Advances in the Geochronology of the Rice Lake – Beresford Lake Area, Southeastern Manitoba

1971 ◽  
Vol 8 (5) ◽  
pp. 572-579 ◽  
Author(s):  
Andrew Turek ◽  
Zell E. Peterman
Keyword(s):  
Greenstone Belt ◽  
Regional Metamorphism ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
Lake Area ◽  
The South ◽  
Quartz Veins ◽  
The North ◽  
Granite Emplacement ◽  
Second Period

The Rice Lake – Beresford Lake area consists of an easterly trending Precambrian greenstone belt which is flanked on the north by granitic rocks and on the south by granitic and metamorphic rocks. Analyses of an intrusive, late tectonic quartz monzonite at Black Lake, yield an isochron age of 2735 ± 55 m.y. with an initial 87Sr/80Sr composition 0.7019 ± 0.0008. This age is a minimum for the granitic rocks to the south of the greenstone belt and is the oldest age obtained in this area. On the other hand, analyses of a quartz diorite pluton intrusive into the greenstones give a metamorphic age of 2555 ± 70 m.y. with an initial 87Sr/86Sr of 0.7016 ± 0.0012. Mylonite zones are developed along the northern and southern boundaries of the greenstone belt. Analyses of whole-rock samples from these zones yield an age of 2345 ± 100 m.y. with initial 87Sr/88Sr 0.7044 ± 0.0024, and is the youngest age obtained in the area.These new data, combined with our previous work, indicate three major events. The first and oldest event is 2730 ± 50 m.y. and is interpreted as a period of regional metamorphism, granite emplacement, and the emplacement of gold–quartz veins which postdate the greenstones. A second period of metamorphism and granite emplacement occurred at 2530 ± 40 m.y. and it affected the area as a whole, as evidenced by updated mineral ages. The third and youngest event, 2345 ± 100 m.y., is recorded by the mylonites and may represent epeirogenic movement in the area.

U–Pb zircon ages for the Rice Lake area, southeastern Manitoba

1989 ◽  
Vol 26 (1) ◽  
pp. 23-30 ◽  
Author(s):  
A. Turek ◽  
R. Keller ◽  
W. R. Van Schmus ◽  
W. Weber
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Quartz Diorite ◽  
Granitic Rocks ◽  
Lake Area ◽  
The South ◽  
Metasedimentary Rocks ◽  
The North ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

The Archean Rice Lake greenstone belt in southeastern Manitoba is made up of mafic to felsic volcanic rocks and associated intrusive and metasedimentary rocks. The belt is flanked to the north by the Wanipigow River granitic complex and to the south by the Manigotagan gneissic belt. The Ross River quartz diorite pluton is intrusive into the centre of the greenstone belt. U–Pb zircon ages indicate a major volcanic and plutonic event in the area at 2730 Ma. Ages for two volcanic units of the Rice Lake Group are 2731 ± 3 and 2729 ± 3 Ma. The Ross River pluton yields an age of 2728 ± 8 Ma and the Gunnar porphyry gives an age of 2731 ± 13 Ma; both intrude rocks of the Rice Lake Group. Granitic rocks of the Wanipigow River granitic complex give ages of 2731 ± 10 and 2880 ± 9 Ma, while a post-tectonic granite in the Manigotagan gneissic belt has an age of 2663 ± 7 Ma.

METAMORPHISM OF THE MEGUMA GROUP OF NOVA SCOTIA

1966 ◽  
Vol 3 (7) ◽  
pp. 959-974 ◽  
Author(s):  
F. C. Taylor ◽  
E. A. Schiller
Keyword(s):  
Nova Scotia ◽  
Regional Metamorphism ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Contact Metamorphism ◽  
Granitic Rocks ◽  
Structural Elements ◽  
Early Ordovician ◽  
Quartz Veins ◽  
Granite Emplacement

The Meguma group of lithic greywacke, feldspathic quartzite, slate siltstone, and argillite is Early Ordovician or older in age and has undergone both regional and contact metamorphism. Both types of metamorphism have resulted in recrystallization and locally in orientation of newly formed minerals. Metasomatism and retrogressive metamorphism are subordinate and only locally important. Regionally metamorphosed rocks are divided into greenschist and almandine–amphibolite facies, although some assemblages cannot be assigned with certainty. Locally, biotite and garnet isograds are mappable within the greenschist zone.Relationships between regional metamorphism and structural elements (folding) show that deformation preceded regional metamorphism. Intrusion of granitic rocks has produced a zone of contact metamorphism (hornblende–hornfels facies) that is superimposed upon regional greenschist facies rocks, which shows that granite emplacement occurred after the regional grade was reached. Gold–quartz veins are confined to areas lying in the greenschist zone of regional metamorphism, which suggests that the almandine–amphibolite zone is not favorable.

