolution ion mass spectrometry (ID-TIMS) U–Pb date of 6 baddeleyite grains from the Belleview sill yielding an age of 1891±3Ma is a positive step to classifying these chloritic metadiabases. This new date has three important implications: (1) it gives a definitive minimum age of Negaunee Iron Formation deposition; (2) it confirms recent stratigraphic correlations that suggest that the Negaunee Iron Formation is older than the Mesabi, Gunflint and Gogebic Iron Ranges and not contemporaneous; and (3) it does not support recent correlations of the Menominee Group chloritic sills with the 1874Ma Hemlock Formation within the Baraga Group of the Marquette Range Supergroup.This new date does not support a more recently proposed synorogenic foredeep depositional environment for the deposition of the Negaunee Iron Formation. Instead, this age date supports an earlier interpretation that the Negaunee Iron Formation is part of continental shelf deposits laid down prior to onset of 1875–1835Ma collision. The age of the Belleview sill suggests that it is the result of extension-related magmatism that is prior to the currently defined Penokean orogenic event.

Early Paleoproterozoic supracrustal assemblages of the Rae domain, Nunavut, Canada: Intracratonic basin development during supercontinent break-up and assembly

The basal Paleoproterozoic supracrustal succession of the Churchill Province in northern Canada comprises sedimentary basins overlying the Archean Rae and Hearne domains. The Rae domain supracrustal succession (e.g. Amer, Ketyet River, Chantrey and Montresor groups) comprises four lithotectonic assemblages which include, in ascending stratigraphic position: (1) shallow marine-fluvial quartzarenite with mainly Neoarchean detrital zircons of local provenance; (2) shallow marine quartzarenite with mainly local provenance that locally includes carbonates ± mafic volcanic flows; (3) abrupt but conformable transition to basinal dark shales and overlying platformal carbonates that pass upward into siltstones and sandstones that record gradual emergence of the platform. Sandstones within this assemblage display a substantially different detrital zircon provenance signature dominated by early Paleoproterozoic zircons, with grains as young as 1.95 Ga; (4) unconformably to conformably overlying immature marine sandstones, including turbidites, with a significant component of 2.0–1.9 Ga detritus probably derived from a combination of local and distal sources. The thickness and relative compositional maturity of the basal lithotectonic assemblage 1 records a protracted period of enhanced weathering on a slowly subsiding but stable supercontinent (e.g. Kenorland). This was followed by mafic volcanism and marine transgression, consistent with partial rifting of the Rae domain and crustal extension attending supercontinent break-up (lithotectonic assemblage 2). Strata of lithotectonic assemblage 3 record basin flooding and deepening followed by platformal sedimentation along the margins of extended continental blocks. Assemblage 4 is interpreted to represent deposition in foreland basins during early amalgamation of Laurentia (part of Nuna) at ca. 1.9 Ga. The stratigraphy and detrital zircon geochronology of the Hurwitz Group, which overlies the Hearne domain, is broadly similar to the supracrustal sequence of the Rae domain, but differs through the presence of basal diamictites and lack of 2.5 Ga detritus, a major local source in the Rae. Our data suggest that the Rae and Hearne domains were assembled together by max. 1.91 Ga (i.e. max. age of deposition of the uppermost Hurwitz and Amer groups). The Paleoproterozoic stratigraphic assemblage framework for the Churchill Province compares well with that of other cratons derived from break-up of Kenorland and ultimately amalgamated in Nuna. Examples from Laurentia include supracrustal rocks that overlie the southern margin of the Superior Province (Southern Province, e.g. Huron Supergroup, Animikie Group, Marquette Range Supergroup, Whitewater Group and Mistassini-Otish Group). The Paleoproterozoic assemblages of the Southern and Churchill provinces exhibit first-order stratigraphic similarities that indicate a shared history of stable continental sedimentation followed by rifting, basin opening and basin closure.

