U–Pb zircon ages from the eastern Savant Lake – Crow Lake metavolcanic–metasedimentary belt, northwest Ontario

1982 ◽  
Vol 19 (4) ◽  
pp. 868-877 ◽  
Author(s):  
D. W. Davis ◽  
N. F. Trowell
Keyword(s):  
Volcanic Belt ◽  
Time Span ◽  
Lake Area ◽  
The South ◽  
Air Abrasion ◽  
Angular Unconformity ◽  
Volcanic Sequence ◽  
Northwest Ontario ◽  
Lake Sample ◽  
Volcanic Cycles

Five rocks from three areas in the eastern part of the Savant Lake – Crow Lake metavolcanic–metasedimentary belt have been dated by U–Pb analysis of zircons.The Sioux Lookout area is composed of a sequence of generally fault-bounded metavolcanic and metasedimentary belts. The age of a felsic tuff in the Central volcanic belt is [Formula: see text]. This is possibly the youngest sequence in the area.The Savant Lake volcanic belt comprises the Jutten volcanic unit at its base separated by an angular unconformity from the Handy Lake volcanic sequence. The age of a dacitic tuff near the base of the Handy Lake volcanic sequence is [Formula: see text].The South Sturgeon Lake volcanic belt is composed of four volcanic cycles. The age of a felsic tuff from the top of the uppermost cycle is [Formula: see text]. The felsic Beidelman Bay pluton and the mafic Pike Lake pluton, which both intruded the lower part of the sequence, give ages of [Formula: see text] and [Formula: see text], respectively. This establishes a minimum time span of [Formula: see text] for deposition of the sequence. This interval, along with the 27 Ma span between the ages of the Handy Lake sample and the volcanic sample from the South Sturgeon Lake area, suggests that the sequences were laid down by a series of discrete volcanic episodes.For samples subjected to multistage lead loss, the reliability of ages has been greatly enhanced by air abrasion of zircons. Several cases of suspected biasing of analyses by the air abrasion process have been encountered. It appears that this biasing problem can be overcome by selection and abrasion of low uranium grains that are free of imperfections.

scholarly journals Detailed mapping and lithogeochemistry of Neoarchean volcanic rocks: Beaulieu volcanic belt, Slave Craton, NWT

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Shelby Brandon Austin-Fafard ◽  
Michelle DeWolfe ◽  
Camille Partin ◽  
Bernadette Knox
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Massive Sulfide ◽  
Lake Area ◽  
Density Currents ◽  
Volcanogenic Massive Sulfide ◽  
The South ◽  
Slave Craton ◽  
Volcaniclastic Rocks ◽  
Tuff Breccia

Neoarchean volcanic rocks of the Beaulieu River volcanic belt structurally overlie basement rocks of the Sleepy Dragon Complex (ca. 2.85 Ga), approximately 100 km east northeast of Yellowknife. The volcanic belt is comprised of complex lithofacies, including basalt, andesite, rhyolite, and associated volcaniclastic rocks, and hosts the Sunrise volcanogenic massive sulfide deposit. The absolute age of the volcanic strata is not known, nor is the stratigraphy well-defined; therefore, the Beaulieu River volcanic belt cannot be easily correlated to other greenstone belts within the Slave craton. The main objective of this study is to document the litho- and chemo-stratigraphy of the volcanic rocks, and particularly the rhyolite dome, located at the south end  of Sunset Lake to reconstruct their volcanic and petrogenetic evolution, and determine their relationship to the volcanic strata that hosts the Sunrise VMS deposit, located ~6km to the north of the study area. Detailed mapping (1:2000) was completed over two field seasons (2018 and 2019) and shows that the volcanic rocks in the south Sunset Lake area comprise a complex stratigraphy consisting of basaltic, andesitic and rhyolitic lithofacies. This includes massive to pillow basalt and andesite, with lesser amounts of massive to in-situ brecciated, weakly quartz-plagioclase porphyritic rhyolite, heterolithic tuff to lapilli- tuff and felsic tuff to tuff breccia. The felsic clasts within the felsic volcaniclastic rocks are similar in composition to the coherent rhyolite. Units have a trace element geochemical signatures that vary from tholeiitic to calc-alkaline, arc-like rocks. Volumetrically, the volcanic strata in the south Sunset Lake area has a significant amount of volcaniclastic rocks, ranging from tuff to tuff breccia units. The volcaniclastic rocks are interpreted to have been deposited by a series of debris flows and eruption-fed density currents. The stratigraphy of the volcanic rocks in south Sunset Lake is very similar to that of the stratigraphy that hosts the Sunrise VMS deposit. Evidence of a vent proximal environment (e.g. rhyolite dome, peperite, syn-volcanic intrusions) and porous, volcanic debris accumulating on the seafloor highlight conditions favourable for volcanogenic massive sulfide-type mineralization in the south Sunset Lake area.

