The geology and geochronology of the basement complex of the central Transantarctic Mountains

1968 ◽  
Vol 5 (3) ◽  
pp. 555-560 ◽  
Author(s):  
Gunter Faure ◽  
J. G. Murtaugh ◽  
R. J. E. Montigny
Keyword(s):  
Granitic Rocks ◽  
Basement Complex ◽  
Metasedimentary Rocks ◽  
Late Cambrian ◽  
Field Evidence ◽  
Metavolcanic Rocks ◽  
Transantarctic Mountain ◽  
Quartz Monzonite ◽  
Transantarctic Mountains ◽  
Mountain Chain

The central part of the Transantarctic Mountain chain consists of a basement complex of igneous and metamorphic rocks overlain nonconformably by sedimentary rocks of late Paleozoic age, including Permian tillites and coal measures. The basement complex is exceptionally well exposed in the Wisconsin Range of the Horlick Mountains, which are located about 500 km from the South Pole. In this area clastic metasedimentary rocks and overlying metavolcanic rocks of probable pyroclastic origin are intruded by a variety of granitic rocks of the Wisconsin Range batholith, including rapakivi granites and quartz diorites, which are in turn cut by bodies of quartz monzonite, and aplite and pegmatite dikes. The basement complex elsewhere in the central Transantarctic Mountains also includes Cambrian limestones overlain by acid volcanic pyroclastic rocks and lava flows.Age determinations by the Rb–Sr method applied to suites of total rock specimens suggest the presence of two orogenic events accompanied by intrusions of granitic plutons. The first of these occurred about 630 ± 25 m.y. ago and was accompanied by the formation of rapakivi granites. The second took place during the Ordovician Period about 480 ± 10 m.y. ago and involved the intrusion of quartz monzonite and pegmatite dikes. The metasedimentary rocks, which were intruded by both of the granitic rocks, give an apparent age of 460 ± 16 m.y., while the overlying pyroclastic unit was dated at 633 ± 13 m.y. A Precambrian age for the metasedimentary and metavolcanic rocks is consistent with the dating and the field evidence. Rhyolites from localities in the Byrd Mountains and the Long Hills were dated at 489 ± 30 and 498 ± 45 m.y. and are late Cambrian to early Ordovician in age.

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.

Geology and Ages of Buried Precambrian Basement Rocks, Manitoulin Island, Ontario

1975 ◽  
Vol 12 (7) ◽  
pp. 1175-1189 ◽  
Author(s):  
W. R. Van Schmus ◽  
K. D. Card ◽  
K. L. Harrower
Keyword(s):  
Granitic Rocks ◽  
Precambrian Basement ◽  
Aeromagnetic Data ◽  
Grenville Province ◽  
Metasedimentary Rocks ◽  
Basement Rocks ◽  
Metavolcanic Rocks ◽  
Northern Half ◽  
East End ◽  
Archean Basement

The geology of the buried Precambrian basement under Manitoulin Island in northern Lake Huron, Ontario, has been re-evaluated on the basis of aeromagnetic data, well cuttings, core samples, and rubidium–strontium and uranium–lead geochronologic data on some of the subsurface samples. We conclude that the northern half of the island is underlain in part by Huronian metasedimentary rocks, but that these are absent from the southern part of the island, which is underlain by granitic, gneissic, and metavolcanic rocks. Granitic and gneissic rocks are also present under the northern half of the island.Geochronologic data show that rocks underlying major positive aeromagnetic anomalies are quartz-monzonitic composite plutons which are about 1500 ± 20 m.y. old. Surrounding metasedimentary. gneissic, and granitic rocks are at least 1700 m.y. old. No evidence was found for extrapolation of the pre-Huroman Archean basement beneath Manitoulin Island; if it is present it has been affected by younger metamorphic overprinting.The south west ward extension of the boundary zone between the Grenville Province and rocks to the west can he traced along the east end of Manitoulin Island on the basis of aeromagnetic data.

