Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks
The well‐known earthquake‐and‐storm‐triggered extremely high physical weathering rate in Taiwan is consistent with present geochemical studies of sediments from different subenvironments (offshore, coastal, river, and lake) and sedimentary rocks of different geological ages, indicating a moderate ch...
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| Veröffentlicht in: | The Journal of geology 2006-01, Vol.114 (1), p.101-116 |
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| creator | Selvaraj, Kandasamy Chen, Chen‐Tung Arthur |
| description | The well‐known earthquake‐and‐storm‐triggered extremely high physical weathering rate in Taiwan is consistent with present geochemical studies of sediments from different subenvironments (offshore, coastal, river, and lake) and sedimentary rocks of different geological ages, indicating a moderate chemical weathering condition. Major and trace element concentrations normalized to the average upper crust of Yangtze Craton show that the sediments and the average composition of sedimentary rocks of Taiwan are depleted in Ca, Mg, Na, and Sr, enriched in Rb and Zr, and unchanged with respect to K, indicating their moderately altered nature. The mean chemical index of alteration (CIA; 71–75) and plagioclase index of alteration (PIA; 81–86) values of coastal and offshore sediments reveal the sediments' derivation from sedimentary rocks by moderate silicate chemical weathering processes. The mean CIA value (62) of sedimentary rocks of Taiwan is similar to that for Chinese sediment (61), further confirming the above inference. A‐CN‐K, (A‐K)‐C‐N, and A‐CNK‐FM plots (
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;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{C}\,=\mathrm{CaO}\,^{\mathrm{*}\,}$ \end{document}
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| doi_str_mv | 10.1086/498102 |
| format | Article |
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\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{A}\,=\mathrm{Al}\,_{2}\mathrm{O}\,_{3}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{C}\,=\mathrm{CaO}\,^{\mathrm{*}\,}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{N}\,=\mathrm{Na}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{K}\,=\mathrm{K}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{F}\,=\mathrm{FeO}\,_{\mathrm{T}\,}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{M}\,=\mathrm{MgO}\,$ \end{document}
) also confirm that the sediments and sedimentary rocks in Taiwan have undergone moderate silicate weathering, an interpretation consistent with CIA and PIA values. The plots also indicate the presence of illite, chlorite, and a subordinate amount of unaltered feldspars in sediments and sedimentary rocks, which are indicative of the physically weathered and/or moderately chemically altered nature of sediments. The dominance of illite, chlorite, and unaltered feldspars as inferred from geochemical data suggests that the immature nature of sediments and sedimentary rocks is probably a result of low residence times in the source region or river basin and quick removal of materials from the soil profile by steep, mountainous rivers (physical weathering dominates). Elemental ratios such as Rb/Sr, K/Rb, molar K/Na, and Al/Na are close to crustal values. Average shale and river particulates such as those from the Yellow River also indicate moderate chemical weathering conditions for sediments and sedimentary rocks, except for high alpine lake sediments, where the prevailing extreme chemical weathering condition over erosion is clearly differentiated by higher CIA (80–84) and PIA (92–96) values and by their positions on triangular plots. These inferences have also been illustratively corroborated by scatter plots of data such as Rb/Sr versus molar K/Na, and Al/Na versus CIA. Additional evidence from published sources noted here also favors moderate chemical weathering conditions for Taiwan. Geochemical variation of offshore, coastal, and river sediments is mainly controlled by non–steady state weathering dominated by erosion. Steady state weathering, however, seems to produce highly weathered sediments in the alpine region of Taiwan.</description><identifier>ISSN: 0022-1376</identifier><identifier>EISSN: 1537-5269</identifier><identifier>DOI: 10.1086/498102</identifier><identifier>CODEN: JGEOAZ</identifier><language>eng</language><publisher>Chicago: The University of Chicago Press</publisher><subject>Chemical composition ; Chemical weathering ; Erosion ; Feldspars ; Freshwater ; Geochemistry ; Geology ; Particulate matter ; Rock deformation ; Rocks ; Sedimentary rocks ; Sediments ; Silicates ; Weathering processes</subject><ispartof>The Journal of geology, 2006-01, Vol.114 (1), p.101-116</ispartof><rights>2006 by The University of Chicago. All rights reserved.