scholarly journals Changes in lake area as a consequence of plant overgrowth in the South Baltic Lakelands (Northern Poland)

2017 ◽  
Vol 12 (1) ◽  
pp. 19-30 ◽  
Author(s):  
Rajmund Skowron ◽  
Tomasz Jaworski
Keyword(s):  
Lake Area ◽  
The South ◽  
Emergent Plants ◽  
Northern Poland

AbstractThe authors carried out the analysis of changes in the plant overgrowth of the lakes based on cartographic materials. Among 6 793 lakes with the area exceeding 1 ha located in the lakelands of Northern Poland, 893 lakes were selected for the analysis. The lakes were selected on the grounds of the existing bathymetric plans and information on their overgrowth and depth relations. Over the last 50 years lake area declined by 1.9% (from 140 975.0 ha do 138 273.7 ha) and so did the lake area covered with emergent plants, i.e. by 0.27% (from 11 219.0 ha down to 10 637.2 ha). Emergent plants cover on average 7.69% of the lake area. In the case of the lakes of smaller areas (below 80 ha) or medium areas (80÷200 ha) the extent of plant overgrowth was 14.3 and 9.6% respectively. The article presents two indicators which determine plant overgrowth of the lakes. These are the coefficient of overgrowing the lakes (%) and the coefficient of overgrowing the shoreline (ha·km-1). These coefficients make it possible to study the extent of lake overgrowing in the South Baltic Lakeland, regardless the direction of these changes.

Event deposits in the Eastern Thermaikos Gulf and Kassandra Peninsula (Northern Greece): evidence of the 479 BC "Herodotus tsunami"

2019 ◽  
Vol 62 (2) ◽  
pp. 101-125
Author(s):  
Margret Mathes-Schmidt ◽  
Ioannis Papanikolaou ◽  
Klaus Reicherter ◽  
Aggelos Pallikarakis
Keyword(s):  
High Energy ◽  
Time Span ◽  
The South ◽  
Northern Greece ◽  
Reservoir Effect ◽  
Tsunami Waves ◽  
Vast Amount ◽  
The North ◽  
First Time ◽  
Bivalve Shells

Event deposits of high-energy waves in the Eastern Thermaikos Gulf and Kassandra Peninsula (Northern Greece) are investigated, and evidence for the 479 BC "Herodotus tsunami" is described for the first time. One of the first historical descriptions of tsunami waves and its effects on Persian troops near Potidaea in 479 BC was made by Herodotus. Sedimentary traces of tsunamis were investigated in cores from different areas from Angelochori in the north to the ruins of ancient Mende in the south (Kassandra peninsula). Evidence for one, locally two high-energy events, on the coasts of Chalkidiki is found. These layers are preserved in flat and lagoonal areas at least from 100 m of the present-day beach. Within ancient Mende, a high-energy layer was encountered. Besides a vast amount of ceramics, the layer also contains articulated bivalve shells. These were dated to a time span between 712 and 521 cal yrs BC by radiocarbon including a reservoir effect of 400 ± 40 years. Resulting ages resemble the time the tsunami mentioned by Herodotus in 479 BC. Deposits of a further event affecting the Thermaikos Gulf were dated between the 7 th to 10 th cent. AD.

