Temporal distribution of granitoid plutonic rocks in the Archean Slave Province, northwest Canadian Shield

1992 ◽  
Vol 29 (10) ◽  
pp. 2186-2199 ◽  
Author(s):  
O. van Breemen ◽  
W. J. Davis ◽  
J. E. King
Keyword(s):  
Continental Margin ◽  
Temporal Distribution ◽  
Lake Area ◽  
Margin Setting ◽  
General Terms ◽  
Slave Province ◽  
Age Variation ◽  
Granitoid Rocks ◽  
Plutonic Rocks ◽  
Granitoid Gneisses

Granitoid rocks in the Slave Province consist of 4.0–2.8 Ga granitoid gneisses that predate the 2.71–2.65 Ga volcanic and turbiditic rocks of the Yellowknife Supergroup and 2.70–2.58 Ga granitoid plutons that intrude the Yellowknife Supergroup. U–Pb zircon ages and Nd and Pb isotopic data indicate that the older granitoids are restricted to the western part of the Slave Province. Granitoid gneisses in the eastern Slave Province, previously suspected to predate the Yellowknife Supergroup, are similar in age to the volcanic rocks.In this paper, the results of a detailed geochronological study of plutonic rocks of the Contwoyto Lake – Nose Lake area of the northcentral Slave Province are reviewed and integrated with the available age data base for plutonic rocks elsewhere in the Slave Province. The data indicate that the timing of the later (<2.7 Ga) plutonism is bimodal, consisting of two distinct magmatic periods separated by approximately 20 Ma of apparent magmatic quiescence. The first period was synvolcanic, dating from 2695 to 2650 Ma. The second period, during which more than 80% of the granitoids presently exposed in the Slave Province were intruded, lasted from 2625 to 2580 Ma, spanning the major Archean deformation events, Syndeformation granitoids, with ages between 2625 and 2595 Ma, are dominantly diorite and tonalité in composition. Late- to post-deformation granitoid rocks, with ages between 2605 and 2580 Ma, range in composition from megacrystic biotite granodiorite to two-mica granite. In general terms, the compositions of the granitoid plutons vary in time from dominantly metaluminous to more strongly peraluminous.Present data show no obvious regional age variation among the younger granitoid rocks across the province. This apparent absence of diachroneity has important implications for models interpreting the magmatism as having evolved in a continental-margin setting, because the extent of contemporaneous plutonism is more than 400 km across strike, considerably broader than in most Mesozoic continental-margin batholiths.

Composition, age, and origin of granitoid rocks in the Davin Lake area, Rottenstone Domain, Trans-Hudson Orogen, northern Saskatchewan

2005 ◽  
Vol 42 (4) ◽  
pp. 599-633 ◽  
Author(s):  
D Barrie Clarke ◽  
Andrew S Henry ◽  
Mike A Hamilton
Keyword(s):  
Granitic Rocks ◽  
Lake Area ◽  
Granitoid Magmatism ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Granitic Magmatism ◽  
Deformation Features ◽  
High Grade Metamorphism ◽  
Granitoid Rocks ◽  
Host Rocks