Thermal history of low metamorphic grade Paleoproterozoic sedimentary rocks of the Penokean orogen, Lake Superior region: Evidence for a widespread 1786 Ma overprint based on xenotime geochronology

Paleoproterozoic strata in northern Michigan, Wisconsin, and Minnesota were deposited between 2.3 and 1.75 Ga within the rifted margin and subsequent foreland basin of the Penokean orogen. These strata show evidence for multiple regional metamorphic events previously attributed entirely to the Penokean orogeny (1875–1835 Ma). Metasandstones from the Marquette Range Supergroup and the Animikie, Mille Lacs, and North Range Groups were sampled at multiple localities across Minnesota, Wisconsin and Michigan for metamorphic xenotime suitable for in situ SHRIMP U–Pb geochronology. All samples are from the northern Penokean foreland basin where the metamorphic grade is greenschist to sub-greenschist and the strata are virtually undeformed. Xenotime U–Pb ages in these samples have a bimodal population with means of 1786 ± 4 Ma ( n = 32) and 1861 ± 10 Ma ( n = 9). Xenotime of both ages are contained in metasandstones from the basal Chocolay Group in Michigan and Wisconsin and the Mille Lacs Group and North Range Groups in Minnesota. The older age records a regional low-temperature thermal event that is slightly older than the overlying Menominee Group in Michigan and the Animikie Group in Minnesota and Ontario. This 1861 Ma event coincides with regional uplift that led to the formation of the unconformity between the Menominee Group and the overlying Baraga Group in Michigan; hence xenotime growth must have occurred at shallow burial depths. Younger units from the Menominee and Baraga Groups in Michigan and the Animikie Group in Minnesota, record only the 1786 Ma event. A dominant 1800–1790 Ma metamorphic monazite population that overprints Penokean-interval monazite has been documented within amphibolite- to granulite-facies rocks immediately north of the Niagara Fault Zone within the vicinity of gneiss domes and granitic plutons. In contrast, the 1786 Ma xenotime ages are from low-grade, virtually undeformed rocks 50–150 km from the high-grade zones and thus do not appear to reflect a local thermal imprint. Rather, the geographic extent of the 1786 Ma xenotime growth event suggests that it reflects a basin-wide, subtle thermal pulse. It is proposed that the xenotime ages record widespread subtle heating triggered by renewed subduction along the orogen due to Yavapai-interval convergence. The 1800–1700 Ma Yavapai terrane forms an accretionary belt throughout the central and southwestern U.S. and truncates the southern part of the Penokean orogen in central Wisconsin and southeastern Minnesota, about 200 km south of the sample sites. Alternatively, an 1800–1765 Ma interval of gravitational collapse of overthickened crust of the Penokean orogen immediately north of the Niagara Fault Zone may have driven a northward flow of hydrothermal fluids which subtly but pervasively altered the northern parts of the Penokean foreland and resulted in xenotime growth.

Age constraints for Paleoproterozoic glaciation in the Lake Superior Region: detrital zircon and hydrothermal xenotime ages for the Chocolay Group, Marquette Range Supergroup

A geochronological study of the Chocolay Group at the base of the Paleoproterozoic Marquette Range Supergroup in Michigan, Lake Superior Region, is attempted for the first time. Age data from detrital zircon grains and hydrothermal xenotime from the basal glaciogenic formation, the Enchantment Lake Formation, and the stratigraphically higher Sturgeon Quartzite and its equivalent, the Sunday Quartzite, provide maximum and minimum age constraints for the Chocolay Group. The youngest detrital zircon population in the Enchantment Lake Formation is 2317 ± 6 Ma; in the Sturgeon Quartzite, it is 2306 ± 9 Ma, and in the Sunday Quartzite, it is 2647 ± 5 Ma. The oldest hydrothermal xenotime age in the Enchantment Lake Formation is 2133 ± 11 Ma; in the Sturgeon Quartzite, it is 2115 ± 5 Ma, and in the Sunday Quartzite, it is 2207 ± 5 Ma. The radiometric age data in this study implies the depositional age of the Chocolay Group is constrained to ~2.3–2.2 Ga, which proves its correlation with part of the Huronian Supergroup in the Lake Huron Region, Ontario, and reveals the unconformity that separates the Chocolay Group from the overlying Menominee Group is up to 325 million years in duration. The source(s) of the ~ 2.3 Ga detrital zircon populations in the Enchantment Lake Formation and Sturgeon Quartzite remains an enigma because no known rock units of this age are known in the Michigan area. It is speculated that once widespread volcano-sedimentary cover sequences in Michigan were removed or concealed prior to Chocolay Group deposition. The hydrothermal xenotime ages probably reflect basinal hydrothermal fluid flow associated with the period of extension, involving rifting and major dyke formation, that affected the North American provinces between 2.2 and 2.1 Ga.