Rubidium–strontium ages of Archean and Proterozoic rocks in the Nejanilini and Great Island domains, Churchill Province, northern Manitoba, Canada

1988 ◽  
Vol 25 (2) ◽  
pp. 246-254 ◽  
Author(s):  
G. S. Clark ◽  
D. C. P. Schledewitz
Keyword(s):  
Granitic Rocks ◽  
Granitic Magma ◽  
Initial Ratio ◽  
Early Proterozoic ◽  
Metasedimentary Rocks ◽  
Field Evidence ◽  
Southern District ◽  
Island Group ◽  
Minimum Age ◽  
Archean Basement

Rubidium–strontium whole-rock ages are reported from the Nejanilini – Great Island area in northeastern Manitoba. This area is part of an extensive zone of Archean basement that was metamorphosed and intruded by granitic magma during the Proterozoic; it extends into Saskatchewan and southern District of Keewatin, Northwest Tertitories. An age of 2577 ± 42 Ma (1σ error) for the extensive Nejanilini granulite massif (Nejanilini domain), considered one of the oldest rock units in the area, is interpreted as a minimum age for late Archean granulite-facies metamorphism. A minimum age of 2052 ± 41 Ma (initial ratio 0.7150) for quartz–feldspar porphyry that intrudes the Seal River volcanic suite constrains the age of these volcanics and could represent a partially reset Archean age. Early Proterozoic quartzite and metagreywacke of the Great Island Group unconformably overlies the quartz–feldspar porphyry. These metasedimentary rocks, which are probably correlative with the Daly Lake Group (Saskatchewan) or the Hurwitz Group (southern District of Keewatin), give an age of 1885 ± 85 Ma, with an initial ratio of 0.7093. The age records the time of closure of the Rb–Sr isotopic system subsequent to early Proterozoic metamorphism. The age and initial ratio are consistent with published results for other, possibly correlative, metasedimentary rocks in this zone. Modelling the Rb–Sr isotopic data constrains the time of sedimentation to between ca. 2100 and 2000 Ma ago. Syn- to late-kinematic, early Proterozoic granite to granodiorite batholiths, which intruded metasedimentary rocks of the Great Island Group, may largely be the product of melting of Archean basement, based on field evidence and high initial 87Sr/86Sr ratios. The Caribou Lake porphyritic quartz monzonite gives an age of 1795 ± 35 Ma, with an initial 87Sr/86Sr ratio of 0.7084. High initial ratios seem to typify early Proterozoic granitic rocks in this remobilized craton.

U–Pb zircon ages and the evolution of the Michipicoten plutonic–volcanic terrane of the Superior Province, Ontario

1984 ◽  
Vol 21 (4) ◽  
pp. 457-464 ◽  
Author(s):  
A. Turek ◽  
Patrick E. Smith ◽  
W. R. Van Schmus
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Tectonic Activity ◽  
Superior Province ◽  
Zircon Geochronology ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Before And After ◽  
Volcanic Cycles

The Archean Michipicoten greenstone belt of the Superior Province in Ontario is made up of supracrustal rocks divided into lower, middle, and upper metavolcanic rocks with associated metasedimentary rocks. The belt has been intruded by granitic rocks and is also surrounded by granitic terranes. Based on U–Pb zircon geochronology it appears that volcanism in the area extended from at least 2749 to 2696 Ma, and plutonism and tectonic activity extended from at least 2888 to 2615 Ma. The various granitic (and also one gabbroic) plutons, both internal and external to the greenstone belt, were emplaced concomitantly with the three volcanic cycles as well as before and after the formation of the volcanic rocks. Zircon ages reported here, together with previously published ages, show that the area evolved in six major volcanic and plutonic events: (I) 2888 Ma—plutonism, (II) 2743 Ma—volcanism and plutonism, (III) 2717 Ma—volcanism and plutonism, (IV) 2696 Ma—volcanism and plutonism, (V) 2668 Ma—plutonism, and (VI) 2615 Ma—plutonism. The oldest rock dated at 2888 ± 2 Ma belongs to the external granitic terrane and may be basement to the supracrustal rocks.