</rights><rights>Copyright University of Chicago, acting through its Press Jan 2006</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-a392t-cfb077e366de526a874f8abd0206a3e066daeefda4c77b9f722803111fd52b583</citedby><cites>FETCH-LOGICAL-a392t-cfb077e366de526a874f8abd0206a3e066daeefda4c77b9f722803111fd52b583</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,803,27924,27925</link.rule.ids></links><search><creatorcontrib>Selvaraj, Kandasamy</creatorcontrib><creatorcontrib>Chen, Chen‐Tung Arthur</creatorcontrib><title>Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks</title><title>The Journal of geology</title><description>The well‐known earthquake‐and‐storm‐triggered extremely high physical weathering rate in Taiwan is consistent with present geochemical studies of sediments from different subenvironments (offshore, coastal, river, and lake) and sedimentary rocks of different geological ages, indicating a moderate chemical weathering condition. Major and trace element concentrations normalized to the average upper crust of Yangtze Craton show that the sediments and the average composition of sedimentary rocks of Taiwan are depleted in Ca, Mg, Na, and Sr, enriched in Rb and Zr, and unchanged with respect to K, indicating their moderately altered nature. The mean chemical index of alteration (CIA; 71–75) and plagioclase index of alteration (PIA; 81–86) values of coastal and offshore sediments reveal the sediments' derivation from sedimentary rocks by moderate silicate chemical weathering processes. The mean CIA value (62) of sedimentary rocks of Taiwan is similar to that for Chinese sediment (61), further confirming the above inference. A‐CN‐K, (A‐K)‐C‐N, and A‐CNK‐FM plots (
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{A}\,=\mathrm{Al}\,_{2}\mathrm{O}\,_{3}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{C}\,=\mathrm{CaO}\,^{\mathrm{*}\,}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{N}\,=\mathrm{Na}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{K}\,=\mathrm{K}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{F}\,=\mathrm{FeO}\,_{\mathrm{T}\,}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{M}\,=\mathrm{MgO}\,$ \end{document}
) also confirm that the sediments and sedimentary rocks in Taiwan have undergone moderate silicate weathering, an interpretation consistent with CIA and PIA values. The plots also indicate the presence of illite, chlorite, and a subordinate amount of unaltered feldspars in sediments and sedimentary rocks, which are indicative of the physically weathered and/or moderately chemically altered nature of sediments. The dominance of illite, chlorite, and unaltered feldspars as inferred from geochemical data suggests that the immature nature of sediments and sedimentary rocks is probably a result of low residence times in the source region or river basin and quick removal of materials from the soil profile by steep, mountainous rivers (physical weathering dominates). Elemental ratios such as Rb/Sr, K/Rb, molar K/Na, and Al/Na are close to crustal values. Average shale and river particulates such as those from the Yellow River also indicate moderate chemical weathering conditions for sediments and sedimentary rocks, except for high alpine lake sediments, where the prevailing extreme chemical weathering condition over erosion is clearly differentiated by higher CIA (80–84) and PIA (92–96) values and by their positions on triangular plots. These inferences have also been illustratively corroborated by scatter plots of data such as Rb/Sr versus molar K/Na, and Al/Na versus CIA. Additional evidence from published sources noted here also favors moderate chemical weathering conditions for Taiwan. Geochemical variation of offshore, coastal, and river sediments is mainly controlled by non–steady state weathering dominated by erosion. Steady state weathering, however, seems to produce highly weathered sediments in the alpine region of Taiwan.</description><subject>Chemical composition</subject><subject>Chemical weathering</subject><subject>Erosion</subject><subject>Feldspars</subject><subject>Freshwater</subject><subject>Geochemistry</subject><subject>Geology</subject><subject>Particulate matter</subject><subject>Rock deformation</subject><subject>Rocks</subject><subject>Sedimentary rocks</subject><subject>Sediments</subject><subject>Silicates</subject><subject>Weathering processes</subject><issn>0022-1376</issn><issn>1537-5269</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2006</creationdate><recordtype>article</recordtype><recordid>eNpdkd1KxDAQhYMouP69gVC88K46Sdom9U4WXQVF8Qcvy7SduF27zZp0Ee_EJ_AZfRKzrih4Ncycj8M5DGM7HA446OwwyTUHscIGPJUqTkWWr7IBgBAxlypbZxveTwC4FCkM2PulrclhT9FwTNOmwjZ6IOzH5JruMbImup2XvbOzb-UOmxfsjqKh7XzvsOl6Hxlnp9GtbZv68-3jeoyeohHZamEWmNdvC6qbKS1g7OrfDYN4Y6snv8XWDLaetn_mJrs_PbkbnsUXV6Pz4fFFjDIXfVyZEpQimWU1hVKoVWI0ljUIyFAShDsSmRqTSqkyN0oIDZJzbupUlKmWm2x_6Ttz9nlOvi9CxIraFjuyc1_wXELOZR7AvX_gxM5dF7IFJkkSnQnx51Y5670jU8xcMw2lCg7F4g_F8g8B3F2CE99b90tJgExrBfIL3bWF3w</recordid><startdate>200601</startdate><enddate>200601</enddate><creator>Selvaraj, Kandasamy</creator><creator>Chen, Chen‐Tung Arthur</creator><general>The University of Chicago Press</general><general>University of Chicago, acting through its Press</general><scope>AAYXX</scope><scope>CITATION</scope><scope>7UA</scope><scope>8FD</scope><scope>C1K</scope><scope>F1W</scope><scope>FR3</scope><scope>H96</scope><scope>KR7</scope><scope>L.G</scope></search><sort><creationdate>200601</creationdate><title>Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks</title><author>Selvaraj, Kandasamy ; Chen, Chen‐Tung Arthur</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a392t-cfb077e366de526a874f8abd0206a3e066daeefda4c77b9f722803111fd52b583</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2006</creationdate><topic>Chemical composition</topic><topic>Chemical weathering</topic><topic>Erosion</topic><topic>Feldspars</topic><topic>Freshwater</topic><topic>Geochemistry</topic><topic>Geology</topic><topic>Particulate matter</topic><topic>Rock