The Rottenstone Domain of the Trans-Hudson orogen is a 25-km-wide granitic–migmatitic belt lying between the La Ronge volcanic–plutonic island arc (1890–1830 Ma) to the southeast and the ensialic Wathaman Batholith (1855 Ma) to the northwest. The Rottenstone Domain consists of three lithotectonic belts parallel to the orogen: (i) southeast — gently folded migmatized quartzo-feldspathic metasedimentary and mafic metavolcanic rocks intruded by small concordant and discordant white tonalite–monzogranite bodies; (ii) central — intensely folded and migmatized metasedimentary rocks and minor metavolcanic rocks intruded by largely discordant, xenolith-rich, pink aplite-pegmatite monzogranite bodies; and (iii) northwest — steeply folded migmatized metasedimentary rocks cut by subvertical white tonalite–monzogranite sheets. Emplacement of granitoid rocks consists predominantly of contiguous, orogen-parallel, steeply dipping, syntectonic and post-tectonic sheets with prominent magmatic schlieren bands, overprinted by parallel solid-state deformation features. The white granitoid rocks have A/CNK (mol Al2O3/(mol CaO + Na2O + K2O)) = 1.14–1.22, K/Rb ≈ 500, ΣREE (sum of rare-earth elements) < 70 ppm, Eu/Eu* > 1, 87Sr/86Sri ≈ 0.7032, and εNdi ≈ –2. The pink monzogranites have A/CNK = 1.11–1.16, K/Rb ≈ 500, ΣREE > 90 ppm, Eu/Eu* < 1, 87Sr/86Sri ≈ 0.7031, and εNdi ≈ –2. The white granitoid rocks show a wider compositional range and more compositional scatter than the pink monzogranites, reflecting some combination of smaller volume melts, less homogenization, and less control by crystal–melt equilibria. All metavolcanic, metasedimentary, and granitic rocks in the Rottenstone Domain have the distinctive geochemical signatures of an arc environment. New sensitive high-resolution ion microprobe (SHRIMP) U–Pb geochronology on the Rottenstone granitoid rocks reveals complex growth histories for monazite and zircon, variably controlled by inheritance, magmatism, and high-grade metamorphism. Monazite ages for the granitoid bodies and migmatites cluster at ~1834 and ~1814 Ma, whereas zircon ages range from ~2480 Ma (rare cores) to ~1900–1830 Ma (cores and mantles), but also ~1818–1814 Ma for low Th/U recrystallized rims, overgrowths, and rare discrete euhedral prisms. These results demonstrate that at least some source material for the granitic magmas included earliest Paleoproterozoic crust (Sask Craton?), or its derived sediments, and that Rottenstone granitic magmatism postdated plutonism in the bounding La Ronge Arc and Wathaman Batholith. We estimate the age of terminal metamorphism in the Davin Lake area to be ~1815 Ma. Petrogenetically, the Rottenstone migmatites and granitoid rocks appear, for the most part, locally derived from their metasedimentary and metavolcanic host rocks, shed from the La Ronge Arc, Sask Craton, and possibly the Hearne Craton. The Rottenstone Domain was the least competent member in the overthrust stack and probably underwent a combination of fluid-present melting and fluid-absent decompression melting, resulting in largely syntectonic granitoid magmatism ~1835–1815 Ma, analogous to granite production in the High Himalayan gneiss belt.

Lead- and sulfur-isotope ratios from the Great Slave Lake area, Canada

1968 ◽  
Vol 5 (5) ◽  
pp. 1269-1276 ◽  
Author(s):  
D. K. Robertson ◽  
G. L. Cumming
Keyword(s):  
Lead Isotope ◽  
Sulfur Isotope ◽  
Isotope Ratios ◽  
Ore Deposits ◽  
Lake Area ◽  
Iron Sulfides ◽  
Tectonic Event ◽  
Slave Province ◽  
Great Slave Lake ◽  
Lead Line

Lead- and sulfur-isotope ratios have been determined for some galenas and iron sulfides from two regions around Yellowknife, Northwest Territories. For the ore deposits, sulfur-isotope ratios are close to the meteoritic value or slightly positive. Lead-isotope ratios fall into two groups, one derived from a source with Th/U = 4.3 and μ = 9–11, and the other from a source with Th/U = 3.5 and μ = 9.0. The ratios fall on an anomalous lead line, which indicates one event of great antiquity (approximately 4000 m.y.), and another about 2800 m.y. ago.Other sulfide samples from areas around Great Slave Lake, primarily outside the ancient (2800 m.y.) Slave Province, indicate events at 2800 m.y. and 1550 m.y., the latter date probably representing the time of the last major tectonic event in the Slave Province. Sulfur-isotope ratios for these samples vary from +1‰ to −13‰ relative to the meteoritic value, suggesting that these leads may have been remobilized by thermal metamorphism, and recombined with crustal sulfur enriched in 32S.

scholarly journals Influence of water diversion on spatial and temporal distribution of flow field and total phosphorus (TP) concentration field in Taihu Lake