Zircon U–Pb ages from the Kakagi Lake area, Wabigoon Subprovince, northwest Ontario

1982 ◽  
Vol 19 (6) ◽  
pp. 1235-1245 ◽  
Author(s):  
Donald W. Davis ◽  
Garth R. Edwards
Keyword(s):  
Early Stage ◽  
Volcanic Rocks ◽  
Age Difference ◽  
Lake Area ◽  
Air Abrasion ◽  
High Gradient Magnetic Separation ◽  
Pyroclastic Rocks ◽  
Gneiss Domes ◽  
The North ◽  
Lake Formation

Five rocks have been dated from the Kakagi Lake area of the Wabigoon Subprovince by means of U–Pb analysis of zircons. Using the techniques of air abrasion and high gradient magnetic separation, zircon fractions from four of the samples have been made concordant.Stratigraphy in the Kakagi Lake area consists of tholeiitic basalts of the Snake Bay and Katimiagamak Lake Formations overlain by mainly calc-alkalic pyroclastic rocks of the Kakagi Lake Group. A felsic tuff collected from the top of the Kakagi Lake Group is dated at [Formula: see text]. This group is intruded by differentiated ultramafic to mafic sills. The age for a gabbro pegmatite from the lowermost sill near the base of the group is [Formula: see text]. The Katimiagamak Lake Formation is intruded by tonalite of the Sabaskong batholith, which gives an age of [Formula: see text]. The tonalite is flanked by the Phinney–Dash Lakes Complex of subvolcanic stocks and dacite to rhyolite volcanic rocks that intrude and overlie the Katimiagamak Lake Formation. A dacite from the complex gives an age of 2727.7 ± 1.1 Ma. A porphyry complex to the north, the Berry Creek Complex, is separated from the other rocks by the Pipestone – Cameron Lakes Fault and gives an age of [Formula: see text] on a quartz porphyry.The predominantly mafic to intermediate pyroclastic rocks of the Kakagi Lake Group are interpreted to be approximately contemporaneous with the Kakagi sills and to have evolved from the basalt magmatism. Tonalitic rocks of the Sabaskong batholith and the Phinney–Dash Lakes Complex were derived from partial melting of the hydrous lower basalts during the early stage of regional granitoid diapirism. Because of the large age difference between the lowermost sill and the felsic tuff from the top of the Kakagi Lake Group, it is suggested that this formation is not part of the group. It and the Berry Creek Complex were formed from felsic melts separating from rising granitoid gneiss domes during a slightly later stage of regional granitoid diapirism that may have resulted from the reactivation of a predominantly sialic basement by the accumulation of heat over and adjacent to the mantle sources of the basalt.

A Discussion on the evolution of the Precambrian crust - The Rhodesian Archaean craton — an essay in cratonic evolution

1973 ◽  
Vol 273 (1235) ◽  
pp. 389-411 ◽  
Keyword(s):  
Recent Work ◽  
Greenstone Belt ◽  
Time Span ◽  
Mobile Belt ◽  
The South ◽  
Great Dyke ◽  
Greenstone Belts

The Rhodesian Archaean craton consisting largely of granite-greenstone terrain is briefly described, and is discussed mainly in the light of points arising from recent work in the south and central parts of the country. The Sebakwian-Bulawayan-Shamvaian terminology and the evidence for more than one age of greenstone belt development are reviewed. An attempt is made to trace the evolution of the craton from the earliest recognized rocks up to the emplacement of the Great Dyke (±2500 Ma). Evidence is presented for the existence of an earlier sialic basement to the main greenstone belt cover, and to show that the main greenstone belts developed during the approximate time-span 3300 to 2900 Ma. Between approximately 2900 and 2500 Ma the main events are traced both in the craton and the Limpopo mobile belt. Proterozoic events at 2000 to 1800 Ma affecting the craton and mobile belt are briefly described and discussed.

U–Pb geochronology of late Neoarchean tonalites in the Flin Flon Belt, Trans-Hudson Orogen: surprise at surface

1994 ◽  
Vol 31 (12) ◽  
pp. 1785-1790 ◽  
Author(s):  
J. David ◽  
E. C. Syme
Keyword(s):  
Shear Zone ◽  
Tectonic Evolution ◽  
Volcanic Belt ◽  
Lake Area ◽  
Magmatic Rocks ◽  
Flin Flon ◽  
First Time

The Flin Flon volcanic belt of the Trans-Hudson Orogen in northern Manitoba comprises magmatic rocks (1.88 – 1.90 Ga) generated in an intra-oceanic arc and identified as one of the best examples of juvenile Paleoproterozoic crust. In the Flin Flon – Athapapuskow Lake area, the belt consists of a series of fault-bounded blocks, each having distinct stratigraphic and magmatic affinities, juxtaposed to form an accretionary collage. Two tonalitic bodies within the Northeast Arm shear zone, a major deformation corridor separating two of the most important blocks in the area, have been dated by the U–Pb zircon method at [Formula: see text] and [Formula: see text]. These results indicate the presence of fragments of late Neoarchean crust within the Flin Flon belt, possibly related to ca. 2.5 Ga granitic bodies found in terranes beyond the western limit of the belt. The presence of ca. 2.5 Ga tonalites within the Flin Flon Belt, herein reported for the first time, has major implications for basement involvement in the early tectonic evolution of the Flin Flon Belt.