Preliminary Rb–Sr geochronology of the Rice Lake – Beresford Lake area, southeastern Manitoba

1968 ◽  
Vol 5 (6) ◽  
pp. 1373-1380 ◽  
Author(s):  
A. Turek ◽  
Z. E. Peterman
Keyword(s):  
Greenstone Belt ◽  
San Antonio ◽  
Regional Metamorphism ◽  
Quartz Diorite ◽  
Lake Area ◽  
Quartz Veins ◽  
Minimum Age ◽  
Basic Rocks

A Rb–Sr geochronologic study of rocks of the Rice Lake – Beresford Lake area, southeastern Manitoba, shows that gold-quartz veins containing sericite and fuchsite were emplaced at 2720 ± 185 m.y. ago (λ87Rb = 1.39 × 10−11 yr−1). The mineralization postdates, and thus provides a minimum age for, the Rice Lake Group as well as for the successively younger intrusive basic rocks, quartz diorite plutons, and the San Antonio Formation. A whole-rock isochron for the potassic granite that lies north of the greenstones indicates an age of 2550 ± 80 m.y., with an initial 87Sr/86Sr of 0.7031 ± 0.0021, which we also consider as the age of regional metamorphism. This is in agreement with a metamorphic age of 2490 ± 90 m.y., as registered by phyllites from the Rice Lake Group. The gneisses and granites that lie south of the greenstone belt are older than 2630 m.y., as determined by a cross-cutting pegmatite. Because the northern granite is younger than the gold-quartz veins, extensive prospecting of the northern granite for gold-quartz mineralization is not likely to be fruitful unless there was a still younger, but presently unrecognized, period of mineralization.

scholarly journals Identifikasi Keterdapatan Mineral Radioaktif pada Urat-Urat Magnetit di Daerah Ella Ilir, Melawi, Kalimantan Barat

EKSPLORIUM ◽  
2019 ◽  
Vol 40 (1) ◽  
pp. 33
Author(s):  
Ngadenin Ngadenin ◽  
Frederikus Dian Indrastomo ◽  
Widodo Widodo ◽  
Kurnia Setiawan Widana
Keyword(s):  
Iron Ore ◽  
Biotite Granite ◽  
Ore Deposits ◽  
Geological Mapping ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
West Kalimantan ◽  
The North ◽  
Iron Ore Deposits ◽  
Radioactive Minerals