2020 ◽  
Vol 20 (3) ◽  
pp. 1059-1071 ◽  
Author(s):  
Ruichen Xu ◽  
Yong Pang ◽  
Zhibing Hu ◽  
Tianyi Zhu ◽  
John Paul Kaisam
Keyword(s):  
Flow Field ◽  
Taihu Lake ◽  
Concentration Field ◽  
Temporal Distribution ◽  
Water Diversion ◽  
Lake Area ◽  
Temporal And Spatial Distribution ◽  
Pearson Coefficient ◽  
East Lake ◽  
Influence Of Water

Abstract In order to evaluate the overall impact of water diversion on Taihu Lake, this paper carries out numerical simulation of the temporal and spatial distribution of the flow field and the TP concentration field in Taihu Lake based on measured data during the water diversion period by using the Euler–Lagrange method. The results show that: (1) the Pearson coefficient of monitoring points in the East Lake area increases significantly during the water diversion period, indicating that the diversion of water may indirectly influence water quality; (2) the diversion of water has a significant influence on the flow rate of the simulated stations in Taihu Lake, and the influence is Taipu (103%) &gt; Gongwan (60%) &gt;East Lake (31%); (3) when the amount of water flow transfer from the Wangyu River to the lake is greater than 100 m3/s, the mean concentration of TP in the Center and East lakes increases significantly (more than 50%). The recommended water diversion discharge is to be controlled in the range 100–200 m3/s and the total water diversion yield between 1.56 and 2.59 billion m3/a.

Provenance and palaeogeographic implications of detrital zircons from the lower Carboniferous Riwanchaka Formation of the central Tibetan Plateau

2019 ◽  
Vol 156 (12) ◽  
pp. 2031-2042 ◽  
Author(s):  
Hu Peng ◽  
Chaoming Xie ◽  
Cai Li ◽  
Zhongyue Zhang
Keyword(s):  
High Pressure ◽  
Continental Margin ◽  
Detrital Zircon ◽  
Suture Zone ◽  
Metamorphic Rocks ◽  
Lower Carboniferous ◽  
Margin Setting ◽  
Depositional Settings ◽  
Tethys Ocean

AbstractThe Longmu Co–Shuanghu suture zone, which divides the Qiangtang terrane into the northern and southern Qiangtang blocks, is regarded as a key locality in reconstructing the evolutionary history of the Palaeo-Tethys Ocean and the break-up of Gondwana. However, although low-temperature – high-pressure metamorphic rocks and ophiolites have been documented within the Longmu Co–Shuanghu suture zone, it remains unclear whether it is an in situ suture zone and represents the relic of the main Palaeo-Tethys Ocean. The uncertainty stems mainly from the limited systematic studies of the provenance, palaeontological evidence and depositional settings of strata on either side of the Longmu Co–Shuanghu suture zone (i.e. northern and southern Qiangtang blocks). Here we report new detrital zircon U–Pb ages and palaeontological data from Lower Carboniferous strata (Riwanchaka Formation) of the northern Qiangtang block, central Tibet. The Riwanchaka Formation contains warm-climate biota with Cathaysian affinities. Provenance analysis reveals that the formation has detrital zircon spectra similar to those from strata of the Yangtze Plate, and it contains a large proportion of zircons with ages (~360 Ma) similar to the timing of synsedimentary magmatic arc activity, implying an active continental margin setting associated with northward subduction of the Palaeo-Tethyan oceanic lithosphere. Conversely, the Carboniferous–Permian strata from the southern Qiangtang block contain cool-water faunas of Gondwanan affinity and exhibit minimum zircon crystallization ages that are markedly older than their depositional ages, suggesting a passive continental margin setting. The differences in provenance, palaeontological assemblages and depositional settings of the Carboniferous to Permian strata either side of the Longmu Co–Shuanghu suture zone indicate the existence of an ancient ocean between the northern and southern Qiangtang blocks. Combining the new findings with previous studies on high-pressure metamorphic rocks, arc magmatism and ophiolites, we support the interpretation that the Longmu Co–Shuanghu suture zone is an in situ suture zone that represents the main suture of the Palaeo-Tethys Ocean.

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