Early Proterozoic climates and plate motions inferred from major element chemistry of lutites
TL;DR: The early Proterozoic Huronian Supergroup of the north shore of Lake Huron (Fig. 1) is a thick succession of sedimentary and volcanic rocks deposited between about 2,500 and 2,100 Myr ago as discussed by the authors.
Abstract: The early Proterozoic Huronian Supergroup of the north shore of Lake Huron (Fig. 1) is a thick (up to 12,000 m) succession of sedimentary and volcanic rocks deposited between about 2,500 and 2,100 Myr ago1. Here we present a palaeoclimatic interpretation of the Huronian based on approximately 200 major elements analyses of lutites. Most of these are new analyses from the Gowganda and Serpent Formations (Fig. 2). The remainder are from published sources cited in Fig. 4. The composition of lutites from the Huronian Supergroup records an early period of intense, probably tropical, weathering followed by climatic deterioration that culminated in widespread deposition of glaciogenic sediments of the Gowganda Formation. Climatic amelioration followed during deposition of the succeeding Huronian formations. The Huronian succession can be interpreted using a uniformitarian approach in that present day seafloor spreading rates and latitude-related climatic variations are compatible with available geochronological and palaeomagnetic data.
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TL;DR: The average chemical composition of the upper continental crust (UC) as a function of age is estimated from chemical analyses, geologic maps, stratigraphic sections and isotopic ages as discussed by the authors.
1,916 citations
TL;DR: In this paper, the proportions of Ca, Na and K released by feldspars of plutonic rocks (granites to gabbros) to weathering solutions were predicted.
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TL;DR: In this paper, a set of functions using oxide Al 2 O 3 ratios are designed for samples influenced by biogenic sedimentation, which are applicable only to rocks which lack significant biogenic fractions, or to those where analyses can be corrected for these inputs.
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TL;DR: In this article, a new chemical index of weathering that can be applied to modern soils and Precambrian paleosis is proposed: CIW = [Al2O3].
1,152 citations
TL;DR: A negative correlation between sediment yield and weathering history, as measured by the chemical alteration (CIA) of the suspended sediment, is observed for many of the world's major rivers and oceans as discussed by the authors.
Abstract: A negative correlation between sediment yield and weathering history, as measured by the chemical alteration (CIA) of the suspended sediment, is observed for many of the world's major rivers and ot
1,088 citations
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09 Mar 2012
TL;DR: The Handbook of Geochemistry Editor-in-chief: K.H. Wedepohl Series Editors: C.W. Shaw, K.K. Turekian, J.M. Zemann as mentioned in this paper
Abstract: Submission information at the series homepage and springer.com/authors Order online at springer.com ▶ or for the Americas call (toll free) 1-800-SPRINGER ▶ or email us at: customerservice@springer.com. ▶ For outside the Americas call +49 (0) 6221-345-4301 ▶ or email us at: customerservice@springer.com. Handbook of Geochemistry Editor-in-chief: K.H. Wedepohl Series Editors: C.W. Correns, D.M. Shaw, K.K. Turekian, J. Zemann
1,447 citations
TL;DR: The Great Lakes tectonic zone is a major Precambrian crustal feature more than 1,200 km long extending eastward from Minnesota into Ontario, Canada as discussed by the authors, and it is a zone of distinctive tectonism, affecting both Archean and early Proterozoic rocks.
Abstract: The Great Lakes tectonic zone is a major Precambrian crustal feature more than 1,200 km long extending eastward from Minnesota into Ontario, Canada. It is a zone of distinctive tectonism, affecting both Archean and early Proterozoic rocks, along the northern margin of the early Proterozoic Penokean fold belt adjacent to the Archean Superior province. The zone coincides with the boundary between two Archean crustal segments recognized in the region: a greenstone-granite terrane (∼2,700 m.y. old) to the north (Superior province) and an older (in part 3,500 m.y. old) gneiss terrane to the south. Tectonism along the zone began in the late Archean, during the joining together of the two terranes into a single continental mass, and culminated in the early Proterozoic, when steep or northward-facing overturned folds were formed in the supracrustal rocks, and intense cataclasis and a penetrative cleavage developed in subjacent basement rocks of the greenstone-granite terrane. The Proterozoic deformation took place under low to intermediate pressures.
Movement occurred along the Great Lakes tectonic zone through much of the Precambrian time recorded in the region. In the early Proterozoic, crustal foundering, which was parallel to the zone and was diachronous, initiated the structural basins in which the early Proterozoic sequences of the Lake Superior and Lake Huron regions were deposited. Later, during the Penokean orogeny (∼1,850 to 1,900 m.y. ago), compression deformed the sequences in both regions. Still later, intermittent (∼1,850 to 1,100 m.y. ago) crustal extension provided sites for emplacement of abundant mafic igneous rocks. There is no definite evidence that any of the extensional events progressed to the stage of development of oceanic crust; probably the zone has been wholly intracratonal since its inception in late Archean time.
During the Phanerozoic, minor differential movements occurred locally in the Great Lakes tectonic zone, as recorded by the thinning of Cretaceous strata and their subsequent tilting and by historic earthquakes in Minnesota.
115 citations
TL;DR: Two profiles from the paleosol underlying the Huronian supergroup at Elliot Lake, Ontario were studied to determine conditions present at the time of their formation as discussed by the authors, and the results indicated that free oxygen was present in the mid-Precambrian atmosphere.
114 citations
TL;DR: 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 as mentioned in this paper.
Abstract: 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.
95 citations
TL;DR: In this paper, an investigation has been made of the chemical and mineralogical transformations which have accompanied the weathering of six basic volcanic rocks from eastern New South Wales, where the alumina content shows a steady increase up the profiles, whereas the alkalis, alkaline earths and some of the silica have been lost in the ground-waters during the mineral transformations.
Abstract: An investigation has been made of the chemical and mineralogical transformations which have accompanied the weathering of six basic volcanic rocks from eastern New South Wales. Montmorillonite is initially formed from the destruction of the olivine, pyroxene, and plagioclase in the parent rock, but, in the near-surface horizons, this mineral is unstable and may form kaolinite, halloysite, or a poorly crystalline montmorillonite. The alumina content shows a steady increase up the profiles, whereas the alkalis, alkaline earths, and some of the silica have been lost in the ground-waters during the mineral transformations. Marked concentrations of iron and titanium occur at specific levels in some of the weathering profiles and explanations of these phenomena are given.
94 citations