Age of volcanic rocks and syndepositional iron formations, Marquette Range Supergroup: implications for the tectonic setting of Paleoproterozoic iron formations of the Lake Superior region

A rhyolite in the Hemlock Formation, a mostly bimodal submarine volcanic deposit that is laterally correlative with the Negaunee Iron-formation, yields a sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon age of 1874 ± 9 Ma, but also contains inherited Archean zircons as old as 3.8 Ga. This precise age determination for the classic Paleoproterozoic stratigraphic sequence of northern Michigan, the Marquette Range Supergroup (MRS), necessitates modification of previous depositional and tectonic models. Our new data indicate that the Menominee Group, previously ascribed to continental rifting during early, pre-collision phases of the Penokean orogenic cycle, is coeval with arc-related volcanic rocks now preserved as accreted terranes immediately to the south and is more aptly interpreted as a foredeep deposit. We interpret these to be second-order basins created by oblique subduction of the continental margin rather than basins formed on a rifting margin. Along with a recently reported age for the Gunflint Formation in Ontario of 1878 ± 2 Ma, our data suggest that an extensive foredeep in the western Lake Superior region was the locus of iron-formation deposition during arc accretion from the south. Further, we interpret the lower MRS (Chocolay Group), a glaciogenic and shallow-marine succession that lies atop Archean basement, to be equivalent to the upper part of the Huronian Supergroup of Ontario and to represent the original continental rifting and passive-margin phase of the Penokean cycle. The upper MRS (Baraga Group) represents deeper marine basins, dominated by turbidites and lesser volcanic rocks, resulting from increased subsidence and continued collision. A stitching pluton, which cuts correlatives of the Hemlock Formation in a thrust sheet, yielded a U–Pb zircon age of 1833 ± 6 Ma, consistent with other post-tectonic plutons in Wisconsin and northern Michigan, indicating that Penokean convergence lasted no longer than ~40 million years.

The lower Proterozoic Fern Creek Formation, northern Michigan: mineral and bulk geochemical evidence for its glaciogenic origin

Bulk chemical data indicate the Fern Creek Formation (Early Proterozoic, Marquette Range Supergroup, Lower Chocolay Group) originated as a glacial till, resolving an old argument about the correct interpretation for diamictite-containing units within the formation. There are poor correlations among SiO2, Al2O3, and K2O, and the chemical index of alteration averages 55. These are qualities characteristic of tills and other sediments accumulated in the absence of chemical weathering and transport-induced sorting and inconsistent with an origin as a fluvial deposit (the principal alternate hypothesis). The Archean Carney Lake Gneiss might be the source for at least the lower portions of the Fern Creek Formation. Compositions are similar, and rare earth element trends in the Fern Creek Formation are consistent with derivation from an Archean high-grade terrane. Pegmatites in the gneiss could be the source for monazite, huttonite, and an unnamed fluor-hydroxy-rare earth mineral that occurs in the midsection of the Fern Creek Formation. In addition, mineral and bulk chemical trends are consistent with models involving deep erosion of a complex Archean source, similar to models previously developed for Gowganda tills in the Huronian Supergroup. Samples of the Sturgeon River Quartzite occurring above the Fern Creek Formation were also analyzed. The bulk chemistry is consistent with a well-sorted, supermature quartz arenite.

