کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4692002 | 1636766 | 2014 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Magnetism of the lower crust: Observations from the Chipman Domain, Athabasca Granulite Terrain, northern Canada
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Magnetism of the lower crust: Observations from the Chipman Domain, Athabasca Granulite Terrain, northern Canada Magnetism of the lower crust: Observations from the Chipman Domain, Athabasca Granulite Terrain, northern Canada](/preview/png/4692002.png)
چکیده انگلیسی
Magnetic properties of lower crustal rocks produce anomalies seen in satellite, aeromagnetic, and ground studies, and are assumed to be responsible for observed long wave-length anomalies (LWA) of +/â 20 nT. The soon to be launched SWARM satellites will provide extensive data on the magnetization of the lower to middle crust. In anticipation of this event we are investigating magnetic properties in a superbly exposed section of lower crust in northern Saskatchewan. The Athabasca Granulite Terrain (AGT) is a complex region of felsic and mafic lower crustal rocks, part of the Snowbird Tectonic zone, stretching NE-SW across the Canadian Shield. The AGT is composed of a sequence of rocks identified as lower crustal in origin by their high pressure (> 1.0 GPa) and high temperature (~ 800 °C) metamorphism, dated at 2.6 Ga and 1.9 Ga, with uplift and exhumation at 1.85-1.80 Ga. The AGT is characterized by low (negative) aeromagnetic anomalies with distinct large positive anomalies in the southern and central regions. The Chipman Domain, on the east side, consists of tonalites, mafic granulites, and granite, intruded by the Chipman dike swarm at ~ 1.9 Ga, where anomalies cut across mapped lithologic boundaries. Susceptibility measurements from both field and lab readings range over several orders of magnitude, from 1 Ã 10â 5 to 3 Ã 10â 1 SI, with higher values related to both mafic granulite and some tonalite samples. Remanence values also show considerable variability, from 0.1 mA/m to 90 A/m, with the weakest magnetization found in the Chipman dikes and the Fehr granite. Forty samples out of 89 have Koenigsberger ratios greater than 1, but low initial remanence limits its influence on anomalies. Hysteresis and low temperature measurements identify magnetite as the predominant iron oxide. This section of lower crustal rocks has paramagnetic granites and dikes, with ferromagnetic mafic granulites and bimodal tonalites, defined by geographic location.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volumes 624â625, 11 June 2014, Pages 66-74
Journal: Tectonophysics - Volumes 624â625, 11 June 2014, Pages 66-74
نویسندگان
Laurie L. Brown, Jeffery Webber, Michael Williams, Sean Regan, Sheila Seaman,