ABSTRAKElla Ilir secara administratif terletak di Kabupaten Melawi, Kalimantan Barat. Geologi regional daerah Ella Ilir tersusun atas batuan malihan berumur Trias–Karbon yang diterobos oleh batuan granitik berumur Yura dan Kapur. Keterdapatan mineral radioaktif di daerah tersebut terindikasi dari radioaktivitas urat-urat magnetit pada batuan malihan berumur Trias–Karbon dengan kisaran nilai 1.000 c/s hingga 15.000 c/s. Tujuan dari penelitian ini adalah menentukan jenis cebakan mineral bijih dan mengidentifikasi keterdapatan mineral radioaktif pada urat-urat bijih magnetit di daerah Ella Ilir. Metode yang digunakan adalah pemetaan geologi, pengukuran radioaktivitas, analisis kadar uranium, dan analisis mineragrafi beberapa sampel urat bijih magnetit. Litologi daerah penelitian tersusun oleh kuarsit biotit, metatuf, metabatulanau, metapelit, granit biotit, dan riolit. Sesar sinistral barat-timur dan sesar dekstral utara-selatan merupakan struktur sesar yang berkembang di daerah ini. Komposisi mineral urat-urat magnetit terdiri dari mineral-mineral bijih besi, sulfida, dan radioaktif. Mineral bijih besi terdiri dari magnetit, hematit, dan gutit. Mineral sulfida terdiri dari pirit, pirhotit, dan molibdenit sedangkan mineral radioaktif terdiri dari uraninit dan gumit. Keterdapatan urat-urat bijih magnetit dikontrol oleh litologi dan struktur geologi. Urat-urat magnetit pada metabatulanau berukuran tebal (1,5–5 m), mengisi rekahan-rekahan yang terdapat di sekitar zona sesar. Sementara itu, urat-urat magnetit pada metapelit berukuran tipis (milimetrik–sentimetrik), mengisi rekahan-rekahan yang sejajar dengan bidang sekistositas. Cebakan mineral bijih di daerah penelitian adalah cebakan bijih besi atau cebakan bijih magnetit berbentuk urat karena proses hidrotermal magmatik.ABSTRACTElla Ilir administratively located in Melawi Regency, West Kalimantan. Regional geology of Ella Ilir area is composed of metamorphic rocks in Triassic–Carboniferous age which are intruded by Jurassic and Cretaceous granitic rocks. Radioactive minerals occurences in the area are indicated by magnetite veins radioactivities on Triassic to Carboniferous metamorphic rocks whose values range from 1,000 c/s to 15,000 c/s. Goal of the study is to determine the type of ore mineral deposits and to identify the presence of radioactive mineral in magnetite veins in Ella Ilir area. The methods used are geological mapping, radioactivity measurements, analysis on uranium grades, and mineragraphy analysis of severe magnetite veins samples. Lithologies of the study area are composed by biotite quartzite, metatuff, metasilt, metapellite, biotite granite, and ryolite. The east-west sinistral fault and the north-south dextral fault are the developed fault structures in this area. Mineral composition of magnetite veins are consists of iron ore, sulfide, and radioactive minerals. Iron ore mineral consists of magnetite, hematit, and goetite. Sulfide minerals consist of pyrite, pirhotite, and molybdenite, while radioactive minerals consist of uraninite and gummite. The occurences of magnetite veins are controlled by lithology and geological structures. The magnetite veins in metasilt are thick (1.5–5 m), filled the fractures in the fault zone. Meanwhile, the magnetite veins in metapellite are thinner (milimetric–centimetric), filled the fractures that are parallel to the schistocity. The ore deposits in the study area are iron ore deposits or magnetite ore deposits formed by magmatic hydrothermal processes. 

Rb–Sr whole-rock geochronology of the Gamitagama area, north central Ontario

1981 ◽  
Vol 18 (2) ◽  
pp. 323-329 ◽  
Author(s):  
A. Turek ◽  
T. E. Smith ◽  
C. H. Huang
Keyword(s):  
Greenstone Belt ◽  
Complex Terrain ◽  
Regional Metamorphism ◽  
Superior Province ◽  
The South ◽  
Stratigraphic Sequence ◽  
North Central ◽  
Metasedimentary Rocks ◽  
Area North ◽  
Radiometric Ages

The Gamitagama greenstone belt is situated to the south of the Archean Wawa belt of the Superior Province, and is about 50 km south of Wawa, Ontario. The Rb–Sr ages being reported here show that the metavolcanic and associated metasedimentary rocks are older than 2665 ± 45 Ma, which is a whole-rock isochron age of the pretectonic or syntectonic trondhjemitic plutons. The Gamitagama Lake complex, a calcalkalic differentiated and multiple diorite pluton, postdates the regional metamorphism and gives an age of 2645 ± 100 Ma. Potassic granitoid stocks, which are considered to be coeval with the Gamitagama Lake complex, define an isochron age of 2590 ± 80 Ma. The greenstone belt and associated intrusives are adjacent to the Southern batholith, a complex terrain of gneisses and migmatites, for which an isochron age of 2570 ± 90 Ma has been obtained. The radiometric ages reported here support the established stratigraphic sequence and prove that the rocks are Archean in age.