Crustal evolution of Archean rocks in the Kakagi Lake area, Wabigoon Subprovince, Ontario, as interpreted from high-precision U–Pb geochronology

1986 ◽  
Vol 23 (2) ◽  
pp. 182-192 ◽  
Author(s):  
D. W. Davis ◽  
G. R. Edwards
Keyword(s):  
Volcanic Rocks ◽  
Time Span ◽  
Time Interval ◽  
Lake Area ◽  
Volcanic Group ◽  
Regional Deformation ◽  
Felsic Volcanism ◽  
Plutonic Complex ◽  
Late Event ◽  
History Of

The evolution of the Archean volcanic–plutonic complex in the Kakagi Lake area occurred during a time interval of ca. 32 Ma. The earliest age is [Formula: see text] from analysis of zircon and baddeleyite in a gabbro intruding the lowermost Katimiagamak Volcanic Group. An age of 2723.2 ± 1.8 Ma on a tonalite gneiss from the interior of the underlying Sabaskong Batholith is indistinguishable from a previously dated massive border phase of the batholith and shows no evidence for inheritance from an older sialic component. An early tonalite phase from the adjacent Aulneau Batholith is dated at [Formula: see text], and the latest granodiorite phase is dated at [Formula: see text]. This defines a time span of about 7 Ma for intrusion of the bulk of the batholith and indicates that previously dated felsic volcanism from the uppermost sequence, above the Kakagi Lake Volcanic Group, is coeval with late plutonic activity in the Aulneau Batholith. The end of regional deformation in the area is given by the ages of two late-tectonic intrusions, the Heronry Lake pluton and the Stephen Lake pluton, dated at 2701.0 ± 1.2 and 2699.2 ± 1.9 Ma, respectively.U–Pb analyses of sphene were carried out on four of the samples in an effort to establish details of the post-folding thermal history of the area. Sphene is least reset in the Heronry Lake pluton (2699.2 ± 1.6 Ma), which is spatially most closely associated with the volcanic rocks and most reset in the Sabaskong gneiss (2673.7 ± 6.6 Ma), the sample most strongly affected by diapirism. The data indicate that regional deformation was a relatively late event, possibly caused by diapirism in the centres of the large batholiths and driven by a long-lived heat source in the mantle or lower crust.

scholarly journals The Geology of the Perches - Terrier Rouge Area, A Potential Copper and Gold Mineralized Belt in Northern Haïti.

2019 ◽  
Author(s):  
Ricardo A. Valls
Keyword(s):  
Volcanic Belt ◽  
The South ◽  
Magmatic Complex ◽  
Volcanic Event ◽  
The North ◽  
Two Samples ◽  
Volcanic Formation ◽  
Lead Zinc ◽  
Geological Observation ◽  
Ore Potential

A geological reconnaissance at an approximated scale of 1:100000 was done over 112 km2, between the townships of Roche Platte to the West, Jasquezyl to the North, Grand Basin to the East, and Perches to the South. A total of 56 points were described for an average of one geological observation per two square kilometers.Also, 18 grab samples were taken from mineralized showings, as well as three heavy mineral concentrates and two samples for whole rock analysis.All the collected information was kept in a database created on MS Access by the author of this report. The database, including the results of the analysis, can be consulted on Mendeley at doi:10.17632/b35fmjntnr.1.A model for the regional geological evolution of the area is presented, as well as a proposal for the denomination of the three basic geological structures found in the area, The Douvray Volcanic Group, the Grand Basin Magmatic Complex, and the Bercera Volcanic Formation, which the author interpreted as the last volcanic event of the Douvray Volcanic Group.This study revealed several new prospective zones for copper to the North, and gold-copper-lead-zinc mineralization to the South, along the volcanic belt and its orogenic intrusives, chiefly related to the occurrences of iron hats.The author recommends more detailed prospecting work, including ground geophysics and trenching, to better evaluate the ore potential of these new areas.

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