Rb–Sr and U–Pb ages of volcanism and granite emplacement in the Michipicoten belt—Wawa, Ontario

1982 ◽  
Vol 19 (8) ◽  
pp. 1608-1626 ◽  
Author(s):  
A. Turek ◽  
Patrick E. Smith ◽  
W. R. Van Schmus
Keyword(s):  
Greenstone Belt ◽  
Granitic Rocks ◽  
Iron Formation ◽  
Superior Province ◽  
Initial Ratio ◽  
Metasedimentary Rocks ◽  
Granite Emplacement ◽  
Time Period ◽  
Metavolcanic Rocks ◽  
Volcanic Belts

The Michipicoten greenstone belt at Wawa, Ontario is typical of Archean volcanic belts in the Superior Province. The supracrustal rocks are divisible into lower, middle, and upper metavolcanic sequences, which are separated by iron formation and clastic metasedimentary rocks. These are intruded by granitic stocks and embayed by granitic batholiths.This study reports whole rock Rb–Sr and zircon U–Pb ages for the lower and upper metavolcanics, for the granitic rocks that are physically within the greenstone belt (internal granites), and for the granitic rocks that embay the greenstone belt (external granites). The apparent Rb–Sr ages for the lower metavolcanics are 2530 ± 90, 2285 ± 70, and 2680 ± 490 Ma. The U–Pb ages are 2749 ± 2 and 2744 ± 10 Ma. The internal granites give an Rb–Sr age of 2560 ± 270 Ma and a U–Pb age of 2737 ± 6 Ma. The external granite at Hawk Lake indicates an Rb–Sr age of 2550 ± 175 Ma and a U–Pb age of 2747 ± 7 Ma. It is possible that this unit contains elements older than 2812 Ma as it contains xenocrystic zircons. The upper volcanics give a U–Pb age of 2696 ± 2 Ma, which indicates that the belt evolved over a time period in excess of 53 Ma. The Rb–Sr ages are significantly younger than the U–Pb zircon ages and have very large uncertainties in age; hence it is unlikely that they have any stratigraphic significance. They probably reflect the Kenoran orogeny at about 2560 Ma. The 2285 ± 70 Ma Rb–Sr isochron age has an initial ratio of 0.7275 ± 0.0052, which is interpreted as a rotational isochron defining a younger post-Kenoran event in the area. The zircon ages appear to be correct chronostratigraphically. Furthermore, it appears that the granitic rocks are coeval and may also be cogenetic with the lower acid metavolcanic rocks.

scholarly journals Geochemical signatures of mineralizing events in the Juomasuo Au–Co deposit, Kuusamo belt, northeastern Finland

2021 ◽  
Author(s):  
Mikael Vasilopoulos ◽  
Ferenc Molnár ◽  
Hugh O’Brien ◽  
Yann Lahaye ◽  
Marie Lefèbvre ◽  
...  
Keyword(s):  
Trace Element ◽  
Sulfur Isotope ◽  
Mineral Chemistry ◽  
Chemical Compositions ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Icp Ms ◽  
Stage 1 ◽  
Host Rocks ◽  
Relationship Of

