U–Pb geochronology in Liverpool Land and Canning Land, East Greenland — the complex record of a polyphase Caledonian orogenyThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 473-494 ◽  
Author(s):  
Fernando Corfu ◽  
Ebbe H. Hartz

The Liverpool Land – Canning Land region in East Greenland is the central-most basement high in the northeast Atlantic Caledonides. It contains a variety of rocks derived from the whole section of the Caledonian crust, permitting correlations and comparisons of tectonomagmatic events at all crustal levels. Here, we present U–Pb thermal ionization mass spectrometry (TIMS) data combined with field studies suggesting that the region can be divided into distinct tectonostratigraphic domains: (1) The Southern Liverpool Land eclogite terrane with garnet-peridotite and eclogite lenses, the product of a polyorogenic history with a latest-Paleoproterozic and Mesoproterozoic origin, eclogitization at 398 Ma and migmatization at 387 Ma. (2) The migmatitic Mariager Fjord Dome in central Liverpool Land with gneisses that formed leucosome at 409 Ma. Both areas are separated by high-strain zones from (3) the overlying Hurry Inlet plutonic terrane, which consists of metasedimentary rocks first intruded by granodiorite to granite at ca. 440–430 Ma, and, after local deformation, by a major 426–424 Ma granitic to monzonitic suite. (4) Structurally higher, and probably above another high-strain zone, low-grade Neoproterozoic to Cambrian sediments are intruded, by syn-contractional 427 Ma leucogranite. All these units are unconformably overlain by Devonian and younger deposits. Collectively our data document a distinct variation in time for Caledonian magmatism and metamorphism in the various tectonostratigraphic domains, implying that the diverse terranes were juxtaposed after magmatism, and that the gneiss domes of Liverpool Land have a different origin than other nappes of the East Greenland Caledonides.

2017 ◽  
Vol 54 (2) ◽  
pp. 173-202 ◽  
Author(s):  
Laura R. Katz ◽  
Daniel J. Kontak ◽  
Benoît Dubé ◽  
Vicki McNicoll

The Archean Côté Gold Au(–Cu) deposit is the first large gold deposit discovered in the Swayze greenstone belt of the Abitibi Subprovince. The deposit is a low-grade, large-tonnage type with a combined indicated and inferred resource of 8.65 M oz Au (245.2 t Au). The deposit is hosted by the Chester intrusive complex (CIC), a multiphase, subvolcanic intrusion composed of low-Al tonalite, diorite, and quartz diorite, plus magmatic and hydrothermal breccia bodies. The age of the tonalite and dioritic phases is constrained at 2741–2739 ± 1 Ma using high-precision isotope dilution – thermal ionization mass spectrometry (ID–TIMS) U–Pb zircon geochronology. Although these phases are co-temporal and co-spatial, they appear to be petrogenetically unrelated. The CIC was emplaced into mafic metavolcanic rocks of the Arbutus Formation whose geochemistry reflects a back-arc environment. The tonalite of the CIC is coeval and co-genetic with the felsic to intermediate metavolcanic rocks of the Yeo Formation. Emplacement of the CIC into a shallow crustal level is inferred based on the incorporation of screens and inclusions of the Yeo Formation and is supported by the presence of textures in tonalite and dioritic rocks (e.g., granophyres, miarolitic cavities, and pegmatites), as well as Al-in-hornblende geobarometry results of ≤1.3 ± 0.6 kbars (1 kbar = 100 MPa). The CIC is petrologically similar to other subvolcanic, low-Al tonalite–trondhjemite–diorite intrusions that underlie volcanogenic massive sulphide (VMS)-type deposits and which themselves may contain syn-intrusion mineralization. Several geochemically unrelated dykes and deformation events crosscut and postdate the CIC.


2013 ◽  
Vol 150 (6) ◽  
pp. 1127-1135 ◽  
Author(s):  
FERNANDO CORFU ◽  
STÉPHANE POLTEAU ◽  
SVERRE PLANKE ◽  
JAN INGE FALEIDE ◽  
HENRIK SVENSEN ◽  
...  

AbstractThe opening of the Arctic oceanic basins in the Mesozoic and Cenozoic proceeded in steps, with episodes of magmatism and sedimentation marking specific stages in this development. In addition to the stratigraphic record provided by sediments and fossils, the intrusive and extrusive rocks yield important information on this evolution. This study has determined the ages of mafic sills and a felsic tuff in Svalbard and Franz Josef Land using the isotope dilution thermal ionization mass spectrometry (ID-TIMS) U–Pb method on zircon, baddeleyite, titanite and rutile. The results indicate crystallization of the Diabasodden sill at 124.5 ± 0.2 Ma and the Linnévatn sill at 124.7 ± 0.3 Ma, the latter also containing slightly younger secondary titanite with an age of 123.9 ± 0.3 Ma. A bentonite in the Helvetiafjellet Formation, also on Svalbard, has an age of 123.3 ± 0.2 Ma. Zircon in mafic sills intersected by drill cores in Franz Josef Land indicate an age of 122.7 Ma for a thick sill on Severnaya Island and a single grain age of ≥122.2 ± 1.1 Ma for a thinner sill on Nagurskaya Island. These data emphasize the importance and relatively short-lived nature of the Cretaceous magmatic event in the region.


2017 ◽  
Vol 32 (7) ◽  
pp. 1388-1399 ◽  
Author(s):  
Elsa Yobregat ◽  
Caroline Fitoussi ◽  
Bernard Bourdon

A new protocol using Eichron™ Sr-resin for high-resolution Sr and Ba isotope measurements using thermal ionization mass spectrometry for cosmochemical samples.


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