INTEGRATING THE CHRONOSTRATIGRAPHIC RECORD OF MIDCONTINENT RIFT VOLCANISM WITH THE HISTORY OF INTRUSIVE ACTIVITY

2020 ◽  
Author(s):  
Nicholas L. Swanson-Hysell ◽  
◽  
Yiming Zhang ◽  
Mark D. Schmitz ◽  
James L. Crowley ◽  
...  
Keyword(s):  
Midcontinent Rift ◽  
History Of ◽  
Intrusive Activity

Early history of the Midcontinent Rift inferred from geochemistry and sedimentology of the Mesoproterozoic Osler Group, northwestern Ontario

2007 ◽  
Vol 44 (3) ◽  
pp. 389-412 ◽  
Author(s):  
Pete Hollings ◽  
Philip Fralick ◽  
Brian Cousens
Keyword(s):  
Alluvial Fan ◽  
Midcontinent Rift ◽  
Fluvial Systems ◽  
The North ◽  
Northwestern Ontario ◽  
History Of ◽  
Group A ◽  
South Axis ◽  
Island Basalt ◽  
East West

The Mesoproterozoic 1108–1105 Ma Osler Group, a 3 km thick succession of basaltic flows and sedimentary units on the north shore of Lake Superior, is among the oldest expressions of the Midcontinent Rift. Basal sediments of the Simpson Island Formation (new name) deposited by braided fluvial systems record westward transport of debris eroded from local Archean and Proterozoic rock units. Strata deposited by this fluvial system are intercalated with, and overlain by, ocean-island basalt (OIB)-like basalts, which become increasingly contaminated up section (εNd(1100Ma) = +0.3 to –5.3). The light rare-earth element (LREE) enriched (La/Smn = 1.5–3.9) and heavy REE (HREE) fractionated (Gd/Ybn = 1.5–3.7) subaerial flows are divisible into two units that correlate with other sections of the Osler Group to the east, but simple correlations with more distant sequences are difficult. The volcanic rock dominated portion of the succession is overlain by a thin (25 m thick) conglomerate–sandstone assemblage representing southeast progradation of an alluvial fan in a semi-arid climatic setting. Clast lithologies and geochemistry indicate no extra-rift detritus was delivered from the hinterland of the fan. Various lines of evidence in both volcanic and sedimentary rocks support a scenario where early, pre-1108 Ma, subsidence along a north–south axis from the western arm of the rift to the Nipigon Embayment was replaced by subsidence along the east–west rift axis between 1108 and 1105 Ma.

scholarly journals Posteruptive Thermal History of the Proterozoic Basaltic North Shore Volcanic Group of the Midcontinent Rift: Evidence from K/Ar Data of Celadonite

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Susanne Theodora Schmidt ◽  
Annette Süssenberger ◽  
Klaus Wemmer
Keyword(s):  
Low Temperature ◽  
Thermal History ◽  
Meteoric Water ◽  
Hydrothermal Activity ◽  
Rift System ◽  
Magmatic Activity ◽  
Midcontinent Rift ◽  
North Shore ◽  
Volcanic Group ◽  
History Of

Abstract This study reports three K/Ar ages on celadonite, a dioctahedral K-Fe mica, in the Proterozoic North Shore Volcanic Group (NSVG) of the Midcontinent Rift in northeastern Minnesota. Celadonite formed during beginning posteruptive, low-temperature conditions at temperatures<100°C and with input of meteoric water. K/Ar ages between 1062±16 Ma and 955.0±12 Ma document a remarkably long posteruptive thermal history of >100 myrs in a thick continental basaltic sequence. In the stratigraphically lower part of the NSVG, celadonite formation occurred at 1062±16 Ma in an amygdule or a vesicle filled with celadonite, while another celadonite amygdule in a stratigraphically higher flow was dated at 1039.4±14 Ma. Both flows are overprinted by a later multistage lower zeolite-phyllosilicate facies assemblage (laumontite-albite-corrensite±chlorite±smectite±prehnite±pumpellyite). In the stratigraphically higher part of the sequence, celadonite crystallization at an amygdule rim is followed by upper zeolite facies conditions (stilbite-heulandite-smectite assemblage) and was dated at 955.0±12.4 Ma. The constrained time frame of 107 myrs indicates a long-lived, probably not continuous and locally occurring, posteruptive thermal alteration process. The data suggest that alteration was depth-controlled and temporally and spatially inhomogeneous and implies the progression of the sequence from a close-to-the-surface alteration mode with input of meteoric water to a burial metamorphic mode and with locally occurring hydrothermal activity due to continuous magmatic activity. Volcanism in the Midcontinent Rift system is supposed to have lasted between 1109 Ma and 1083 Ma based on U/Pb zircon ages. The first crystallization of celadonite is recorded in the lower part of the NSVG and occurred ca. 30 myrs after the emplacement of the Silver Bay aplite intrusion in the upper part of the NSVG. Burial rates are determined to be 0.04 km·Ma-1and 0.10 km·Ma-1. The hydrothermal alteration under low-temperature burial conditions clearly postdates the rift-related alkaline and tholeiitic magmatism of the Midcontinent Rift and overlaps with the depositional window of the sedimentary rocks that overlie the Midcontinent Rift volcanics, as well as crustal-scale fault systems that were active during Grenvillian tectonic uplift after the cessation of magmatic activity.

