کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9533805 | 1639751 | 2005 | 25 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Proterozoic mafic dykes as monitors of HP granulite facies metamorphism in the Grenville Front Tectonic Zone (western Quebec)
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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![عکس صفحه اول مقاله: Proterozoic mafic dykes as monitors of HP granulite facies metamorphism in the Grenville Front Tectonic Zone (western Quebec) Proterozoic mafic dykes as monitors of HP granulite facies metamorphism in the Grenville Front Tectonic Zone (western Quebec)](/preview/png/9533805.png)
چکیده انگلیسی
Metamorphosed mafic dykes and pods in the Grenville Front Tectonic Zone (GFTZ) are correlated, on the bases of map patterns and geochemical trends, with Paleo- and Mesoproterozoic dykes that cross-cut Archean rocks of the foreland, NW of the Grenville Front. The GFTZ consists of a SE-dipping 30 km thick slab of quartzo-feldspathic granulites and biotite-garnet (±opx) gneisses overriding, along the McLaurin thrust, a 4 km thick zone of muscovite-sillimanite micaschists that abuts on the Grenville Front. The granulite slab in turn dips under amphibolite-grade migmatites of the Réservoir Dozois terrane along the Dorval detachment. According to published U-Pb and new U-Th-Pb ages on monazite, the granulites, the gneisses and the schists of the GFTZ were metamorphosed at ca. 2.7-2.8 Ga and reworked at ca. 1.0 Ga (Grenvillian). Proterozoic mafic dykes and pods cross-cutting the GFTZ are thus monocyclic, i.e. they went through the Grenvillian metamorphic event only. Several of these metamorphosed mafic dykes and pods have preserved evidence of emplacement in a brittle regime such as intersection of the gneissic foliation, chilled margins, magmatic layering, this in spite of a strong metamorphic overprint attested by coronitic fabrics. In particular, metamorphosed mafic dykes of the granulite slab, contain large pyroxenes rimmed by garnet coronas with minute quartz inclusions, suggesting the reaction pl + opx = grt + qtz. These garnet coronas, in turn, are locally replaced by symplectites of opx, hbl, pl and qtz, probably formed through back-reactions grt + cpx + qtz = pl + opx and grt + cpx = hbl + qtz. Thermobarometric calculations using the above assemblages indicate peak equilibration at about 1.2-1.5 GPa at temperatures of about 800 °C followed by a quasi-isothermal decompression down to 0.9 GPa at temperatures around 700 °C. Proterozoic mafic dykes thus record a Grenvillian HP granulite metamorphism resulting from burial of upper crustal levels down to sub-Moho depths with concomitant heating. This event was followed by rapid exhumation of the GFTZ zone probably controlled by normal displacement along the Dorval detachment.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Precambrian Research - Volume 138, Issues 3â4, 9 August 2005, Pages 183-207
Journal: Precambrian Research - Volume 138, Issues 3â4, 9 August 2005, Pages 183-207
نویسندگان
Jacques Martignole, Jean-Emmanuel Martelat,