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Topic: Mesoarchean


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In the News (Sun 23 Jun 19)

  
  Mesoarchean - Wikipedia, the free encyclopedia
The Mesoarchean is a geologic era within the Archean, spanning 3200 Ma to 2800 Ma (million years ago).
The period is defined chronometrically and is not referenced to a specific level in a rock section on Earth.
Fossils from Australia show that stromatolites have lived on Earth since the Mesoarchean.
en.wikipedia.org /wiki/Mesoarchean   (82 words)

  
 Globeinvestor.com: Wildcat Exploration Ltd. - Exploration Results - Bissett Mining Camp - Summer 2003
is underlain by rocks of Mesoarchean and Neoarchean age separated by an unconformity along which extensive shearing is accompanied by iron carbonate alteration.
A priority exploration target for the 2004 field season on the Siderock property is the unconformity between Mesoarchean and Neoarchean rocks.
The northern part of the property is underlain by komatiitic and mafic flows and iron formation of Mesoarchean age.
www.globeinvestor.com /servlet/ArticleNews/print/CNW/20040301/1203015374   (544 words)

  
 Manitoba Geology | Geological Survey | Mineral Resources Division | Manitoba Industry, Economic Development and Mines
The Uchi domain is bounded to the north by the Berens River Domain which, along with the Island Lake Domain, comprises the North Caribou terrane, a potential Mesoarchean, ca 3.0Ga protocontinent that is approximately 400 by 850 km in size.
The Uchi domain includes several strands of Mesoarchean and Neoarchean volcanic rocks that comprise the Rice Lake greenstone belt in Manitoba and the Red Lake, Bee Lake and Pickle Lake greenstone belts in Ontario.
Mesoarchean volcanic rocks in the Rice Lake belt include mainly komatiites and komatiitic basalts whereas the Neoarchean volcanic rocks are more lithologically diverse and include both tholeiitic and calc alkaline volcanic members.
www.gov.mb.ca /itm/mrd/geo/exp-sup/mbgeology.html   (4694 words)

  
 SEISMIC IMAGING OF A LOWER-CRUSTAL OCEANIC SLAB: EVIDENCE FOR NEOARCHEAN TECTONIC ACCRETION IN THE WESTERN SUPERIOR ...   (Site not responding. Last check: 2007-10-24)
Drawing an analogy between the subprovinces and the belt-like superterranes of the Canadian Cordillera, the structural pattern of Western Superior Province was used as possible evidence for lateral accretion in early plate-tectonic models for the formation of Archean continental crust.
Although subsequent geological mapping, geochronological and geochemical work appeared to be compatible with accretion of Neoarchean (<2.8 Ga) oceanic crust, island arcs and sedimentary prisms, with amalgamated Mesoarchean continental fragments, against the southern margin of the >3 Ga composite North Caribou superterrane, various aspects of field relationships, surface structure and age patterns remain equivocal.
Along the northern suture, a Mesoarchean continental fragment of the eastern Wabigoon Subprovince is thrust beneath the North Caribou superterrane.
gsa.confex.com /gsa/2001AM/finalprogram/abstract_19821.htm   (491 words)

  
 Wildcat Exploration - Exploration   (Site not responding. Last check: 2007-10-24)
The older group is termed "Mesoarchean", and radiometric dating has established that the rocks of this group are 2.85 to 3.0 Ga years old.
The distinction between Mesoarchean and Neoarchean supracrustal rocks is relatively recent, and has come about through U-Pb dating since 1995.
Several Mesoarchean assemblages have now been recognized: the Lewis-Storey assemblage, the Wanipigow North and Little Beaver assemblages, the Wallace assemblage, and the Garner assemblage (Bailes et al., 2003).
www.wildcat.ca /explore.php?id=bisse&detail=geo   (1753 words)

  
 Mineral Deposits of Canada - Geology and metallogeny of the Superior Province, Canada
Several domains of Mesoarchean age are recognized in spite of pervasive Neoarchean magmatism, metamorphism and deformation.
In the west, Mesoarchean basement (3.33-2.79 Ga) is unconformably overlain by the clastic Apple formation, which hosts uranium-gold occurrences (Roscoe and Donaldson, 1988), and 2.75-2.73 Ga volcanic strata (Goutier and Dion, 2004).
Characteristics of Mesoarchean and Neoarchean supracrustal sequences at the southern margin of North Caribou terrane in the Wallace Lake greenstone belt, Superior Province, Canada.
gsc.nrcan.gc.ca /mindep/synth_prov/superior/index_e.php   (16214 words)