Crustal‐scale thrusting and origin of the Montreal River monocline‐A 35‐km‐thick cross section of the midcontinent rift in northern Michigan and Wisconsin

A structurally simple, 35‐km‐thick, north facing stratigraphic succession of Late Archean to Middle Proterozoic rocks is exposed near the Montreal River, which forms the border between northern Wisconsin and Michigan. This structure, the Montreal River monocline, is composed of steeply dipping to vertical sedimentary rocks and flood basalts of the Keweenawan Supergroup (Middle Proterozoic) along the south limb of the Midcontinent rift, and disconformably underlying sedimentary rocks of the Marquette Range Supergroup (Early Proterozoic). These rocks lie on an Archean granite‐greenstone complex, about 10 km of which is included in the monocline. This remarkable thickness of rocks appears to be essentially structurally intact and lacks evidence of tectonic thickening or repetition.Tilting to form the monocline resulted from southward thrusting on listric faults of crustal dimension. The faults responsible for the monocline are newly recognized components of a well‐known regional fault system that partly closed and inverted the Midcontinent rift system. Resetting of biotite ages on the upper plate of the faults indicates that faulting and uplift occurred at about 1060 +/−20 Ma and followed very shortly after extension that formed the Midcontinent rift system.

Nd isotopes and the origin of 1.9-1.7 Ga Penokean continental crust of the Lake Superior region

Nd isotopic data on 26 samples demonstrate the origin of the Early Proterozoic crust of the Penokean orogen. The three major components are (1) the Marquette Range Supergroup, a predominantly miogeoclinal continental-margin sequence deposited before 1.85 Ga on Archean basement; (2) ca. 1.88 Ga felsic metavolcanic rocks of the Wisconsin magmatic terrane to the south, of evolved island-arc affinity; and (3) 1.87-1.76 Ga granitoids that intrude the metavolcanic rocks. Initial ϵ Nd values for the metavolcanic rocks of the magmatic terrane range between 0.0 and +2.4 and T DM ages between 1.9 and 2.2 b.y. The volcanic rocks primarily represent new crustal material that had only a limited Archean input, probably through mixing of subducted sediments into the magma source area. ϵ Nd (T) values for sedimentary rocks in the lower part of the Marquette Range Supergroup indicate an Archean source, most likely the 2.7 Ga Superior province to the north. On the other hand, the sedimentary rocks in the upper part of the Marquette Range Supergroup (graywackes of the upper Michigamme Formation) have initial ϵ Nd values between -0.8 and +1.5, indicative of an Early Proterozoic source. These graywackes probably are foredeep deposits derived from the volcanic rocks of the Wisconsin magmatic terrane to the south. Thus, the time of deposition of the upper Michigamme Formation dates the final convergence of the Wisconsin magmatic terrane with the continental margin. The granitoids of the Wisconsin magmatic terrane have a wide range of ϵ Nd (T) values, from -4.5 to +4.0. They represent mixtures of variable amounts of new crustal material and recycled Archean detritus. The more negative ϵ Nd (T) values occur in samples close to the northern boundary of the Wisconsin magmatic terrane, which is marked by a mylonitic shear zone (the Niagara fault zone). We suggest that the miogeoclinal lower Marquette Range Supergroup rocks having an Archean Nd signature became involved in magma genesis close to the collisional boundary, whereas increasingly lesser amounts of this older material were available for mixing farther away from the suture. The 1.9-1.7 Ga Penokean events involved major growth of new crust from the mantle.