Pre-Priabonian Palaeogene formations in southwestern Bulgaria and northern Greece: stratigraphy and tectonic implications

1998 ◽  
Vol 135 (1) ◽  
pp. 101-119 ◽  
Author(s):  
IVAN S. ZAGORCHEV
Keyword(s):  
Late Cretaceous ◽  
Middle Eocene ◽  
Regional Metamorphism ◽  
Late Eocene ◽  
Thin Layers ◽  
The South ◽  
Northern Greece ◽  
The North ◽  
Early Oligocene ◽  
Metamorphic Core

The Paril Formation (South Pirin and Slavyanka Mountains, southwestern Bulgaria) and the Prodromos Formation (Orvilos and Menikion Mountains, northern Greece) consist of breccia and olistostrome built up predominantly of marble fragments from the Precambrian Dobrostan Marble Formation (Bulgaria) and its equivalent Bos-Dag Marble Formation (Greece). The breccia and olistostrome are interbedded with thin layers of calcarenites (with occasional marble pebbles), siltstones, sandstones and limestones. The Paril and Prodromos formations unconformably cover the Precambrian marbles, and are themselves covered unconformably by Miocene and Pliocene sediments (Nevrokop Formation). The rocks of the Paril Formation are intruded by the Palaeogene (Late Eocene–Early Oligocene) Teshovo granitoid pluton, and are deformed and preserved in the two limbs of a Palaeogene anticline cored by the Teshovo pluton (Teshovo anticline). The Palaeocene–Middle Eocene age of the formations is based on these contact relations, and on occasional finds of Tertiary pollen, as well as on correlations with similar formations of the Laki (Kroumovgrad) Group throughout the Rhodope region.The presence of Palaeogene sediments within the pre-Palaeogene Pirin–Pangaion structural zone invalidates the concept of a ‘Rhodope metamorphic core complex’ that supposedly has undergone Palaeogene amphibolite-facies regional metamorphism, and afterwards has been exhumed by rapid crustal extension in Late Oligocene–Miocene times along a regional detachment surface. Other Palaeogene formations of pre-Priabonian (Middle Eocene and/or Bartonian) or earliest Priabonian age occur at the base of the Palaeogene sections in the Mesta graben complex (Dobrinishka Formation) and the Padesh basin (Souhostrel and Komatinitsa formations). The deposition of coarse continental sediments grading into marine formations (Laki or Kroumovgrad Group) in the Rhodope region at the beginning of the Palaeogene Period marks the first intense fragmentation of the mid- to late Cretaceous orogen, in particular, of the thickened body of the Morava-Rhodope structural zone situated to the south of the Srednogorie zone. The Srednogorie zone itself was folded and uplifted in Late Cretaceous time, thus dividing Palaeocene–Middle Eocene flysch of the Louda Kamchiya trough to the north, from the newly formed East Rhodope–West Thrace depression to the south.

Orthoquartzite pebbles in Archean conglomerate, North Spirit Lake, northwestern Ontario

1977 ◽  
Vol 14 (9) ◽  
pp. 1980-1990 ◽  
Author(s):  
J. A. Donaldson ◽  
Richard W. Ojakangas
Keyword(s):  
Greenstone Belt ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Superior Province ◽  
Lake Area ◽  
Definite Evidence ◽  
The North ◽  
Northwestern Ontario ◽  
Form Part ◽  
Quartz Grains

An Archean conglomerate in the North Spirit Lake area of northwestern Ontario contains rare orthoquartzite pebbles. Detailed study of these pebbles shows that mineralogically they are very mature, consisting of as much as 99.8 percent quartz and a heavy mineral suite of zircon, tourmaline, and apatite. Textures are typically bimodal, characterized by rounded sand-sized quartz grains set in a 'matrix-cement' of thoroughly recrystallized finer quartz grains. These orthoquartzite pebbles provide the first definite evidence for local tectonic stability of the Canadian Shield before deposition of the immature sedimentary rocks that form part of an Archean (>2.6 Ga) greenstone belt of the Superior Province.

Conditions and timing of metamorphism in the southern Abitibi greenstone belt, Quebec

1995 ◽  
Vol 32 (6) ◽  
pp. 787-805 ◽  
Author(s):  
W. G. Powell ◽  
D. M. Carmichael ◽  
C. J. Hodgson
Keyword(s):  
Greenstone Belt ◽  
Regional Metamorphism ◽  
Geothermal Gradient ◽  
Fault Zones ◽  
Low Grade ◽  
Metasedimentary Rocks ◽  
Abitibi Greenstone Belt ◽  
The North ◽  
Major Fault ◽  
Facies Transition