  
 Wildcat Exploration Ltd.
is underlain by rocks of Mesoarchean and Neoarchean age, separated by an unconformity, along which extensive and intensive shearing is accompanied by iron carbonate alteration.
Mesoarchean assemblages contain komatiitic and mafic flows, gabbro and iron formation.
The Garner Lake property is underlain dominantly by Mesoarchean volcanic, plutonic and sedimentary rocks that are transected by the Beresford shear zone and splay off the latter structure.
www.nafinance.com /Listed_Co/English/wildcat_e.htm   (2797 words)

  
 SEG - Regional V.P. Lecturer Program   (Site not responding. Last check: 2007-10-24)
However, he has also worked extensively on the siliciclastic gold-bearing beds of the Mesoarchean Witwatersrand and Pongola Supergroups and was the first to prove that they are correlative and had been deposited in the same basin.
He received the Draper Medal, the highest award from the Geological Society of South Africa, in 2002 and Honorary Fellowship from the Geological Society of America in 2004.
Their stratigraphic work is coupled with paleomagnetic studies and detrital zircon age dating to allow paleo-geographic and provenance reconstructions.
www.segweb.org /RegVPLect.html   (345 words)

  
 Selected Abstracts
There are five main geocronological units in the Precambrian history of the Ukrainian Shield: the Paleoarchean, the Mesoarchean, the Neoarchean, and the Paleoproterozoic (the last unit is subdivided into two sub-units: the Paleoproterozoic-I, and the Paleoproterozoic-II).
The typical volcanic-plutonic rock assemblages of the greenstone belts are generated during the Mesoarchean.
Thus, subdivisions of the Archean of the Ukrainian Shield correspond to geochronological units of the International Scale of the Geological Time (the upper limits are for the Paleoarchean, 3.2 Ga; the Mesoarchean, 2.8 Ga and the Neoarchean, 2.5 Ga).
www.geofuel.lviv.net /MISCEL/MPSab/sab019.htm   (689 words)

  
 NEW SHRIMP U-PB ZIRCON AGES FOR THE PALEOARCHEAN TO MESOARCHEAN ROCKS OF THE MINNESOTA RIVER VALLEY
Interest in Paleoarchean to early Mesoarchean crust in North America has been sparked by the recent identification of ca.
Thus, these rocks were formed in the late Paleoarchean and show a history of igneous activity and metamorphism in the Mesoarchean and Neoarchean.
Because ancient crustal rocks occur on both the northern and southern margins of the ca.
gsa.confex.com /gsa/2004AM/finalprogram/abstract_75677.htm   (501 words)

  
 Astrobiology Magazine
Studying samples of pillow lava taken from the Mesoarchean Barberton Greenstone Belt in South Africa, scientists have found mineralized tubes that were formed in the pillow lava, suggesting microbes colonized basaltic glass of the early oceanic crust, much in the same way as they do modern volcanic glass.
Harald Furnes from the University of Bergen in Norway, Neil Banerjee from the U of A, Hubert Staudigel from the University of California and Maarten de Wit from the University of Cape Town, studied samples of pillow lava taken from the Mesoarchean Barberton Greenstone Belt in South Africa.
They found mineralized tubes that were formed in the pillow lava, suggesting microbes colonized basaltic glass of the early oceanic crust, much in the same way as they do modern volcanic glass.
www.astrobio.net /news/print.php?sid=935   (709 words)

  
 t11c in fm05
AB: The 3.0 Ga Ivisaartoq greenstone belt is the largest Mesoarchean (~3075 Ma) supracrustal assemblage in southern West Greenland.
The diopside-quartz-plagioclase-epidote metasomatic assemblage in the pillow cores is interpreted as metamorphosed epidosite formed under upper-greenschist to lower-amphibolite facies metamorphic conditions during hydrothermal alteration of the Mesoarchean oceanic crust.
Given the observations that epidosites and subduction zone geochemical signatures have been identified in several Phanerozoic ophiolites, the Ivisaartoq belt is interpreted as the crustal section of a dismembered Mesoarchean supra-subduction zone ophiolite.
www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm05&database=/data/epubs/wais/indexes/fm05/fm05&maxhits=200&="T11C"   (3527 words)

  
 Lakehead University - Geology - Dr. Philip W. Fralick
Work on genesis of iron formations centers on understanding the shelf or deep marine hydrodynamic and chemical processes which lead to the precipitation of these odd sediments.
The use of depositional environment and provenance to ascertain the basin-fill architecture of sedimentary units in Mesoproterozoic to Mesoarchean terrains.
Categorization of basin-fill processes, combined with the use of geochemistry (see Fralick and Kronberg, 1977) and single zircon U/Pb geochronology to identify sediment source areas allows models to be proposed for tectonically-linked basin formation processes.
bolt.lakeheadu.ca /~geology/research/Fralick/main.php   (201 words)