Early proterozoic geology of the great lakes region

The Belleview metadiabase sill crosscuts the Siamo Slate and the Negaunee Iron Formation of the Marquette Range Supergroup, Michigan. It is one of a series of metamorphosed diabase sills that intrudes the Menominee Group and possibly the Baraga Group. Chloritic sills within the Marquette Range Supergroup have yet to be officially grouped as one or more series or swarms and therefore stratigraphic correlations and temporal relationships between these sills remain speculative. The recovery of the first sensitive high-resolution ion mass spectrometry (ID-TIMS) U–Pb date of 6 baddeleyite grains from the Belleview sill yielding an age of 1891 ± 3 Ma is a positive step to classifying these chloritic metadiabases. This new date has three important implications: (1) it gives a definitive minimum age of Negaunee Iron Formation deposition; (2) it confirms recent stratigraphic correlations that suggest that the Negaunee Iron Formation is older than the Mesabi, Gunflint and Gogebic Iron Ranges and not contemporaneous; and (3) it does not support recent correlations of the Menominee Group chloritic sills with the 1874 Ma Hemlock Formation within the Baraga Group of the Marquette Range Supergroup.This new date does not support a more recently proposed synorogenic foredeep depositional environment for the deposition of the Negaunee Iron Formation. Instead, this age date supports an earlier interpretation that the Negaunee Iron Formation is part of continental shelf deposits laid down prior to onset of 1875–1835 Ma collision. The age of the Belleview sill suggests that it is the result of extension-related magmatism that is prior to the currently defined Penokean orogenic event.

The Dunbar Gneiss-granitoid dome: Implications for early Proterozoic tectonic evolution of northern Wisconsin

The Dunbar dome in northeastern Wisconsin is a critical structural feature in the early Proterozoic Penokean orogen. It provides exposures of gneisses (Dunbar Gneiss) that structurally underlie the voluminous metavolcanic rocks of northeastern Wisconsin, and exposures of abundant granitoid rocks ranging from tonalite to granite. The granitoid rocks cut both the gneisses in the core and the supracrustal (cover) metavolcanic rocks and were emplaced essentially along the core-cover boundary. The Dunbar Gneiss is calc-alkaline and was derived from volcanic and intrusive rocks of intermediate composition. The various intrusive rocks have calcic, calc-alkaline, and alkali to alkali-calcic compositions, and they progress with time to more SiO 2 and K 2 -rich compositions. U-Pb zircon ages indicate that accumulation of the layered rocks in the core and cover, deformation and metamorphism, and intrusion of the granitoid rocks spanned a relatively short time, ∼1865–1835 Ma. We interpret the dome as being a large-scale, fold-interference structure resulting from polydeformation modified by diapirism. Northeast-oriented folds (F 3 ) and a related mylonitic foliation (S 3 ), nearly confined to the dome, are superposed on northwest-oriented folds (F 2 ) that developed during regional deformation. In the core-cover boundary, these structures are obliterated by a zone of intense deformation—a mylonitic foliation and a steeply plunging stretching lineation—as much as 500 m wide, which we interpret as resulting from diapirism. Metamorphic zoning is concentric: amphibolite facies in inner parts of the mantle and greenschist facies in the outer part of the mantle. The Wisconsin magmatic terrane, as represented by the rocks in the Dunbar dome, differs from the epicratonic, early Proterozoic sedimentary-volcanic sequence (Marquette Range Supergroup) in Michigan, to the north, in stratigraphy, structure, and volume and composition of igneous rocks. Whereas the basalts in northern Michigan are compositionally similar to continental rift basalts, the volcanic rocks in the Dunbar dome have over-all island-arc compositional affinities. The over-all calc-alkaline compositions of the intrusive rocks are similar to those in magmatic arcs formed at convergent plate-margin settings. Accordingly, we interpret the Wisconsin magmatic terrane as an oceanic-arc complex that was sutured to the North American continent during development of the Penokean orogen. Similar interpretations based on broad regional observations have been proposed previously.

