کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5782882 | 1637528 | 2016 | 39 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Regolith production and chemical weathering of granitic rocks in central Chile
ترجمه فارسی عنوان
تولید رگولیت و هوای شیمیایی سنگهای گرانیتی در مرکز شیلی
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
چکیده انگلیسی
We have evaluated the long-term chemical and physical weathering mass balance of an anomalously thick saprolite profile (> 30 m thickness) developed in granitic rocks near CuracavÃ, Coastal Range of central Chile. The results of geochemical mass balance calculations for the regolith profile point to a moderate depletion for Na and Sr due to the plagioclase dissolution and precipitation of kaolinite. Furthermore, silicon shows a predominantly constant behaviour along the profile that is indicative of incongruent weathering of plagioclase, strongly suggesting that quartz dissolution conditions are not reached. In addition, low depletion of K, Mg, Ca, Rb, and Ba in the saprolite indicates a low degree of K-feldspar, biotite and hornblende weathering. Denudation rates calculated using cosmogenic 10Be data range from 20 to 70 m/Ma. If the saprolite thickness has reached a steady-state condition, the reported denudation rates lead to mineral residence times in the upper part of the saprolite profile of about 0.5 to 1.8 Ma. With such duration a higher weathering degree than observed at Curacavà would be expected. This apparent contradiction might be explained if all of the weatherable plagioclase has been dissolved under the present-day precipitation and temperature conditions of the Curacavi region. Therefore, we propose that the Curacavà profile could be in local equilibrium with respect to the weatherable fraction of plagioclase. A local equilibrium regime may be reached when the overall degree of depletion is small in a weathering profile. Uniform elemental distribution and low weathering degree in the thick weathering profile at Curacavà defy the traditional notion of weathering regimes and reveal the importance of exploratory studies in order to better understand weathering process in Mediterranean and semi-arid climate regions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 446, 23 December 2016, Pages 87-98
Journal: Chemical Geology - Volume 446, 23 December 2016, Pages 87-98
نویسندگان
Mercedes Vázquez, Sebastián RamÃrez, Diego Morata, Martin Reich, Jean-Jacques Braun, Sebastien Carretier,