  
 Geoscience Jobs : University of Johannesburg - Postdoctoral Researcher - Paleoproterozoic Mineralization Research Group ...   (Site not responding. Last check: 2007-10-24)
The Paleoproterozoic Mineralization Research Group (PPM), one of South Africa's leading research groups in the geosciences, seeks applicants for the position of postdoctoral researcher.
The successful applicant will design and conduct a research program focused on the temporal evolution and paleogeographic reconstruction of Mesoarchean and Paleoproterozoic cratonic cover sequences on the Kaapvaal Craton.
The successful applicant will work closely with staff associated with PPM, the Department of Geology and Spectrau (the central analytical facility of the Faculty of Sciences, University of Johannesburg).
www.earthworks-jobs.com /geoscience/rau6071.html   (267 words)

  
 ALAN G JONES Publications: No. 87   (Site not responding. Last check: 2007-10-24)
We argue that the nature of these tectonic events is difficult to reconcile with early, pre 2.7 Ga development and preservation of a thick tectosphere, and suggest that crust-mantle coupling and stabilization occured only late in the orogenic development of the craton.
The extent and repetitiveness off the tectonic reworking documented within the Mesoarchean basement complex of the western Slave, together with the development of large-volume, extensional mafic magmatism at 2.7 Ga within the basement complex argue against preservation of a widespread, thick, cool Mesoarchean tectosphere beneath the western Slave craton prior to Neoarchean tectonism.
Broad-scale geological and geophysical features of the Slave craton, including orientation of an early F1 fold belt, distribution of ca.
www.geophysics.dias.ie /~ajones/papers/87.html   (187 words)

  
 Projects of the Mineralogical Institute Würzburg
Situated in a low-grade metamorphosed siliclastic fill of a Mesoarchean foreland basin in the Archean Kaapvaal craton of South Africa, the Witwatersrand goldfields have yielded close to 40 percent of all gold ever mined and they remain the world's largest repository of known gold reserves.
As the orebodies occur strictly stratiform within fluvial to fluvio-deltaic, predominantly pyrite- and, in places, uraninite-rich quartz pebble conglomerates (reefs) on top of regional unconformity surfaces, where the gold grade is controlled by sedimentary facies, a paleoplacer model has been adopted by most exploration and mining geologists in the past.
Pb in hydrothermal sulphide minerals and bitumen from the Ventersdorp Contact Reef, South Africa: Mineralogy and Petrology, v.
www.uni-wuerzburg.de /mineralogie/projects/frimmel01.html   (730 words)

  
 Abstract 51173: DISTRIBUTION OF ARCHEAN STROMATOLITES IN TIME AND SPACE
Abstract: Stromatolites are morphologically circumscribed accretionary growth structures with a primary lamination that is, or may be biologically influenced (biogenic).
The earliest records date back to nearly 3.5 Ga, and their worldwide distribution and abundance increase as time progresses: Paleoarchean occurrences (3) are outnumbered by those in the Mesoarchean (7) and Neoarchean (13), while the remaining occurrences are questionably Archean, or questionably stromatolites.
Stromatolites are generally found in Archean sedimentary carbonate rocks, almost always associated with extensive volcanic sequences.
rock.geosociety.org /absindex/annual/1998/51173.htm   (393 words)

  
 Geological Survey of Canada - Directory of Geoscience Expertise
Application of geochronology to unraveling the tectonic evolution of orogenic belts, specifically the Canadian Cordillera and Appalachians.
Research involves U-Pb dating in a wide variety of geological terranes and environments ranging from Mesoarchean to Eocene in age.
Current research projects involve precise U-Pb dating with application to chronostratigraphic and biochronological timescales.
gsc.nrcan.gc.ca /dir/index_e.php?id=14878   (101 words)

  
 UNBSJ Ward Chipman Library Current Research Geological Survey of Canada Canadian Shield   (Site not responding. Last check: 2007-10-24)
Structure, stratigraphy, and geochemistry of the Mesoarchean Wallace Lake greenstone belt, southeastern Manitoba
Hanmer, S. and Williams, M.L. Mesoarchean western margin of the Superior Craton in the Lake Winnipeg area, Manitoba
Percival, J.A., Bailes, A.H. and McNicoll, V. Mesoarchean western margin of the Superior Craton in the Lake Winnipeg area, Manitoba
www.unbsj.ca /library/govdocs/gsc3.htm   (1474 words)

  
 UNBSJ Ward Chipman Library Current Research Geological Survey Summer Unclassified Release   (Site not responding. Last check: 2007-10-24)
Electrical resistivity stability characteristics of water used to saturate rocks from Giant and Con mines, Yellowknife, Northwest Territories
Geochemistry and Nd isotopes of granitoid rocks in the Shikag-Garden lakes area, Ontario: recycled Mesoarchean crust in the central Wabigoon Subprovince
Near-surface seismic-reflection studies to outline a buried bedrock basin in eastern Ontario
www.unbsj.ca /library/govdocs/gsc5.htm   (713 words)

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