Early Proterozoic Sedimentary Basins of the Lake Superior Region

Studies of the complexly folded and metamorphosed early Proterozoic strata (1.8 to 2.1 b.y. B.P.; Van Schmus, 1976) of the Lake Superior region (Fig. 1) have revealed features indicating a complex sedimentary-tectonic evolution. These rocks, termed “the Marquette Range Supergroup,” and which include stratigraphic equivalents in Minnesota and Ontario (Cannon and Gair, 1970), have been divided into four groups (James, 1958), which, in ascending order, are the Chocolay, Menominee, Baraga, and Paint River Groups. In Minnesota and Ontario, the stratigraphic equivalents of the Chocolay, Menominee, and Baraga Groups are the Mille Lacs (Chocolay Group equivalent in the Cuyuna area), and lower (Menominee Group equivalent) and upper (Baraga Group equivalent) Animikie Group (Morey, 1978a) (Table 1). The stratified rocks of the Marquette Range Supergroup and stratigraphic equivalents occur in four structural settings (Fig. 1A): (1) elongate, generally synclinal, structural troughs bounded by Archean rocks; (2) extensive homoclines; (3) outliers on granitic basement; and (4) mantling rims around early Proterozoic gneiss domes (Sims, 1976). Some rims also form steep narrow troughs (for example, the Michigan River trough; Klasner and Cannon, 1974), which are here grouped with gneiss-dome rims as opposed to the other structural troughs (type 1 above) which appear to show no genetic relation to gneiss domes. Most of the data discussed herein concern the first two types of structural settings. It is the purpose of this paper to suggest a relationship between the four types of structural settings and the mode of original sedimentation. Specifically, we propose that elongate early Proterozoic sedimentary basins existed in eastern Upper Michigan at the sites of what became structural troughs later in the early Proterozoic; that is, the eastern Upper Michigan structural troughs are simply appressed sedimentary basins. As will be discussed, the Animikie basin (as reported by Morey, 1967; Morey and Ojakangas, 1970; and Alwin, 1979) represents a more “stable” type of sediment receptacle (types 1, 2 structural exposure) with a sedimentary history broadly comparable to the eastern Upper Michigan basins. Finally, it is noted that individual basin history was complex, with some more areas showing evidence of both basinal and platformal sedimentation.

A Discussion on global tectonics in Proterozoic times - Early and Middle Proterozoic history of the Great Lakes area, North America

Two major supracrustal sequences, the Huronian Supergroup in Ontario and the Marquette Range Supergroup and Animikie Group of Michigan and Minnesota, overlie an Archean basement. These sequences are about 2200—2300 Ma and 1900-2000 Ma old respectively. The major Early Proterozoic tectonic event is the ‘Penokean Orogeny’, which occurred about 1850-1900 Ma ago and included deformation, high-grade regional metamorphism, and extrusive and intrusive igneous activity. This was followed by formation of rhyolitic, ignimbritic volcanic rocks and emplacement of associated granites about 1790 Ma ago. The entire region was subsequently subjected to low-grade regional metamorphism 1650-1700 Ma ago, followed by emplacement of anorogenic quartz-monzonite, in part rapakivi, plutons 1500 Ma ago. Late Proterozoic Grenville and Keweenawan events represent the youngest major Precambrian activity in the region. The rocks involved in the Penokean Orogeny lie along the southern margin of the Archean craton of the Superior Province and are interpreted as representing Early Proterozoic cratonic-margin orogenic activity. The distribution of rocks types and structures associated with the Penokean Orogeny and with similar orogenic belts along the margin of the Archean craton of North America suggest that these orogenic belts may have formed as a result of processes similar to modern plate tectonics, although the data are far from conclusive at present.

A Revision of Stratigraphic Nomenclature for Middle Precambrian Rocks in Northern Michigan

The name Marquette Range Supergroup is proposed to supplant the term Animikie Series for middle Precambrian strata of the Northern Peninsula of Michigan and adjacent areas of Wisconsin. The Marquette Range Supergroup consists of the Chocolay, Menominee, Baraga, and Paint River Groups, as defined in previous literature. We feel that this new name to apply to Northern Peninsula rock units is appropriate, as continued investigations have failed to show unequivocal correlation between middle Precambrian rocks of Michigan and the Huronian Supergroup of Ontario. Although the equivalence of the Animikie Group in Ontario and Minnesota with parts of the Michigan rocks is likely, the Stratigraphic complexity of the Michigan sequence requires supergroup rank. The inherent confusion of an Animikie Group in Ontario and Minnesota, and an Animikie Supergroup in Michigan, makes a local name such as Marquette Range Supergroup preferable to Animikie for the middle Precambrian rocks of Michigan.