deformation</topic><topic>Rocks</topic><topic>Sedimentary rocks</topic><topic>Sediments</topic><topic>Silicates</topic><topic>Weathering processes</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Selvaraj, Kandasamy</creatorcontrib><creatorcontrib>Chen, Chen‐Tung Arthur</creatorcontrib><collection>CrossRef</collection><collection>Water Resources Abstracts</collection><collection>Technology Research Database</collection><collection>Environmental Sciences and Pollution Management</collection><collection>ASFA: Aquatic Sciences and Fisheries Abstracts</collection><collection>Engineering Research Database</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) 2: Ocean Technology, Policy & Non-Living Resources</collection><collection>Civil Engineering Abstracts</collection><collection>Aquatic Science & Fisheries Abstracts (ASFA) Professional</collection><jtitle>The Journal of geology</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Selvaraj, Kandasamy</au><au>Chen, Chen‐Tung Arthur</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks</atitle><jtitle>The Journal of geology</jtitle><date>2006-01</date><risdate>2006</risdate><volume>114</volume><issue>1</issue><spage>101</spage><epage>116</epage><pages>101-116</pages><issn>0022-1376</issn><eissn>1537-5269</eissn><coden>JGEOAZ</coden><abstract>The well‐known earthquake‐and‐storm‐triggered extremely high physical weathering rate in Taiwan is consistent with present geochemical studies of sediments from different subenvironments (offshore, coastal, river, and lake) and sedimentary rocks of different geological ages, indicating a moderate chemical weathering condition. Major and trace element concentrations normalized to the average upper crust of Yangtze Craton show that the sediments and the average composition of sedimentary rocks of Taiwan are depleted in Ca, Mg, Na, and Sr, enriched in Rb and Zr, and unchanged with respect to K, indicating their moderately altered nature. The mean chemical index of alteration (CIA; 71–75) and plagioclase index of alteration (PIA; 81–86) values of coastal and offshore sediments reveal the sediments' derivation from sedimentary rocks by moderate silicate chemical weathering processes. The mean CIA value (62) of sedimentary rocks of Taiwan is similar to that for Chinese sediment (61), further confirming the above inference. A‐CN‐K, (A‐K)‐C‐N, and A‐CNK‐FM plots (
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{A}\,=\mathrm{Al}\,_{2}\mathrm{O}\,_{3}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{C}\,=\mathrm{CaO}\,^{\mathrm{*}\,}$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{N}\,=\mathrm{Na}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{K}\,=\mathrm{K}\,_{2}\mathrm{O}\,$ \end{document}
;
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{F}\,=\mathrm{FeO}\,_{\mathrm{T}\,}$ \end{document}
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\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{M}\,=\mathrm{MgO}\,$ \end{document}
) also confirm that the sediments and sedimentary rocks in Taiwan have undergone moderate silicate weathering, an interpretation consistent with CIA and PIA values. The plots also indicate the presence of illite, chlorite, and a subordinate amount of unaltered feldspars in sediments and sedimentary rocks, which are indicative of the physically weathered and/or moderately chemically altered nature of sediments. The dominance of illite, chlorite, and unaltered feldspars as inferred from geochemical data suggests that the immature nature of sediments and sedimentary rocks is probably a result of low residence times in the source region or river basin and quick removal of materials from the soil profile by steep, mountainous rivers (physical weathering dominates). Elemental ratios such as Rb/Sr, K/Rb, molar K/Na, and Al/Na are close to crustal values. Average shale and river particulates such as those from the Yellow River also indicate moderate chemical weathering conditions for sediments and sedimentary rocks, except for high alpine lake sediments, where the prevailing extreme chemical weathering condition over erosion is clearly differentiated by higher CIA (80–84) and PIA (92–96) values and by their positions on triangular plots. These inferences have also been illustratively corroborated by scatter plots of data such as Rb/Sr versus molar K/Na, and Al/Na versus CIA. Additional evidence from published sources noted here also favors moderate chemical weathering conditions for Taiwan. Geochemical variation of offshore, coastal, and river sediments is mainly controlled by non–steady state weathering dominated by erosion. Steady state weathering, however, seems to produce highly weathered sediments in the alpine region of Taiwan.</abstract><cop>Chicago</cop><pub>The University of Chicago Press</pub><doi>10.1086/498102</doi><tpages>16</tpages></addata></record> |
| fulltext | fulltext |
| identifier | ISSN: 0022-1376 |
| ispartof | The Journal of geology, 2006-01, Vol.114 (1), p.101-116 |
| issn | 0022-1376 1537-5269 |
| language | eng |
| recordid | cdi_proquest_miscellaneous_19309139 |
| source | JSTOR Archive Collection A-Z Listing |
| subjects | Chemical composition Chemical weathering Erosion Feldspars Freshwater Geochemistry Geology Particulate matter Rock deformation Rocks Sedimentary rocks Sediments Silicates Weathering processes |
| title | Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks |
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