AbstractThe Juomasuo Au–Co deposit, currently classified as an orogenic gold deposit with atypical metal association, is located in the Paleoproterozoic Kuusamo belt in northeastern Finland. The volcano-sedimentary sequence that hosts the deposit was intensely altered, deformed, and metamorphosed to greenschist facies during the 1.93–1.76 Ga Svecofennian orogeny. In this study, we investigate the temporal relationship between Co and Au deposition and the relationship of metal enrichment with protolith composition and alteration mineralogy by utilizing lithogeochemical data and petrographic observations. We also investigate the nature of fluids involved in deposit formation based on sulfide trace element and sulfur isotope LA-ICP-MS data together with tourmaline mineral chemistry and boron isotopes. Classification of original protoliths was made on the basis of geochemically immobile elements; recognized lithologies are metasedimentary rocks, mafic, intermediate-composition, and felsic metavolcanic rocks, and an ultramafic sill. The composition of the host rocks does not control the type or intensity of mineralization. Sulfur isotope values (δ34S − 2.6 to + 7.1‰) and trace element data obtained for pyrite, chalcopyrite, and pyrrhotite indicate that the two geochemically distinct Au–Co and Co ore types formed from fluids of different compositions and origins. A reduced, metamorphic fluid was responsible for deposition of the pyrrhotite-dominant, Co-rich ore, whereas a relatively oxidized fluid deposited the pyrite-dominant Au–Co ore. The main alteration and mineralization stages at Juomasuo are as follows: (1) widespread albitization that predates both types of mineralization; (2) stage 1, Co-rich mineralization associated with chlorite (± biotite ± amphibole) alteration; (3) stage 2, Au–Co mineralization related to sericitization. Crystal-chemical compositions for tourmaline suggest the involvement of evaporite-related fluids in formation of the deposit; boron isotope data also allow for this conclusion. Results of our research indicate that the metal association in the Juomasuo Au–Co deposit was formed by spatially coincident and multiple hydrothermal processes.

On an Occurrence of Fayalite Quartz-Monzonite in the Basement Complex around Bauchi, Northern Nigeria

1961 ◽  
Vol 98 (6) ◽  
pp. 473-482 ◽  
Author(s):  
M. O. Oyawoye
Keyword(s):  
Linear Structure ◽  
Northern Nigeria ◽  
Basement Complex ◽  
Green Colour ◽  
Quartz Monzonite ◽  
Ring Complexes ◽  
High Level ◽  
Mineral Constituents ◽  
Ring Dyke

AbstractAn unusual fayalite-bearing quartz-monzonite occurs around Bauchi in Northern Nigeria and is distinguished from the high-level fayalite granites of the Newer Granites ring complexes by the presence of a linear structure conformable with those in the surrounding rocks, the gradational nature of its contacts, the extreme coarseness of its mineral constituents and the abundance of myrmekite. It is similar to them in its distinctive green colour and in the high FeO: Fe2O3 ratio. The rock is believed to be definitely older than the rocks of the ring-dyke complexes.

The Notch Peak Contact Metamorphic Aureole, Utah: Paleomagnetism of the metasedimentary rocks and the quartz monzonite stock

1982 ◽  
Vol 87 (B7) ◽  
pp. 5375-5390 ◽  
Author(s):  
Stephen L. Gillett ◽  
Victoria C. Hover ◽  
James J. Papike
Keyword(s):  
Metasedimentary Rocks ◽  
Quartz Monzonite ◽  
Notch Peak

scholarly journals Project SUPRASYD 1993 - granitic rocks and shear zones with possible gold potential, Julianehåb batholith, South Greenland

1994 ◽  
Vol 160 ◽  
pp. 28-31
Author(s):  
A.A Garde ◽  
H.K Schønwandt
Keyword(s):  
East Coast ◽  
Economic Assessment ◽  
Shear Zones ◽  
Geological Survey ◽  
Granitic Rocks ◽  
Significant Potential ◽  
Metavolcanic Rocks ◽  
Sulphide Deposits ◽  
Important Constituent

In 1992 the Geological Survey of Greenland (GGU) initiated the project SUPRASYD in order to carry out an economic assessment of the Ketilidian orogen in South Greenland, especially the supracrustal rocks in the southern and eastern parts of the orogen (see Dawes & Schønwandt, 1992). Geological investigations in the area east of Nanortalik and along the east coast of South Greenland as far as 62°N had previously indicated that acid metavolcanic rocks were an important constituent of the supracrustal rocks, and it was therefore expected that the region might have a significant potential for sulphide deposits.

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