scholarly journals Burial and exhumation history of the Jameson Land Basin, East Greenland, estimated from thermochronological data from the Blokelv-1 core

2018 ◽  
pp. 133-147
Author(s):  
Paul F. Green ◽  
Peter Japsen
Keyword(s):  
Middle Eocene ◽  
Vitrinite Reflectance ◽  
Upper Jurassic ◽  
Late Eocene ◽  
Early Eocene ◽  
Ocean Drilling Program ◽  
East Greenland ◽  
Ocean Drilling ◽  
History Of ◽  
Intrusive Activity

Apatite fission-track analysis (AFTA) data in two Upper Jurassic core samples from the 231 m deep Blokelv-1 borehole, Jameson Land, East Greenland, combined with vitrinite reflectance data and regional AFTA data, define three palaeo-thermal episodes. We interpret localised early Eocene (55– 50 Ma) palaeotemperatures as representing localised early Eocene heating related to intrusive activity whereas we interpret late Eocene (40–35 Ma) and late Miocene (c. 10 Ma) palaeotemperatures as representing deeper burial followed by successive episodes of exhumation. For a palaeogeothermal gradient of 30°C/km and likely palaeo-surface temperatures, the late Eocene palaeotemperatures require that the Upper Jurassic marine section in the borehole was buried below a 2750 m thick cover of Upper Jurassic – Eocene rocks prior to the onset of late Eocene exhumation. As these sediments are now near outcrop at c. 200 m above sea level, they have been uplifted by at least 3 km since maximum burial during post-rift thermal subsidence. The results are consistent with estimates of rock uplift on Milne Land since the late Eocene and with interpretation of Ocean Drilling Program (ODP) data off South-East Greenland suggesting that mid-Cenozoic uplift of the margin triggered the marked influx of coarse clastic turbidites during the late Oligocene above a middle Eocene to upper Oligocene hiatus.

Geochemistry of the Mamainse Point volcanics, Ontario, and implications for the Keweenawan paleomagnetic record

1990 ◽  
Vol 27 (9) ◽  
pp. 1194-1199 ◽  
Author(s):  
Kenneth W. Klewin ◽  
Jonathan H. Berg
Keyword(s):  
North America ◽  
Lake Superior ◽  
Lava Flows ◽  
Geochemical Data ◽  
Basaltic Lava ◽  
Trace Element Data ◽  
Eastern Shore ◽  
Midcontinent Rift ◽  
History Of ◽  
Entire Sequence

The Keweenawan (1100 Ma) Mamainse Point volcanics, located along the eastern shore of Lake Superior in Ontario, formed in the Midcontinent Rift of North America. They are a 5250 m thick sequence of over 350 predominantly basaltic lava flows. The Mamainse Point section is the most continuous Keweenawan volcanic sequence and spans nearly the entire igneous history of the rift. The lower part of the section consists of high-MgO picrites and basalts, but the upper part of the section is composed of olivine tholeiites intercalated with numerous conglomerate layers. Major- and trace-element data reveal that the section consists of numerous stratigraphically constrained, geochemically distinct groups of lava flows. The comprehensive geochemical data on the entire sequence indicate that the section has no repetition due to faulting, as has been suggested by other workers on the basis of paleomagnetic studies. Evidently, the three paleomagnetic reversals previously found in the Mamainse Point section are real, and therefore there were multiple paleomagnetic reversals during Keweenawan time.

Seismic history of Minnesota and its geological significance

1981 ◽  
Vol 71 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Harold M. Mooney ◽  
G. B. Morey
Keyword(s):  
Maximum Intensity ◽  
Rift System ◽  
Tectonic Zone ◽  
Midcontinent Rift ◽  
Western Margin ◽  
The North ◽  
Midcontinent Rift System ◽  
History Of ◽  
Tectonic Features ◽  
Felt Area

