کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8911240 | 1638264 | 2018 | 59 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
The Malpaisillo Formation: A sequence of explosive eruptions in the mid to late Pleistocene (Nicaragua, Central America)
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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چکیده انگلیسی
The 11â¯km-wide Malpaisillo Caldera and ~3.5â¯km-wide Monte Galán Caldera, located ~50â¯km northwest of Managua, are surrounded by tens of meters of rhyolitic tephras. These pyroclastic flow and fall deposits extend proximally at least 11â¯km to the southeast and 23â¯km to the southwest, with observed depositional thicknesses of >16â¯m for a single ignimbrite unit (or >25â¯m for the entire section). Distal deposits are found as far as 350â¯km offshore in the Pacific. At least twelve highly explosive large-volume eruptive phases with corresponding tephra deposits (LPTâ¯=â¯La Paz Centro Tephra, PPTâ¯=â¯Punta de Plancha Tephra, LCbTâ¯=â¯Lower Chibola Tephra, GTâ¯=â¯Guacucal Tephra, UCbTâ¯=â¯Upper Chibola Tephra, FeTâ¯=â¯La Fuente Tephra, STâ¯=â¯Sabanettas Tephra, MgTâ¯=â¯Miralago Tephra, ToTâ¯=â¯Tolapa Tephra, LMT, MMT, UMTâ¯=â¯Lower, Middle, and Upper Maderas Negras Tephras) are distinguished based on geochemical correlations and similar depositional characteristics. Radiometric 40Ar/39Ar ages indicate that most activity related to the large Malpaisillo Caldera occurred between ~570 and ~420â¯ka. The large Pleistocene Malpaisillo and Monte Galán Calderas are characterized by a long-lived history and, if evolved, a distinctly alkaline (K2Oâ¯=â¯2.3-3.8â¯wt%; Na2Oâ¯=â¯4.0-4.9â¯wt%) geochemical signature compared to the other Nicaraguan tephra deposits. As a result, the previously defined Malpaisillo Formation has been considerably extended and revised. Our findings contribute to fill a considerable gap in the long-term eruptive history of Nicaraguan volcanoes, with prominent implications for volcanic hazard evaluation for Nicaragua.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Volcanology and Geothermal Research - Volume 359, 15 June 2018, Pages 47-67
Journal: Journal of Volcanology and Geothermal Research - Volume 359, 15 June 2018, Pages 47-67
نویسندگان
Line Stoppa, Steffen Kutterolf, Juanita Rausch, Bernard Grobety, Thomas Pettke, Kuo-Lung Wang, Sidney Hemming,