Some Aspects of Sedimentology of the Missi Group and its Environment of Deposition

Mukherjee, A. C.

doi:10.1139/e74-099

Cited by 2 publications

(1 citation statement)

References 2 publications

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“…Post-accretion ("successor") plutonic granitoids were emplaced between 1.87 and 1.84 Ga during continued subduction beneath the FFB, "stitching" together the assemblages of the collage. Sedimentation was coeval with this plutonism, resulting in shallow marine and continental successor basin deposits that span a depositional age range from 1.87 to 1.84 Ga. One of these deposits is the Missi Groupsandstone and conglomerate interpreted to represent the deposition of alluvial fan to braided stream sediments in synorogenic, structurally controlled basins (Mukherjee 1974;Stauffer 1990). The Missi Group unconformably overlies the volcanic and synvolcanic intrusive rocks of the Flin Flon arc assemblage in addition to some of the successor arc plutonic rocks.…”

Section: Regional Geologymentioning

confidence: 99%

The Flin Flon paleosol revisited

Babechuk

Kamber

2013

Can. J. Earth Sci.

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A ca. 1.85 Ga paleosol developed on seafloor-altered mafic rocks is preserved beneath continental sandstones and conglomerates of the Missi Group near Flin Flon, Manitoba. Previous work has focused on a locality where the paleosol is developed on pillowed greenstone (chlorite + albite + epidote + calcite + quartz + Fe–Ti oxides ± mica). This area has been revisited and a new (∼5 m) profile was excavated and sampled at a very high density for geochemical (major element; ∼60 samples) and mineralogical (petrography, X-ray diffraction) investigation. The high sampling density has revealed a relatively sharp immobile-element offset (e.g., Al/Ti) in the profile. This could reflect weathering across two separate parent rocks or preferential addition of allochthonous material into the top of the profile. Regardless, comparison with a wide suite of volcanic rocks in the stratigraphy suggests that the original concentration of Fe and probably also Ca and Mg in the greenstone on either side of the boundary was similar, permitting quantitative treatment of major-element trends. The profile shows pronounced upward loss of Ca, Mg, Mn2+, and Fe2+ and a corresponding increase in Al, Ti, and total Fe. Physical weathering features, such as corestones, are well preserved and show progressive alteration upwards in the profile in parallel with the chemical trends. Deep in the profile, Na and Ca are lower than the greenstone due to the weathering of albite and epidote, whereas Mg, Fe, and Mn were largely retained in chlorite and secondary dolomite. Upwards in the profile, the loss of chlorite and dolomite and the increase of illite – mixed-layer clays and white mica (probably 2:1 layer or mixed-layer clays originally) and hematite are accompanied by a transition from green to maroon colour. Above a well-defined depth in the profile, carbonate is virtually absent, and the paleosol is highly depleted in Ca. This transition in the paleosol coincides with the immobile-element offset. The significance of this coincidence remains to be explored. Reworking of regolith (e.g., rip-up clasts) occurred during deposition of the Missi sediments, and burial and subsequent metamorphism resulted in the upward enrichment of K and Na and the associated conversion of pedogenic clays to illite and micas (muscovite and paragonite). Crosscutting quartz and epidote veins and tourmaline formation near the unconformity contact implies minor post-burial fluid movement. Despite these complexities, there is consistent retention of Fe through formation of pedogenic Fe oxides, attested by the near-constant ∑Fe/Al ratio in the profile. There is very little evidence for subsequent Fe reduction by hydrothermal or organic fluids. Instead, trends in the Fe speciation are controlled predominantly by the modal variation of Fe–Ti oxides in the greenstone and spheroidal weathering textures in the paleosol.

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Section: Regional Geologymentioning

confidence: 99%

The Flin Flon paleosol revisited

Babechuk

Kamber

2013

Can. J. Earth Sci.

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Early Proterozoic deformation along the southern margin of the Kisseynew gneiss belt, Trans-Hudson Orogen: a 30 Ma progressive deformation cycle

Norman¹,

Williams²,

Ansdell³

1995

Can. J. Earth Sci.

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Fold axes and lineations across the southern margin of the Kisseynew gneiss belt were progressively reoriented from northwesterly to northeasterly during an Early Proterozoic, southwest-directed, compressive deformation cycle. Partitioning of deformation resulted in a concentration of non-coaxial strain along the boundary between the Kisseynew gneiss belt and Flin Flon–Snow Lake belt. The structural evolution was complicated by streamlining of the movement vector around the comparatively rigid Flin Flon–Snow Lake belt. The relationship of metamorphic assemblages to kinematic fabrics indicates that deformation was coeval with a prograde–retrograde metamorphic cycle. Progressive deformation occurred during a period of 30 Ma, which is consistent with Phanerozoic orogenic time scales.

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Some Aspects of Sedimentology of the Missi Group and its Environment of Deposition

Cited by 2 publications

References 2 publications

The Flin Flon paleosol revisited

The Flin Flon paleosol revisited

Early Proterozoic deformation along the southern margin of the Kisseynew gneiss belt, Trans-Hudson Orogen: a 30 Ma progressive deformation cycle

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