abstract Twelve earthquakes have been documented in Minnesota in the last 120 yr. The first nine were felt, whereas the last three (all in 1979) were detected instrumentally by a six-element seismic array which has recently been put into operation. Estimated magnitudes range from 0.1 (instrumental only) to 4.8, with four of magnitude 4.3 or greater. The highest intensity values were VI to VII. Depths where obtainable are estimated at 5 to 20 km. The best documented event occurred on 9 July 1975 near Morris, Minnesota, with a magnitude of 4.6, a maximum intensity of VI, and a felt area of 82,000 km2 covering parts of four states. The event was recorded to epicentral distances of at least 38°. The epicenters show a clear relationship to tectonic features of the state. Four epicenters lie along the newly defined Great Lakes Tectonic Zone, an east-northeast-trending belt extending across several states and into Canada. The zone separates 3,000 to 3,600 m.y. rocks of a gneissic terrane to the south from 2,700 m.y. rocks of a greenstone-granite terrane to the north. Four other events lie on known major northwest-trending faults in the greenstone-granite terrane. Two and possibly three events are associated with the western margin of the Midcontinent Rift System.

Exploring rift magmatism and evolution through gravity analysis of North America's failed rifts

2021 ◽  
Author(s):  
Reece Elling ◽  
Seth Stein ◽  
Carol Stein ◽  
G. Randy Keller
Keyword(s):  
Gravity Data ◽  
Gravity Anomalies ◽  
High Density ◽  
Normal Faults ◽  
Positive Anomaly ◽  
The West ◽  
Midcontinent Rift ◽  
Magmatic Underplating ◽  
Continental Rifts ◽  
History Of

<p>Comparative study of North America’s failed continental rifts allows investigation of the effects of extension, magmatism, magmatic underplating and rift inversion in the evolution of rifting. We explore this issue by examining the gravity signatures of the Midcontinent Rift (MCR), Reelfoot Rift (RR), and Southern Oklahoman Aulacogen (SOA). The ~1.1 Ga MCR records aspects of the complex assembly of Rodina, while the structures related to the ~560 Ma RR and SOA formed during the later breakup of Rodinia and subsequent assembly of Pangea. Combining average gravity anomalies along each rift with seismic data, we examine whether these data support the existence of high-density residual melt underplates (“rift pillows”), reflect the possible amounts of inversion, and whether these rifts should be considered analogs of one another at different stages in rift evolution. The MCR and SOA have strong gravity highs along much of their length. Furthermore, the west and east arms of the MCR have different gravity signatures. The west arm of the MCR has a positive gravity anomaly of 80-100 mgals, while the east arm and SOA have positive anomalies of only 40-50 mgals. The RR does not exhibit a high positive anomaly along much of its length. The positive anomalies of both arms of the MCR and SOA reflect 10-20 km thick underplates at the base of the crust. These gravity anomalies also reflect greater amounts of inversion, during which the rift-bounding normal faults are reactivated by later compression, bringing the high-density igneous rocks closer to the surface. By averaging gravity data along the length of each failed rift, we can more easily distinguish between the history of individual rifts and general features of rifting that apply to other failed or active rifts around the world.</p>

Geochemistry of the Mesoproterozoic intrusive rocks of the Nipigon Embayment, northwestern Ontario: evaluating the earliest phases of rift development

2007 ◽  
Vol 44 (8) ◽  
pp. 1087-1110 ◽  
Author(s):  
Thomas Hart ◽  
Adam Richardson ◽  
Carole Anne MacDonald ◽  
Pete Hollings
Keyword(s):  
Continental Crust ◽  
Geochemical Characteristics ◽  
Geochemical Data ◽  
Olivine Gabbro ◽  
Midcontinent Rift ◽  
Northwestern Ontario ◽  
Intrusive Rocks ◽  
History Of

The intrusive rocks of the Nipigon Embayment comprise a series of four mafic to ultramafic intrusions and a number of laterally extensive diabase sills that are among the oldest expression of the ~1.1 Ga Mesoproterozoic Mid-continent Rift. New geochemical data indicate that the sills can be subdivided into five distinct groups: three mafic sills (Nipigon, Inspiration, and McIntyre diabase sills), with the Nipigon sills forming the bulk of the outcrop, and two spatially restricted ultramafic to mafic sills (Jackfish and Shillabeer sills). The latter mafic sills are typically massive, medium-grained, intergranular textured gabbros ranging in thickness from a few metres to more than 250 m. Two of the ultramafic intrusions included in this study (Disraeli and Hele) consist of a core of pyroxene peridotite with olivine gabbro along the margins. The geochemical characteristics of the ultramafic intrusions and diabase sills are consistent with plume-derived melts that have undergone subsequent fractionation and been contaminated by continental crust, likely at depth, but a few samples from the Hele and Disraeli intrusions have the characteristics of primary, uncontaminated melts that have been rapidly transported through the lithosphere with little interaction with wall rocks. The field and geochemical characteristics of the intrusions and sills are consistent with the ultramafic intrusions having been emplaced before the diabase sills and indicate that the history of the Midcontinent Rift is more complex and protracted than previously recognized.

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