Regional metamorphism, ranging in grade from the subgreenschist-facies to the greenschist–amphibolite-facies transition, affects all Archean supracrustal rocks (>2677 Ma) in the Rouyn–Noranda area. Contact metamorphic minerals associated with the posttectonic Preissac–Lacorne batholith (2643 Ma) show no evidence of a regional retrograde event. Accordingly, the age of regional metamorphism can be bracketed between 2677 and 2643 Ma. Three reaction isograds were mapped in subgreenschist-facies metabasites, dividing the low-grade rocks into three metamorphic zones: the pumpellyite–actinolite zone, the prehnite–pumpellyite zone, and the prehnite–epidote zone. In addition, the pumpellyite–actinolite–epidote–quartz bathograd, corresponding to a pressure of approximately 200 MPa, occurs on both sides of the Porcupine–Destor fault. Low-pressure regional metamorphism is also indicated both by the occurrence of an actinolite–oligoclase zone, and the persistence of pre-regional-metamorphic andalusite. The coincidence of andalusite and the actinolite-oligoclase zone indicates that pressure was <330 MPa at the greenschist-amphibolite transition. The geothermal gradient during metamorphism was approximately 30 °C/km. Regionally, isograds dip shallowly to the north and trend subparallel to lithological and structural trends. Metamorphic minerals in metabasites define tectonic fabrics only near major fault zones and in zones of CO2 metasomatism. In biotite zone metasedimentary rocks the schistosity is defined by mica and amphibole. These textures indicate that metamorphism and fabric development were coeval. However, the actinolite–epidote isograd cuts the Porcupine–Destor fault, indicating that regional metamorphism postdates movement along this fault. The strong fabrics associated with the Porcupine–Destor and Larder Lake–Cadillac faults must have developed through a process dominated by flattening strain.

Geochronology and tectonic implications of magmatism and metamorphism, southern Kootenay Arc and neighbouring regions, southeastern British Columbia. Part I: Jurassic to mid-Cretaceous

1983 ◽  
Vol 20 (12) ◽  
pp. 1891-1913 ◽  
Author(s):  
D. A. Archibald ◽  
J. K. Glover ◽  
R. A. Price ◽  
E. Farrar ◽  
D. M. Carmichael
Keyword(s):  
British Columbia ◽  
North America ◽  
Regional Metamorphism ◽  
Granitic Rocks ◽  
Early Paleozoic ◽  
Small Bodies ◽  
Western Margin ◽  
The North ◽  
Windermere Supergroup ◽  
Igneous Activity

K–Ar dates and U–Pb zircon dates define three periods of igneous activity in the southern Kootenay Arc: (1) emplacement of late-synkinematic to post-kinematic granodioritic plutons in mid-Jurassic time (170–165 Ma) accompanying amphibolite-facies regional metamorphism; (2) emplacement of post-kinematic granitic plutons in mid-Cretaceous time (~100 Ma); and (3) emplacement of small bodies of syenite in Eocene time (~50 Ma) in the western part of the area. Micas from mid-Jurassic plutons that yield the oldest K–Ar dates (158–166 Ma) also yield plateau-shaped 40Ar/39Ar age spectra. Age spectra for biotites younger than these but older than 125 Ma reflect thermal overprinting.In southeastern British Columbia, the Kootenay Arc marks the transition from the North American rocks of the Cordilleran miogeocline to the tectonic collage of allochthonous terranes that have been accreted to it.Deformation, metamorphism, and plutonism recorded in rocks of the southern Kootenay Arc commenced in mid-Jurassic time as a composite allochthonous terrane was accreted to and overlapped the western margin of North America. The geochronology and metamorphic geothermobarometry show that in less than 10 Ma between 166 and 156 Ma: (1) rocks as young as the late Proterozoic Windermere Supergroup and the early Paleozoic Lardeau Group were carried rapidly to depths of 20–24 km while being deformed and intruded by granitic rocks of a hornblende–biotite suite that were also being emplaced at a much shallower level in the overriding allochthonous terrane; and (2) the miogeoclinal rocks of the Windermere Supergroup in the southern Kootenay Arc were then uplifted by more than 7 km at an estimated rate of 2 mm/year, and thrust over the allochthonous terrane prior to being intruded by post-kinematic granitic rocks, many of which belong to the two-mica suite of mid-Cretaceous age..

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