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Clays and Clay Minerals

, Volume 30, Issue 5, pp 321–326 | Cite as

Mixed-Layer Kerolite/Stevensite from the Amargosa Desert, Nevada

  • Dennis D. Eberl
  • Blair F. Jones
  • Hani N. Khoury
Article

Abstract

Mixed-layer clays composed of randomly interstratified kerolite/stevensite occur as lake and/or spring deposits of probable Pliocene and Pleistocene age in the Amargosa Desert of southern Nevada, U.S.A. The percentage of expandable layers of these clays, determined from computer-simulated X-ray diffractograms, ranges from almost 0 to about 80%. This range in expandabilities most likely results from differences in solution chemistry and/or temperature at the time of formation. An average structural formula for the purest clay (sample P-7), a clay with about 70% expandable layers, is:
$${\left[ {\left( {M{g_{2,72}}A{l_{0,07}}F{e_{0.03}}L{i_{0.09}}} \right)\left( {S{i_{3.96}}A{l_{0.04}}} \right){O_{10}}{{\left( {OH} \right)}_2}} \right]^{ - 0.21}}{\left[ {X_{0.21}^ + } \right]^{ + 0.21}}.$$

The data suggest that talc, kerolite, and stevensite form a continuous structural series based on layer charge.

Key Words

Hectorite Kerolite Layer charge Mixed layer Smectite Stevensite Talc 

Резюме

Резюме—Смешано-слойные глины, составленные из случайно внутринапластованного керолита/стевенсита залегают как озерные и/или источниковые осадки, вероятно, плиоценовой и плейсто-ценовой эпохи на пустыни Амаргоса в южной Неваде, С.Ш. Процентное отношение расширя-ющихся слоев в этих глинах, определенное путем компьютерномоделированных рентгеновских дифрактограммов, находится в диапазоне от 0 до 80%. Этот диапазон, вероятно, есть результатом различной химии растворов и/или разных температур во время формирования. Средняя струк-турная формула наиболее чистого образца глины (Р-7) с около 70% растирающихся слоев есть:
$${\left[ {\left( {M{g_{2,72}}A{l_{0,07}}F{e_{0.03}}L{i_{0.09}}} \right)\left( {S{i_{3.96}}A{l_{0.04}}} \right){O_{10}}{{\left( {OH} \right)}_2}} \right]^{ - 0.21}}{\left[ {X_{0.21}^ + } \right]^{ + 0.21}}.$$

Эти новые данные указывают на то, что тальк, керолит и стевенсит формируют непрерывные структурные серии на основе слойного заряда. [Е.С.]

Resümee

Unregelmäßige Wechsellagerungen aus Kerolit/Stevensit treten als Ablagerungen von Seen und Quellen, wahrscheinlich aus dem Pliozän und Pleistozän, in der Amargosa Wüste, Südnevada, USA, auf. Der Anteil quellfähiger Lagen in diesen Tonen, der mittels Computer-simulierten Röntegendiffraktogrammen bestimmt wurde, reicht von nahezu 0 bis etwa 80%. Diese unterschiedliche Expandierbarkeit resultiert höchstwahrscheinlich aus der unterschiedlichen Lösungszusammensetzung und/oder Temperatur während der Bildung. Eine durchschnittliche Strukturformel für den reinsten Ton (Probe P-7), ein Ton mit 70% quellfähigen Schichten, lautet:
$${\left[ {\left( {M{g_{2,72}}A{l_{0,07}}F{e_{0.03}}L{i_{0.09}}} \right)\left( {S{i_{3.96}}A{l_{0.04}}} \right){O_{10}}{{\left( {OH} \right)}_2}} \right]^{ - 0.21}}{\left[ {X_{0.21}^ + } \right]^{ + 0.21}}.$$

Aus diesen neuen Ergebnisse geht hervor, daß Talk, Kerolit, und Stevensit eine kontinuierliche strukturelle Serie darstellen, die auf unterschiedlichen Schichtladungen beruht. [U.W.]

Résumé

Des argiles à couches mélangées composées de kef olite/stévensite interstratifiées au hasard sont trouvées comme dépôts de lacs et/ou de sources, probablement d’âge pliocène et pleistocene dans le Desert Amargosa du Nevada du sud, U.S.A. Le pourcentage de couches expansibles de ces argiles, déterminé par des diffractogrammes aux rayons-X simulés par l’ordinateur, varie de zero à à peu près 80%. Cette étendue d’expansions est sans doute le résultat de différences dans la chimie et/ou la température lors de la formation. Une formule structurale moyenne pour l’échantillon d’argile le plus pur (P-7), une argile ayant des couches approximativement 70% expansibles, est:
$${\left[ {\left( {M{g_{2,72}}A{l_{0,07}}F{e_{0.03}}L{i_{0.09}}} \right)\left( {S{i_{3.96}}A{l_{0.04}}} \right){O_{10}}{{\left( {OH} \right)}_2}} \right]^{ - 0.21}}{\left[ {X_{0.21}^ + } \right]^{ + 0.21}}.$$

A partir de ces nouvelles données, on suggère que le talc, la kérolite, et la stevensite forment une série structurale continue basée sur la charge de couche. [D.J.]

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Copyright information

© The Clay Minerals Society 1982

Authors and Affiliations

  • Dennis D. Eberl
    • 1
  • Blair F. Jones
    • 2
  • Hani N. Khoury
    • 3
  1. 1.U.S. Geological SurveyDenver Federal CenterDenverUSA
  2. 2.U.S. Geological SurveyNational CenterRestonUSA
  3. 3.Department of Geology and MineralogyUniversity of JordanAmmanJordan

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